tricky power and torque question
#1
02-19-2008 | 07:44 PM
Thread Starter
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1st Gear
Joined: Feb 2008
Posts: 27
From:
tricky power and torque question
Generally speaking people talk about the BHP of the car, in other words, engine output power rather than power at the wheels.
Normally this is measured on a rolling road, but how does the tester know what to add on to the measured output power to get a BHP value?
Next, the RR tester will also tell you your torque, now is this the actual measured torque or once again a factored torque equivalent at the crank without any losses.
The reason I ask is that the torque reading from VAG-COM does not match up with the torque calculated from the BHP calculation of MAF/0.8. It is lower than the one I calculate.
Perhaps the vag-com torque is with the losses whereas the value I calculate is a theoretical one without losses.
I need to get to the bottom of this to know which is the correct one to show on my boost gauge below.
Normally this is measured on a rolling road, but how does the tester know what to add on to the measured output power to get a BHP value?
Next, the RR tester will also tell you your torque, now is this the actual measured torque or once again a factored torque equivalent at the crank without any losses.
The reason I ask is that the torque reading from VAG-COM does not match up with the torque calculated from the BHP calculation of MAF/0.8. It is lower than the one I calculate.
Perhaps the vag-com torque is with the losses whereas the value I calculate is a theoretical one without losses.
I need to get to the bottom of this to know which is the correct one to show on my boost gauge below.
#2
02-19-2008 | 07:49 PM
I'm make believe
Joined: Dec 2006
Posts: 17,587
From: In my head
RE: tricky power and torque question
I do believe that the vagcom (butt dyno i believe its called) takes out 12-15% for drivetrain loss. You know that we in the US only car about whp numbers. Im not sure how people account the powertrain loss for the BHP in your neck of the woods.
#5
02-19-2008 | 07:55 PM
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1st Gear
Joined: Feb 2008
Posts: 27
From:
RE: tricky power and torque question
Its a small micro and a display out of a mobile phone, it graphs or shows on a gauge all the normal vag-com data, I also extrapolate for power and throw in g force measurement also for fun.
#10
02-19-2008 | 08:51 PM
I'm make believe
Joined: Dec 2006
Posts: 17,587
From: In my head
RE: tricky power and torque question
ORIGINAL: eliTTe
how do you read power with vagcom? I didn't know you could do that
how do you read power with vagcom? I didn't know you could do that