Hey, my friend who isn't in the forum sent me a couple of logs to check out since his car wasn't running as strong as it used to. So I plugged it in JOT's Virtual Dyno and this came up. He has a 30R on race gas or E85(not sure which fuel) and has all bolt ons on stock clutch.


So, Is this how it looks like to have the clutch slipping on the JOT Virtual Dyno? If not, then what could be the problem? Thanks guys.

 

do you log speed?

plot rpm vs speed

 

He wasn't logging speed. I'll ask him to log speed tomorrow. But can a slipping clutch cause that? The log showed tip in knock of 1 count and then disappeared, so it cant be a knock issue pulling timing.

 

could do...

but log speed vs rpm - if the line isn't straight (ish) then you know the clutch is slipping

 

You should know if the clutch is slipping. Engine free revs like crazy once you over power it. Mine would slip around full boost once it started to go. A slipping clutch would cause a drop in power cuz it wouldn't be putting the power to the tranny.

 

it wouldn't cause a powerdrop on a rpm based dyno tool like VDR

 

Looking at the TPSvsRPM graph on EvoScan, it shows this..

 

I thought It would. I don't know how VDR works, but I thought those kind of programs calculated load into it and if the motor is free revving there wouldn't be as high a load on the engine so the hp output wouldn't look as high. Im not trying to argue as I am not sure how it works, just trying to help the best I can.

 

nah they use how much time it takes to go through the RPM's.

nothing todo with load.

^^ that looks pretty screwed

still for educational purposes do the rpm vs speed thing

 

VDR works with RPM, so the faster you rev the higher the power you'll get. Which is why my first guess was that his clutch was slipping because if you look at the graph the moment he hit full boost his power jumped up really high, then settles back down when his boost tapered off. My friend doesn't live near me so I can't check for myself.

 

Ahh, I see. Haha he should keep the graph and print it out so it looks like he has the mad whp

 

His first logs didn't have this problem and looking at the RPM graph, it's very smooth and has no bumps. So I guess we can somewhat assume that this is indeed a clutch problem?