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Discussion Starter #1
Some of the NW Z Bruthas ran their bone stock 2002 Zs on the dyno last weekend. Two of them go nearly identical measurements of 358 RWHP, SAE corrected.

The dyno operator was claiming that the typical drive train loss should be about 18~20%, but if you use this assumption that means these guy's 02s where putting out ...

448 FWHP with 20% loss
437 FWHP with 18% loss

If I assume the widely accepted standard for the C5 to be 15% loss, then it becomes 421 FWHP.

In any case, it looks like the 02s are puttin' down more than the rated 405 FWHP .... or was the dyno these guys used all messed up? I have seen alot of posts showing ~350 RWHP so that tends to make me believe the numbers these guys where seeing on the dyno where probably accurate.

So, do you guys think the 02s are somewhat under rated based on this 'evidence'? :D
 

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15% is pretty accurate but you did not mention whether or not the numbers were corrected for atmospheric conditions or not.
 

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My 02 did 346 RWHP with 1300 miles on it. The other two that were in the 350 range both had a couple of thousand more miles than mine and one of them had an approximate 10 HP increase from the first time dynoed when the mileage was in my range.

I believe Jim Hall stated that his 02 averaged 344 RWHP which he said equated to the 405 crank HP. Mileage unknown.

It would appear that in general these motors continue to make more HP long after the 500 mile breakin.

Pat
 

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Zee oh

What brand Dyno were you using........if it was a Mustang, figure around 5-8 rwhp too high.........

And yes, the '02's and the '01's are/were underated........see my sig on the '01 I Dyno'[email protected] the 15% figure, ( for manual tranny's) mine is 408 @ the crank..........

Use the 20% for Automatics.
;)
 

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I think there is too much fuzz on this question for a straight answer yet.

My questions are:
What were the temp, humidity, and baro pressure for the dyno runs?
Were these readings verified by seperate instruments?

Jim Hall says the computer in these cars makes dyno readings inaccurate for anything other than standard conditions.

A 1/4 mile speed of 115 mph would indicate about 405 HP in SAE standard conditions.

A drivetrain loss of 18-20% is what I would associate with a torque converter machine. For a direct drive system I would expect a 12-15% loss.

Data needs to be gathered in order to come to a conclusion. I would start with a plain stock '02 Z06. Make several runs on the same dyno over various air densities (different days) to get calibration data for the SAE HP correction equation. There are several versions of this corection technique around but most do not use the newest SAE data. I would do this with the same set of independent gages for temp, humidity, and baro pressure. Next, take the same car to a drag track for a speed run. And use the same instruments to correct the observed results. Then we would have the answer.
 

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ZeeOhSix said:
Some of the NW Z Bruthas ran their bone stock 2002 Zs on the dyno last weekend. Two of them go nearly identical measurements of 358 RWHP, SAE corrected.

In any case, it looks like the 02s are puttin' down more than the rated 405 FWHP .... or was the dyno these guys used all messed up? I have seen alot of posts showing ~350 RWHP so that tends to make me believe the numbers these guys where seeing on the dyno where probably accurate.

So, do you guys think the 02s are somewhat under rated based on this 'evidence'? :D
Those numbers sound about right for an '02 with some miles on it (like over 3000 miles).

I have said this before...I call BS on a linear % of power lost through the driveline.

I've been doing the late-model hot-rod thing for over a decade now. That doesn't make me an expert _for sure_, but I have reason to believe that the HP lost through the drivetrain is more of a fixed number that will rise a bit as more power is applied...but I don't believe its a percentage.

Case in point: Z06 #1 puts out 350rwhp. It's stock. Z06 #2 puts out 600rwhp. Let's assume car #2 has the same driveline.
Do you think the driveline in car #2 robs 1.71 times the amount of power as the driveline in car #1.

I don't. I think it will rob more power, but not almost twice as much. If car #1 loses 55hp through the drivetrain, I'd say car #2 loses about 70hp. More net power lost, but a much lower percentage of loss.

So, I don't know if your friends' cars are over-rated or not. Maybe the driveline is loosening up some, there's not as much friction/heat buildup and its more efficient now...but the motor is still around 405 flywheel HP? Or maybe indeed they have strong motors. It's all a guess, IMHO.
 

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Re: Zee oh

ZO6LS6 said:
What brand Dyno were you using........if it was a Mustang, figure around 5-8 rwhp too high.........

