KrisD1

So 1 month after I bought my red rx8-5speed(192hp/141kW@ 7000rpm) I got it tested on the dyno. Results: 142hp/104.6kW to the weels and 18.9kW los from the flyweel to the weels, this means I have about 168hp that is 24hp less than advertised. Also, it didn't gain anymore horsepower after it hit 5000rpm.
So I went back to the dealership and showed them the results. They faxed them over to mazda belgium and they send it to mazda japan. They said the would look into it. It's about 6 months later and they still haven't found a result.
So what do i have to do???

Go48

Is that all the dealership did? I would request that they check the engine compression and other possible causes of a loss of power. Otherwise, contact the Mazda regional representative directly and detail your issue to him/her.

Someone else can better explain this possibly, but my guess is that the method Mazda uses to rate the car is not necessarily comparable to results from any/all dyno runs. So you may be comparing apples and oranges if this is, in fact, the case.

KrisD1

Yes, that is all. About a month later I got a letter from Mazda Japan that they are looking for a sollution to my problem. As a compensation for my waiting they payd my service at 30000km and they will give me a set of new tires. Problem is when the engineer of mazda Belgium heard about this problem he went out and got his rx8-5speed checked on the dyno. And he has just the same problem as I have. So I think they're using his car to look for a solution or maybe another rx8 with the same problem running in Japan.

Brice-RX8

Not sure I am following you here. The motor is rated at 192hp, yet you dynoed at 142hp, for a driveline loss of 26%. When you take the standard 238hp 6-speed US version and figure in the 26% driveline loss it gives you 176hp, which seems to be were a lot of us US owners are dynoing at. I don't see an issue with your car, there is not a standard driveline loss calculation, all models are different, and some of the same models are the same.

Now if you car is not making power from 7k up to I guess you have the same 9.2k redline, then that does sound like something might be wrong.

KrisD1

Maybe it is not so clearly put. I have 142hp to the wheels, and a driveline los of 26hp(not %) that means it got 168hp to the flywheel. So I am still missing about 24hp to the flywheel. The 5speed has the same engine as the auto's, so it's a 4port and it redlines at about 8k, max. horsepower should be at 7.2k, but with my car that's at 5k, so I have absolutly no hp gain after 5k.
Has someone off the auto owner dynoed there car's and what were the results?

Brice-RX8

How do you know you have a driveline loss of 26hp (not %), unless you have dynoed the engine out of the car, you don't. You can only go off what Mazda says the car has from the factory which 190 something hp. I am just unsure of where your figures are coming from, you know you dyno 142 to the wheels, and the car "supposibly" has 192 flywheel horsepower. Where does 26hp lose come from? 26% yes, 26hp is more like 50hp.

KrisD1

I have it here with me, when i dynotested it the dyno calculates the loss from the flywheel to the wheels.I think someone here knows how it's done. They rev the engine up and then let the gaspedal go so it returns to 0 rpm. And it says Ploss=18.9kW.
I can't say how correct these numbers are. But my main concern is not how much horsepower it has, but why there isn't more gain afther I hit 5k rpm. Also there's a dip in hp between 5k and about 6.5k rpm. What could be causing this?

Brice-RX8

Not sure about your top end, but based on the calculations I showed you earlier, you are seeing the same amount of losses that us US spec 6-speed owners are. I have never dynoed mine, but I can assume it will have around 175-180hp to the wheels where most others are getting.

I have never heard of a dyno that can calculate losses for you, I would be interested to hear how that works, but it doesn't sound accurate based on what we have seen on this board from others.

lurch519

another thing to take into consideration, is you have an automatic transmission, which also contributes to the loss of horsepower through the drive train. thats why they are commonly referred to as slushboxes.

KrisD1

It's actually a manual 5 speed here in Belgium. I just got the new flash done a week ago and in the beginning I feld an improvement in torque at lower rpm's but no improvement at higher rpm's. But Yesterday when I returned from a driftevent ,that all of a sudden changed and it just kept on pulling untill it hit the red line. All I can say is SWEET!!!
Before I feld some hesitation at 5k rpm like something was choking the enige but now it really feels like it flows freely and it reacts much directer without the lag it had before.
One downside maybe, it uses more fuel and runs more rich. eg. before i could drive 400km with a full fueltank, now it just 330km (16.7liter/100km)