RUF-BTR2 Dyno sheet
Nordschleife Master
Joined: Dec 2001
Posts: 8,305
Likes: 16
From: Kingston, NY
That is a Dynapack dyno which measures RWHP with the dyno pods bolted directly to the hubs. It is impossible for there to be wheel spin on this type of dyno. The torque numbers are axle torque. To find the RWTQ, you would take the axle torque and divide by the transmission gear ratio. So a peak of 1351 divided by the gear ratio input into the system of 3.4 = 397.35 peak torque. If the dyno operator had pushed the page down key four times it would have moved to an identical graph except it would be showing the RWTQ numbers instead of axle torque numbers. Further, if he had used the user defined graph, he would be able to plot any 2 variables on the screen.
The horizontal movement of the torque curve at 3300 is most likely a result of the wastegates opening, bleeding off exhaust to the turbochargers. From the shape of the curve at this point, it looks like there is some overboost, then the wastegates open, reducing pressure, therefore, reducing torque. This is not uncommon, especially when the ECU has not been programmed for the faster boost rise and can be easily seen if the torque was plotted against the manifold pressure. There is a way to export the file to a diskette, and if you want to email me the file, we can show the other graph format.
Using a 25% drivetrain loss figure, this shows about 510hp (std) at the flywheel.
The horizontal movement of the torque curve at 3300 is most likely a result of the wastegates opening, bleeding off exhaust to the turbochargers. From the shape of the curve at this point, it looks like there is some overboost, then the wastegates open, reducing pressure, therefore, reducing torque. This is not uncommon, especially when the ECU has not been programmed for the faster boost rise and can be easily seen if the torque was plotted against the manifold pressure. There is a way to export the file to a diskette, and if you want to email me the file, we can show the other graph format.
Using a 25% drivetrain loss figure, this shows about 510hp (std) at the flywheel.
Last edited by Geoffrey; Feb 14, 2005 at 09:21 AM.
Race Director
Joined: Jun 2003
Posts: 15,122
Likes: 337
From: Los Altos, CA
Geoffrey,
One question, your 25% drive-train loss ratio, is that for torque, HP, or both?
Viperbob suggested I use 17% as an estimate. Power loss through the drive-train should be a function of the car, not the type of dyno machine. No?
In any case, 380 ft-lb peak torque at the wheel is really impressive. Congratulations Dan.
CP
One question, your 25% drive-train loss ratio, is that for torque, HP, or both?
Viperbob suggested I use 17% as an estimate. Power loss through the drive-train should be a function of the car, not the type of dyno machine. No?
In any case, 380 ft-lb peak torque at the wheel is really impressive. Congratulations Dan.
CP
Nordschleife Master
Joined: Dec 2001
Posts: 8,305
Likes: 16
From: Kingston, NY
The dyno only measures torque, HP is calculated using the formula HP = TQ*RPM/5252. So the loss is for both hp and torque. I have measured the loss of a G50/50 to be 15% on the given day I tested it, with fully warm transmission fluid. I have measured the G50 6speed of an AWD twin turbo to be more like 25% with fully warm transmission fluid. While converting from rwhp to fwhp is an estimate at best, I've had engines on engine dynos, then retested them in the car to get a rough estimate of what the losses really are. This is what my testing shows for a Dynapack dyno. I'd be interested in how Bob arrives at the 17% loss and what dynos he has used to calculate it.
Power loss is the loss through the drivetrain, not the dyno. On any given day, different brand dynos will all show different power numbers. Dynojet are typically high because they use F=MA, Dyno Dynamics and Dynapack are average with factory calibration that does not change, and Mustang dynos can be anywhere depending on how they have been calibrated and the user can make it ready whatever they want.
Power loss is the loss through the drivetrain, not the dyno. On any given day, different brand dynos will all show different power numbers. Dynojet are typically high because they use F=MA, Dyno Dynamics and Dynapack are average with factory calibration that does not change, and Mustang dynos can be anywhere depending on how they have been calibrated and the user can make it ready whatever they want.
Race Director
Joined: Jun 2003
Posts: 15,122
Likes: 337
From: Los Altos, CA
Originally Posted by Geoffrey
I have measured the loss of a G50/50 to be 15% on the given day I tested it, with fully warm transmission fluid. I have measured the G50 6speed of an AWD twin turbo to be more like 25% with fully warm transmission fluid.
