P00Man

i was just at the starmazda site and it says 170hp from a sealed mazda 13b...whatever that is

i know its bi-rotor, but is it the renesiss?

edit:
whats the series with all the rx-8s racing around?
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compaddict

That's the old engine, the new 2004 Pro Formula Mazda uses the Renesiss.

Vince

P00Man

is that to say that the site isnt updated yet or that i was at the wrong one?
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compaddict

http://www.starmazda.com/

Second box down!

Vince

KyngNothing

240?

wakeech

yeah, slightly detuned for that series (longevity in mind or something??)... anyways, they outa still shoot flames like mad :D

a guy on the Speed Channel (before it became SPEED) on one of the first Mazda Star broadcast thought they were turbos ('cause of the flames and backfires).

P00Man

oh, i must have seen the 2003 specs.

so, the power is there
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LovelyWendie99

jmanolov

This is not true!

Here. I can show you a dyno graphs of a friend's Miata - same runs both at the wheels and at the crank. The dyno we did was on a nice machine - Dynamics Test Systems one.

Here is what the dyno measured for crank and wheels power:




The run shows 119.8hp at the crank and 103hp at the wheels.
This is only a 14% drivetrain loss! And this is what the other folks are getting too ...

My Miata is at about 170 hp at the wheels, and at around 195hp at the crank - which is close to the 14% too. With 23% drivetrain loss my engine should be in the 210hp ballpark which is just not true!


If we asume the RX8 has Miata's drivetrain losses (it has almost the same 6 speed Miata gearbox unit, etc). 14% of 247 hp are 34.58 hp. Which means the RX-8 should dyno around 212 hp at the wheels. Whatever the problem with the RX-8 is - it is not the drivetrain losses. Probably it is the current fuel and ignition maps, etc.

BRealistic

Does anybody have a dyno sheet to post for the RX8 yet? I just wonder if the power is flatlining at 6grand like the SportCompactCar pre-production RX8 did. They didn't even post the dyno, since they could tell the engine had a sixth port problem.

FredB

Well I just can't help myself and have to throw some more fuel on the fire. For some in depth info on the inaccuracies of chassis dynos and more info on power transmission losses try this site:

http://toyotaperformance.com/dyno.htm

And the link to puma racing at the bottom of that page goes into very great detail about dyno testing, losses, etc. These sites suggest that for a modern 100-200 HP RWD car, in the absence of exacting measurement of the losses, would be about 17%. Or about 205 RWHP for the RX-8. Or applying another formula there about 207 RWHP. But they do caution that this is only typical losses and there could be some variance, but probably small.

The article suggests that the % losses should be somewhat less as the HP increases beyond 200 hp because some of the frictional losses are independent of Power. It further states that 30% losses are totally out of the question unless something is very, very wrong. Anyway....it's a very good source and in line with what I've found elsewhere from other "experts".

The other point I'd like to make is that I see one person make the claim that the losses on a specific car are "precisely" 23% and in another post a guy shows that his losses on the same vehicle are 14% should raise a red flag with everyone. There's nothing very precise about a chassis dyno unless the testing is very very carefully controlled and corrections applied using resonable/accurate sources of temperatures, etc. Even back to back runs can show improvements due to temperature increases instead of some modification the tuner did. Lots of things can and do go wrong. It will be interesting to see Mazda's explaination when it comes. Soon I hope. Hope you enjoy the article.

Shamus

Sigh... Jmanalov...I know you post over at the Miata forum so how's about doing a simple search of what people generally get on a DynoJet dyno for their Miatas before you call me a fink?!?

Ok, if pictures work for you then here's a stock 99 and 01 on a DynoJet - (it's charts like this one that forced Mazda to lower the rated hp to 142... http://www.flyinmiata.com/tech/dyno_...ell_112700.pdf

This chart and others can be found at http://www.flyinmiata.com/tech/dyno.asp

Then there is this tidbit from a fine article appropriately named "The Bullsh*t Filter" from none other than Sports Compact Car regarding the dyno number on their 2001 -

"...expected to see around 129 hp at the wheels. Instead, we saw 112...
"http://www.sportcompactcarweb.com/editors/technobabble/0112scc_technobabble/


Here's just a few threads and quotes from posters about this issue from Miataforum...

