If i have a surge/hunting issue and I have a scan of the problem occuring and I send you (the experienced HTP person) the scan could someone with a LOT of HPT tuing knowledge tell me what the hell is going on?

High kPa at idle and low engine load, low vacuum FMS cam = huntiing. Now WTF do I do??

Jim

 

Sorry, I just can't bring myself to help a Seminole fan......j/k

So I take it you just installed the FMS cam & then this problem started?

 

No...the cam has been in the car/motor for about 9 months along with the 383 rotating assembly. The top end was torn down a second time to rework the heads as I had a 25% lean condition and could not figure out where it was coming from. So, back together, and 2 tuners tried to tune it with LS1edit. The tune is right on (I think) other than this hunting/low vacuum/surging issue. I need help with HPT's figuring out how to use it. Like the auto config feature?? Anyway, I believe the O2's show it lean at idle and low engine loads( parking scenarios expose this best along with quick on/off clutch driving conditions such as a 3 point turn) so it hunts for idle especially when in closed loop. I HATE THIS !!

Any ideas?
Jim

 

What are your IAC counts at idle? Probably an easy fix.

 

32-45 IAC desired position

 

desired or actual?

 

When you go lean on throttle tip in it probably means you need to add to your ve table in that region. I guess a lot of stroker guys have problems with this. Have you changed your cylinder volume to match your larger displacement?

 

Great question...I have no clue if the tuners tune currently in the car has done this but I'd guess yes.

 

I just went thru a hunting / surgjing issue when I installed a converter and this is what worked for me:

Raise the target idle to ~950rpm
Raise the timing in the lower cells (400-1200rpm in the 4-5 lowest g/cyl cells) to 24-28*
Crank your idle screw on the TB up 1/2 to 1 turn

I also had to do other things that don't apply to you (I have an A4)

A friend had luck with adj the Crank VE table lower to get rid of initial surging at startup.

And you should also ask them if they bumped up your PE Enrichment table. I had to for a cam, intake & bigger injectors to quit going lean @ WOT. Seems a must for a stroker.

Good luck.

DISCLAIMER - I am NOT an HPT expert.....

 

I was trying the auto configure cut-n-paste w/ the histogram for LTFT. At lower vacuum its really lean. If I reset the LTFT button the runs good for a while but after several ignitions cycles the VCM relearns it old habits and it starts to hunt again.