New member with VE table Q's

[Joe Shuhy]

Hey guys, I'm new to this list and modifying ECM tables.  My name is Joe 
and I have a '92 Camaro with various mods.  It's been running well until 
recently when I put on AFR 190 heads and a 212/218 CC cam, then the off 
idle drivability became poor.  I have a Diacom I use to capture the car's 
sensor readings and try to figure things out.

The MAP readings at idle went from 25-30 kpa before the swap to 50-60 kpa 
after it.  The stock fuel map appears to give the engine too much fuel at 
idle now and the BLM drops to 108.  When the car starts moving, the MAP and 
integrator values increase but the BLM stays at 108, the O2 readings get 
very low, and the car hesitates.  The computer finally figures it out and 
increases the BLM to mid 120's and it drives better.  What I'm interest in 
doing is modifying the VE table for low RPMs to lean out the mixture.  I 
believe this would stop the BLM from dropping to 108 at idle and then 
produce better acceleration off idle.

The diy-efi list archives seem to be down so I can't search them to see if 
this issue has been covered.  First of all, have others seen the MAP 
readings go up considerably at idle after a head/cam swap or is there 
something else causing this?

I've read my stock prom and a hypertech prom and I'm using winbin to modify 
them.  The 7730v3.ecu file I'm using lists the VE tables at 0x6EE (low rpm) 
and 0x79A (high rpm).  The data from my chips map into this range nicely, 
but I want to verify that this is the correct known location for these 
tables.  One concern I have with the ecm file is that it lists 1600 RPM in 
both low and high tables.  Is this correct and if so, why?  Another concern 
is that I've seen another '730 ecu file that has VE tables in the same 
location, but laid out differently (basically RPM/kpa swapped).  Is the 
7730v3 table layout correct?

I believe that lowering the numbers in the VE tables tells the ecm the 
engine is less efficient and will reduce the amount of fuel given to the 
engine.  I'm really only interested in the low rpm table at this 
point.  How sensitive is the ECM to changes in the VE table?  If I lower 
the values for RPMs below 800 with MAP readings below 70 kpa, should I 
lower them by 1 point, 2 points, 5 points?  I know 1 point at a time would 
be safest, but if someone already knows that the tables don't produce a 
large difference then maybe I can tune them in quicker with larger steps 
and fewer prom burning cycles.

Any help with this would be appreciated.

Joe
92 Z28
http://home.cfl.rr.com/shuhy/chevy.htm

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org