This is just what it sounds like. This is a Renesis that has had peripheral ports cut into it. The side intake ports are no longer used. The side exhaust port configuration is retained. We've been curious about it. Here it is.

The results are very interesting. As predicted, power does go up. However it isn't anywhere near what a peripheral intake and exhaust engines can do. It is interesting to note how much the powerband changes between 19" in length and 22" in length. Look at what rpm it makes more power than the stock engine.

http://www.rotaryeng.net/RX8PPB-Stock-RX8.jpg

http://www.rotaryeng.net/RX8PP264a-Stock-RX8.jpg

Here's how they built it:

http://www.rotaryeng.net/Welded-steel-p-port.html

263 for PP? well, the graph does make more power, much faster than the stock even if the peak hp is a little disappointing

It should be pointed out that the most powerful periperpheral ported engines make their peak power up over 9K so this may actually not be that bad.

The 19" runner graph shows power being greater than stock above 6100 rpm. That's pretty high. If you look at the extreme left though it implies more power below 5000 rpm as well. If the tuning trend could be extended down lower, it would probably make more power between about 3500-5000 rpm as well. That is assuming that these runs didn't just start at 5K but rather the graph does.

Here's a dyno of a conventional all peripheral port (non Renesis) engine with 24.5" long runners. A shorter runner setup should be more powerful. This shows a peak power level of about 245 hp which is more than the shorter (22") intake runner p-port Renesis.

http://www.rotaryeng.net/Weber58-24.5inch-runners-dyno-curve2.jpg

This implies that the peripheral exhaust port is still superior when used with a peripheral intake port. I'd tend to agree as you need to have similar timing characteristics between intake and exhaust port to get full potential.

Here it is on the dyno at Mazdatrix:

http://www.rotaryeng.net/Idle3.wmv

http://www.rotaryeng.net/Standoff3.wmv

????? You are contradicting yourself.

Wow, that's a lot of work for 60 HP.
Does it idle?

How so?

You just said those sheets are wrong then you said you trust it far more than others.

Thanks for the post RG! I'd never actualy seen a peripheral port before :)

Wow, that's a lot of work for 60 HP.
Does it idle?

It's idling around 1300 rpm. Here in Texas your car needs to idle below 1000 rpm to pass inspection. This engine is also using a carb and not fuel injection so there is probably some power to be had and a lower idle that could be obtained.

Wow, that's a lot of work for 60 HP.

I +1 on that

and from what I've read on here, PP renny = not safe with turbo.......so......wtf

I'll just cut to the chase rather than play around; whomever prepared those first two sheets wasn't even smart enough to make sure that the torque and h.p. lines intersected at 5,252 rpms for the engine they were supposed to be measuring. In the last sheet you posted the lines DO cross, as they are supposed to.


Actually they do cross at 5252. The stock dyno lines are hand drawn in for rough reference only.

its the problem with the graphing not the results. they are not scaled the same, ray.. we see that allot with dyno plots

dang... hp goes up but so does tq. for someone who isn't rolling in cash, this is well worth it if u already have the engine out or replacing one... but to pay for labor for all that mmm~

Wow, that's a lot of work for 60 HP.
Does it idle?

not to mention that some renesis' with just a smart rebuild and masterful tuning have seen 262 on an engine dyno. so the Pport seems hardly worth it

Good luck trying to make this work with the stock ecu. I guess it could be done. You would need a new intake manifold though. It's not something I'd do to my engine. I'm still convinced that the all side port rotary is the perfect street combination.

well it's BS from the sense that the PP exhaust was modified extensively in other areas, so it's hardly a relative comparison to a bone stock Renesis for the point at hand

Good luck trying to make this work with the stock ecu. I guess it could be done. You would need a new intake manifold though. It's not something I'd do to my engine. I'm still convinced that the all side port rotary is the perfect street combination.


How are you still convinced??? It makes very little power when modified in N/A form (compared to previous gen) and it doesn't run any better than the old 13b's. :lol:

well it's BS from the sense that the PP exhaust was modified extensively in other areas, so it's hardly a relative comparison to a bone stock Renesis for the point at hand


Look at it again. It doesn't have a peripheral port exhaust. It's all side port exhaust. Only the intake ports are peripheral.

Keep in mind this engine isn't for a car. It's for an airplane. He only cares about what it does at 1 particular rpm and doesn't need a big powerband.

I always thought the exhaust ports were more of a restriction than the intake ports? I understand that there is power to be had by improving the intake ports but couldn't we see a larger increase in power from exhaust porting?

Forgive me as I am not well versed in porting and its pros and cons...

They are. There's more to power than pure static flow numbers. Many people don't understand this.

Look at it again. It doesn't have a peripheral port exhaust. It's all side port exhaust. Only the intake ports are peripheral.

Keep in mind this engine isn't for a car. It's for an airplane. He only cares about what it does at 1 particular rpm and doesn't need a big powerband.

aaack, my bad, guess I don't see any need for doing such on the intake as opposed to the exhaust

sideways oval would be better than a round port IMO, harder to make though

I know who he is and what he's doing, not impressive at all considering those are flywheel #s :dunno:

Those peak power numbers aren't impressive if all you are looking at is the peak. Look at what rpm those peaks occur at though compared to engines that make more power and it really isn't bad.

Those peak power numbers aren't impressive if all you are looking at is the peak. Look at what rpm those peaks occur at though compared to engines that make more power and it really isn't bad.

And its not very good for the kind of port that was done.

How many other peripheral intake, side exhaust port engines have you seen? I stated earlier that it was lower in power compared to an all p-port engine. It should be. The exhaust port timing is all wrong in relation to the intake timing.

How are the corner and apex seals dealing with the perip port? Are OEM seals being used?

How many other peripheral intake, side exhaust port engines have you seen? I stated earlier that it was lower in power compared to an all p-port engine. It should be. The exhaust port timing is all wrong in relation to the intake timing.

My apologizes I missed that statement.

I know of only 1 other one but it didn't hold up. The owner switched to 13brew PP config and now making 340 rwhp @ 9500rpm lol.

The owner switched to 13brew PP config and now making 340 rwhp @ 9500rpm lol.

That's what is so incredible about these little engines!

I'd be curious to see how much power he was making at 7500 and compare it to what this engine made there.

That's what is so incredible about these little engines!

I'd be curious to see how much power he was making at 7500 and compare it to what this engine made there.

Would be nice but I'm sure the 16x makes more in factory trim. lol :lol:

Displacement is a good thing.

Would be nice but I'm sure the 16x makes more in factory trim. lol :lol:

it better, if not mazda will fall

it better, if not mazda will fall

Well the 16x should be an improvement without any doubt just based on the displacement increase alone without Direct Injection or the Larger Ports. (assuming emissions are met) Now include DI and LP along with better fuel economy ...how can Failure even cross your mind? RX8 sold solely on marketing so improve it in all areas a bit and why would it not sell well again?

If your referring to the RX7 well that is a different story, they have so many directions they can take the car but which will they choose. I'm sure R&D will figure it out and lets hope its not the way of the new Miata. :lol:

i was merely saying that the 16X BETTER be better, if not mazda would be failing big time because of all the reasons you listed

i highly doubt it would though, but still, I highly doubted mazda rx8 sales could have gotten any lower and here we are now

it better, if not mazda will fall

Not exactly a business major, are you?

Kind of makes you wonder why mazda doesn't just make a new small suv and stuff a 4 rotor in it.

1) would get around emissions laws for sedans/coupes
2) could be easily swapped into the 8 or 7 or whatever

Interesting they used 87 Octane...

87 makes the highest power on a N/A rotary

87 makes the highest power on a N/A rotary

Really? Any proof of this? Why is it recommended to put in 91 or higher.

Really? Any proof of this? Why is it recommended to put in 91 or higher.