- http://www.miataforum.com/ubb/ultima...=014101#000016
"...the Miata has been dynoed by people here for years. Thus nearly everyone is aware of what the typical dyno pulls should be. Its been standardized so to speak. Typically, the '90-'93 1.6L is good for 90-95rwhp, '94-'97 around 100-105rwhp and the '99+ is good for roughly 110rwhp (maybe a few more in some cases)..."

"...Stock 2001 Miatas dont' make 115-116 hp at the wheels, not on a DynoJet anyway. 109-110 is what they typically make. Using the 26 hp observed (observed Randy Stocker and others) loss in the Miata drive train..."

- http://www.miataforum.com/cgi-bin/ul...c;f=6;t=011984
"...My stock 99 dynoed at 112 rear wheel HP..."

- http://www.miataforum.com/cgi-bin/ul...c;f=6;t=013833
"... Flywheel: 140HP standard, 138HP LEV (CA, et al.) Typically around 109 at the wheels based on dyno results people have posted here..."

- http://www.miataforum.com/cgi-bin/ul...c;f=1;t=019861
"...Figures came back at 110 RWHP (with the hood up -- Keith says it dropped to 107 with the hood down)..."

Now, I'm not even going to get into the fact that the numbers on a Dyno Dynamics are not going to be the same as on a Dyno Jet, or Mustang etc... or question how the Dyno Dynamics can possibly tell you what the hp at the crank is because I've already done too much of your research for you.

pelucidor

Funny you should ask - the first post of this very thread has Compaddicts RX-8 dyno graph, which started the whole discussion here. You will see it does not flatline and has little blips are the ports open etc.

Talking about parasitic losses - isn't the idea of electric power steering and one piece carbon fiber driveshafts in the RX-8 to reduce these losses? I would expect under 17% if that is the case.

Shamus

You're completely correct, that's why it's important to use words like generally rather than precisely and have several different sources that have results close to the same figure.

It's also very true that various different dyno's give various results.

P00Man

"It's also very true that various different dyno's give various results." - Shamus

that being said, is it possible to "tune" a dyno to more accurately represent a particular cars power output?
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Shamus

Honestly, I don't know if some dynos can be tuned to attain more accuracy or not. I suppose that dyno's vary from manufacturer to manufacturer for a reason, and that each has their own way of getting to their numbers which they think are more accurate than their counterparts. I don't know which ones are inherently better and more accurate, but I do know that the different resulting hp numbers are really only comparable within that brand of dyno unless you apply a general mathmatical rule like Dynojets are always this much more than a Mustang etc...

The accepted standard due to sheer numbers for the USA seems to be Dynojet by a large margin. That doesn't mean it's more accurate, just that since that's what most everyone is using, the results can be compared to one another.

The results CAN be affected greatly by outside factors that can be altered to obtain more parity (I wouldn't say accuracy). Ambient temp, dynamic cooling (fans blowing on the motor on intake), and altitude to start with. Then there is the car itself and the scenario in which it's tested - what tire pressures, what accessories are running, what gear is it in, what grade of fuel and oil, is their a limited slip, is the stability management on or not, is the hood up or down, is the car warmed up or not, is the driver a chili head or a wussy... and on and on... it's all very technical. (grin)

Shamus

My point in all of this has never been that 23% drivetrain losses are what we should expect or accept for the new RX-8, just that 17-18% ain't written in stone, and that modern Mazda's with 6-speeds can and do lose around 23% in their drivetrain from what the company says the hp at the crank is. That's all.

One question I do have about drivetrain losses is this: Does the ability of an engine to absorb and combat parasitic loss increase if the engine has higher torque? I wonder if an engine's torque number and placement has any relationship with parasitic losses. I don't really know, just asking someone who might know the physics better than I do.

Also, does the engine do anything freaky if the tire monitors detect a problem? This is pure speculation and completely un-researched, but I have heard that hitting a curb too hard with tire like when you're parking will trigger the air pressure sensors in the wheel. I wonder if being shackled to a dyno puts a stress on the front tires during the run to the point that the tire pressure monitors are triggered. Again, pure speculation on my part.

eccles

It seems that the vast majority of dynos over here are of the "single-run, fixed load" variety, where the power is calculated from the rate at which a set of large heavy rollers can be spun up by the drive wheels. These work well enough, but for fine tuning and diagnosis, one really needs a variable-load dyno.

