olddragger

iTrader: (3)

thanks for the information. It is interesting and yamamoto does state moving the sparkplug kernal closer to the combustion camber would have positive benefits.
A good ignition system that could support a surface gap sparkplug would help with this but I dont think the oem rx8 ignition system is up to that job?
My measurements in some old housings I have revealed are posted here. Both with and without the plugs washer.
Now location of the lead plug is not in question--only its size and its recession depth.

TeamRX8

iTrader: (25)

you are overlooking thermal expansion in general and between dissimilar metals in particular, plus that also being one of the highest thermal stress areas in the entire engine

the pressure in the leading chamber, which is housing the combustion process at the very moment of rotation when the apex seal is passing over the leading plug and also at a point when the same chamber is not open to the exhaust port, is not less than the next chamber which is only just barely starting to compress the intake cycle. If anything, combustion gases are flowing back into the next intake cycle that is about to compress, not the other way around as you are stating

You may have a PhD in shadetree theory, but you fail in real world analysis

wow

TeamRX8

iTrader: (25)

Did you even watch the video link I posted earlier (quoted at the bottom)?

the frozen picture below from that video is the point of engine rotation/cycle we are discussing - anyone who thinks the blue intake cycle pressure is higher than the red combustion cycle pressure doesn't understand the first thing about internal combustion engines. That red combustion pressure cycle is what is powering a 3000# vehicle forward. When the exhaust port is finally exposed to it the gasses rush out at supersonic speed ...

olddragger

iTrader: (3)

There is not a concern with thermal expansion/contraction causing problems. Although this has not been done in the RX8 yet--it has been done in other rotary engines results without any problems.
Granted -you would not want to make an adapter out on any piece of metal just laying around.

Actually the sparkplug itself is a dissimilar metal---isnt it?

Face to face leakage does occur to the rear --so to speak. Doesnt the EGR gasses get carried forward within the tub?

Harlan

iTrader: (3)

Please post pressures if you are going to make that statement. Mazda picked that point and made the plug hole that big because differential pressure is minimal there, care to tell me which side it favors and by how much? Oh and if you are actually going to post some hard data, please tell me how the differential pressure changes as the apex travels over the hole. I'm really wondering about that myself.

Oh and "thermal expansion in general and between dissimilar metals in particular" lovely. So you're saying that a spark plug cooled by a water jacket is magically going to have enough thermal expansion to creep far enough into the housing to impact the apex seal. Dissimilar metals has almost no bearing on anything, especially considering the rotor housing is lined with a dissimilar metal. By your argument our engines shouldn't work at all! Sure the plug/insert is going to need a gap before protruding into the housing, but take a spare housing and a spare plug and ask yourself if it really needs that much.

This entire thread is speculation until something is tested, and we know it. If your going to insult us for it at least do it without wild *** speculations of your own.

Harlan

iTrader: (3)

I know it's just us shadetree mechanics here talking out our butts, but it appears the apex is directly over the leading plug and the exhaust port is pretty far open. I took it a little way both directions, but the pictures didn't turn out as well. The exhaust port begins to open slightly before the apex begins its pass over the leading plug.

olddragger

iTrader: (3)

well i be damn!

olddragger

iTrader: (3)

I spoke with Rick and Paul ( Mazmart) about the possibility of a sparkplug insert adapter that would remove most of the recession the lead plug has. Much discussion/thought was done, some measuring was also done.
It seems in the 3 sparkplug engine, its lead sparkplug hole is approx 1/2 the size of ours
Rick said that he thought that it may help with some of the face to face leakage that occurs.
.
Moving the plug closer to the combustion chamber--not so much. Rick stated it is close enough and the changes I saw where probably due to the changes of the ignition timing that happened when I moved it futher in.

So insert should be pursued!! Now to find a plug that will work etc, etc!
They request we keep them informed.

TeamRX8

iTrader: (25)

The issue is which side has the higher pressure, if either. There virtually is nothing more than near-atmospheric pressure in the latter intake cycle at the apex/lead plug crossover

Mr Shadetree in the video was likely referring to an earlier 13B rather than the Renesis



So you intend to go build a part before actually doing any testing to determine if your most basic assumptions are even valid but at least you confirmed the positioning to the port. That's all I'm really driving at.

Mazda has so many years and yen invested in the rotary development that you think it's simple and was easily overlooked by them then by all means continue ... maybe they should feel insulted.

question: did you also look at the rotor position to the intake port at the same point? Just curious.

.

olddragger

iTrader: (3)

remember Team--Mazda also built and released the RX8 cooling system. They also advised a 5w20 motor oil.I could go on......
Point is mazda is not perfect.
Perhaps some clarification needs to take place? I dont think we have ever said or inferred that there is any kind of overlap between the intake and exhaust ports. What we have discussed is that the exhaust port is open as the trailing apex seal passes buy the lead sparkplug hole.

Bottom line--it is accepted by the rotary community that there is face to face leakage that occurs as the apex seal passes by the lead sparkplug.