Mazsport Scott tuned the N/A for 91 93 87 and 89, he found that 87 made more power than higher octane gases.

91 is used to combat the high temps the engine experiences in stop and go daily driving and fouling of the plugs, etc.

Naturally aspirated rotaries have always loved low octane fuel. The only reason the Renesis doesn't doesn't have anything to do with the engine. It has everything to do with the tuning. Retune a Renesis and it would love low octane too.

I've always wondered whether a PP + side intake rotary would work.
That is, at low speeds a butterfly valve in the PP intake runner is shut and the engine works just like a regular side intake engine, then above a certain point the valve opens and the PP starts doing its dirty job... It could possibly be used instead of the aux side intake port.

I know that a similar setup was used many years ago for a racing engine (possibly a 12A), but would it be feasible for a road engine?
Also, would a similar butterfly valve controlled exhaust Peripherial port be possible? I've been thinking about it for a while, and while carbon deposits may be an issue, the actuators could be instructed to flip the valve 180° every time the engine goes to deceleration fuel cut-off, so that the valve "sweeps" its seat and keeps it clean. Any thoughts?

They are. There's more to power than pure static flow numbers. Many people don't understand this.

Ain't that the truth. The engine is a dynamic environment -- it's not about how big you can make a port or whether or not you can cut it so big that you can shove a lemon through it. Bigger isn't better and frequently it produces negative, back-peddling results. The largest aspect is velocity -- how fast can the charge (air and fuel combination prior to compression) move and swim through your intake into the compression stroke. The second thing is the utilization of reversion -- when the rotor closes the intake port/when the intake valve on a piston motor is shut the charge slams into it and reverts its way backwards (all fluids and gasses take the path of least resistance) creating an effect called reversion which, when changing intake runner diameter and length, can have a positive effect on higher RPM engine operation.

MazaManiac, it's not about peak power; it's not about spending (x) dollars on a setup to "get 60hp". It's about the torque and horsepower band, it's about when torque begins to rise and how quickly it rises per (x) RPM, and it's about peak torque and horsepower. Not to mention it's a nice experiment that gives some very useful data that's worth much more than the money spent to do it.

B

Mazsport Scott tuned the N/A for 91 93 87 and 89, he found that 87 made more power than higher octane gases.

91 is used to combat the high temps the engine experiences in stop and go daily driving and fouling of the plugs, etc.

I understand what you're saying Staticlag, but I wouldn't think of it in terms of "combating" but instead consider it more as a part (not only a part but a critical part) of a system with several parts that have to be "well-balanced" concerning the goal of the system (creating (x) power or producing (x) load).

Fuel is a funny thing. It's the catalyst that allows for the combustion of O2 molecules. Along with charge density and air/fuel mixture, it determines the rate of deflagration (speed of the flame front). It can have a positive effect on pulling heat out of the chamber overall. It dictates when the spark plug can be fired and how strong that spark must be. It also dictates not only what kind of spark plugs must be used (in terms of heat range) but also what effective compression ratio can be used in the motor.

In terms of the use of a non-turbocharged motor like the stock 10:1 Renesis, of course a lower octane fuel will yield more power. One of the greatest misconceptions the unsuspecting public has is that 91-93 octane fuel, which is more expensive at the pump, is somehow more powerful and better to use in their grocery-getter, putter-putter cars. Infact, it's not, even though there may be certain additives and detergents added to that higher octane fuel that may lend towards longer engine life (depending on the manufacturer and vendor). Octane rating in a nutshell is an established measurement of an engine's resiliency to engine knock, be it pre-ignition or detonation, depending on the circumstance. The lower the octane rating, the more volatile and easily lit the fuel is. Lower octane fuel yields greater power per stroke (in the form of BTU's; heat energy). In the case of the Renesis N/A motor, like the older non-turbocharged 13B's preceeding it, a more volatile fuel is perfectly fine to use, will produce more power, and will cost alot less too. Boosted is a different story however in that not only will intake air temperatures (IAT's) be higher but also the load on the motor will be more severe in that the density of the charge is greater, requiring a more stable fuel due to the fact that once the denser charge fires, it will burn with more rapidity.

The things that determine a fuel's efficacy as a heat exchanger in a combustion chamber is its latent heat of evapouration (how much heat it draws when it flashes from a fluid to a gas) and its specific heat (how much heat it can "hold" prior to heating up itself. Lower octane fuels usually have lesser of both of these. Gasoline in general isn't high on the list at all. Infact, it's low and is comparatively-speaking a very poor heat exchanger. Alcohol fuels are the anti-thesis of all that is bad about using fuel as an anti-knock agent. Methyl and ethyl alcohol fuels are through the roof on latent heat. Water, although not a fuel, is amazing on the specific heat index. The main deterrant to knock for a fuel will be its auto-ignition temperature which is challenged in its fullest fury just prior to TDC (during the end of the compression stroke) and thereafter once the charge is fired and when both pressure and temperature rise. Gasoline fuels range from mid 400*F to mid-high 600*F. Alcohols are in the high 700*F's to low 800*F's.

Hope this helps elucidate some of this sometimes-complicated topic. On a side note, once you understand all of this, you'll also understand why E85 is such a bad idea for any heavily non-FI'd vehicle. ;)

B

I understand what you're saying Staticlag, but I wouldn't think of it in terms of "combating" but instead consider it more as a part (not only a part but a critical part) of a system with several parts that have to be "well-balanced" concerning the goal of the system (creating (x) power or producing (x) load).

Fuel is a funny thing. It's the catalyst that allows for the combustion of O2 molecules. Along with charge density and air/fuel mixture, it determines the rate of deflagration (speed of the flame front). It can have a positive effect on pulling heat out of the chamber overall. It dictates when the spark plug can be fired and how strong that spark must be. It also dictates not only what kind of spark plugs must be used (in terms of heat range) but also what effective compression ratio can be used in the motor.

In terms of the use of a non-turbocharged motor like the stock 10:1 Renesis, of course a lower octane fuel will yield more power. One of the greatest misconceptions the unsuspecting public has is that 91-93 octane fuel, which is more expensive at the pump, is somehow more powerful and better to use in their grocery-getter, putter-putter cars. Infact, it's not, even though there may be certain additives and detergents added to that higher octane fuel that may lend towards longer engine life (depending on the manufacturer and vendor). Octane rating in a nutshell is an established measurement of an engine's resiliency to engine knock, be it pre-ignition or detonation, depending on the circumstance. The lower the octane rating, the more volatile and easily lit the fuel is. Lower octane fuel yields greater power per stroke (in the form of BTU's; heat energy). In the case of the Renesis N/A motor, like the older non-turbocharged 13B's preceeding it, a more volatile fuel is perfectly fine to use, will produce more power, and will cost alot less too. Boosted is a different story however in that not only will intake air temperatures (IAT's) be higher but also the load on the motor will be more severe in that the density of the charge is greater, requiring a more stable fuel due to the fact that once the denser charge fires, it will burn with more rapidity.

The things that determine a fuel's efficacy as a heat exchanger in a combustion chamber is its latent heat of evapouration (how much heat it draws when it flashes from a fluid to a gas) and its specific heat (how much heat it can "hold" prior to heating up itself. Lower octane fuels usually have lesser of both of these. Gasoline in general isn't high on the list at all. Infact, it's low and is comparatively-speaking a very poor heat exchanger. Alcohol fuels are the anti-thesis of all that is bad about using fuel as an anti-knock agent. Methyl and ethyl alcohol fuels are through the roof on latent heat. Water, although not a fuel, is amazing on the specific heat index. The main deterrant to knock for a fuel will be its auto-ignition temperature which is challenged in its fullest fury just prior to TDC (during the end of the compression stroke) and thereafter once the charge is fired and when both pressure and temperature rise. Gasoline fuels range from mid 400*F to mid-high 600*F. Alcohols are in the high 700*F's to low 800*F's.

