Ike

This safemode stuff is nonsense, if those turbo RX-8s were going into some magical safemode then any tuner worth his salt would see it. Plus do you honestly think that knocking 10-20whp out of the equation is going to make anything more "safe" if something is seriously wrong? In fact most of the early turbo guys were outspoken along with me that safemode was not an issue when they were on dynos and getting tuned.

Ike

Throw out all the SAE numbers, all of Mazda's old horsepower claims, and the dyno numbers. Trap speeds don't lie, and the RX-8 traps speed indicate it's putting less horsepower to the wheels than a 230hp car of its weight should. Hell, the RSX Type S which just got lowered to 201hp is faster (traps higher) than the RX-8. So either the drivetrain is eating up more horsepower than it should be thorugh its drivetrain, the '06 is making a little more power than the 04/05 due to some tweaks from Mazda, or the SAE numbers are still a little off.

As far as I know the only difference with the SAE testing is there are SAE certified whitnesses present when the testing is done. There is absolutely nothing to keep Mazda or any other manufacturer from making ECU tweaks or other small changes to the engine before testing begins (I hope I'm wrong on this). There's also nothing keeping manufacturers from finding a particularly strong engine to test. Not saying that's the case, but new SAE system is hardly foolproof. To me real world results is what really matters.

Sportura_Collection

That's basically what I was suggesting may be possible in multiple posts (even though I don't know specifics) and eventually these people started ignoring me. People need to not be so naive.

playdoh43

^^^ its more than just a witness. the old rules had some ambiguous things that are up to interpretation by the automaker. essentially a lot of wiggle room for companies to be overoptimistic. The new SAE net regulations are much stricter and eliminates a lot of the old loopholes and becomes more standarized. Its not perfect, but much better than before.

Sportura_Collection

Tonight I was reading the Feb issues of R&T and C&D and in a Honda ad in one of the mags (I forgot which one), Honda reports 237 HP for the S2000.

playdoh43

yeah my theory is that the crank hp of the 2 cars are probably pretty close. in fact the renesis might just be the decisively better engine since its so much smoother. there might be something draining more power on the rx8 between the engine and the wheels than the s2k resulting in the real world performance gap.

Roaddemon

Well skeptics will always have thier 2 cents because they think they know everything about everything. I'm just happy to know the crank hp of this car. Since all cars are rated by the same system, power is all relative to the next car. Safe mode explains the dyno problem period. Trap times vary by conditions and do not accurately measure Hp. It's not an exact science. Try measuring same day/time trap times to other cars the same weight/tires and hp as determined by the sae. Then report back here with the results. lets be scientific.

zoom44

trap speeds dont lie- we can all agree on that. but what is trap speed an indicator of? whel hp or crank hp. also is there a formula that you use to find HP from trap speed?

the FWD rsx should and probably does have less drivetrain losses than the RWD RX-8

Ike

There is a large enough sample of most cars that you don't need same day conditions. Besides, when I make my statement I'm using the RX-8s best trap speeds, not what the average person is getting. Also, that is a compeling argument for safemode. Ignorance is bliss.

Ike

There is a forumula and trap speed is an indicator of whp. Keep in mind it's not an exact science, I've never claimed that any of it is dead accurate but trap speed can be pretty damn close. But when you get to the point that all the evidence points to the RX-8 being around 185 or so whp on the most generous of dynos then it's time to just accept that Mazda was not being truthful or the RX-8 drivetrain is fubar.

zoom44

what is the formula and does it indicate BHP or WHP?

btw the advertised power still needs top be within 5% of the actual power

Roaddemon

No, Your wrong on the safe mode. Rotary news explains even if you disconnect all sensors the car registers no feedback and something isn't right. It goes to a different map. the The new map makes everthing rich so no damage can't occur. The Emc changes to a setting that will handle conditions that negate safety sensors.

As for trap speeds, how can it possibley measure hp at the crank. hp is a measurement of how fast work is done over a given distance. Low tq needs high rpm to make time. Higher torque should get you there faster and at higher speed than low torque, depending how long it takes the low tq car to get up to it's rev range. Trap speeds are not reliable hp indicators. Not unless you know all the mechanical and natural conditions involved.

swiftnet

Wouldn't different vehicle's aerodynamics (drag) cause trap speeds to vary?

RX8-TX

Then what about the 4-ports sold in the UK & Japan wearing a 5MT tranny....?

Ike

I'm fully aware of that, which is exactly why the car was set at 238hp. Some people prebought the car at 250hp so Mazda did the math and 238hp is just slightly below 5% while 237hp is slightly above.

