Synopsis of Dyno/Horsepower Issue
 

Synopsis of Dyno/Horsepower Issue

Summary:

Rear wheel dyno runs by owners of 'showroom' purchased cars show a lower than expected power output of the North American spec RENESIS 'high power' engine.

Dyno Run #1:
http://www.rx8forum.com/showthread.php?s=&threadid=6890
By 'adamp316' Boca Raton, FL
HP: 173.8 @ NL Tq: NL

Dyno Run #2:
http://www.rx8forum.com/showthread.php?s=&threadid=7533
By '1stRX8' Houston, TX
HP: 184 @ 8500 Tq: 130.7 @ (estimated) 6200

Dyno Run #3:
http://www.rx8forum.com/showthread.php?s=&threadid=7863
By 'compaddict' Auburn, CA
HP: 178.02 @ 8500 Tq: 123.23 @ (estimated) 6000

Torque RPM is estimated because the curve is very flat and it's difficult to see the peak.

Average rear wheel horsepower (rwhp): 178.61

Parasitic loss from published 247 bhp SAE
Run #1: 29.64%
Run #2: 25.50%
Run #3: 27.93%

Average of 3 runs: 27.69%

Assumptions and Averages:

The most COMMON parasitic loss for a manual transmission, rear-wheel drive car is between 15% - 20%.

Assuming an average (rounded up) of 18% and a rwhp rating of 179, then we ASSUME the RENESIS is making 211bhp SAE 'at the crank.'

Adding in the 5% loss that is common of new piston engines we arrive at: 222bhp SAE

Looking at torque only: Average of 127lb-ft which would equate to 157lb-ft 'at the crank.' 159lb-ft is the listed rating.

This torques suggests the issue is at the top of the RPM band, above 6000 RPM.

Possible Root Causes Stated:

· Improper dyno operation
· The DSC was left on or improperly disengaged
· 'Tight' engines that require a 'break-in' period
· A 'break-in' engine control software cutting engine power deliberately until a certain mileage is reached
· A deliberate change of engine control software for emission purposes
· A mechanical defect or design flaw
· The engine never made nor was designed to make 247bhp SAE
· There is no problem as the amount of parasitic loss is not excessive


Relevant Statements:

· Listed on dyno run #3 is a '93 RX-7 showing 207.57 rwhp. The '93 RX-7 is listed at 255bhp giving a parasitic loss of 18.6%

· It has been stated that the Miata has had around 23% parasitic loss.

· Wheels dynos are difficult to operate and mistakes are common

· Stated on Rotarynews.com: http://rotarynews.com/view.php?id=193
Q:How much horsepower does it make to the rear wheels?
A: About 204-207

· A Japanese 210PS 5MT and 250PS 6MT show similar performance
http://www.artex.co.jp/Pages/Car/RX-...03_6-26_03.jpg

· There was a Japanese tuning company that dyno'd a hi-power with their exhaust on , 212bhp at the wheels.
http://www.rx8forum.com/showthread.php?threadid=6259

· Air/Fuel graph shows a 'rich' running engine at the upper RPM range

· Torque reading on the dyno is not excessively low

Relevant Threads and Links:
http://www.rx8forum.com/showthread.php?s=&threadid=6890
http://www.rx8forum.com/showthread.php?s=&threadid=7533
http://www.rx8forum.com/showthread.php?s=&threadid=7863
http://rotarynews.com/view.php?id=193
http://www.rx8forum.com/showthread.php?s=&threadid=7976
http://www.rx8forum.com/showthread....90711#post90711
http://www.rx8forum.com/showthread.php?threadid=6259
http://www.rx8forum.com/showthread.php?s=&threadid=8579



Mazda issued Power/Torque curve as measured at the flywheel

http://mysite.verizon.net/romano.michael/3.jpg

Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you!

RomanoM's POST could concisely show Mazda or whom ever what we are concerned about, what we want an explaination for. I was getting Soooo frustrated and confused reading all the speculation on all the many threads. I hope any who post here follow your lead.

Thank you RomanoM!!

