Power loss - Gearbox

Mk1 · Post by **Mk1** » Mon Sep 16, 2002 11:50 pm

Hello All
I was at the dyno guys today to have the car setup again and have a service. Since the last time of the service and setup all I have done to the car is rebuild and reinforce the gearbox and put in a new uprated clutch. Now the question. I was making 110kw at the flywheel and now today I see I am only making 100kw. I was told that the old box had no resistance and so allowed more power through it. Now because it is new ( done 1500km) it is tougher for the motor is this true? I would have thought it would be the other way round!! Really miss that power!!!!

Cheers

mad driver · Post by **mad driver** » Tue Sep 17, 2002 7:22 am

Yes it could be true see the more friction you have from the flywheel to the wheels the less power you gonna put out. But your car whould still make the same amount of power on the fly wheel just a diffrant readding on the wheels.

Theo · Post by **Theo** » Tue Sep 17, 2002 7:46 am

No. That flies in the face of how the Hyperpower dynos work. If you have more drivetrain drag, it should be accounted for with the coastdown. You'd therefore make less power on the wheels, with higher coastdown figures and the same power at the flywheel as before. That's the theory, anyway.

What was the coastdown figures before, and what are they now? They're indicated as the power and torque loss below:

Mk1 · Post by **Mk1** » Tue Sep 17, 2002 9:27 am

Hi Theo
I looked at my dyno sheet and it does not say anything about drive train. What exactly does that mean. Even at the flywheel power has dropped. ???

Theo · Post by **Theo** » Tue Sep 17, 2002 9:42 am

It won't say drivetrain - those comments were added afterwards. You graph should have two figures in the bottom right-hand corner. What power does it make at the wheels now?

Thing is, it's prudent to have an independent dyno run done before and after mods, no matter where you take your car. If you have any doubts, book a run at KSD or Ferroli, and ask the guys if your motor is healthy.

As long as you're roughly making the same power at the wheels, you shouldn't be too concerned. The conversion to flyhweel power is only an estimate, and not very reliable.

Mk1 · Post by **Mk1** » Tue Sep 17, 2002 12:01 pm

Hello Theo
I was making 99kw on the wheels before now I am only making 91kw even the torque is quite a bit down about 20nm
Maybe I must speek to KSD !!! ???
Cheers

Theo · Post by **Theo** » Tue Sep 17, 2002 12:10 pm

Hmmm....99kw sounds a bit optimistic. As you can see from that dyno graph, I made about 101kw at the wheels after the 2.0l conversion on my car. The 1800 Challenge cars on Kjet also make around 90-95kw on the wheels, if I'm not mistaken. So you're right on the money. Mind scanning the graph and mailing it to me - the one where you made 99kw?

Mk1 · Post by **Mk1** » Tue Sep 17, 2002 9:21 pm

Hi theo
Will get a copy to you. Do you have a fax by any chance?
Other wise I will make another plan.
Tx
Cheers