Mugatu

iTrader: (1)

do a search and you'll get your answer.

leigh44

Thank you for the correction but i have two concerns. 1-how can a 1.8t v.w. be rated at 180hp and on a dyno put out 168. while our cars are rated at 238 and dyno at 170-180. 2- my point was you would pay an arm and a leg for a dependable, warrentied 10-20 hp and yet its just NOT THERE. I know this has been brought up 100 times I just wanted to know if anyone REALLY knew why.......thanks

dmp

There's a good chance VW under-rates their engines.


...hence our frustrations. One aspect I'll check - most owners dyno in 3rd or 4th gear...I think 5th gear dynos are more accurate, as gearing doesn't affect the outcome.

I'll letchy'all know in a few weeks

MazdaManiac

iTrader: (3)

Then main advantage to a 3rd gear dyno on the RX-8 is that speed times 100 equals RPM.
This was particularly useful for me since the dyno had a difficult time picking up RPM. Others have had a similar experience.

dmp

Good point. I'll make a couple runs, in a couple different gears to see if the results change.

cretinx

A RWD car should lose about 15% through the drivetrain, that translates into 202.3 hp - if its losing any more than that on a dyno its either been misrated by the manufacturer at the flywheel or something fishy is happening. A 180 wheel horsepower car should be rated at about 215 horsepower by the manufacturer.

For example - the S2000 is rated at 240 hp and dynos around 200. The GS-T Eclipse was rated at 210 by the manufacturer and dynos around 180.

My frickin Celica GT-S was dynoing 175 with an AEM intake and a TRD exhaust.

Unless there's some reasonable explanation I think we should all sue Mazda. My guess is that is has something to do with DSC - I turned it off (hold for 8 seconds) completely and wound up getting slightly better gas mileage - perhaps its sucking up drivetrain power

Does anybody have back to back dynos with DSC on, DSC disengaged (just touch the button), and then DSC fully off?

Gord96BRG

What an incredibly unoriginal idea - and it was just as stupid the first dozen times. You really shouldn't be so lazy, and become more familiar with the search function. Here's the most recent stupid lawsuit discussion, but they go back over 1.5 years: Lawsuit Against Mazda, regarding Horsepower? . There are plenty of discussions about this, and that recent thread has discussions about drivetrain losses (there is no such thing as a standard 15% drivetrain loss).

Again, there are lots of threads about dyno testing and how it's accomplished. Put simply - the RX-8 is not easy to get an accurate dyno run, and DSC definitely interferes. It's all been discussed - it would be worth your while to spend some time reading, rather than expecting to be spoon-fed all the answers!

Regards,
Gordon

cretinx

Well, I just read about 40 pages, in particular the thread about suiing Mazda, the thread about low dynos, and the thread with the guy screaming in all caps about his "boy" hooking him up and restoring JDM rated power.

All I can tell is that the car feels quick, quick enough that I don't feel like I wasted my money, not to mention the chassis is FAR better than my old FD3S, and with similar modifications (such as full coilovers, single turbo and 6-piston brakes) should blow that car out of the water.

From what I've read, there seem to be a bunch of explanations and excuses, but this is the best thing I've seen so far.

As such, let the tuning begin.

RX8-TX

The whole 'lawsuit', power re-rating, outcomes and schools of thought should all be included on the revised FAQ's.

zoom44

how many times have i said that in the last 2 years? probably 3 times a month or more...

MazdaManiac

iTrader: (3)

Actually, what happens is the PCM sees the rear wheels spin without the front and it simply fails the entire system and turns it off and lights the indicators.
That is all.
No power gets pulled and nothing gets altered in the fuel delivery.

philodox

^^^ I concur.. Jeff is correct. I've dyno'd my 8 a number of times and the results are correct.

Gord96BRG

Yeah, I've seen you guys say this a couple of times lately - I need to spend more time reading the dyno and tuning threads! I was basing my recent comments on the info provided by Canzoomer from a year ago when he was first getting into developing his Canzoomer plug-in ECU, and the discussions about his dyno testing problems. Of course, it didn't help that it was reported that Mazda said the PCM would pull power from this mode, etc...

Regards,
Gordon

zoom44

how to explain then what dmp reports here? - https://www.rx8club.com/showthread.p...766#post712766

cretinx

Alright, some interesting news

After contacting KD Rotary (who race preps RX-7s and 8s), they told me that some of their customers used MOTEC and engine dynos, and that the RX-8 dynoed at 241 at the flywheel - which means that Mazda actually OVERrated the RX-8's horsepower!

He also told me alot about the rotor shape, how our cars aren't likely to see more than 300 at the wheels with FI, and that the midpipe/exhaust is an excellent investment which scored 200 horsepower on their dyno.

rotarygod

I'm going to raise the bs flag on that one. If rotor shape were so critical to not being able to get over 300 rwhp, how have past rotaries with the same rotor shape done it? The speculated 300 hp number is not based on rotor shape but rather on the limits of the cars stock fuel system capability.

twospoons_

I think I see a pattern here. Triangle. 3000 pounds. 300 hps. Scary. Bermuda?

philodox

I agree with RG. That's BS. Also, a midpipe and exhaust will not get you 200 at the wheels. They are pulling your strings.

RX8-TX

Wasn't it determined by GuitarJunkie & RG that the bends and shape of the exhaust ports is relatively poor on the engine to being with? Therefore, rendering any improvements in exhaust restrictions after the exhaust manifold useless.

So, yeah.....even removing everything from the cat & on an replacing it with a straight pipe wouldn't do much good.

grapes

gxsilver-It's been about a week since your first DYNO post, i'm sure you could sqeeze in some time so that you could post the dyno sheet results. Thanks

ethan113

Hi, thought I would post my charts here for discussion. This was dynoed at the flywheel. Before and After Decat and Piggyback.

philodox

Those numbers in kilo watts or horsepower?

dmp

PS = Pferdestarke, or, literally, Horse Strength/Power.

231PS = 228HP


Dyno'd at the flywheel? Did I miss where the guy said he pulled his engine?

philodox

I dunno.. unless there's a machine where you can drop the tranny and connect directly to the flywheel and measure that way

cretinx

If the car dynos at 180 to the wheels, and both GReddy/RB Midpipe and B&B claim 20 at the wheels from their cat-less setups, that would put you at 200 hp.

I'm not saying I'm gonna go out and buy those products from some dynos I see on the manufacturer page or from a shop (in fact I just set the date for my turbo install, so you know where I think the $ is best spent on this car), it doesn't seem unreasonable that you'd gain 20 peak hp from both of these mods together. This is all mere speculation on my part of course, I haven't seen any independent dynos of a catless exhaust yet.