Richard Paul

iTrader: (5)

I can't finish reading this tread, I can't keep up with the back and forth.
Let me help you guys out a little. The formula are only ballpark, Why? Item 1, What if you ran with the doors fully open? Or a pizza delivery sign on top? Would your trap speed be the same? So then how does the calculator know that? There is no input for Cd and Frontal area is there. So it is only close.
Item 2, The damn thing only makes between 212 and 219 at the flywheel as shown by test many engines. I can't tell you who you'll just have to have faith.
The Rx8 may use more power in the driveline then some for some reason I don't know.

As far as the numbers you guys are getting I think they are very close. I'd be happy with the calculator.

The other thing is that the dyno figure you use is from a day when the actual power was more then the corrected power. Why do you chose to use that number and not the corrected one. Now there is the next variable, you need to correct trap speed for conditions. Espesially the altitude and RH and temp.

Be happy your within reasonable expectations. Your test equipment isn't advanced enough to be scientific. Only use it to compar the changes you make to your particular car.

As for dynos, a good dyno will read within 1% of another when in proper condition. More so the high end ones as to keep it accurite all through the range is hard but doable. If you hang a weight off the center by 1 foot and the weight is 10 lbs then no matter who's dyno it should read 10 foot lbs.

This can't be done with the low end style dynos only the brake dynos. The Eddie current are accurite In their own way but not as easy to test.

That should now put this to bed as I see no further arguments. Everybody just go have beer. And pretzels. Or nuts.

124Spider

This is a fascinating mathematical discussion, but I'm wondering why a theoretical discussion makes more sense than the dyno.

Five RX-8s dyno'd at or very near 186, uncorrected. That's about 178hp corrected, for the conditions and altitude of the shop.

So, it seems that 178 rwhp was a very consistent number. While I hear 18% as the typical drivetrain loss for a RWD car, let's be kind and say 20%. That's 222.5hp at the crank. That sounds about right, to me. I'll grant that this is "only" 6.5% lower than the rated 238hp, but why rate a car at 238 when few, if any, stock examples actually put out that much? If the typical stock RX-8 puts out, say, 225, shouldn't Mazda rate it at 225? Whether Mazda is committing fraud in the legal sense, they certainly are being very optimistic in their rating of their car.

Contrast that to Honda; on the same morning, at the same place as the RX-8s were tested, my S2k did 210hp, corrected, on a car rated at 240hp. Nobody is wondering whether Honda is being optimistic.

I think that dmp (like others) is annoyed at the disconnect between advertised power and actual power. I agree with him.

dmp

You hit the nail on the head - it's about accuracy...not 'ballpark' figures that matter to me in terms of HP.

zoom44

what theoretical discusion? lots of people said in 2003 " the car should trap faster" . its not theory- a car weighing this much with x hp should trap at Y speed. there must bea chart or a formula that people go by to decide this. or do they all believe it just cause someone said so?

so then when mazda derated the hp the provided the timeslips and lots of peole said " yep thats what a car with that hp should trap at"

now we have someone saying "my car should trap faster so mazda is lieing". thats what was said in 2003. i say if 9 out of 10 cars trap at the speed "everyone says" it should then the 1 has a problem. i can only think of 2 things to choose from

1. the driver made an error
2. the car has a mechanical/electronic problem that needs correcting

am i wrong? if his car traps slower than other people's cars by 5mph do you think its because mazda lied or that there is something wrong with his car/1/4 mile run?

rkostolni

There is no way the RX8 is making 238 hp. How many more peices of evidence do people need?? Put the peices together and draw the most logical conclusion.

Said peices:
1. RB dyno'd the engine and got 216.
2. Trap speed, based upon above formulas indicates 210-220.
3. 90% of all RX8's dyno between 175 and 185. Assuming a standard drivetrain loss of 15% and using the median 180, that gives 211hp.
4. It doesn't even feel like it has 240hp, it feels more along the lines of a acura rsx type S (200hp).
5. Richard Paul claims to know many others who have dyno'd the engine and confirmed RB's dyno results.

Anyone of these peices of could be an incorrect representation of the actual power due to unknown interactions, but all of them, very unlikely. Rather the most reasonable answer is that the Renesis is only making about 215hp. I just can't believe Mazda has gotten away with this for two years now. Maybe no one will call them out on it.

foxman

Sad but true.