Hope this helps elucidate some of this sometimes-complicated topic. On a side note, once you understand all of this, you'll also understand why E85 is such a bad idea for any heavily non-FI'd vehicle. ;)

B

How is fuel a catalyst that allows for combustion of O2 molecules?

Why is a low octane fuel more volatile than a high octane fuel?

How does lower octane generate more power per stroke?

How does this specific heat work?

why is E85 such a bad choice for non-heavily FI'ed vehicle, isn't it cheap?

How is fuel a catalyst that allows for combustion of O2 molecules? Why is a low octane fuel more volatile than a high octane fuel?

Higher octane fuels take more energy to light and burn more slowly. Higher octane fuels are more stable and can therefore be used with higher loads or hotter environments. Higher octane fuels, all else remaining the same, produces less torque per stroke due to its lesser volatility.

http://en.wikipedia.org/wiki/Deflagration

How does lower octane generate more power per stroke?

It's a more volatile fuel. Takes less energy typically to light and start burning. It burns more quickly, so each punch of energy that's produced is stronger. It's more ferocious than a higher octane fuel. Think of it that way.

How does this specific heat work?

Try a peek at this:
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html

Gasoline fuel's specific heat sucks, IMO, where alcohol and water far excel. The reason why it's common for tuners to run such rich air/fuel ratios while under boost (for example: 12psi of boost running 11.5:1 AFR) is because the extra fuel in the charge, making the chamber awash, is used as a heat exchanger to pull heat out of the chamber that's being created because of running boost (high loads) in the first place.

why is E85 such a bad choice for non-heavily FI'ed vehicle, isn't it cheap?

Per volume, it produces nowhere near the amount of power per stroke that straight gasoline does. It might be cheap, but you need alot more of it per stroke to make the same power. Ever wonder why you need more (and/or larger) fuel injectors and pump on the back-end for it? E85 is 85% ethyl alcohol (ethanol) and 15% gasoline (not sure what octane or kind). E85 takes more energy to produce than what it outputs. It's also a drain on the economy in that it's made primarily from corn which raises the cost of most other food but that's a different discussion altogether. Don't get me wrong; I think it's great for a very boosted setup simply because it's almost all alcohol. I just don't think it's practical for your every-day, daily driver car that's not like what we're doing.

B

Hey Brian....how's the Alky Control thread going...missed your updates :)

Hey Brian....how's the Alky Control thread going...missed your updates :)

I wish I were able to load-tune the car but I can't because the clutch is finally starting to slip. I've got an ACT un-sprung 6-puck disc that I bought and installed in August of '99. I've had it in there for over 8 years and it's finally starting to see sunset. I can't load the car out past about 9-10psi of boost because it begins to slip off. Oh well. I'll replace the disc soon (got a good deal) and get back to load tuning. I hope to break 500 to the wheels with this new turbo and methanol.

B

What, nuthin' about fuel as a catalyst?:)

I really love Wikipedia, Ray. http://en.wikipedia.org/wiki/Combustion

I hope I'm not ruining this thread. :(

B

I wish I were able to load-tune the car but I can't because the clutch is finally starting to slip. I've got an ACT un-sprung 6-puck disc that I bought and installed in August of '99. I've had it in there for over 8 years and it's finally starting to see sunset. I can't load the car out past about 9-10psi of boost because it begins to slip off. Oh well. I'll replace the disc soon (got a good deal) and get back to load tuning. I hope to break 500 to the wheels with this new turbo and methanol.

B

Sounds like a good X-mas day project :lol: I told my wife that what I wanted for Christmas was NO hassles about putting the engine back in my car before dinner:)

Brian - I applaud you for answering this stuff.
I didn't have it in me to do it again.
And again.
And again.

I think this is a sticky somewhere, isn't it? Oh, that's right:
http://www.rx8club.com/showthread.php?t=100333

Brian - I applaud you for answering this stuff.
I didn't have it in me to do it again.
And again.
And again.

I think this is a sticky somewhere, isn't it? Oh, that's right:
http://www.rx8club.com/showthread.php?t=100333

Cool. Who wrote that originally?

B

That would be me.
There are a couple of paraphrases of Jeff Hartman mixed in, but most of it is my original material.

That would be me.
There are a couple of paraphrases of Jeff Hartman mixed in, but most of it is my original material.

Paraphrases?

http://books.google.com/books?id=ze_w0i3xZmAC&pg=PA136&lpg=PA136&dq=%22gasoline+being+a+stew+of+hydrocarbons+of+var ying+structure%22&source=web&ots=mY2E5eUoiP&sig=LXpl0FjQ84Rug6V0ThK4BCkqxmM#PPA136,M1

Nice work!

B

Yeah, most of his timing/pulse width stuff is pretty generic, so I had to go through it and rework some of the math so it would apply to the rotary.
"Overview of the Combustion Process" (which is what we were talking about here), is completely bespoke.
That is what was cumulative to this thread: http://www.rx8club.com/showthread.php?t=106294

Yeah, most of his timing/pulse width stuff is pretty generic, so I had to go through it and rework some of the math so it would apply to the rotary.
"Overview of the Combustion Process" (which is what we were talking about here), is completely bespoke.
That is what was cumulative to this thread: http://www.rx8club.com/showthread.php?t=106294

Ahhh. Right. ;)

B

Yep.

That would be me.
There are a couple of paraphrases of Jeff Hartman mixed in, but most of it is my original material.

You've gotta be kidding me. I can't let this go in good conscience. This is really quite humorous. I juxtaposed your post under the 'Target Air/Fuel Ratios' portion up against what's written in Jeff Hartman's book. Here's the only two differences in what you wrote vs. what's written in the book:

- You removed the sentence, "Bob Norwood typically saves up a calibration by removing 2-3 percent timing and adding the same percentage of fuel" from the tail-end of the paragraph starting, "Assuming the engine is not knock-limited..."
- You added the words, "ported engines" and "highly ported engines" when the words "big-cammed" and "mild-cammed" popped up twice

Perhaps you should credit Jeff Hartman for having written this section of his book How to Tune & Modify Engine Management Systems (page 136). Otherwise, it's complete plagiarism. You certainly didn't write this and it's nowhere near "paraphrasing".

B

Quotation of sources have been added as applicable.

You gotta realize, I soak this stuff up like a sponge. I dial 411 and I've forgotten the first 3 numbers before I get to the end of the next 4.
But when I even skim an SAE paper or something similar, all of the content gets stuck in my brain like a thorny burr.
I can tell you what my datalogged ignition timing was at 7200 RPM on my last 4th gear run last Thursday off the top of my head.
However, I have no idea what's the date of Thanksgiving.

Quotation of sources have been added as applicable.

Baloney. You plagiarised; plain and simple. You took credit for someone else's research and work in three ways:

- Implicitly by implying that it was yours in your initial posts
- Explicitly when your response to my question was, "That would be me." but also when you tried to pass it off as, "paraphrasing"
- Tacitly when you neglected to respond to the many posts by others on this forum who responded to your initial thread. You were willing to accept the praise but none of the responsibility by way of your lack of forthright response regarding the real source.

I think you're trying to assume the glory of Jeff Hartman's work instead of having the fortitude to tell the truth -- he wrote that and you did not. What's even more noteworthy about it is the scant, few words you added/modified still don't even give it the impression that it has anything to do with rotaries even though that appears to be your motive. If you're willing to borrow someone else's writing, it compels me to wonder that perhaps you really don't know what you are talking about, especially seeing as how your attempt to show-off and one-up me with this link to Jeff Hartman's plagiarised work that you so dutifully cut and pasted had little to nothing to do with what I was writing about in the first place.