Our approach is to reduce the size of the hole and thereby reduce the amount of leakage.

You know good and well we dont have the equipment to validate the amount of leakage that is occurring. Get real. Do people measure their sparkplug tip temperatures before they know they need to run a colder sparkplug? Dont think so.They make decisions based on previously accepted reasoning/findings. Then they evaluate their results and move on.
Besides the amount of gases that "spitback" contains is but one of the issues.

Harlan

iTrader: (3)

Yes the differential pressure is low across the seal at the leading plug hole, but it's not atmospheric on either side. The exhaust side is rapidly changing pressure as the exhaust port opens and the intake side is compressing the charge. So the high pressure side goes low and the low pressure side goes high. That's why that point was chosen.

I have more pictures here showing the secondary intake closing, the aux intake closing and the apex finishing it's pass over the leading plug. I looked at primaries but I didn't feel like taking any more pictures. This mod may not be the best for reliability, or it may have any number of other shortcomings, but that doesn't make it a bad idea. You can see a bit of compression has already happened when the seal passes over the leading plug, especially if the aux ports are closed.

I do understand what you are getting at, but Mazda did what was right for them in designing the engine, not the best for performance or the cheapest or the most reliable, but a balance. Mazda didn't put an OMP on the car because it was the best way to lubricate the seals, they did it because it was the best way to keep the car reliable with unreliable users.

j9fd3s

the more i tear into the Rx8 the more inconsistent it is. the suspension is really world class excellent, however if you aim your garden hose at the intersection of the trunk, quarter panel and rear window, and watch how they intended water to drain, its actually funny. whoever did that didn't seem to have a firm grasp of gravity!

i would actually say that there are many different people who worked on the car, the suspension team is great, the water cooling people; as usual get a B-, the FD is mediocre in the cooling department too.

there is an SAE paper on oil for the R26B engine, and they know the trade offs with the oil weights.

anyways, in rereading the SAE papers i ran across this picture. it seems that there actually IS overlap between the intake and exhaust ports, because they are both on the side housing, except that this overlap area is between the side seal and oil seal. so the cutoff seal's job is actually to cut off this overlap, by taking up that space. not a very elegant solution imo

olddragger

iTrader: (3)

That has to increase the drag

Harlan

iTrader: (3)

Setting up to try different spark plugs.

RX what?

This is a little off topic but may be relevant.


In this video the fuel is being 'atomized' but as you can see that it is puddling up on the surface being sprayed.

Why would the suspended fuel particles in the intake phase not just puddle up on the trailing apex seal? Is the velocity of the fuel particles fast enough to be compressed without the apex seal catching them first? Also I know that fuel is being sprayed without any air from an intake.

RX what?

Also found this, would vaporized gasoline be beneficial to rotaries?

Harlan

iTrader: (3)

Fuel does puddle up by the trailing apex, and mazda exploited that for lean burn on an Rx4. Fuel also puddles in the intake ports.

I thought about gasoline vaporization for a while, but came to the conclusion that when the gas comes in the port and hits the hot rotor it vaporizes anyway. Any droplets sufficient small should vaporize when they hit hot metal, anything larger and you get waste. This is part of the reason I'm skeptical about the use of larger injectors for P1s, but nobody seems to have much of a problem.

RX what?

Yeah, i'm wondering if a copper (or proper metal) coil wrapped around an exhaust component with fuel passing through it will heat up the gasoline passing to a temperature that results in better if not full vaporization. Ignition temp is around 500F but i'm not sure how hot the exhaust is.

skc

Generally you need cool fuel for more power. Boiling fuel will cause big problems.

RX what?

What about this cool (temp) vaporized mist being injected into the UIM? What do you guys think would be the result?

wcs

iTrader: (2)

LOL that guy pour gasoline vapour over a open circuit board.
Check it out at 2:40 in the vid

Harlan

iTrader: (3)

Injecting straight vapor would have some benefits, but how do you do it? The problem is metering a controlled amount of vapor.The Ford model Ts had a plate after the carburetor that was heated by the exhaust, the liquid fuel would be metered by the carburetor and then vaporized by the plate.

You can't just heat the fuel in the lines, this would cause a fuel vapor mixture and the fuel injectors would not meter it accurately or consistently. And as I said before this effect already happens to some degree as the fuel hits the hot surfaces of the engine. I think if you actually built an engine to test working vapor injection you would end up with a minimal gain in fuel economy after very major modifications.

olddragger

iTrader: (3)

no--heating fuel in the correct way can increase the homogeneity within the combustion chamber---resulting in a more efficient engine ( power and gas mileage). read about Smokey Y's stuff in the older hotrodding days! But you are right--it is not as simple as "boiling the fuel"--that is bad.
velocity of the intake air helps! That is one reason FI works so well on this engine.

RX what?

[IMG][/IMG]

Like this the second throttle (cable) would be used to ensure the correct ratio of oxygen to vaporized fuel.

RX what?

This video is the basis for that quick drawing.