Paul_in_DC

Forgive the temporary interruption to the flamefest. Just curious - has anybody ever had the presense of mind to run the dyno numbers BEFORE making their mod, as well as AFTER? I mean, if you want to know the effect of your kick-*** mod, it would help to start with a baseline number beforehand.

Anybody who HAS done so, please chime in.

Lufa

I realize some of you are new to the forum, and some of you refuse to see the reality of the situation, for what ever reason...

The fact is the average RX8 on the lot does not produce 238 HP at the flywheel prior to modification.

All evidence points to 210-220, this includes numerous Dyno's, traps times and engine dyno's.

Do some RX8's produce 238? Yes, are most of them modified aftermarket... I would guess about 95% of those producing 238 now, did not, off of the dealers lot. I am pretty sure that I am not one of the lucky ones as well.

Personally, I am perfectly happy with my 220HP RX8, and do not care if there is a lawsuite or not, because in the end my car is a blast to drive. If you want to say it's closer to 215 or 210, sure why not, it bothers me not.

Just 5 more years for my warranty to expire then i will be pushing 250+rwhp anyways.

zoom44

one caveat to what gordo said in his first part up there- except material that was printed prior to the official announcment at NAIAS. many brochures were still laying around that said 250* where the * meant targeted subject to change.

the second point gordo made is what i was trying to say earlier and i thought what IKE and others were saying. that the actual HP of the car is less than the current marketed number but is within the allowed 5% as stated by mazda when they restated the number. if IKe or any of the others was making some allusion to 247-5%=238 then it was lost on me and is wrong. forget that 247 number. it is not applicable to the topic at hand. the legality of that number was already dealt with. the issue is whether or not the car makes the currently market 238 SAE HP =/- 5% number. seems to me that it does.

Ike

Not a brat, just a little slower than the rest of the kids in its grade :p I'm not saying it's not a great car, I just can't understand why people are so steadfast that the car is making 238hp when there is pretty substantial evidence that it isn't.

Paul, take a look at the Greedy turbo kit installed thread, I think philodox ran a baseline run of about 175whp and then dynoed 240whp with his turbo, which falls right in line with the gain he should make using that setup. He and Mazdamaniac (another Greedy turbo guy) both seem to agree that the RX-8 isn't making the advertised power from the factory, and also that people saying the RX-8 can't be dynoed properly is false.

Lufa, if you're happy with the car that's all that really matters in the end.

SHOWOFF

I can't even use my free oil changes b/c "your car is too low to fit on the lift sir."

**** that. Gimme my money! (and my HP)

Ike

Why does it seem to you that is does make 238 though Zoom? All the evidence really supports otherwise. I can remember when we were going through this a year ago and people were saying well until someone puts the Renesis on a engine dyno I won't believe it has anything other than 238hp. Someone did put it on an engine dyno (RB) and it didn't even hit 220hp, the trap speeds all suggest around 215-220hp, the chassis dynos all suggest around the same hp. Not being a jerk, I'm just trying to understand how you can ignore all that.

zoom44

havent we all seen dyno sheets where the graph gets all "jaggety" at the top? was this explained in some other way, that i am not aware of? ive held 2 in my hand from 2 different cars that showed this. could it be 25% because the runs were done in 3rd instead of 5th? really asking this because i dont know.

as far as the brochures- every brochure i have seen( and most i still have copies of) always has legalese that says "as of the time of publication things can change". not just about the HP but all of the info contained. the only numbers in question are what was printed as legally binding on the window sticker-250 was never there. only 247. i still have mine if i need to scan it. They Never published 250 on a legally binding doc in the states.

zoom44

bullshit thats a legally binding contract between you and MNAO. you have alegal right to free service. start screaming on the phone to someone.

Ike

I've asked around about this 3rd/4th gear vs. 5th gear dyno pull thing that prober mentioned. So far all I've heard is there may be a difference in drivetrain loss but it's minimal at best, we're talking maybe a percentage or two. Others have mentioned that the dyno takes into account what gear you're in so it's not even an issue. I don't know exactly the answer either, but a extra 5-10% loss from being in 3rd or 4th gear rather 5th which is 1:1 by all accounts is nearly impossible.

250 was never on the window sticker but I can guarantee you some if not all or most presale people were told 250, whether or not that would mean anything in a court of law I have no idea. But I think we both agree that it doesn't really matter because it's very unlikely this issue is making it to court.

