what's wrong with this dyno graph?

#1

Here is my dyno from the week before the NASA-mid-atl Feb VIR event last month.

air-fuel is everwhere, any guesses as to why so jumpy, and is that affecting HP?

compression is 150 to 170 in all cylinders

leakdown is 2% for most 9% for two cylinders

any other thoughts/suggestions

#2

Get the data and download the software. Then create your own graph that better shows what is going on. Something like…1 run at a time, 3500-6200rpm, and focusing on a narrow range of F/A like 12-14 or something. The red run looks pretty good.

Double-check that your TPS is working. Check it at the DME by removing the cable at the DME and using test lead in the appropriate pin. The pin-out is in Bentley. Mark the WOT pin with a felt maker so you can easily check it again in the future.

#3

You will notice that the AFR is consistent above 5k, which is when the DME no longer is using AFM data when at WOT. That suggests that the AFM data is driving the variation. That could be bad connections to the AFM, a bad AFM, a bad wiring harness, or a problem in the AFM input circuits in the DME. You could try a different DME, but since the AFR wasn’t consistently off below 5k I tend to suspect something other than the DME.

#4

Would be interesting to see what a run w/ the AFM unplugged would look like.

I agree that AFM’s can certainly be a problem child.