Anyone catch the SCC article on the RX8 HP saga in the Dec issue? If not, it's an interesting read so be on the lookout.

They said sources at Mazda claim the RX8 goes into dont-overheat-the-cat mode (tries lowering exhaust temp by running extra rich) when the rear wheels are turning faster than the front, meaning when dyno'd, the numbers will be lower than they are in reality.

They tried several runs, using several tricks to override the various computers and came up with varied results (ex. 139 hp/93t, using G-tech with ABS disabled). Using the Dynojet, the production 8 they dyno'd made 188 hp and 135 l-f of torque, compared to the S2k's 202 and 134.

Anyway, check out the article for a better explanation.

 

SCC?

sorry, can you provide more info

 

Sport Compact Car

 

Surely SCC must have access to a 4WD dyno? With the front and rear rollers linked, the system would have no way of knowing it wasn't out on the open road.

 

They should compare the RX-8 dyno results with Crossfire or Mercedes C320 Coupe dyno runs.

These cars have similar amount of power.

 

Did Supercharger really speak instead of copy/paste! Finally!

Actually I think the 'old' S2000 is a better comparison as it has very similar HP (240 vs 238), torque (153 vs 159) and rev range (9000 vs 9000).

 

I think Bern has tried to hint that it is not just the wheel speed but also involves the airflow through the intake that makes it go into safe mode. This was in response to Canzoomers finding that tricking the rear sensors produced no difference in dyno.

 

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The best and imo most important comment is the last paragraph

 

graph

 

The last paragraph says it all.

-Dave

 

that is what most of us here on the forum have been saying ever since the car came out. glad to see that more people are "getting it".

take care

santino

also, thanks Neit for saving me a few bucks and copying the article. i was about to buy it just for that.

 

thanks for the articles, very nice read

 

A 4wd dyno rollers can not be linked.....they spin seperatly as the wheel of the car turns it.

I also agree with the last paragraph of the article.

And heres a bit of info for you guys....had a RX8 on the dyno here over the weekend and with the go ahead from the owner we topped it out....at 9krpm in 6th the speedo read 175.....

 

First off I would like to make the following special announcement:

1. "The car isn't putting out the claimed power."

and

2. "The car is quick and fun to drive"

Are two seperate issues. It's totally possible for someone to believe 1 and believe 2 as well. So, people, please don't immediately make the leap from one to the other.

Personally I don't think the car quite makes 238HP AND I think it is fun to drive so I kept it.

Alright, now where were we - It would have been cool if SCC did a G-tech measurement of the Honda as well on the road, that would have been an apples to apples comparison. The Gtech Pro seems to read low in general but it should at least read consistantly low for the two cars.

Anyway, the RX-8 is a high reving car that still has a good size clutch flywheel. That means that especially in low gears it is going to have extensive inertial losses. I don't think the Gtech Pro is accounting for that (but the S200 should be similar so it should cancel out when comparing the two cars with a Gtech)

With that in mind, a colleague of mine did some of our own calculations based on the acceleration values (i.e. g's) from a calibrated G-Timer II made by Passport. We did various tests to determine interial component of the drivetrain losses, rolling resistance and wind resistance. The only thing we had to guess on was frictional component of the drivetrain losses.

After factoring all of that in and assuming 10% frictional drivetrain losses, we got 228.5 HP at 8480 RPM. I will retest shortly now that my car has more break-in.

228.5 isn't quite 238 but close. It definitely isn't 247.

Now are people complaining too much about 10 or so horsepower? Maybe, but the squeaky wheel got the grease. And for those who complained about people questioning the 247, I sure hope they didn't accept the $500 or the free service; the "whiners" are probably the only reason we got payoff from Mazda.

-Mr. Wigggles

 

Well Mr. Wigggles, I think you got that just about right. Now get out there take Rotary Extreme up on his money back offer and try his new intake system!

Tom