RX8-TX

In connection with that....Philodox has a dyno sheet with both a 3rd & 4th gear pull. The 3rd gear pull shows peak output @ 233whp (somewhere in there) the 4th gear pull came out @ 240.x whp.

That's a 3% difference -for whatever's worth. Does anyone know the final gear ratio difference (%) between 3rd & 4th?

zoom44

how would i tell if you were being a jerk? :p :D (im sure someone will reply with the standard answer to "how do you know when a lawyer is lieing" )

what i said was in the context of this threadwhich i stand by: Mazda picked 238 because it is within 5% of actual.

now as to what RB got on their engine dyno- were they testing it to compliance with SAE or whatever US Govt standard or were they just testing to get a baseline for thier work. i dont know -ill ask them.

what we do know is what you said before and i agreed with- mazda didnt pull any engines to get to 238- they ran some cars on dynos and the strip and back calcualted based on what they believe to be the correct driveline loss number for this car. we don't know that number.

zoom44

see that- we're at 20% already

Ike

They were also tuning at the time were they not, not sure though. I've also seen some dyno runs where there are say 5 runs all done in 3rd gear, there is still variance of up to a few % just based on that so it's hard to say if it was the gearing or just normal variance on the dyno from whatever factors. I've never claimed chassis dynos to be dead accurate, but when not a single stock RX-8 has even come close to 200whp odds are it doesn't have 200whp.

Genom

Just to toss more fuel on the little fire, the guys at Speesource where making 258HP (or so, it's been a year since I saw the plot) at the crank last year when prepping their cars for racing. Other than usign a Motec ECU, the engines where stock.

Yeah, when that lawsuit gets off the ground and mazda learns their lesson (lol) let me know. I'll find that bandwagon and jump right on it....

Paul_in_DC

As I understand it, if we take the 175whp and correct for 25% loss to the wheels, that ends up being ~233hp. That's within 2% of the advertised number of 238, and well within the possible error of measuring equipment, variances for temperature, etc.

So as I read it, there isn't a problem?

Ike

The problem is standard loss for a RWD car is about 17%, which means the number should be more like 197 or 198whp.

Ike

Just talked to a very reputable tuner about how load changes dyno results. He claims on a roller dyno like a dynojet load it can be a factor, but on a dynapack it isn't a factor. Not sure what type of dyno the turbo boys dynoed on, perhaps someone knows or one of them will pop by this thread.

blksf8

Ike, Philodox and mazdamaniac were on a dynojet. Also, most of the baseline dynos like mine were on dynojets as well and registered like you said around 169.

Ike

So if you were doing 3rd and 4th gear pulls it's probably safe to say you're making a little more whp than the dynojet results. I guess that's the reason why so many people say dynojet results tend to run on the low side. Probably also safe to say that those that were getting closer to 180whp were not on dynojets. The only time I've had one of my cars dynoed was on a dynapack so I was unaware as to why dynojets run low, at least we know that one now :p

NomisR

One thing people are forgetting though, those of us who bough tthe 238hp models has probably signed a waiver showing that you know the hp is 238 and will not hold Mazda liable for originally stating it was 247/250. So a law suit over that issue is out of the question.

Another thing is, the Lancer Evo were also dynoed at around 180-190hp to the wheel on dynos for AWD cars. So if a car with about 50 hp more than our car even with greater loss is getting the same hp from dyno, we're doing just fine!

blksf8

good points on last 2 posts ^^^

r0tor

iTrader: (1)

it should be pretty obvious how much what gear you use effects a dyno... a flywheel mod in 3rd gear results in a good 5 hp gain over a stock 3rd gear pull, but doesn't even show up in a 4th gear pull yet alone a 5th gear pull - and thats just the difference of a few pounds in the drivetrain, imagine the gain/loss of the entire drivetrain

you need to dyno in the 1:1 gear if you want to get a good rwhp number, end of story

Ike

There was one Evo that dynoed that(well maybe more considering Vishnu dynos a lot of Evos), it was by Vishnu which has a notoriously low reading dyno they got about 180 with 91 octane and 190 with 93 octane. There is also variance with the amount of boost the Evo is coming with from the factory (at least there was). Just about every other Evo that's been dynoed on a different dyno reads higher than that and is prettymuch in line with Mitsubishi's claims when considering the extra drivetrain loss. Take an Rx-8 to the Vishnu dyno, I bet you have a hard time cracking 165whp. S2Ks can't usually crack 190whp on that dyno and they dyno around or over 200whp on every other dyno I've seen.