124Spider

Again, I don't care about trap speed, or other things which depend on one car and one driver's performance. I saw a bunch of RX-8s dyno at 178 hp, corrected. That doesn't translate to 238 at the crank. Methinks Mazda is being optimistic in their claims. I'm not the only one.

Do you think that the typical stock RX-8 makes 238hp at the crank? I don't.

zoom44

you guys dont get it- his car trapped 5 miles an hour less than most other cars even tho on a dyno he got aboot the same as most other cars. he claimed his car trapped 5mph less because mazda lied. does that sound right to you? that his car is 5mph slower thru the traps than other 8s because mazda lied about everyone's hp?

124Spider

No, we do get it. Whether dmp is unhappy because of the trap speed, or the dyno, there is ample evidence that Mazda is fudging the claimed power rating of this engine.

Do you think that the typical stock RX-8 makes 238hp at the crank? I don't.

zoom44

even tho this will get away from everyones point i hav eto say something here.

you have a dyno numbers numbers of 216 and 175 to 185. using 180 as you said plus the known 216 that makes 17% drivetrain loss while you and others keep saying 15 is normal. and in an earlier post i used the miata numbers from the links provided to show a 19% loss. and yet you and others keep saying it should be no more than 15.

zoom44

no you obviously dont get it- his car is 5 mph slower thru the traps than most other 8s. why do you think that is?

124Spider

Zoom, for the record, are you arguing for the heck of it, or do you believe that the typical stock RX-8 makes 238hp at the crank?

zoom44

it doesnt matter!! why does his car trap slower?

124Spider

I don't care. Ignore that trap speed. Look at all the dynos, which have nothing to do with driver technique, or atmospheric conditions. The corrected dynos all indicate that this car doesn't make 238hp at the crank. Do you think that it makes 238hp at the crank?

zoom44

for the record- it doesnt have to make 238bhp. it has to, as the claimed when they re-stated in 2003, make within 5% of 238bhp. and it doesn tmatter what i think or anyoen else it matters what you can prove. and its quite eaasy to show 226 or beter bhp which is within 5%.
their own techs who submitted an SAE tech paper at aSAE conference in europe put 231ps in the sae paper.

124Spider

What doesn't matter? The actual hp of the car? How do you figure that?

Do you think that the typical stock RX-8 makes 238hp at the crank? I don't.

zoom44

you cant because thats what this whole thread is about his claim that his trap speed shows that mazda is lieing- i am saying tha this trap speed indicates a problem with his car.

124Spider

As I said in an earlier post, I'm not talking about whether Mazda is committing legal fraud, or is just taking advantage of a legal loophole which allows them to claim 238hp for a car which actually makes 226hp. If it makes 226hp (which may be a bit optimistic, also), then say so. If it makes 238hp, then why do practically all dynos indicate that it makes around 220-225?

zoom44

because he said

thats how i figure that. we either can or cant use trap speed to derive hp. if we can then alot of cars trap correctly and his doesnt.

zoom44

and he can go on blaming mazda or he can try to find out why his doesnt.

124Spider

I'm just curious, but apparently haven't asked in a clear way: :p Do you think that the typical stock RX-8 makes 238hp (not 226hp or any other number less than 238hp; not "within 5% of 238hp) at the crank? I don't.

zoom44

see see thats what im saying- keep talking about the hp issue but dont bother to answer the question of his car. i have asked that as clear as i can at least 5 times now and nobody wants to answer. ill answer yours

i dont care what the avg rx8 makes at the crank but hers a number 150. hows that?

now answer my question-
is his car 5mph slower thru the traps than otehr 8s because mazda lied? or because his car or his run has a problem?

124Spider

Gee, zoom44, that is a very helpful response. I guess you also don't believe that the typical RX-8 makes 238hp at the crank.

Perhaps both. I don't believe that his car makes 238hp at the crank (indeed, I don't believe that many RX-8s make 238hp at the crank), and there may have been something wrong with his car or his run.

zoom44

you say im not being helpful? how would what i believe about something i cant prove be helpful to dmp or you? what we can prove is his car ran slower than other 8s. i argued with him only to try to get him and others to look at that fact instead of hanging on to the "woe is me" mentality of "its because i was lied to".

ok good. now shouldnt he find out why his car traps slower than other 8s?

124Spider

Sure. But the title of this thread is "does my car not make the advertised HP?" I'll bet it doesn't. And I think that at least a part of that is that practically no stock RX-8 makes the advertised HP.