You gotta realize, I soak this stuff up like a sponge. I dial 411 and I've forgotten the first 3 numbers before I get to the end of the next 4.
But when I even skim an SAE paper or something similar, all of the content gets stuck in my brain like a thorny burr.
I can tell you what my datalogged ignition timing was at 7200 RPM on my last 4th gear run last Thursday off the top of my head.
However, I have no idea what's the date of Thanksgiving.

That's called backpeddling. I hope it doesn't fool anyone.

B

Would you like for me to just delete it? Or, is it more fun for you to just keep bashing me?
Either way is fine with me, just let me know what you prefer.

Ok this has gone on long enough. Back on topic please.

87 makes the highest power on a N/A rotary

maybe on your Renesis, but not on mine

we proved beyond a doubt over many dyno runs that the difference between 91 and what I run (yeah, I'm not telling you the specific higher number) was an automatic 10 HP peak loss, 87 was substantially worse than 91 ...

Wow. The "peak combustion pressure" argument is going on in a bunch of different places on this forum simultaneously!

Pick one! I need to prepare. This scotch is kicking my ass!

maybe on your Renesis, but not on mine

we proved beyond a doubt over many dyno runs that the difference between 91 and what I run (yeah, I'm not telling you the specific higher number) was an automatic 10 HP peak loss, 87 was substantially worse than 91 ...

Yeah, and we proved beyond a doubt over many dyno runs that the difference between 96 and what I run (yeah, I'm not telling you the specific lower number) was an automatic 15 HP peak loss, 96 was substantially worse than 91 ... :)

And I've proved beyond a shadow of a doubt that due to my wallet being lighter (I'm not telling you by how much though), expensive high octane fuels make me faster!

Is that the Glenlivet you referred to on another thread? Have you seen the movie "Swingers"? "Glenfiddich, Glenlivet, any Glen will do".


Indeed. I have a copy of that movie around here, somewhere...

I can prove, beyond a shadow of a doubt, that my wallet, being exactly the same weight as it was when I bought it a Target 6 or 7 years ago, indicates that I have absolutely no conclusive proof that high octane fuel makes any God damn difference other than knock resistance.

Which do you drink Jeff?

Which do you drink Jeff?

I've got the 21-year-old bottle of Glenlivet in front of me.

I love that movie! I watch that back-to-back with "Death to Smoochy".

I'm only sipping, though. I not big on getting drunk, especially on a weekday afternoon, by myself at home.

Yeah, and we proved beyond a doubt over many dyno runs that the difference between 96 and what I run (yeah, I'm not telling you the specific lower number) was an automatic 15 HP peak loss, 96 was substantially worse than 91 ... :)

But in any sense, its hardly an equal comparison to match pump gas vs. your special blend that probably cost you $7 a gallon.

I'll kick his ass! :shocking: :boink: :boxing_sm

But in any sense, its hardly an equal comparison to match pump gas vs. your special blend that probably cost you $7 a gallon.

But here gas DOES cost $7 per gallon. Does it mean that my Fiat Grande Punto (http://en.wikipedia.org/wiki/Grande_punto) produces 90 hp instead of the advertised 75???? :p: :rollingla :rollingla :rollingla

Glenmorangie (http://www.glenmorangie.com/):)


Higher octane fuels take more energy to light and burn more slowly. Higher octane fuels are more stable and can therefore be used with higher loads or hotter environments. Higher octane fuels, all else remaining the same, produces less torque per stroke due to its lesser volatility.

http://en.wikipedia.org/wiki/Deflagration



It's a more volatile fuel. Takes less energy typically to light and start burning. It burns more quickly, so each punch of energy that's produced is stronger. It's more ferocious than a higher octane fuel. Think of it that way.



thats just not correct.

octane is not a measure of how fast or slow any given gasoline will burn. it is only a measure of the fuel's resistance to pre-ignition. pre-ignition is defined as the fuel igniting on its own due to pressure and heat before the arrival of the flame front.

http://www.faqs.org/faqs/autos/gasoline-faq/part3/ importantly 6.2 and 6.3 as well as 6.13 6.16 and 6.17

on modern engine management systems you will only get the most power out of a given engine by using the octane that limits knock effectively. if you go lower than that number the PCM will hear the knock and adjust your timing to reduce power.

If you're using a standalone and doing your own tuning you may be able to tune for a lower octane than originally called for by the manufacturer - since they always leave a margin of error- but by doing so you leave yourself at the mercy of one bad tank of gas.

I think I'd like to see a renesis with a small auxilary peripheral exhaust port and the centre plates merged side exit welded up, keeping the other side exits to give 4 exhaust ports as normal but two of them peripheral and far better flowing with no pulse interferance.

i know how to make overlap in the renesis :) carlos told me:)

Glenmorangie (http://www.glenmorangie.com/):)




thats just not correct.

octane is not a measure of how fast or slow any given gasoline will burn. it is only a measure of the fuel's resistance to pre-ignition. pre-ignition is defined as the fuel igniting on its own due to pressure and heat before the arrival of the flame front.

Hi Charlie,

I disagree. I never said that octane was a measure of how fast or slow it burned although it's been my experience that it's implicitly related. I said it was a fuel's resiliency to knock. It seems however that a higher octane fuel is less volatile and burns more slowly with a more controlled and stable flame-front depending upon what it is. Alcohol is one example.

Also on pre-ignition, it strikes me that it's defined as the occurrence of any type of knock that fires the charge prior to and outside the confines of a well-timed spark event. I can think of a few things -- heat and pressure as you've mentioned, any kind of glow-plug effect from an external source, just plain firing the plug too early because of poor tuning, and the biggie auto-ignition of the fuel in the charge.

I'll give the URL you've linked a read and see what it has to say. Thanks for it.

http://www.faqs.org/faqs/autos/gasoline-faq/part3/ importantly 6.2 and 6.3 as well as 6.13 6.16 and 6.17

on modern engine management systems you will only get the most power out of a given engine by using the octane that limits knock effectively. if you go lower than that number the PCM will hear the knock and adjust your timing to reduce power.

Some PCM's sure, but I have a question -- if you're correct in asserting that burn rate has nothing to do with octane (if I understand your point correctly), then why would a PCM be designed to pull spark back in the first place when it's knock sensor encountered knock? If burn rate is of no consequence and if what you say about pre-ignition is correct "pre-ignition is defined as the fuel igniting on its own due to pressure and heat before the arrival of the flame front", then I'd say that it wouldn't matter when you fired spark; knock would occur anyways because the same pressure and heat exist, unless you're possibly confusing pre-ignition with detonation. In this scenario, all else being equal, there'd be no reason to be variable on when spark is fired since the burn rate is always the same. Prolonging firing the spark a few to several degrees would have no effect, I would think.

On the contrary, there's two major things I can think of just off the top of my head that effect burn rate -- charge density and fuel type (even though there's a host of other factors). When using a higher octane fuel, such as leaded race gas or perhaps an alcohol, I can keep everything else remaining as close as possible to the same (turbo, engine, boost pressure, whatever) and can get away with firing the plug lots earlier than I would with a more volatile pump fuel. I've done it more times than I can count.

Example: http://www.youtube.com/watch?v=_9o5T0PIWVA On this setup, I was running 65-70% fuel (I reduced the load on the EFI system) and replaced the other 30-35% missing fuel with methyl alcohol (enough to bring the mixture back into low 11's:1) at 25psi of boost. Here's the kicker -- normally I wouldn't tune a car on pump gas past 14-15psi as I fear it's instability for not only what you've eluded to (bad tank of gas) but also for other factors that ultimately boil down to its untrustworthiness. At that boost, I fire the plug at 13-14* with a split of 9-11* depending on the CR of the motor and its port work. On the setup linked to the video above, at 25psi (10psi more boost), I was firing the plug at 16*BTDC with a split of 6* and I beat the crap out of that thing like that for months!

