Ogulcan

Firstly hello everyone. I have a 2010 RX-8 with some bolt ons (Race pipe(no cat no muffler), 76 Catback, RB Headers, BHR Ignition System, Pulley kit, Lw Flywheel, Aem CAI. We did a dyno run with the cars and the numbers were unbelieveable... 219,5 BHP, 175,6 WHP @ 8480 RPM 200NM @ 6780 RPM. They said these were the highest values of a rx-8 the ever measured. They said rx's are generally doing 200-210 bhp. After the run I went to service for a compression test and the numbers were fully healty. We are sure that car is a R3 and came with 231 hp 13b msp engine. Car is about 10K miles. We tested 100-200 KMH time and its about 16.5 Seconds. And Before I intsalled the Flywheel, and Pulleys We did a roll with a friends AP2 S2000 with Header, Cai, Exhaust there were 2 people in S2000 and I was alone in RX8 and the cars went exacty the same till 245 kmh. I did another dyno run on a different dyno and numbers are almost same with the first one.. Can anyone tell whats wrong :S Heres the dyno chart and video with s2k

http://www.youtube....h?v=_NwPPQ3w9_w Video

Dyno Chart:

dynamho

Fixed video link:

dynamho

I guess that implies there's something wrong with your friend's S2000 also.
I wouldn't be so fixated on numbers. Dynos all report differently depending on circumstance.

Ogulcan

Tried some Ep3s and Other s2000s too results are similiar

RIWWP

iTrader: (2)

Read this.

http://www.motoiq.com/magazine_artic...lieve-one.aspx



Seriously. Read it. Good article on what you are facing.

bse50

that's because 231hp is a flywheel figure.

Ogulcan

Great article, thanks for sharing! This could give me some answers and probably what I've been through.


I really respect your knowledge about rotary thanks for helping every subject I opened. So you say a stock RX 8 can never reach 231 hp on dyno ?

RIWWP

iTrader: (2)

Well...that's a very subjective question.

If you are talking about whp, (hp at the wheels) then no, it won't legitimately. Think about it. The crank HP is always higher than the wheel hp, simply because there is always drivetrain power loss (power used to spin the transmission, clutch, flywheel, driveshaft, diff, axles, churn the transmission and diff fluid, pump the coolant, run the alternator, etc...)

In theory, you can have a miscalibrated dyno that reads unusually high or low numbers that could get you to 231whp with a stock 8, but that isn't an accurate value.

Then there are dynos that take the WHP and add a % to it to "account" for an estimated drivetrain loss and they show what they are guessing is the power at the crank. This % varies from car to car, so it's entirely viable that they guess wrong, delivering an inaccurate number.

Getting 231whp out of an RX-8 requires lots of cash, either in the form of mild forced induction or heavy engine rebuild mods, drivetrain friction treating, etc...

Ogulcan

I was talking about 231 BHP , As you said 231 Whp is almost impossible on N/A form only if you use 50 shot nos or etc. Im going FI so my next step will be street porting but before the porting I wanted to see how far I came from stock so I went for a dyno Run. As you can see I was shocked lol. The owner of the dyno said this is normal and RX-8s are never been able to reach 231 BHP. All the cars he tested are gave figures like 205-210 BHP. Than I said "maybe you are doing something wrong. entering wrong parameters etc." than he said no everywhere around the world the fact is a stock rx 8 can never give 231 hp on dyno. Than I did some research and saw thats not the fact..

RIWWP

iTrader: (2)

231bhp is the public manufacturer flywheel number. (edit before people jump on me. BHP has always been 231 to my knowledge. SAE HP is different than BHP, and rates a bit higher, getting the North American 232hp number, though it has been restated down to 242, and then corrected with a revised number down to 238, 232, etc... TopGear notes "228bhp" in their clip, so there may be published BHP variances I am unaware of.)

The only way a dyno would give you this number is if the dyno operator is making a correction for drivetrain loss or they literally removed your engine to dyno at the engine itself.

whp dyno's for stock RX-8s are in the range of 180-190whp. Your first post states "219bhp" so I believe the dyno operator is adding a correction for drivetrain loss. However, that doesn't mean it's an accurate correction.