Nice try though :p

Shamblerock

IKe, I might as well add my 2 cents. Based on what you are saying, a RSX type-S probably has the same power than we do if we can only get 165 on the dyno. The RSX comes with 200 HP in 04 and 210 in 05. So I assume they would be around 165-170 on the dyno. Therefore they should be faster because they are lighter and their gear ratios are closer!!! Right! NOT!

Here are some specs for you, Einstien :

http://www.modernracer.com/archives.html

TAKEN FROM MODERN RACER WEB SITE



RSX Type –S


Engine : 4 cylinder, DOHC, front engine FWD
Displacement : 1,998 cc
Valve : 16 valves, 4 valves per cylinder
Transmission : 6-spd manual
Fuel economy : city - 23-24 mpg
highway - 31 mpg

Suspension : F - Independent MacPherson strut
R - Independent double wishbone
Brakes : F - Vented discs
R - Solid discs

Horsepower : 200 hp @ 7400 rpm('02-'04), 210 hp @ 7800 rpm('05+)
Torque : 142 lb-ft @ 6000 rpm('02-'04), 143 lb-ft @ 7000 rpm('05+)
Redline : 7900-8100 rpm

Top speed : 145 mph
0-60 mph : 6.7 sec.('02-'04), 6.5 sec.('05)
0-¼ mile : 15.2 sec @ 92.7 mph('02-'04)
60-0 braking distance : 135 ft
200 ft skidpad : 0.86 g

Curb Weight : 2769-2840 lbs
Overall length : 172.4 in.
Wheelbase : 101.2 in.
Overall Width : 67.9 in.
Height : 54.9-55.1 in.

Car and Driver – 2003 review shift points
1st – 39
2nd- 61
3rd-85
4th- 112
5th – 139
6th – 133


Final 4.39




RX-8

Engine : 2-rotor Wankel, front engine RWD
Displacement : 1,308 cc
Valve : n/a
Transmission : 4-spd automanual, 6-spd manual
Fuel economy : city - 18 mpg
highway - 24-25 mpg

Suspension : F - Independent double wishbone
R - Independent five-link
Brakes : F - Vented discs
R - Vented discs

Horsepower : 197 hp @ 7200 rpm(auto), 238 hp @ 8500 rpm(manual)
Torque : 164 lb-ft @ 5000 rpm(auto), 159 lb-ft @ 5500 rpm(manual)
Redline : 7500 rpm(auto), 9000 rpm(manual)

Top speed : 148 mph(electronically limited)
0-60 mph : 5.9 sec.
0-¼ mile : 14.5 sec @ 95.6 mph(manual)
60-0 braking distance : 114 ft
200 ft skidpad : 0.88 g

Curb Weight : 3029-3053 lbs
Overall length : 174.3 in.
Wheelbase : 106.4 in.
Overall Width : 69.7 in.
Height : 52.8 in.

Car and Driver – 2003 review shift points
1st – 41
2nd- 68
3rd-94
4th- 131
5th – 144
6th – 142


Final 4.44


NOTE: The RX-8 is approx. 200lbs heavier, has longer gears, and is 0.6 seconds faster than the 210hp version of the RSX, 0.7 seconds faster than the 200HP version in the quarter mile and has a higher top speed. If the Rx-8 had the same gears as the RSX, it would be faster by yet a greater margin. So all things being equal, it would seem quite reasonable by the gaping margins that the RX-8 probably has 25-35 HP more than the rsx. Both cars get going when they are revved high. DO YOU UNDERSTAND NOW!!!!!!

Furthermore, did you read Mazda's response to all the dyno talk? Probably not! For your further education, here is what they said:

QUOTE

Statement:

There is no true way to generate flywheel horsepower from a chassis dynamometer because of frictional losses in the driveline, clutch, transmission, differential and tires. Also, variations in testing procedures will cause highly disparate readings: open/closed hood, high/low humidity, high/low ambient temperature, tire pressure, how tightly the car is tied down, which gear the car is tested in, etc.

In addition, we have determined that, in order to prevent damage to the catalytic converter and the entire driveline, when the PCM determines unusual operating parameters such as excessive slip in the drivetrain from the front to the rear wheels, it causes a rich high-RPM mixture and retardation of the timing. All these items combine to cause apparent considerable horsepower loss.