And yes, the '02's and the '01's are/were underated........see my sig on the '01 I Dyno'[email protected] the 15% figure, ( for manual tranny's) mine is 408 @ the crank..........

Use the 20% for Automatics.
;)
It was a Dynojet 248C. The numbers were SAE corrected.

I know how subjective dynoing is. There are simply too many variables for people to agree on.

My only interest was to get a stock baseline for my car before I do any underhood mods.

Mission accomplished.

Pat :D
 

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Guys,

Headed to Dyno this weekend, there will be at least four '02 Z06's, none have been moded. All of us are looking for baseline. I'll try to post results Monday, along with all the atmospheric data and type of dyno. Maybe that will validate or put to rest the questions.

Joe :roll: ;) :D
 

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Discussion Starter #11
VettTheRipper said:
15% is pretty accurate but you did not mention whether or not the numbers were corrected for atmospheric conditions or not.
Read my original post again. I said "SAE corrected", which means the numbers are corrected for air conditions :D.
 

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ZeeOhSix:


Those #s look to be right there for a stock set up. They are slightly better than the 01s, which were going at 330 to 340 HP depending on the dyno, car milage, and conditions, which is what you would expect. :)
 

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Discussion Starter #13 (Edited)
Re: Re: Drivetrain Losses and 2002 RWHP

WA 2 FST said:


I have said this before...I call BS on a linear % of power lost through the driveline.

I have reason to believe that the HP lost through the drivetrain is more of a fixed number that will rise a bit as more power is applied...but I don't believe its a percentage.

Case in point: Z06 #1 puts out 350rwhp. It's stock. Z06 #2 puts out 600rwhp. Let's assume car #2 has the same driveline.
Do you think the driveline in car #2 robs 1.71 times the amount of power as the driveline in car #1.

I don't. I think it will rob more power, but not almost twice as much. If car #1 loses 55hp through the drivetrain, I'd say car #2 loses about 70hp. More net power lost, but a much lower percentage of loss.

So, I don't know if your friends' cars are over-rated or not. Maybe the driveline is loosening up some, there's not as much friction/heat buildup and its more efficient now...but the motor is still around 405 flywheel HP? Or maybe indeed they have strong motors. It's all a guess, IMHO.
I tend to agree with you, but I don't know what the real relationship is.

Here is some engineering viewpoint about this issue. If the friction in the driveline is a constant (which may not quite be the case, but lets say it is for now), then the HP losses in the driveline will increase linearly with increased RPMs. In other words, if you could put a torque measuring device on the input side of the driveshaft and measure how many ft-lbs it took to make the whole system just start turning, then that would be the torque required to overcome the system's inherant friction. Lets say that torque measured out to be 50 ft-lbs (a number I'm just pulling out of my hat :D) and remains constant. Lets also assume that the car is in 4th gear on the dyno, where the ratio is 1:1 which will make the drive shaft and axles turn at the same RPM as the engine. If the tranny is not in 4th gear, then half of the driveline will be turning at a different speed vs. the other half, and this could change the total HP loss throught the system.

So, using the baseline I setup above, how much HP is lost?

A Z06 in 4th gear will make the driveshaft/tranny/axles turn at 1:1 with the engine RPMs. HP = (T x RPM)/5252. This formula can also be used to find the HP loss, using T as the constant frictional torque of 50 ft-lbs above.

At 0 RPMs there is 0 driveline HP loss.
At 3000 RPMs there is a 28.6 HP loss.
At 6000 RPMs there is a 57.1 HP loss.

You can already see that this is a linear relationship. Obviously, the HP curve of any engine is usually not linear, but has a peak hump somewhere before its red-line RPM, then falls off with increased RPMs. But if you could measure the HP loss in a manner like I described above, then you could determine the % loss at any given point along the RWHP curve -- and it would not be a linear % of the HP at any given point.

Of course the point of most interest would be at the peak HP RPM, and this is the point which the 15% 'standard' is assumed to occur at for the C5 :D -- the same point where peak FWHP would be produced.
 

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You got the exact same numbers I did. My car was on the 248c at MTI and turned 358 corrected, and 374 actual (The air was good that day). So, your numbers are right on the money. I have seen most chassis numbers for 2002 I have seen posted here have been from 350 - 361.
 

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Chevy always underates the HP on their high performance cars:
Corvette and the Camaro Z28/SS

I think its for Govt EPA and Insurance purposes.
 
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