Very good summary. I will be contacting Mazda. I have been waiting on my car to arrive, but am hesitant after reading the multple threads about this. I hope we get a definite answer from Mazda, wether it is break in or the ECU that changes over. Also If it is the ECU I hope it doesn't wait until 20,000 to kick over. That would not be good.

No problem.

I too was getting confused with all the threads and posts.

Admin/Moderators how about putting this as a sticky on the appropriate Topic.

Thanks

Do all US cars have the DSC/TSC? I have a GS in Canada with no such thing. It's only on the GT in Canada..... hmmm, maybe I'll get a better run?

All but the base car gets DSC (which includes TC).

Do you really think they don't know?

Mazda's investigating, but I suspect it will be a frustratingly long time before they say anything one way or another (probably more like months than weeks or days...)

You know IF the high-power is making around 220bhp SAE that's equal to 223bhp DIN(PS) or close to the Euro engine.

Just thinking out loud, that's all.



BTW: 228bhp DIN is 225bhp SAE

a few questions:

1) has ANYONE with a J-Spec Hi-Power Renesis dynoed their car yet? there has to be quite a few out there that have that also have over 2000 miles by now...

2) does anyone know what REALLY happened at the port when they were held?

3) there are still some advertisements i see with the Hi-Power Renesis putting out 250hp NOT 247hp...since it was a fuel emission thing, could it be that they lowered the hp a little too much?

There was a Japanese tuning company that dyno'd a hi-power with their exhaust on , 212bhp at the wheels.

Scans were posted here with the data+pic of the car on the rolling road etc. dunno under what title.

http://www.rx8forum.com/showthread.php?threadid=6259
I think this is what you're talking about?

Yep

Looking at torque only: Average of 127lb-ft which would equate to 157lb-ft 'at the crank' assuming the 18% plus 5% for 'tightness' in the engine. 159lb-ft is the listed rating.

This torques suggests the issue is at the top of the RPM band, above 6000 RPM.

...which is precisely where the ECU decides to run AF ratios of 11:1, and who knows what kind of ignition timing.

BOOSTD7 brought evidence that it's not mechanically related as the Star Mazda car (for next season) is having no trouble getting the power down, further entrenching my belief that this is an extremely fixable "problem", if it wasn't intended in the first place.

I have come to the same conclusion after finally putting all the info in a form easy for me to digest.

Very good summary. I also think that this is probably an ECU map issue. Wether it's an incorrect fuel map or a "break in" map, I guess we'll see when/if Mazda decides to provide some feedback.

hahaha... yes yes, and kudos to you Romano.

I really think it would be of great use to see some automatic rx8 dyno results, because although i drive the 6 speed, it the automatic indeed makes similar rwhp as the hipower then we will have a new piece of evidence.

Well we all know that the Renesis is certainly capable of generating the claimed 247bhp because the early reviews of the pre production cars stated performance figures that could only have been attained with that output. The question perhaps is can the Renesis be made to produce that power and still be LEGAL?

Now that is a very good question.

And if a reflash was available that unleashed the full potential but wasn't CARB/EPA/whatever legal, would we care? ;)

Yes because at least in Canada we have emission testing after 3 years I think. Also, I wouldn't want to pollute the environment anymore than I have to.

There's always going to be 'gremlins' when a new car is first released. I think as long as Mazda keeps people informed and updated, then I don't think the image of the car will be hurt any. Yes, I'll be holding back until I see what happens, but for those of you who have already purchased yours, I wouldn't worry too much about it, as Mazda will set it right in time, I'm sure.

i think there should be a CSI episode about this :D

The Euro version was originally advertised as 240 ps, but then down graded to 228 hp due to emissions. Mazda knows the US is its largest market, they would have to get the emissions right here as well. With all the years spent engineering this thing, I find an 11th hour port ECU mapping change due to US emissions highly unlikely.

But I also agree that this is all probably due to the ECU map, my feeling is that it is by design. Either the cars are still too green (even with 2K miles) and/or the dyno environment has something to do with it. I'm at peace with the situation, but like all, would like the definitive answer.