individual cylinder fuel trim tables
07-29-2003, 11:55 AM
#2
Registered User
Join Date: Feb 2000
Location: Cincinnati, OH, USA
Posts: 1,009
They modify fueling to each cylinder.
AFAIK, they do it by multiplying the commanded injector pulse-width for the respective side of the engine by the number in the table.
So if the left side is commanded a PW of 12, and your #2 cylinder is set to 1.03, its PW will be changed to 12.36.
AFAIK, they do it by multiplying the commanded injector pulse-width for the respective side of the engine by the number in the table.
So if the left side is commanded a PW of 12, and your #2 cylinder is set to 1.03, its PW will be changed to 12.36.
07-29-2003, 12:04 PM
#4
Registered User
Join Date: Feb 2000
Location: Cincinnati, OH, USA
Posts: 1,009
It's calculated from the various tables.
In open loop it uses the AFR x 10 table.
In closed loop it uses VE (for speed density) or MAF sensor (for MAFS) tables.
At WOT it uses the previous calculation + the correction in the %Change at WOT tables.
In other words, there's no actual table for the final PW. It's calculated from other inputs.
In open loop it uses the AFR x 10 table.
In closed loop it uses VE (for speed density) or MAF sensor (for MAFS) tables.
At WOT it uses the previous calculation + the correction in the %Change at WOT tables.
In other words, there's no actual table for the final PW. It's calculated from other inputs.
08-13-2003, 10:57 PM
#7
Registered User
Join Date: Jul 2002
Location: Phoenix, AZ
Posts: 1,277
Unless you have a way of determining your correct fueling for each cylinder, I would leave it as stock.
I did try to use a IR thermometer to check each header on my car, but truthfully I am not sure of how accurate you can really get with this since LT1's have that damn siamese exhaust scenario.
I was interesting to see my headers did have different temp values.
I did try to use a IR thermometer to check each header on my car, but truthfully I am not sure of how accurate you can really get with this since LT1's have that damn siamese exhaust scenario.
I was interesting to see my headers did have different temp values.
08-13-2003, 11:47 PM
#8
Registered User
Join Date: Jul 2001
Location: so close I can taste it...
Posts: 1,009
I'm sure those tables have to do with what cylinders get xx amount of air, as they all don't actually get the same amount of airflow. I wouldn't screw with it either.
On the GN intake/plenum someone has made a spacer plate that goes between the intake and plenum and evens out the airflow distribution to near perfect. What it does is allows us to run more timing on pump gas as the airflow going to each cylinder is now the same.
I think these tables basically do the same thing here. Leave them alone unless you have some actual data to support your changes with. GM must have done some sort of testing on what cylinders get how much fuel. Of course with a non-stock cam and/or ported intake these numbers go out the window. But how far off will they be?
On the GN intake/plenum someone has made a spacer plate that goes between the intake and plenum and evens out the airflow distribution to near perfect. What it does is allows us to run more timing on pump gas as the airflow going to each cylinder is now the same.
I think these tables basically do the same thing here. Leave them alone unless you have some actual data to support your changes with. GM must have done some sort of testing on what cylinders get how much fuel. Of course with a non-stock cam and/or ported intake these numbers go out the window. But how far off will they be?
08-14-2003, 02:18 AM
#9
Moderator
Join Date: Dec 1969
Location: Buffalo, New York
Posts: 10,745
Over the winter. I was going to put some bungs in my headers for EGT sensors. This would allow tuning each cylinder individually. Unfortunately, that idea got sidetracked and I never did it. This winter, I am going to try it and use the fuel trim tables for the purpose stated.
If you don't have EGT data for each cylinder, I wouldn't mess with them though. I suppose if one cylinder was consistently lean as shown by plug readings, and you were sure there wasn't a bad injector or something like that, it might make sense to make a change in the trims and add fuel to that hole. But I'd sure be cautious about making any cylinder leaner without being pretty sure it was rich.
Rich Krause
If you don't have EGT data for each cylinder, I wouldn't mess with them though. I suppose if one cylinder was consistently lean as shown by plug readings, and you were sure there wasn't a bad injector or something like that, it might make sense to make a change in the trims and add fuel to that hole. But I'd sure be cautious about making any cylinder leaner without being pretty sure it was rich.
Rich Krause
Thread
Thread Starter
Forum
Replies
Last Post
dbusch22
Forced Induction
6
10-31-2016 11:09 AM
chevroletfreak
LT1 Based Engine Tech
202
07-04-2005 05:00 PM