Tbone

1200 miles on car. dyno'd at 175 HP. Just FYI. Got lots of looks and questions on the car. I LOVE my 8, just not sure why it's only dyno'd at 175 HP if it's a claimed 238 at the flywheel. is 26% loss normal for other cars? I disabled the DC and TSC withe 7 second button push before runs.

Stone stock 8 with 92 octane pump gas.

RXE16T

I think the percentage loss is to do with the type of Dyno you are running on.
I read somewhere that some will account for a 15% loss whereas some are as high as 30%.

Can someone validate this?

RX8-TX

Does it look like mine :p Dyno

rx8wannahave

Yes please...can someone give us more information on this...I'm very interested!

Lufa

Very typical to get 170-180 RWHP on Bone stock 8 dyno's.

There have been a billion posts on this topic... Needless to say there is a large amount of evidence that they Dyno's are accurate, and Mazda's pants are on fire.

Red Devil

I've seen the slips from Polak of the 14.5 1/4 mile, and that's a good enough starting point for me. Though I would like to dyno it for a baseline before I start modifying the powertrain, but that won't be until late next summer so I have some time to go...

NavyDood

Go back at the 10,000 mile mark and re dyno it. It seems as though the engines get better after you get some miles on them.

RX8-TX

I dyno'd with over 16K miles....I am sorry, but I think the 10K mile / 20K mile switch over to hi-po is bullshit.

Lufa

It's true, and the best Polak's car could get from a canzoomer was an extra 5hp... In other words, his car runs like everyone's is supposed too (at least like Mazda claims our cars should), it came out of the factory with a performance tuned engine. He gets some of the best gas mileage as well.

Everyone else, well... we either have to wait for a new PCM flash from Mazda to make more power (not bloody likely) or take matters into our own hands and Tune the engine to where it actually produces 230-240 HP with any of the ECU piggy backs available. The engine is completly capable of advertised performance, unfortunatley only a small percentage actually do bone stock.

I personally will address it when I think my 215-220HP 8 isn't fun to drive anymore.

Gord96BRG

He didn't say anything about an ECU switch to different programming as you imply - he simply said that the engines tend to make more power as they get more miles on them. That is common with quite a few engines that have very tight tolerances when brand new - in other words, simple break-in takes ROUGHLY 10,000 miles or more before the engines produce peak power. Nothing whatsoever to do with an ECU switch to different programming.

Regards,
Gordon

Gord96BRG

For comparative purposes (before/after) for modding your own car, that result is good enough. However, many dyno thread discussions here have come to the conclusion that simply doing the 7 second DSC disable isn't enough to eliminate ECU interference in the dyno results. There are still safe modes triggered by the different wheel speeds front to back. Canzoomer stated he got better dyno results if he unbolted and tied back the rear wheel speed sensors, and even then a dyno run lasting longer than 10 (?IIRC) seconds triggered various safe modes. In other words - it's extremely difficult to generate accurate RX-8 power curves on a chassis dyno. Your car, on the road, is putting down closer to 190 rwhp, but you can't measure that on a dyno because your operating conditions are different.

Regards,
Gordon

RX8-TX

Alright, let's take your assumption then. Wouldn't an engine like the Renesis (as any other engine) lose compression with time and use, thus decreasing power output as well? I am not saying 10K miles is enough to lose compression though....

Red Devil

I always heard the general rule is that between 20-60K is the best your engine will ever perform. I never gave it much creedence one way or another, but I do believe an engine may loosen up a bit over time.

As far as Polak's car compared to others, or my own...my vin is fairly late in the '04 year, it was built post the "M" TSB. I can say as compared to two others with earlier vin's that I've driven that mine feels stronger in the low end and about the same up top. Point being, I think just about everyone's cars with the "M" flash should be capable of a similar run, given the right conditions.

rx8wannahave

Thanks for the dyno results…something more than words to look at.

Me too, I just worry because people keep saying they can’t reach those numbers. Keep in mind no one is giving hard evidence on that topic. We need more actual test results and less talk…LOL

Has Polak gone to a dyno? I’d probably should ask him…but I was just wondering. Yeah, I’ve heard about his mpg…27 on a trip he went on…impressive.

You see…that’s what I’m saying…why?