BACKGROUND:

Horsepower Measurement

There is only one true method for measuring engine horsepower: on an engine dynamometer at constant speed and utilizing variable load.

The engine should use the same intake and exhaust system as in the car. HP results must be corrected to SAE J1349 standards as listed below:

77 degrees Fahrenheit
Sea level
0% humidity
Correction factors must be applied to reference the measurements to SAE J1349 standards. Any correction factor beyond 7% is considered invalid.

Chassis Dynamometers

SAE has produced a technical paper (SAE Technical Paper Series 2002-01-0887) that attempts to address the ongoing debate about inertia dyno horsepower versus OEM net horsepower. You can order a copy by visiting their website at www.sae.org -- we have no intentions of getting mired in the middle of this discussion.

Bottom line: If used properly, chassis dynos are great tools to assist with tuning and modifying vehicles. It is impossible to measure the actual flywheel horsepower because there are simply too many variables.

Other issues that are unique to the RX-8:

The RX-8 uses a very advanced engine management system. Besides precisely controlling the operating parameters of the engine, self-preservation (of both the engine and the catalytic converter) is also considered.

The engine management system continuously monitors all engine functions and adjusts accordingly. For example:

Under heavy load acceleration, the timing is retarded and the fuel mixture richened to reduce the likelihood of pre-ignition or spark knock. If spark knock is encountered, a knock sensor senses the condition and further retards the timing. Gradually timing is advanced and fuel mixture leaned after the load is reduced.

A second reason for fuel enrichment is that when timing is retarded, exhaust temperatures increase; a richer mixture lowers the exhaust temperatures and reduces the chances of damaging the catalytic converter.

In real world driving, this all goes unnoticed to the driver and appears seamless with no disruptions to the performance of the engine. The car encounters a load under acceleration but the load quickly diminishes as the car accelerates in each gear.

Operating on a chassis dynamometer, however, creates a completely different environment. Inertia dynos use a known mass that is accelerated to measure torque at the wheels. This is usually done in one gear under heavy load conditions:

Only the rear wheels are turning while the front tires remain stationary.

On cars equipped with DSC with traction control, the difference in speed between the front and rear wheels is sensed and the power is reduced immediately to compensate for what the car senses as excess wheel spin.

If the DSC is turned off, the traction control is disabled but the brake functions of the DSC are still operational.

If the DSC system is completely disabled, this removes the brake functions from the equation, however it does not fully remove the engine management system functions.

The ABS hydraulic unit/control module (HU/CM), or the DSC HU/CM for cars with DSC, determines vehicle speed by comparing the speed of all four wheels. If two are turning and two are stationary, it will still compute a speed but senses that the car is experiencing excessive wheel spin. To protect against engine or catalyst damage:

The engine management system compares the throttle opening, gear selection (determined by engine speed and road speed) charging efficiency and engine coolant temperature to determine the driving condition.

Since the car is under heavy load, in a tall gear (testing is usually performed in third or fourth gear), with a wide throttle position angle (wide open), spark timing is reduced and the fuel mixture is richened to reduce the occurrence of spark knock and to reduce catalytic converter temperatures.

UNQUOTE


The problem is, you don't understand rotary engines, how they work or how to get the most out of them but you always talk like you do. You wanted numbers, I gave you numbers that are verifiable.

Now explain yourself.

RX8-TX

I am not questioning the fact that the renesis is/isn't layng down the smack @ 238 SAE. I really don't think it is. And I've seen dynos sheets, done back to back (specially on turbo cars which suffer from heat soak) where each subsequent result is lower and lower when done under the same conditions. But what do I know?

It is not really clear whether Philodox was able to do anything. His eManage unit is (was) still locked, so he didn't have much to play with. MazdaManiac was....I think. And the referenced dyno is from Philodox (he's got the Greddy unit, MazdaManiac built the entire kit himself...btw)

Alright, going on with the effective final ratios....I found the numbers...

Alright, 4th gear is approx. 27% longer than 3rd (5.275 & 7.310 respectively) - In other words, the roughly 3% difference in a dyno pull done in 3rd / 4th gear, doesn't seem too relevant in contrast with a 27% difference in the effective final ratio (gear). Does that make any sense?

How do they influence results? sheesh..I don't know!