If the aspect of the speed of the flame front isn't related to the overall octane rating of the fuel or atleast implicitly factored in, then why do you suppose that I and others can repeatedly get away with this kind of fairly radical timing advance without killing the motor by way of manually inducing pre-ignition? What's your thoughts on that? Is there something else I am not thinking of that's perhaps related?

If you're using a standalone and doing your own tuning you may be able to tune for a lower octane than originally called for by the manufacturer - since they always leave a margin of error- but by doing so you leave yourself at the mercy of one bad tank of gas.

Agreed. Don't get me started on what I think about pump gas. :rant: :rl:

B

ive always considered the differences between the two to be putting to fine an edge on it. but for purposes of this discussion we need to set the defintions as charles said so

Detonation
Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug.

Pre-ignition
Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. This can happen so far ahead of spark that it is happening during compression. so the fuel my be trying to expand while the engine is trying to compress.

deferring to your terminolgy then when i previously wrote pre-ignition i was talking about detonation. the difference being that pre-ignition literally happens BEFORE spark plug fire while the other happens after.

controlling the timing of spark fire allows the engine to ramp down the heat as well as try to eliminate the offset of the seperate pressure waves by controlling the one that it can. if the engine managment is firing the plugs too early this can ramp up the pressure too soon contributing to the detonation

more to write later- for now i have to clean up Henry and get him some lunch

It's good to see that Charlie understands the difference between detonation and pre-ignition!

but i agree with Jeff as well- the two are only seperated by the spark event. that is the only thing that distinguishes them. either can cause the other. they are both combustion events when you dont want them which cause pressure rises when you dont want them. to me , as i said before, it puts to fine a point on it to seperate them. you could just as easily say that pre-ignition is a form of detonation.

detonation - in the context of the definitions above- can be fatal to an engine. pre-ignition is nearly always fatal. the times its not it causes more detonation and more heat leading to another pre-ignition event that is fatal.

but as with a different thread where it was tried- I agree to these definitions so we can talk about the POINT of the discussion.

Jeff is correct from the standpoint that each is bad for the engine. I disagree that you can say that pre-ignition is a form of detonation. It isn't. It is however accurate to say that pre-ignition can lead to detonation. That is accurate. You can have detonation without preignition. You can have preignition without detonation. You can also have both. They are still two separate but closely related phenomenon.

like apathy in alzheimers!

The video of the motor on the dyno clearly shows a mismatch combination of parts. That has to be one of the worse cases of reversion I've seen in modern times. That setup is either never going to show the true potential of the combination or it's allready showing the limits.

Charlie, I spoke to Brian on the phone at length about this today. He'll get on here and post later. He did get a bit confused while he typed his response. After I threw out a few scenarios he realized it. It is coincidental that the types of fuels that he has used all just so happen to both burn slower and have higher octane ratings. Specifically Methanol and leaded gas in relation to standard pump gas. If only these fuels are compared it is easy to see draw the conclusion that higher octane must mean slower burn.

As you pointed out it doesn't and you are correct that octane rating is merely a numerical representation of resistance to pre-ignition. It is not indicitive of rate of burn. There are 2 prime examples. Hydrogen and Diesel fuel. Diesel fuel has a very low octane rating of somewhere between 20 and 40 yet burns very slowly. Hydrogen has a higher octane rating than gasoline yet burns much faster. You can make great power with diesel but can't with hydrogen. What further throws more confusion into all of this is that based on the known information of octane and flame front travel, you still can't draw a conclusion as to how auto ignition temperature fits in. It's all pretty complex. It's easy to draw conclusions when you only see a small aspect of the available information. In Brian's case, the fuels he used do have slower flame travel and higher octane. When that's the only info you see it's very easy to draw conclusions from it. When more info is made available however it becomes apparent that some things just happen to be coincidental.

From my experience when dealing with different fuel types when appiled to a rotary motor, octane numbers are the least important.
The burn rate, specific gravity and most important cooling effects are what affects the rotary motor the most. Not all fuel types no matter what octane will have the cooling affects that a rotary loves be it NA or FI. I've yet to see a pure NA rotary make more useable/reliable power with high octane fuel.

I agree with that entirely. If we are only talking about gasoline and nothing else, it's perfectly fine to look at only octane number. Of course I am speaking in terms of forced induction. However if alternative fuels come into play my foremost concern is not the octane number unless it absolutely sucks!

You do also bring up another good point regarding fuels that wasn't mentioned and that is cooling ability.

thats because the octane of the fuel doesnt make a bit of difference how much power an engine can make on it as long as there is no detonation/knock/pre-ignition

Maximum Best Torque (MBT) by a given fuel is mainly determined by WHEN the ingition occurs and Flame Front speed. Flame front speed is determined by the shape of the chamber and how much turbulence is created(turbulence i.e. swirling increase flame front propagation) by that shape , and by the burn speed of the fuel.

the OCTANE of the fuel has no bearing on what the speed is. Only what is mixed in the fuel does.The specific mixture of paraffins, olefins , aromatics oxygenates are what determine the flame speed. some octane boosters may lead to lower flame speeds while others can increase it. and the pressures can effect how much the given chemical will increase or decrease the speed.

some other links in no particular order of importance

http://www.daytona-sensors.com/tech_tuning.html

http://72.14.205.104/search?q=cache:1qxnfnqPOaYJ:www.wipo.int/pctdb/en/wo.jsp%3Fwo%3D2005007781%26IA%3DWO2005007781%26DIS PLAY%3DDESC+higher+octane+generally+means+slower+f lame+speed&hl=en&ct=clnk&cd=10&gl=us&client=firefox-a

http://www.sacskyranch.com/deton.htm

http://72.14.205.104/search?q=cache:NpfmfcIVe5EJ:www.motorcycle.com/how-to/wrenching-with-robchemical-soup-the-mystery-of-detonation-3420.html+higher+octane+generally+means+slower+fla me+speed&hl=en&ct=clnk&cd=3&gl=us&client=firefox-a

alcohol is actually a good example. high octane because of its cooling properties and high energy due to high flame speed. it works well in the injected scenario above because it is cooling AND fuel

You do agree that there is difference between maximum power and torque?
The requirement for high rpm vs low rpm use on the same application is sometime different and that's where burn speed plays an important role.

welll.. power is torque times work so no, not really the way you pose the question. when you are tuning you are trying to find MBT. your looking for the timing that gives you the best power without knock + a safety margin.

OEMs are going to have a bigger safety margin than racers. Drag Racers can have an even smaller safety margin because the limited amount of time the car is doing its thing leaves less chance for detonation or pre-ignition. circuit or road racers have different margins dependant on their need to balance against fuel consumption and when you are tuning for specific fuels then burn speed is very important.

most however are tuning street cars for a wide variety of fuels. fuels that change formulation throughout the year, from area to area some with more olefins,some with more oxygenates etc

Generally, you tune for best torque, which will be .5 to 1.0 richer than best power.

How the hell does that work?!

How the hell does that work?!

What do you mean? How does what work?

welll.. power is torque times work

I know what you meant.

Power = Torque multiplied by rpm and a constant at any given rpm, so if you've tuned for best power, you have got best torque, you can't possibly have a different afr for one and another for the other with breaking the universe.

oh boy, MM is gonna rip you a new one, as you are wrong on both counts. I don't know all the details about the tuning and the math etc,



hp= (torque x rpm)/5252

Well, nice to know someone that doesn't know the details tells me I'm wrong and then posts an attempt of the equation that proves I'm right......;)

uh, they are functions,

horsepower is a measurement of work done "E"

torque is a static load placed at a certain distance from the radius

the only reason they intersect is because they are part of an engine function, if it was a constantly defined function like you are implying, then all engines would have the same powerband, they dont :(

No it wouldn't, as it still depends on the torque output at any given rpm the engine is capable of.

example:

okay, you have to torque your lug nuts to 100 ft/lbs so the momentary force applied is 100ft/lbs at any given tangent.

