JonSnow

I thought it was blatantly obvious when a clutch is slipping on the dyno, by seeing basically a mountain range on the dyno sheet.

This time I don't think its that obvious, but I think it's still happening. A good engineer I've been working with told me to look at the data closer

Take a look at my dyno sheet





The weird thing is that typically after a few pulls the car gets hotter and the power drops. In my case the car is getting more powerful with each pull

These pulls are back to back within seconds of each other

First off the torque is very low for a 550hp car.

So after the first pull I gained 5hp and 19TQ
then after the second pull I gained 7hp and 26TQ

you would think someone was tuning the car! This leads me to believe the clutch isn't holding the power as it should, perhaps with the heat its holding better

2nd example

look at the speed vs hp graph below






If I plug in the data here http://www.wallaceracing.com/calcmph.php

put in my tire height of 27.15, stock z06 gear ratio and rpm

I start off even and end even but at 5,250 I'm off by 12mph to the slipping side. So the dyno says I should going 112mph when I should be going 124+. At 4,000rpm it is about the same.



Are we wrong? Crazy? Opinions?

Undy

By your graph it doesn't appear to be slipping.

50 4Ever

I would think if your clutch was slipping, when in 4th gear at WOT you would expect to see the RPM's rise rapidly compared to wheel speed. These graphs look similar to mine. With 3 pulls, back to back, I see hp and tq increases also, this is normal.

JonSnow

Thanks guys.

Is the clutch slip always that obvious though? Just wondering if im making any valid points or way off base.

Also the low torque numbers are whats getting me.

This is a HCI Z06

08mojo

Your torque is not that far off from mine. I put down 547 hp and 482 ft-lbs.

Landru

Bet RPM spike would be proportional to slippage, easily seen.

x88

Best way to tell is go WOT in 6th at 1500 RPM... if it shoots up then your clutch is shot. It should hold steady and climb at a normal rate

JonSnow

Thanks for the input. Once the car is back together I will try the clutch test procedure

MyLS1Hauls

I don't see anything that looks like clutch slippage there. Not surprising that it gained power with each pull. As the engine oil, trans fluid, and diff fluid heat up, there is less parasitic loss. The only reason the motor would make less power after a few pulls, is if the coolant temp or IAT is too high.

When I've seen organic clutches slip on the dyno, there is usually clutch dust coming out from behind the car, that looks like it is from the exhaust. Not sure what clutch you have.