I thought all BTRs are single turbo (in RUF speak CTRs are twin-turbos), I'm puzzled that you suggest Dan's BTR is a twin-turbo. I also don't know if his is AWD or 2WD like mine.
Also, in your experience, can ambient conditions cause a 10% varient in dyno numbers with the same car?
CP
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Nordschleife Master
Joined: Dec 2001
Posts: 8,305
Likes: 16
From: Kingston, NY
I'm sorry, I didn't mean to assume anything about Dan's car in terms of turbo or drivetrain configuration, I'm not really up on my RUF nomenclature, nor the years available. I thought it was a converted car because I saw the AWD at the top of the dyno sheet. If it is 2WD, then I'd apply a 15% loss and if it is AWD, then I'd apply a 25% loss. I only mentioned the losses I've measured from engine dyno to chassis dyno which happen to be the aformentioned transmissions. A G50 6speed out of N/A car would have less of a loss because it has a smaller R&P.
Intake air temps, engine temps, and trans temp can all make a measureable difference on a chassis dyno and can be as much as 10% difference. You can see a difference in a given dyno session from run to run.
Intake air temps, engine temps, and trans temp can all make a measureable difference on a chassis dyno and can be as much as 10% difference. You can see a difference in a given dyno session from run to run.
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Thread Starter
Racer
Joined: Apr 2004
Posts: 294
Likes: 0
From: New Zealand
FTR ... the car is one turbo and 2wd. I prefer Geoffrey's first estimate though 
The car is RUF factory spec, no aftermarket modifications have been done. It has the latest RUF 993 BTR computer which was done this year when I replaced the faulty wiring loom (which damaged the old computer)
Putting the numbers aside, looking at the shapes of the curves, the impressive thing to me is the steepness of the torque curve and how early in the rev range it happens.
A friend of mine owns the dyno so it was a quick session in between customers. We didn't hook up boost or lambda.
I have a lambda and boost gauge in the car and I get 14.5 pounds (1 bar) and the lambda shows 9% CO (11:1 AFR) all through the run.
The factory 420hp is with 0.8 bar so the 1 bar I get explains the flywheel 450hp I guess.
The car is RUF factory spec, no aftermarket modifications have been done. It has the latest RUF 993 BTR computer which was done this year when I replaced the faulty wiring loom (which damaged the old computer)
Putting the numbers aside, looking at the shapes of the curves, the impressive thing to me is the steepness of the torque curve and how early in the rev range it happens.
A friend of mine owns the dyno so it was a quick session in between customers. We didn't hook up boost or lambda.
I have a lambda and boost gauge in the car and I get 14.5 pounds (1 bar) and the lambda shows 9% CO (11:1 AFR) all through the run.
The factory 420hp is with 0.8 bar so the 1 bar I get explains the flywheel 450hp I guess.
Thread Starter
Racer
Joined: Apr 2004
Posts: 294
Likes: 0
From: New Zealand
CP, the early models had .8-.85 bar and the latter had .9-.95 bar (I got this info direct from Lieb at RUF). The early model computers were a 964 wiring loom plug cpu and the latter is now a 993. It is a motronics with a RUF chip in it.
The wiring loom is not a porsche loom it is a RUF modified loom. I think they have made other modifications to the computer/harness as well as the remapped cpu.
What is good is my old computer never worked with a ps2 and the new one now does.
The wiring loom is not a porsche loom it is a RUF modified loom. I think they have made other modifications to the computer/harness as well as the remapped cpu.
What is good is my old computer never worked with a ps2 and the new one now does.
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Originally Posted by Geoffrey
I'm sorry, I didn't mean to assume anything about Dan's car in terms of turbo or drivetrain configuration, I'm not really up on my RUF nomenclature, nor the years available. I thought it was a converted car because I saw the AWD at the top of the dyno sheet. If it is 2WD, then I'd apply a 15% loss and if it is AWD, then I'd apply a 25% loss. I only mentioned the losses I've measured from engine dyno to chassis dyno which happen to be the aformentioned transmissions. A G50 6speed out of N/A car would have less of a loss because it has a smaller R&P.
Intake air temps, engine temps, and trans temp can all make a measureable difference on a chassis dyno and can be as much as 10% difference. You can see a difference in a given dyno session from run to run.
Intake air temps, engine temps, and trans temp can all make a measureable difference on a chassis dyno and can be as much as 10% difference. You can see a difference in a given dyno session from run to run.
Geoffrey what do you estimate the CF for the dyno jet 2wd dyno to determin crank HP?
THIA