Now your muscles have to use X amount of ENERGY to get your arm to apply this 100ft/lbs of torque. Uh, this is horsepower.

Yes they intersect and are related in this one application: engines.

No they are not always related.

Well unfortunately that is the application we are talking about, or hadn't you noticed?

Bit difficult to change the afr of your arm muscles, and you can still manipulate the engine function to fit the muscle scenario, if you couldn't then there would be a problem with your physics model.

Well unfortunately that is the application we are talking about, or hadn't you noticed?

I did notice, tell me, whats the constant?

The conversion factor between measurements. What does this have to do with anything?

A constant is a constant - more power at one rpm=more torque at that rpm, you can't tune for them seperately.

Well unfortunately that is the application we are talking about, or hadn't you noticed?

Bit difficult to change the afr of your arm muscles, and you can still manipulate the engine function to fit the muscle scenario, if you couldn't then there would be a problem with your physics model.

So your telling me that my arm can make 250 ft/lbs of torque while only expending 1/4 of its available power? and later in the graph can only make 100ft/lbs of torque by expending 100 of its available energy?

but i agree with Jeff as well- the two are only seperated by the spark event. that is the only thing that distinguishes them. either can cause the other. they are both combustion events when you dont want them which cause pressure rises when you dont want them. to me , as i said before, it puts to fine a point on it to seperate them. you could just as easily say that pre-ignition is a form of detonation.

detonation - in the context of the definitions above- can be fatal to an engine. pre-ignition is nearly always fatal. the times its not it causes more detonation and more heat leading to another pre-ignition event that is fatal.

but as with a different thread where it was tried- I agree to these definitions so we can talk about the POINT of the discussion.

You still haven't answered my question in response to your post, Charlie. ;)

B

hp is a function of torque, not the other way around

torque is force

horsepower is work

and yes you can tune for them seperately

So your telling me that my arm can make 250 ft/lbs of torque while only expending 1/4 of its available power? and later in the graph can only make 100ft/lbs of torque by expending 100 of its available energy?

That depends how fast you are trying to move your arm and apply pressure at the time.

hp is a function of torque, not the other way around

torque is force

horsepower is work

and yes you can tune for them seperately


Ok, if you can tune for them seperatey, at a given rpm point, talk me through how you would do it :squint:


You've just told me yourself one is a function of the other ffs!

I'm not talking about the constant or the calculation.
Maximum power will occur at LBT. However, we don't tune for LBT because MBT is higher and safer (and on a turbo motor we tune for RBT). The torque curve will change shape because of this. Since peak power occurs at a higher RPM than peak torque, the peak power will be a function of the instantaneous torque at that RPM, which will be somewhat less than "optimum" because of the slightly richer A/F.

[[Didn't this entire discussion already happen about a million times on this forum over the past 3 years?]]

The conversion factor between measurements. What does this have to do with anything?

A constant is a constant - more power at one rpm=more torque at that rpm, you can't tune for them seperately.

the only constant is what you divide the product of your torque multiplied by rpm

The conversion factor between measurements. What does this have to do with anything?

A constant is a constant - more power at one rpm=more torque at that rpm, you can't tune for them seperately.

Lol, kind of convenient if you make up a random number that magically fits what you are trying to prove.

I can do that also,

watch

my bank account X constant

Hmm, I want a million dollars


$1 x $1,000,000

No, its not applied in all situations,

Lol, kind of convenient if you make up a random number that magically fits what you are trying to prove.

I can do that also,

watch

my bank account X constant

Hmm, I want a million dollars


$1 x $1,000,000

No, its not applied in all situations,


Now this is getting weird, the constant is a simple conversion rate between units, what are you smoking?
If the unit conversion were taken out of it it'd simply be

Power= Torque x RPM

Now, as we at a single RPM point when altering AFR (as per the original remark), we now get the equation

Power = Torque.

Now, please explain how you'd increase one without the other?!

I'm not talking about the constant or the calculation.
Maximum power will occur at LBT. However, we don't tune for LBT because MBT is higher and safer (and on a turbo motor we tune for RBT). The torque curve will change shape because of this. Since peak power occurs at a higher RPM than peak torque, the peak power will be a function of the instantaneous torque at that RPM, which will be somewhat less than "optimum" because of the slightly richer A/F.

[[Didn't this entire discussion already happen about a million times on this forum over the past 3 years?]]

Truce!

I'm with MM

I'm not talking about the constant or the calculation.
Maximum power will occur at LBT. However, we don't tune for LBT because MBT is higher and safer (and on a turbo motor we tune for RBT). The torque curve will change shape because of this. Since peak power occurs at a higher RPM than peak torque, the peak power will be a function of the instantaneous torque at that RPM, which will be somewhat less than "optimum" because of the slightly richer A/F.

[[Didn't this entire discussion already happen about a million times on this forum over the past 3 years?]]

Your maximum 'safe' power and torque should be the same regardless, provided your not just shifting the ignition by a set amount over the entire power band, which is never good.

As you said, you'd only get more power by shifting away from that to a riskier map, but even then you'll get more torque too!

:grouphug: :grouphug: :grouphug:

Now, please explain how you'd increase one without the other?!

I think you are kinda missing the forest cause you found the biggest tree.

The A/F that will yield the highest torque peak will not be the A/F that will make the highest power peak because of the constant - time.
If the power peak occurred at the same time as the torque peak, they would be in lock step.

Your maximum 'safe' power and torque should be the same regardless, provided your not just shifting the ignition by a set amount over the entire power band, which is never good.

Your maximum power will happen at one ratio. Your maximum torque at another.
"Safe" is a side benefit. On an FI motor, the flame front is fastest at RBT.

Now this is getting weird, the constant is a simple conversion rate between units, what are you smoking?
If the unit conversion were taken out of it it'd simply be

Power= Torque x RPM

Now, as we at a single RPM point when altering AFR (as per the original remark), we now get the equation

Power = Torque.

Now, please explain how you'd increase one without the other?!

Damn you!

Your totally right!

Now this is getting weird, the constant is a simple conversion rate between units, what are you smoking?
If the unit conversion were taken out of it it'd simply be

Power= Torque x RPM

Now, as we at a single RPM point when altering AFR (as per the original remark), we now get the equation

Power = Torque.

Now, please explain how you'd increase one without the other?!

your equation doesnt balance now. you cant take something away from one side without taking it away from the other

your equation should be

(power x 5252)/rpm = torque

I can because 5252 doesn't make any difference to the relationship and the rpm is not changing and becomes a constant!

you drive your car around and the engine doesnt change rpm?

I think you are kinda missing the forest cause you found the biggest tree.

The A/F that will yield the highest torque peak will not be the A/F that will make the highest power peak because of the constant - time.
If the power peak occurred at the same time as the torque peak, they would be in lock step.



Your maximum power will happen at one ratio. Your maximum torque at another.
"Safe" is a side benefit. On an FI motor, the flame front is fastest at RBT.

Again, since maximum power is a function of torque at that rpm you have to make more torque to make more power, bit of crossed wire here as what you are refering to is the peak power and peak torque spots?
Obviously occuring at different rpm, but even then you should be able to compensate for that on a proper map by adding a little ignition advance up top to compensate for the slightly lower flame front speed.

you drive your car around and the engine doesnt change rpm?

I'd hope not if I was sat on the dyno trying to map it!

Again, since maximum power is a function of torque at that rpm you have to make more torque to make more power, bit of crossed wire here as what you are refering to is the peak power and peak torque spots?
Obviously occuring at different rpm, but even then you should be able to compensate for that on a proper map by adding a little ignition advance up top to compensate for the slightly lower flame front speed.