Thank you Gordon…thank you… :D

JmurphRx8

I've read that the rx8 can sense when the front wheels arent spinning and it goes into safe mode which cuts off the power...this is prolly why the dynos seem low

Gord96BRG

It's not MY assumption - it's a fairly well known fact. It's easy to read about too - look up long term tests from Car and Driver, Edmunds, etc., for example. C+D always runs performance tests on their long term vehicles at the start and end of their long term tests. It's quite common for a car to get quicker after their test period, which runs about 1 year and 20K+ miles.

There's valid reasons for this to happen. The power output of an vehicle to the wheels is a result of a combination of factors - power generated minus internal engine and drivetrain friction. You presume that an engine makes maximum compression when new, and that it will lose compression with use (with time? If I park my car for 6 months, it will have lower compression at the end of the 6 months period of no miles?). However, it's pretty easy to make a case to say that an engine will gain compression with use for an initial period, as the break-in process improves the seal of the rings to the cylinder walls (or apex seals to the rotor chamber). With slight gains in compression would come increased power. The bigger factor, though, will be reduced internal friction through the entire drivetrain over a usage period. The engine's bearings, and the gearbox and differential bearings and wear faces, will wear in to each other and result in less power being required to rotate them. Given the large magnitude of frictional drivetrain losses (remember, 15% to 20%), it's pretty easy to see where a properly broken in gearbox, differential, and engine can result in lower friction resulting in a significant decrease in hp losses.

Regards,
Gordon

rx8wannahave

He is 100% right...I've seen the tests he is talking about.

Thanks Professor Gordon, LOL, AKA Doc Rotary...

Tbone

yep, they look a lot like yours. 130 torque, and 175 HP. I am curious about some of the things written here:

That the 8 seems to cut power if all 4 wheels aren't spinning.

It seemed like it took a while to get to redline in 4th gear on the dyno. I thought the thing was puting up resistance that was out of the ordinary and that was making it slower. Seemed that way, but hard to tell. I've never dyno'd before.

Also, does it matter which gear you are in? 3rd seems to pull the hardest for me ( and from what I've read for most out there). Would it affect my dyno numbers?

Lastly, I think the car was definitely not "up to speed" on the dyno because there was no power/fuel cutoff at 9k, nor did I get the "beep" when I got there. The computer definitely didn't think all was good, or I assume that I would have had that happen on the dyno as it does the street. Any thoughts on that one?

Tbone

PoLaK

iTrader: (1)

I have gone to the Dyno, just to reiterate that 14.5@94.55 was WITHOUT Canzoomer on the car and so is the dyno below. ("3rd Gear Mflash")

My personal best Dyno was 187rwhp (L Flash) and worst 173rwhp(Mflash) these are dynos from 2 different days and 2 different dynos with over 4000miles (on the car) apart.

The 187 was with Canzoomer on and I believe with it turned off it was 185, I only have a print out because the network at TurboTrix was down, I couldn't figure out how to save the data onto my USB key from the Dyno software, and they weren’t keen on helping me. If you would like the data from any of the other runs to view in RunViewer let me know.

Here is a Run I did at KD rotary, total of 9 runs done that day.

RX8-TX

Gord, no need to be a jackass. You know perfectly well what I meant in my original sentence.
Without getting into it too deeply, I understand your point and the general notion of a Bell curve application: gains are obtained to a certain point, from there on is free fall.

But, I am still doubtful that frictional drivetrain loses are well over 20% in ANY modern, well designed vehicle and that a break in period will render obscenely noticeable improvements.

Cheers!

zevans

To me, all these runs look like they're choking above 7.5k and it's an airflow problem.

What we can we do about that then... ? I've heard that none of the aftermarket exhausts help because Mazda did a good job on standard - so how can we flow more air through the damn thing? (Without forcing it, I might add.)

Red Devil

Leaining the fuel mixture through an aftermarked computer along with ignition alteration seem to be the answers to gaining above 7.5k.

Gord96BRG

It's not an airflow problem - it's an ECU problem where the computer is adding fuel or pulling timing because it's detected that the car is stationary while running at high rpm. The difficulty is simply that getting an accurate dyno run is very difficult because the ECU is too smart for it's own good.

Regards,
Gordon

mtnpass

It seems as though the advances in technology between the fd and rx8 are hindering consistent dyno graphs and outputs from visit to visit

zevans

Well, if it's an artefact of the dyno, then I don't care. People get far too excited about dynos. Personally, I think lap times are the important thing, eh?