open loop fueling question
07-04-2005, 11:09 AM
#1
open loop fueling question so i have problems on cold start the idle will dip. started to fix it by decreasing the start up spark retard (startup spark correction) but im still having some issues and i think it has to do with the fueling, here is whta i was thinking
ok so with a cam the VE is not as good low end so at idle the car wont need as much fuel, but with more spark you need more fuel right? so i decreased the spark retard by half. i adjsuted the open loop f/a in the higher map areas so it ran leaner, jsut about how stock was. so im wondering if some of the problem i am having has to do with too much fuel? im wondering if for the colder starts i should have the numbers closer to 1.05 instead of 1.13 or so. im just not really too sure about this so i hope that some of you guys that know more about this can help me out
also here is whta its doing, i start the car up, rpms go up to 1500 then dip down to about 600 and then they recover, this is all right at start up in the first 10-15 seconds or so. one time i satarted the car up it did ok but then it stopped so i dont know waht the deal is. hope you guys can help me out. thanks
ok so with a cam the VE is not as good low end so at idle the car wont need as much fuel, but with more spark you need more fuel right? so i decreased the spark retard by half. i adjsuted the open loop f/a in the higher map areas so it ran leaner, jsut about how stock was. so im wondering if some of the problem i am having has to do with too much fuel? im wondering if for the colder starts i should have the numbers closer to 1.05 instead of 1.13 or so. im just not really too sure about this so i hope that some of you guys that know more about this can help me out
also here is whta its doing, i start the car up, rpms go up to 1500 then dip down to about 600 and then they recover, this is all right at start up in the first 10-15 seconds or so. one time i satarted the car up it did ok but then it stopped so i dont know waht the deal is. hope you guys can help me out. thanks
07-04-2005, 06:19 PM
#3
On The Tree
Join Date: Sep 2004
Location: St. Clair
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
I didn't mess with the open loop F/A numbers at all...I took the stock VE table and multiplied the entire table by 1.05...Then mulitiplied the first 5 columns (400, 800, 1200, 1600 and 2000 rpm columns) by 0.97, then the first 4 columns by 0.97, then the first 3 columns by 0.97, then the first 2 columns by 0.97, then the 1st column by 0.97...The car idles great and transitions through throttle changes really well...
You may need to adjust your MAF Frequency after driving a bit, because your LTrims will change a little...Then monitor your O2's and make some adjustments to your PE...
I've tried all different timing settings and the only thing that gave me decent idle was adjusting the VE Table as described...
Peace...Gman
You may need to adjust your MAF Frequency after driving a bit, because your LTrims will change a little...Then monitor your O2's and make some adjustments to your PE...
I've tried all different timing settings and the only thing that gave me decent idle was adjusting the VE Table as described...
Peace...Gman
07-04-2005, 06:51 PM
#4
the ve is fine, all the idle setting are right, big cam needs more timing and less low end fueling. i dont have the maf on the car so thats no issue. i just need to dial in the open loop table right, the higher map values are resulting in 9:1 afr before i changed it
07-04-2005, 06:58 PM
#5
On The Tree
Join Date: Sep 2004
Location: St. Clair
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
Didn't realize you running MAF-less...Even still, when running a MAF, then PCM uses the VE table alot under 4000 rpms, more so at low rpms, and dropping the VE values down low, sure cured my stalling problems...
Peace...Gman
Peace...Gman
07-04-2005, 07:02 PM
#6
yeah ive got the ve worked out, i have no problems when the car is hot and closed loop its only cold start open loop. i dont think the ve will help me here it was one of the first things i have tried, but what did you fix for cold start? i decreased the first row by about 60% and tweaked it from there and i pretty much have the ve right where i want it
07-04-2005, 07:08 PM
#7
Don't alter the VE table if it is already in line. What does your open loop af table look like? I understand you have a multiplier of 1.13, but where do you have this in the table. More then likely I would suspect that the car is rich and needs to be leaned out. I would take the open loop table and from temps up to 122* reduce it by 10% at a time to see how the car reacts. I have also found out that the Initial ECT enrichment table made my car all wacky so I personally zero'd out that table.
Another thing I found is I tried a long time ago to dial in my ve table at 1.13 to find out after I had it set to where I wanted and put the table back to stock or when I wanted to command 14.63(1.00), it would be off. Need to make sure that you have the table exactly where you need it to be otherwise, you will be chaising your tail.
Another thing I found is I tried a long time ago to dial in my ve table at 1.13 to find out after I had it set to where I wanted and put the table back to stock or when I wanted to command 14.63(1.00), it would be off. Need to make sure that you have the table exactly where you need it to be otherwise, you will be chaising your tail.
Trending Topics
07-04-2005, 07:15 PM
#8
On The Tree
Join Date: Sep 2004
Location: St. Clair
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
One of the things I changed was Idle Airflow vs. coolant temp., I multiplied the entire table by 90%...
I took out all the negative timing values in the Engine Coolant Temp vs. g/cyl. that show up in the lower coolant temps...
Other than that, made adjustments to the lower frequency, 3000 hz and below, to get the trims correct at idle and low rpms...
Peace...Gman
I took out all the negative timing values in the Engine Coolant Temp vs. g/cyl. that show up in the lower coolant temps...
Other than that, made adjustments to the lower frequency, 3000 hz and below, to get the trims correct at idle and low rpms...
Peace...Gman
07-04-2005, 07:25 PM
#9
ok, yeah i have it at 20-30 * c from 55-65 map, where i idle at and adjsuted from there. ill try what i have now and decrease until i get it better, i just dont want to lean it out too muhc you know? but i would imagine its rich as **** even if u shift the high map areas to the lower ones it used to idle at
07-04-2005, 07:53 PM
#12
I take it you don't have a wideband. 1.05 is ~13.9. That isn't the problem. The issue is other tables that affect the Commanded AFR also. If you look at the PIDs for fueling, you will see Commanded Air Fuel Ratio. That is what the car is commanding, NOT the actual AFR the car is seeing.
