VE and idle
04-25-2005, 09:52 AM
#1
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VE and idle Hi guys,
Here's my dilemma. I have all bolt-ons and an F13 cam. I went to SD and modified the VE table until all LTFTs were 0 or -1.
So far so good.
I then disabled LTFT's and modified the VE table again to bring the STFTs closer to zero. I got them down to values between 1 and -1, but this causes my idle to hang at around 600 rpm's, and surge up and down whenever I am stopped (idle is set at 900 rpm's). If I load back the file I previously had (the one where only the LTFT's are adjusted for), then the car runs great, idles right at 900. I'm guessing the idle hangs/surges due to the fact that the values of the VE table are a little too small after tuning both STFTs and LTFTs. What am I doing wrong here? Or how can I fix the idle problem? Thanks!
-turo
Here's my dilemma. I have all bolt-ons and an F13 cam. I went to SD and modified the VE table until all LTFTs were 0 or -1.
So far so good.
I then disabled LTFT's and modified the VE table again to bring the STFTs closer to zero. I got them down to values between 1 and -1, but this causes my idle to hang at around 600 rpm's, and surge up and down whenever I am stopped (idle is set at 900 rpm's). If I load back the file I previously had (the one where only the LTFT's are adjusted for), then the car runs great, idles right at 900. I'm guessing the idle hangs/surges due to the fact that the values of the VE table are a little too small after tuning both STFTs and LTFTs. What am I doing wrong here? Or how can I fix the idle problem? Thanks!
-turo
04-25-2005, 11:55 AM
#2
do you have stock injectors? u know i was having the same issue tuning for my injecotrs. the car ran like **** if i took more fuel out of the VE i assume thisis the same problem u are having. from what i see on the logs is that the o2 switching got very slow, do you have any logs of this? im interested in seeing a lot and i may have some recommendations based on my experiences.
budchevy358@yahoo.com if u can get some hp tuners logs of the o2 oscillation at idle and the fuel trim numbers and the rpm. also, did you fuel trims get more negative after the changes? mine did
budchevy358@yahoo.com if u can get some hp tuners logs of the o2 oscillation at idle and the fuel trim numbers and the rpm. also, did you fuel trims get more negative after the changes? mine did
04-25-2005, 12:01 PM
#3
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Could this have anything to do with it?
https://ls1tech.com/forums/pcm-diagnostics-tuning/309671-iac-position-vs-effective-area.html
Also, did you try this part of the "Tuning 101?"
https://ls1tech.com/forums/pcm-diagnostics-tuning/309671-iac-position-vs-effective-area.html
Also, did you try this part of the "Tuning 101?"
3: Idle
Now that we have verified everything is in proper working order we can begin tuning. Idle is the best place to start. Previously we set the desired idle rpm - subjectively decide if this rpm correct. If not, change the value and re-evaluate. Once the desired idle rpm is achieved, we can begin tweaking it for stability. Take note of the IAC counts. In a no load situation (neutral, no ac) they should be no lower than 30, and no higher than 50. A hole may need to be drilled in the throttle body or enlarge the one that is already there to bring down the IAC values. Do this until they are acceptable. Now put a load on the car (D if automatic, and put the AC on). The values here should be no higher than 120 or so. If they are enlarge the hole.
Repeat the above process until the IAC values fall inline. If the idle is still unacceptable then try adjusting the timing. Be careful of adding to much timing - it can give a great no load idle, but with any kind of load will become erratic. A "hunting" idle is a sure sign of too much timing. To adjust the timing at idle the base spark tables are the easiest place. The tables are scaled vs. rpm and g/cyl of airflow. The rpm part is evident. To calculate the g/cyl use the following formula:
g/cyl = 15 * MAF(g/sec) / RPM
Now that we have verified everything is in proper working order we can begin tuning. Idle is the best place to start. Previously we set the desired idle rpm - subjectively decide if this rpm correct. If not, change the value and re-evaluate. Once the desired idle rpm is achieved, we can begin tweaking it for stability. Take note of the IAC counts. In a no load situation (neutral, no ac) they should be no lower than 30, and no higher than 50. A hole may need to be drilled in the throttle body or enlarge the one that is already there to bring down the IAC values. Do this until they are acceptable. Now put a load on the car (D if automatic, and put the AC on). The values here should be no higher than 120 or so. If they are enlarge the hole.
Repeat the above process until the IAC values fall inline. If the idle is still unacceptable then try adjusting the timing. Be careful of adding to much timing - it can give a great no load idle, but with any kind of load will become erratic. A "hunting" idle is a sure sign of too much timing. To adjust the timing at idle the base spark tables are the easiest place. The tables are scaled vs. rpm and g/cyl of airflow. The rpm part is evident. To calculate the g/cyl use the following formula:
g/cyl = 15 * MAF(g/sec) / RPM
04-25-2005, 02:08 PM
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Originally Posted by WS6FirebirdTA00
do you have stock injectors? u know i was having the same issue tuning for my injecotrs. the car ran like **** if i took more fuel out of the VE i assume thisis the same problem u are having. from what i see on the logs is that the o2 switching got very slow, do you have any logs of this? im interested in seeing a lot and i may have some recommendations based on my experiences.
budchevy358@yahoo.com if u can get some hp tuners logs of the o2 oscillation at idle and the fuel trim numbers and the rpm. also, did you fuel trims get more negative after the changes? mine did
budchevy358@yahoo.com if u can get some hp tuners logs of the o2 oscillation at idle and the fuel trim numbers and the rpm. also, did you fuel trims get more negative after the changes? mine did
Originally Posted by SSpdDmon
04-25-2005, 03:00 PM
#5
see i took out more fuel in the VE and it made the oscillation suck on the o2s because the fuel charge wasnt enough to cause oscillation. i was having issues with my injecotrs but this is the same thing you are describing so there must be another problem. i was doing that idle stuff in that other link, didnt help stumble muhc but it helped recovery back to set RPM at idle, but i woudl definately do the stuff in that post.