As for the formula now I'm not sure if it's WHP or BHP even though I said WHP earlier. The formula works sometimes and other times it really doesn't IIRC. When I say trap speed is a good indicator I'm moreso going by what cars with similar dyno numbers and weights trap. For instance the WRX traps around 94mph (maybe a touch lower than the 8 and weighs slightly more), it regularly dynos around 175-180whp on a dynojet.

Here's a link if you want to play around... http://www.ajdesigner.com/phphorsepo...horsepower.php

Roaddemon

Isn't the wrx awd? I thought it had a big advantage from a start. I'm surprised the 8 would stay with it from the dig. On a roll I'd give it to the 8. There's alot of obvious and not so obvious dynamics involved in track times and racing. That's what makes it so interesting as a participant and spectator sport.

RX8-TX

Reason why the WRX gets better ETs than a comparable RWD vehicle with the same power output; however, it generally puts out a lower trap speed. Am I right this time?

r0tor

iTrader: (1)

umm.. all the pieces tested come off of the production line

Ike

Are you sure about that or have anything to back that up, because it would make me feel alot better about the validity of the new SAE numbers.

Ike

If you're talking two cars with the same WHP and similar weight the trap speed will be very close. The WRX weighs a touch more than the RX-8 and the RX-8 dynos around 5-10whp more than the WRX on a similar dyno which is why the RX-8 traps about 1mph more than the RX-8. But yeah, the dynos for the RX-8 are all inaccurate If that's true then all the dynos for the WRXs are wrong as well.

With all the flashes that have gone on since the car was first released it wouldn't shock me at all if Mazda has extracted a little more horsepower out of the car from when it was first released. When I first test drove the RX-8 it was rated at 247, and I came back and said it felt like it was more like 220 or 225hp and then got flamed like mad. Looks like I wasn't so far off afterall.

zoom44

actually no- the reason they had to re-state it from the ADVERTISED PRODUCTION number of 247hp to 238hp is because 247 was NOT with in 5% but 238 was/is. that the 2006 models are ADVERTISED at 232 suggests that they are closer than 5 percent of the actual.

Trap speed is an indicator of WHP. It has been accepted and thouroughly examined since the late 50s or earlier 60s. the formula which is used is

((.00426 times x MPH) to the third power) times a weight of xlbs

darin and i had a discussion about this some time ago- https://www.rx8club.com/showthread.p...hlight=formula

to calculate the flywheel hp from that you have to know the losses thru the drivetrain in eitehr percentage or hard number. that is a huge debate in itself. some will choose to be on the exact number side "drivetrain A will always lose 25 hp no matter what engine it is connected to". some (including me) will choose the percentage side "it cant be an exact number because it is affected by rpm and rate of rpm change".

people tend to say that cars should have 15% drivetrain losses. well that seems optimistic. look thru that thread and i have shown examples of 17 and 19 percent. hell FWD cars should have less losses and they seem to have 13-17 percent fromt he ones i have looked at. i have seen figures as high as 25% for rwd cars(some of the newer limslip difs cause high losses). those run down tests on dynos are no good because they are slowing down and the losses are different (more) when accelerating (affected by rpm and rate of change of rpm).

and neither side will agree on the drivetrain losses- so we cant get anywhere that way. there is only one way to test the engines power- take it out of the car but keep allthe accessories on it the full exhaust too. test it on a standardised engine dyno that has been rigourously test itself. run several tests with the accessories all on adn then average them. funny that sounds like the SAE standard.

2 years ago some engineers submitted a paper to SAE on the renesis. in that paper they showed the output to be 231ps. thats 228bhp or guess what? 5% less than the advertised 238. im not suprised by the new number of 232

zoom44

you were troll back then and the trap speeds of non troll-like members confirmed it wasnt making the 247hp.

Ike

You know as well as I do that there were plenty of people that prebought when the car was being advertised at 250hp. Don't make me dig out my old C&Ds to prove that they were advertised at 250hp right up to release. Even Mazda brochures had 250hp in them. I've also seen people on here state that when they prebought the car they were told 250hp. Before you say it, no I'm not thinking 250ps. The 238 number was thought up by Mazda lawyers and I'll never be convinced otherwise. It's just too screwy of a number and too perfect to be coincidence IMO.

Beodude123

I don't see why you people even care. It's the same car!! If you are so worried about a silly number for the engine you have been driving for the past X months / years, get rid of your car because you don't deserve it. There are a lot of people that would kill to get a car like the RX-8 (Myself included).

Anyways, the reason that the WRX and RX-8 have similar 1/4 mile times with different traps is because the WRX can launch a lot faster than the 8, resulting in a lesser 60 ft time. But after launch, the RX-8 can catch up because of gearing etc.

BunnyGirl

Very well put!!!! As far as I'm concerned, it doesn't matter what number they attach to the horsepower. What matters is that I like the car and it suits my uses just fine.