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New member with VE table Q's
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
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