We are not talking about ignition. Just A/F.
But, even so, you are adding ignition as you increase RPM, so your detonation threshold remains constant (because your BMEP should fall at the same crank angle).
So, no, you can't. (Only in your theoretical world.)

But ignition changes will affect A/F, especially if you tune simply to a lambda reading, which isn't advisable as they aren't infalliable.


The extra fuel when moving away to MBT-R should raise the detonation threshold from the cooling effect at the top end, after all the only reason you are keeping your torque peak and dropping the power peak is because you've effective de-optimised your ignition timing at the top end as the flame front speed has more effect here, the torque peak isn't so effected because of it's position in the rpm range, but it's still changed slightly.

If you're shifting 1 point richer and getting better torque but lower peak power then there something wrong with the map.

You still haven't answered my question in response to your post, Charlie. ;)

B

i did sort of here

thats because the octane of the fuel doesnt make a bit of difference how much power an engine can make on it as long as there is no detonation/knock/pre-ignition

Maximum Best Torque (MBT) by a given fuel is mainly determined by WHEN the ingition occurs and Flame Front speed. Flame front speed is determined by the shape of the chamber and how much turbulence is created(turbulence i.e. swirling increase flame front propagation) by that shape , and by the burn speed of the fuel.

the OCTANE of the fuel has no bearing on what the speed is. Only what is mixed in the fuel does.The specific mixture of paraffins, olefins , aromatics oxygenates are what determine the flame speed. some octane boosters may lead to lower flame speeds while others can increase it. and the pressures can effect how much the given chemical will increase or decrease the speed.

some other links in no particular order of importance

http://www.daytona-sensors.com/tech_tuning.html

http://72.14.205.104/search?q=cache:1qxnfnqPOaYJ:www.wipo.int/pctdb/en/wo.jsp%3Fwo%3D2005007781%26IA%3DWO2005007781%26DIS PLAY%3DDESC+higher+octane+generally+means+slower+f lame+speed&hl=en&ct=clnk&cd=10&gl=us&client=firefox-a

http://www.sacskyranch.com/deton.htm

http://72.14.205.104/search?q=cache:NpfmfcIVe5EJ:www.motorcycle.com/how-to/wrenching-with-robchemical-soup-the-mystery-of-detonation-3420.html+higher+octane+generally+means+slower+fla me+speed&hl=en&ct=clnk&cd=3&gl=us&client=firefox-a

alcohol is actually a good example. high octane because of its cooling properties and high energy due to high flame speed. it works well in the injected scenario above because it is cooling AND fuel

But ignition changes will affect A/F, especially if you tune simply to a lambda reading, which isn't advisable as they aren't infalliable.


Though it is true that ignition changes will affect the effective A/F, its not as significant as injector duration changes.
If the last part of your statement were effectively true, the entire industry would be in a LOT of trouble.

The extra fuel when moving away to MBT-R should raise the detonation threshold from the cooling effect at the top end,

The "cooling" effect of fuel is negligible - especially as RPMs rise.


after all the only reason you are keeping your torque peak and dropping the power peak is because you've effective de-optimised your ignition timing at the top end as the flame front speed has more effect here, the torque peak isn't so effected because of it's position in the rpm range, but it's still changed slightly.

No, that's wrong and I've already explained that here and in a bunch of other places on the site, so I'm not going to do it again.


If you're shifting 1 point richer and getting better torque but lower peak power then there something wrong with the map.

You haven't actually done a lot of this before, have you?

[[Didn't this entire discussion already happen about a million times on this forum over the past 3 years?]]

yes

for clarity

LBT = Lean Best Torque
MBT= Mean Best Torque. sometimes written Maximum Best Torque. also have seen it as Maximum Brake Torque
RBT = Rich Best Torque

one of the previous discussions http://www.rx8club.com/showthread.php?t=108455

i was actually speaking about timing more than AFR the charts in this link i previously posted are helpful (albeit from apiston view point;))

http://www.daytona-sensors.com/tech_tuning.html

on the af side i believe this might have been bandied about earlier by BDC bu ti offer it now only because i found it while google researching

Jeff Hartmans book http://books.google.com/books?id=ze_w0i3xZmAC&pg=PA136&lpg=PA136&dq=mean+best+torque+timing&source=web&ots=mY2E8a_tcY&sig=WWQ7NaTHC4q1ZQQb93Ar6eLD67o

(Only in your theoretical world.)

Often proven wrong in the real world.
Just the belief that knock and peak torque goes together. Some motors are knock happy way before or after peak torque. I call it the knock zone and the only way to find that out is through trial and error. The rotary motor happens to be one of those that will always knock in a certain area of the curve even if the torque peak occurs much higher or lower. Also by moving the torque peak away form that area knock threshold increases.
Where would you say this motor would be most knock prone?

http://i238.photobucket.com/albums/ff279/uspmotorsports/V8killa-1.jpg

"Alex - I'll take 'Things that knock @ 5200' for $100, please."

"Alex - I'll take 'Things that knock @ 5200' for $100, please."

Who's Alex?

You can't be serious

"I'm gonna kill you Trebec."

Though it is true that ignition changes will affect the effective A/F, its not as significant as injector duration changes.
If the last part of your statement were effectively true, the entire industry would be in a LOT of trouble.

Good Lord! Have you ever done this stuff before or are you just regurgitating junk you've read (some of which you're gleefully willing to call your own)?? Of course firing spark at different points has a significant effect! If you've ever parked your rear-end in a car for a few hours on a dyno while changing spark advance tables you'd know this in a heart beat!

The "cooling" effect of fuel is negligible - especially as RPMs rise.

Oh, boy. Stare at an EGT and look at the differences between running 11:1 and 12.5:1 at the same load, same RPM when running the car hard. You'll see just how "negligible" this difference is. :lol:

You haven't actually done a lot of this before, have you?

Talk about the pot calling the kettle "black".

B

i did sort of here

Yes you did sort of Charlie, but with all due respect, I asked a pointed question that was attempting to assert (at least in that video-linked example) the difference in burn rate and why, if I were to fire a plug later to somehow stave off knock (pre-ignition I believe is what you called it), and if burn rate had nothing to do with, why then have I and others who've done this countless times been able to change fuels to run more advance and produce considerable more power and torque, all things else remaining equal?

I know that I didn't charactise my thoughts well between the relationship on octane vs. burn rate and I appreciate Fred correcting me on it, but in my experience, atleast with the fuels I've messed with, it seems to me that the higher octane stuff I go and purchase at the speed shop (like VP Racing C16 117L race fuel or methyl alcohol) do also have slower burn rates by way of comparison between when I can fire plugs on those vs garden-variety pump gas. Perhaps it's true that in the strictest sense the term "octane" isn't inclusive of this factor but it strikes me that the two seem to coincide with one another atleast in some cases.

B

Often proven wrong in the real world.
Just the belief that knock and peak torque goes together. Some motors are knock happy way before or after peak torque. I call it the knock zone and the only way to find that out is through trial and error. The rotary motor happens to be one of those that will always knock in a certain area of the curve even if the torque peak occurs much higher or lower. Also by moving the torque peak away form that area knock threshold increases.
Where would you say this motor would be most knock prone?

http://i238.photobucket.com/albums/ff279/uspmotorsports/V8killa-1.jpg

+1

My guess is between 6000 and 7500rpm.

B

Good Lord! Have you ever done this stuff before or are you just regurgitating junk you've read (some of which you're gleefully willing to call your own)?? Of course firing spark at different points has a significant effect! If you've ever parked your rear-end in a car for a few hours on a dyno while changing spark advance tables you'd know this in a heart beat!

Oh, boy. Stare at an EGT and look at the differences between running 11:1 and 12.5:1 at the same load, same RPM when running the car hard. You'll see just how "negligible" this difference is. :lol:



Boy, you've just got my number, dontcha?

I'm not even going to address the first "paragraph" because I think you just missed the point.