Nearly every dyno operator that I've heard about that adds a drivetrain loss correction to get the crank or bhp number uses a flat % regardless of if that % is accurate for that car. Most piston engines are roughly similar in drivetrain loss, but there are certainly variances. One thing that most of these guys are not taking into account is that we dyno 50% more rpm than most piston engine cars (most, not all), and we take a correspondingly larger drivetrain power loss. Just read any discussion about the level of heat generated by our engine as you pass 7,000rpm. That heat is wasted power, and it's an exponential increase, not a linear increase. I would even hazard an opinion that most of these dyno operators insist on a flat percentage without any actual data to back it up, and/or blinders on to ways that the percentage can be different, or even slowly change over time. For example, if you get to talking with them about oil, unrelated to dynos, they acknowledge that thinner oil produces less pumping loss than thicker oil, but I am not aware of a single one that will adjust their correction % based on the weight of the oil in the car. Then there is advancements in drivetrain technology. I am positive that the cars of today have less drivetrain loss than cars of the 60s and 70s. And then there is the size of the drivetrain components themselves, etc... A flat number simply can not be accurate. "Close enough", but not "accurate."


EricMeyer got his NA race cars up to the 230s (whp), though one of the big things he did was treat his diff and transmission (and possibly more) with anti-friction treatments to reduce drivetrain losses. His effective BHP is probably similar to the non-race team BHP ratings in the 215-220whp range. He just removed more of the drivetrain loss.


So, kind of side tracked here, but since he used "bhp" and not "whp" in his statement of numbers, I'm betting he has an incorrect (too low) % increase to account for drivetrain loss.



But, in the end, the reality is, as the article states, you can only use that dyno as a baseline if you then re-dyno later on the same dyno under the same conditions. Who cares what the individual number is, it's the difference you want to see, pre and post.

dynamho

I was taking a playful jab at your suspicion that something's wrong with your car. If your car can keep up with an S2000 and if there's something wrong with your car, then there must be something wrong with the S2000 also. See?

There's nothing abnormal about your car as RIWWP pointed out.

Think of all dynos as a bathroom scale. Your weight will vary significantly over various scales (some miscalibrated), locales, and circumstance.

Bladecutter

I'm sorry, what is your actual complaint?

Your car is young, with a strong motor in it, is an S2, and is putting pretty decent power to the ground. You have a couple mods on it.

So, what number are you complaining about?

Are you unhappy that your car isn't making 231 hp, or are you complaining that you don't think your car is actually making the 219 hp at the engine that the dyno sheet says it is?

And it's making 175 hp at the wheel, according to your dyno sheet.

Oh yeah, one last thing...

You posted in the wrong section of the forum.
Why didn't you post this in the S2 section?

BC.

bse50

175 at the wheel isn't too bad anyway, given where he lives and the crappy fuel they get down there...
I have personally dynoed some stock cars with fresh engines with around 200rwhp. I guess that good gasoline is a good thing

Ogulcan

Hahaha :D do you think fuel effects that much ? actually my exceptions were 250 bhp 190-200 rwhp. But my E92 does 100-200 same as other e92's in europe and has the same dyno figures :S

One more question ! Does it important to Roll front wheels at same speed with the rear wheels in dyno for RX-8 ??

Ogulcan

Okay my complaints is about Dynos around here. I know my car is healty and going like how is it suppose to be, My point was the dyno owners are doing something wrong why all RX-8s around here giving similiar numbers. BTW I opened the thread here because Members reading series 1 is more exprienced and has more knowledge...

bse50

The e92 is pretty forgiving, like almost any piston car given how they deal with flame propagation. Our engine is a bitch though, changes in fuel mean a lot.

As other members already pointed out don't focus too much on the dyno, just use it as a reference for future mods or project.

mushkid

iTrader: (6)

I see that we are ok with street racing....

Seriously dude, if numbers are your thing-then obviously you bought the wrong car. Keping up with an s2k is not an easy task.