LT8 idle and overrun problems
 

Hi,

I have an LT8 running on my single-turbo 3rd gen, have been tuning using the TechEdge Wideband, but cannot get a steady idle. I'm also getting fluctuation problems on the overrun. Apart from this the engine pulls strongly up to 6000rpm (I'm cautious about higher revs ATM).

I've been using the DataLogger on the LT8 to diagnose the problems. I set the idle to 800-1000rpm when the engine's warmed up, but every few seconds the idle dips and the 'Status' changes from RPMCrs (ie. cruise mode) to 'Crank'! When it does this the injector pulse time jumps up by about 50% and the engine wants to cut-out. I set the RPMCrs value to 14"Hg, but there seems to be no way I can change the RPMCrank or RPMIdle values or even find out what they're set to (if indeed they they exist!). Could they be changed?

Also, on the overrun I noticed that the 'Status' is continually changing between RPMCrs and TPS_Cal as the TPS varies from 0-1%, which has an effect on timing as well as injector pulse time (BTW at full-throttle TPS is 97-98%, which seems OK). Why is this happening?

I would greatly appreciate any helpful comments.

Thanks,

Adrian
(in the UK)

What's the status when it's idleing? It should say IDLE not RPMCrs. That's a result of the TPS not being set.

The Status is definitely not IDLE. It says either RPMCrs or nothing at all! The dealer in the UK, that loaded up the basic map for me, was supposed to set up the TPS. But, I am getting 0% on closed throttle and 97-98% at WOT, which seems fine to me.
Does the value that RPMCrs is set to (eg. 17"Hg) have any effect on the idle?

Thanks for your reply,

Adrian

your tps is not calabrated correctly,

you may need to undo the 2 bolts that hold the tps on and move it slightly to get it right, i have had to do this in the past ,

Dale

OK, I'll do the TPS calibration and see if that fixes the problems.

Thanks,

Adrian