A variable-load dyno uses some sort of brake to vary the resistance of the rollers. The one we used to use for my race cars Down Under used a large electric brake unit as fitted on many large busses and coaches (Swedish-made, IIRC). With this setup, one selected the desired speed, and ran the engine up to that point. Once there, the dyno automatically adjusted the braking in opposition to the input power, so you could test and tweak settings at anything from 10% to 100% throttle at any given point in the rev range. We spent a day fine tuning our Motec at 10% throttle increments every 500rpm from 2000 to the redline, and the results were spectacular. You could never do that with a fixed-load Dyno.

Does anyone know of any US shops that have this sort of equipment?

nk_Rx8

I don't think this is true, since if you take the generic ~20% loss for rwd and ~15% loss for fwd, S2000's which have an even slightly lower HP and lower torque rating than an RX8, dyno ~200whp and my Integra GSR which has an even lower torque and hp dynoed (~149whp) right where estimates would place it also.

So either something is fishy or there is a lot more drive train loss in the RX8 than 'normal'. But either way, it would be a shame. Most modern cars should be striving for efficiency in the drive train these days. And when you couple that with what I think is below avg MPG, this doesn't make me too excited about the car. Plus I was really expecting to see a lower than avg drive train loss because I thought that the rotary was a more direct "connection" to the driveshaft. So I am hoping there is another cause. Also I thought the FD had the normal rear wheel drive train loss also.

TurboSE

Okay, let me try and clear up a point once and for all. 23% drivetrain loss as seen in a miata is possible. It just means something is not right. The clutch was not upto par or the tranny was having higher heat losses or something of that nature. It does NOT mean that it should be expected of every mazda drivetrain, particularly not a brand spankin new RX-8. Like I said before, higher mileage cars can yield such a result but it is not valid as an argument in this thread. Dyno numbers vary but not that much. Heck I got pretty close to dyno numbers (within 4%) using a plain ol' g-tech on a level surface. I think all the new rx-8 owners concerned about this should buy one and see where their performance is at. I will be surprised if it can do a 15 sec 1/4 mile. I do hope that timing and afr changes occur to help this poor little engine otherwise it won't be anywhere near the performance of a 3rd gen and maybe not even a t2 2nd gen considering it is the heaviest rotary powered car ever built. I want to see progress damn it not performance decline.

neit_jnf

I believe the drivetrain losses on the RX-8 should be a lot less than those of the Miata, why? because the power steering is electric as well as the cold start air pump and the drive shaft is a one-piece carbon fiber which further reduces loss... but of course I'm no expert

1stRX8

Pro Teknik is the shop that ran my 8. Thier dyno has a variable load capability. They use it to tune Ferarris and TT 911s. Certainly one of the more capable shops in the area, but are clueless about rotary specific issues. The shop does a lot of motec programming for GT class porches, so they have a wealth of diagnostic equipment to tune the $500,000 cars they work with. Fun place to hang out for sure.

They only charged me about $80 for almost two hours in which they gave me about three guys to help.

rxeightr

In an earlier post, it was said that Mazda did not provide the 247 HP figure, and that it was supplied by the US EPA.

My question is, what method does the US Gov't use to determine horsepower ratings?

Shamus

Man, I just got back from another extended test drive and it really made me realize how little all this hp stuff matters to me, this car is flat awesome. Incredibly smooth power, mind-blowing brakes, and handling that is frankly incredible. This thing will be seriously competing with my R package Miata for the roll of occasional track car at Portland Intl.

You know, I agree that the electric steering, cold start pump and carbon driveshaft should yield less parasitic losses than a Miata, but the Oliver Stone in me makes me wonder if a parasitic loss issue is WHY they added all those bits and really the engine is making the right hp after all. Or not, I don't even pretend to know.

But in all actuality, it really doesn't matter to me anymore after that last test drive. If there is an issue I know from history that Mazda will take care of it's customers and I know from recent personal experience that this car is ripping good fun!

Now, if you'll excuse me, I have to sell my Maxima SE to make room for the new Rotary Rocket... (Titanium on black leather, what do ya think?

compaddict

It's you!

Vince

P00Man

nice car man
love the sig

thanks for the explaination

edit:
not sig, char icon
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