Idle related problem...would need some direction
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From: Quebec,Canada
Idle related problem...would need some direction Ok im trying to help my tuner.I got a g5x3 with longtube,vararam and fast 90/90 ls2 tb.
-The car run great
-The idle is set at 850 rpm and its perfect
-The part throttle is also perfect with no surging and 12.8 afr at WOT.
But when sitting at idle ,in neutral, if i snap the gas maybe to 2000rpm and let off the gas my rpm will drop to 200rpm then will work really hard to get it to 1100rpm than it would goes down to 200rpm and would go back to 1000rpm.It would do this 3-4 times and will get back to 850 rpm and stay there.
It would also do the same thing if im cruising at any speed and would need to stop(red light,stop sign).While driving if i put the car in neutral for stopping the rpm will do the same up and down thing 3-4 times before going back to the 850 rpm setting.
So what table do i need to play with.The car pull like a train but is a real pain to drive in city and dont let me start on parking :ack:
Thanks
-The car run great
-The idle is set at 850 rpm and its perfect
-The part throttle is also perfect with no surging and 12.8 afr at WOT.
But when sitting at idle ,in neutral, if i snap the gas maybe to 2000rpm and let off the gas my rpm will drop to 200rpm then will work really hard to get it to 1100rpm than it would goes down to 200rpm and would go back to 1000rpm.It would do this 3-4 times and will get back to 850 rpm and stay there.
It would also do the same thing if im cruising at any speed and would need to stop(red light,stop sign).While driving if i put the car in neutral for stopping the rpm will do the same up and down thing 3-4 times before going back to the 850 rpm setting.
So what table do i need to play with.The car pull like a train but is a real pain to drive in city and dont let me start on parking :ack:
Thanks
1 - make sure VE is spot on, not just MAF, too many "tuners" totally ignore the VE table
2 - tune RAF (Base Running Airflow) - use the specific config file out there to do it, it works
3 - Throttle Cracker and Throttle Follower
where do you live?
2 - tune RAF (Base Running Airflow) - use the specific config file out there to do it, it works
3 - Throttle Cracker and Throttle Follower
where do you live?
Per his account, fueling is good. A good RAF is necessary - but not likely the cause here. Throttle cracker has nothing to do with when the car is sitting still. Throttle follower may help solve the problem some by allowing the revs to come down slower.
Check the idle thread over on EFI Live's forums:
http://forum.efilive.com/showthread....ul-Info-Inside
The likely problem is, there are tables that still have factory values that are causing the surging. Specifically, the idle spark overspeed/underspeed corrections and the IAC tables that support idle.
Log the problem to understand what is happening (examples of what to look for: spark is falling off and coming back on too much or desired idle airflow is swinging). This will point you in the right direction for where you need to make your corrections.
My money is on timing and direct airflow correction tables. For when the vehicle is in motion, you can add some airflow to the Throttle Cracker table in the smallest RPM row (or column in HPT) to act as a stall saver.
Check the idle thread over on EFI Live's forums:
http://forum.efilive.com/showthread....ul-Info-Inside
The likely problem is, there are tables that still have factory values that are causing the surging. Specifically, the idle spark overspeed/underspeed corrections and the IAC tables that support idle.
Log the problem to understand what is happening (examples of what to look for: spark is falling off and coming back on too much or desired idle airflow is swinging). This will point you in the right direction for where you need to make your corrections.
My money is on timing and direct airflow correction tables. For when the vehicle is in motion, you can add some airflow to the Throttle Cracker table in the smallest RPM row (or column in HPT) to act as a stall saver.
Dude, that was totally my number 4 - timing! I sat there before I submitted the post thinking, what the hell was the other thing I was going to say??? lol.
I also put timing at and all around the idle cell(s) to one set value (mine is 28 or 29 deg)
My cam is a pretty decent size but I was able to leave the correction tables stock and it idles very smoothly. I should do an idle video tomorrow.
I also put timing at and all around the idle cell(s) to one set value (mine is 28 or 29 deg)
My cam is a pretty decent size but I was able to leave the correction tables stock and it idles very smoothly. I should do an idle video tomorrow.
You mean like this???
http://www.youtube.com/watch?v=jiK6YIZEcXo
I had idle dialed in so well, I was able to take the 24x duration cam down to 650 without it dying on me. The lights were starting to flicker with the alternator struggling.
PS - this is a MAF only tune with the VE table disabled (airflow threshold set to 100rpm instead of the stock 4000rpm). 
http://www.youtube.com/watch?v=jiK6YIZEcXo
I had idle dialed in so well, I was able to take the 24x duration cam down to 650 without it dying on me. The lights were starting to flicker with the alternator struggling.
PS - this is a MAF only tune with the VE table disabled (airflow threshold set to 100rpm instead of the stock 4000rpm). Thanks - I normally keep mine around 900 to promote a little more manifold vacuum. I bought it with a tune that kept in at 1000 for that same reason. But, I had to sacrifice a few kPa for personal taste reasons (i.e. better lope).
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