I stare at EGT all day long. In fact, I just upgraded to a dual display with fast probes (so I can monitor the two ports instead of the throat), so its kind of apropos that you asked.
Changing the A/F does more than just "cool" the charge. It changes the flame front speed, so its point in the combustion cycle will be different by the time it reaches the exhaust port, which changes the temp as well.
The difference in EGTs between those A/Fs can be anywhere from "none" to 500°F or more. Its not relevant until you've established what you believe the proper EGT should be at the torque peak at MBT.
Plus, you just got done going on about how much difference ignition timing changes EGTs and now you want to talk about A/Fs without including the effective A/F shift from changes in ignition timing.


I'm not sure what your problem is (you might be a great guy and a capable tuner), but you might get a more interesting conversation going if you tried being a bit less hysterical.
I've got hours and hours of datalogs of this stuff if you are interested. Maybe you could get that under your belt and reintroduce yourself around here because as it stands now, you are just generating some really entertaining arrivals in my inbox.

But you should be able to compensate for the change in flame front speed with more ignition advance while still keeping your safety margin on the ignition side the same.


And while I'm here I'll put my guess in at around the 5500rpm area.

Yes you did sort of Charlie, but with all due respect, I asked a pointed question that was attempting to assert (at least in that video-linked example) the difference in burn rate and why, if I were to fire a plug later to somehow stave off knock (pre-ignition I believe is what you called it), and if burn rate had nothing to do with, why then have I and others who've done this countless times been able to change fuels to run more advance and produce considerable more power and torque, all things else remaining equal?



well it does. but i believe you are looking at it the wrong way around.

Ignition at the wrong time can cause detontation. if you fire the plug and the fuel burns so fast that the pressure rises too quickly and cause the end gases to detonate then what was the cause? was it the octane of the gas or the flame speed? no it was the timing. the timing was innapropriate for the fuel. not the other way around. add an anit knock agent and you CAN run that timing.

as to why you can do what you did? its because of the alcohol which is the reason you chose it in the first place. the alcohol has a high resistance to knock but a fast burn rate. its resistance to knock is of its cooling attributes not in its effect on flame speed/burn rate. but its anti-knock ability is why it is used and why you can get so aggresive with the timing- but you already know that, it s why you choose to use it


page 3
http://www.epa.gov/otaq/presentations/epa-fev-isaf-no55.pdf

Light load stability, meanwhile, is improved by the high compression ratio, which raises the temperature of compression and enhances the already comparatively high flame propagation velocities of alcohol fuels.

and the currently ever present jeff hartman

http://books.google.com/books?id=ze_w0i3xZmAC&pg=PA131&lpg=PA131&dq=alcohol+flame+speed&source=web&ots=mY2E8fXsgX&sig=g63k6hUKJScfaF_VBLNYbkhd0Wk

starting in the left column where he writes "Turbulence and swirl are extremely important factors in flame speed- more important,within limits, than mixture strength or exact composition" and continueing into the next column

I'm not sure what your problem is (you might be a great guy and a capable tuner), but you might get a more interesting conversation going if you tried being a bit less hysterical.
I've got hours and hours of datalogs of this stuff if you are interested. Maybe you could get that under your belt and reintroduce yourself around here because as it stands now, you are just generating some really entertaining arrivals in my inbox.



I hope you understand that there is a HUGE difference in ones datalogging experience vs someone who has numerious years of hands on experience with completely different applications?

Good Lord! Have you ever done this stuff before or are you just regurgitating junk you've read (some of which you're gleefully willing to call your own)?? B




BDC be careful! This place isn't like the rx7 forum. People have a funny way of completely DELETING threads when someone (who is supposed to be hi ranking) gets called out for not really knowing their stuff. I know this from experience as a thread I was involved in complete vanished because I proved a mod wrong. I think it's funny as hell as what some of these guys think they know. Crispeed and RG excluded.

Peace!

not people and not mods. the plural is not necessary . that an individual did such a thing i can believe. but dont paint us all with that same brush. id like to know who it was though . privately

^ There's no need for a private discussion as I don't know who it actually was. I will say this, you were heavily involved in that thread and should know who it was....I'll leave it at that!

I did notice one thing that was not included in this discussion that might help clear up the confusion; IMO- I relate Octane Rating to Flash point primarily.

The mixture of the fuel (Ethanol, Additives, Gasoline, etc) is actually used to determine the flame front speed (both Laminar and Turbulent) which in themselves are related. By doing the flame speed calculation based on Moles; you can see how the small molecular weight changes impact the Brisance.

As for determining knock; the math exists to forecast knock - the biggest problem is that we lack the sensor values required by the model.

An example (from my explosives work) we measure TNT in two areas; Stability and Sensitivity. Civilian grade TNT and military both have the same Brisance rating (or an RE of 1); but military grade is less sensitive and more stable due to additives - so it can take some heat, being dropped etc... what it requires is a higher INITIAL energy input to begin the chemical transformation.

I hope you understand that there is a HUGE difference in ones datalogging experience vs someone who has numerious years of hands on experience with completely different applications?

Of course. Did you think those datalogs just came out of thin air?
I just figured he might want to look at the numbers since actually being at a past tuning session is not possible.

BDC be careful! This place isn't like the rx7 forum.

Amen to that. Its like a bunch of teenagers with a bottle of Thunderbird over there.

I know this from experience as a thread I was involved in complete vanished because I proved a mod wrong.

I'm quite sure that your idea of "proved" might need some tweaking.

^ There's no need for a private discussion as I don't know who it actually was. I will say this, you were heavily involved in that thread and should know who it was....I'll leave it at that!


which thread then?

http://www.mazdamaniac.com/images/misc/undead.jpg

Well the load is off my back! Here is a thread that goes off topic more then mine. I'm happy to join as a spectator only, I will not get involved. Just happy it is here.
Mods do not remove it, please.
But I might add that the only avitar that is showing up today belongs to Zoom44.
Veeerrrryyy interesting.:spank:

But I might add that the only avitar that is showing up today belongs to Zoom44.
Veeerrrryyy interesting.:spank:

Weird.

weird x2- i can see everyones avatar

OK, they are all showing up now but I know you did it.:eyetwitch

no i didnt- whats weird tho is you learning how to bold something in your post after all of this time :)

Its a conspiracy! C. O. N.....spiracy.

darn missed that- saw it was on but started watching something else. ill have to catch it next time

I saw that show a few months ago. Interesting.

Anyone play "Assassin's Creed"?

Not yet. I want to check it out, but i've been too busy getting my ass kicked by 6 year old kids on COD4.

Not yet. I want to check it out, but i've been too busy getting my ass kicked by 6 year old kids on COD4.

Its badass. Its "Splinter Cell" in the 13th century.

After all this talk about torque and hp, burn rate and knock restency.. does anyone have an update what happened with this engine? is it tested at higher revs and shorter intake runners to see the full potential? were there stock rx8 style seals used, or were the rotors machiened for higher seals (like the earilier engines) to prevent excessive flexing when passing the peripheral intake port?

don't waste your time, it was done sppecifically for an airplane engine application that only focuses on a very narrow operating range (lower rpms to keep from throwing the prop off), completely useless in a car application, unported stock block Renesis engines have turned considerably higher output numbers

don't waste your time, it was done sppecifically for an airplane engine application that only focuses on a very narrow operating range (lower rpms to keep from throwing the prop off), completely useless in a car application, unported stock block Renesis engines have turned considerably higher output numbers

Please tell me more.. 260-270hp below 8000rpm seems quite optimistic for an unopened engine, also if I look to the racingbeat results from there ported engine they are just shy of 250hp around 9000rpm..

my engine is producing it's rated power (177kW), with a stock exh (.3bar exh backpressure), but adjusting the afr or timing doesn't bring anything extra..