question Hp rear wheel power vs fly wheel power
 

hello iam new to this so excuse me for asking a dum question with all this stuff going on with the rx8 hp power and no one is getting the 238 hp that mazda says the car has. what is the difference when they say that they dyno and it had lets say 200hp rear wheel pwer vs what mazda says the car has 238 hp at the flywheel? is it the same ,so why is no one getting the 238 on the dyno is it because of the limp mode? should we try to sue them ??? :confused:

There is "driveline" loss. You loose some power in the transmission (gear and oil friction). You also loose power in the rear differential - same cause. Quite a bit, actually. Check out how hot the transmission and rear diff. are right after you stop. Estimates of total loss range from 10 to 20%. We see 180 HP +or- on a dyno, so using the estimated loss the engine is producing around 200-225 HP. Most knowledgable people in the buisness think it's around 215, and not the 238. I'm told the claimed 238 has a tolerance of 10%, and if you do the calculation from 215 (215/.9) you get, remarkably, 238.8!

I'm not sure what you'd sue them for. I don't think you would be sucessful anyway, based on my calculation above.

also, there is lots of loss between the tyre and roller on the dyno itself, and can even be some between the clutch and flywheel. but yes, the energy that the engine makes is being used up to accelerate the driveline itself, before the rest of the energy can get to the roller to be measured.

yes, sometimes there is a significant limp mode when the cars dyno, sometimes not. no, i can't offer you a satasfying answer as to why, talk to Hymee about it.

no, you wouldn't be successful in a suit, and it's nothing to worry about. get Canzoomer's mod (it's all you need) and save money on gas.

yes iam going to get canzoomers mod i emailed him about the stage 2 and what do i need for the 40 + hp he says ,but no respond yet .i rather get the 40 + hp then 20 iam looking to put my 8 to be in the 280 hp with no turbo hopefully i can do it. thanks

Along with what everyone has already said, a lawsuit will get you nowhere. Especially since Mazda has already published the fact that the RX-8 can not accurately be measured om a chassis dyno.

You can't go by formulas to determine driveline loss. Every car is different. This includes other cars of the same style. Each transmission/drivetain will have slightly different resistances. The only way to measure actual driveline loss is to measure that exact vehicles performance differences on an engine dyno as well as a chassis dyno. This doesn't mean that the other guys with the same car will get the exact same numbers. They should be very close though. Also different engines will produce different power numbers. Mazda makes 3 rotors at a time on the assembly line and they try to match up the most similar ones with others that are closest to it. One persons engine may aveage 10.02:1 compression ratio where another engine may have 9.97:1 compression ratio. You get the point. The point is that there can be no absolute certain way to determine exact power loss for an entire model. Numbers will always be very close between all of the engines though and definitely close enough to make a good estimate but until someone actually measures both we won't know for sure. The above differences may only account for a few horsepower difference betwwen all of the cars so you would really need to measure several cars and average the results. Even the weight of your wheels/tires will make a difference on a dyno.