idle hangs in decel...with clutch pushed in
05-26-2005, 04:12 PM
#1
idle hangs in decel...with clutch pushed in helping tune a buddies car...
he just changed over to 42.5 # injectors and a fast intake...
working on VE now...
I noticed that when he pushes in his clutch that the rpm ramps up to 2000rpm hangs for a few seconds and then slowly settles back down to idle...
the car has always done this after a cam
his mods are longtubes/true duals/lsx/injectors/X1 cam/5.3 heads
what tables do I need to edit to get his idle to settle normally instead of hanging..
he just changed over to 42.5 # injectors and a fast intake...
working on VE now...
I noticed that when he pushes in his clutch that the rpm ramps up to 2000rpm hangs for a few seconds and then slowly settles back down to idle...
the car has always done this after a cam
his mods are longtubes/true duals/lsx/injectors/X1 cam/5.3 heads
what tables do I need to edit to get his idle to settle normally instead of hanging..
05-26-2005, 04:22 PM
#2
My similar issue just ended up being a crack in my intake manifold. You may want to run some carb cleaner around the edges of the manifold and TB just to doublecheck.
After that, there are three places that I would work with. If you have time, consider trying al three for the experience of it.
The first, of course, is the running airflow. People often raise this to clean up the idle, but end up creating a decent bit of "hang" before coming to a stop.
Second, I would look into shifting the IAC effective area vs. position curve to the right a little. Ported throttle bodies and other ways that we fix a cammed idle (openning/drilling the TB a little) creates open area that exists even when the IAC is shut. shifting the table to the right is a way of saying "I've thrown som square millimeters of openning into the mix" so that the car knows that for a given opening, it doesnt have to open the IAC as far. Because this behaviour is while the car is moving, generally, it doesnt learn this with LTIT and STIT.
Lastly, you may want to look into the throttle cracker. For *my* purposes, I zero'd the TC out until I got everything else worked in, adn then slowly added it back in until I liked where it sat. I zero'd it out for other tuning because it was one too many variable for the "while moving" idle.
That IAC effective area curve (#2) really made some interesting differences in my car, and I hope that folks around here start building some how-to's that involve it.
Getting the idle of these cars spot on is becoming quite a long procedure! But at least its finally being fleshed out.
Chris
After that, there are three places that I would work with. If you have time, consider trying al three for the experience of it.
The first, of course, is the running airflow. People often raise this to clean up the idle, but end up creating a decent bit of "hang" before coming to a stop.
Second, I would look into shifting the IAC effective area vs. position curve to the right a little. Ported throttle bodies and other ways that we fix a cammed idle (openning/drilling the TB a little) creates open area that exists even when the IAC is shut. shifting the table to the right is a way of saying "I've thrown som square millimeters of openning into the mix" so that the car knows that for a given opening, it doesnt have to open the IAC as far. Because this behaviour is while the car is moving, generally, it doesnt learn this with LTIT and STIT.
Lastly, you may want to look into the throttle cracker. For *my* purposes, I zero'd the TC out until I got everything else worked in, adn then slowly added it back in until I liked where it sat. I zero'd it out for other tuning because it was one too many variable for the "while moving" idle.
That IAC effective area curve (#2) really made some interesting differences in my car, and I hope that folks around here start building some how-to's that involve it.
Getting the idle of these cars spot on is becoming quite a long procedure! But at least its finally being fleshed out.
Chris
05-26-2005, 04:34 PM
#3
also I have a question about idle timing...
where do I add it to if any at all?? to make his car idle right...
I am considering just redoing all the idle stuff completely...
his car...used to be my car...
and after seeing some other peoles tunes...I think the guy that did the tune on this car originally...didnt have any idea...
The original tuner told me that he did ltft tuning...but the table was still just the same as the stock table...and it was everything in mods list above except for lsx was ls6
where do I add it to if any at all?? to make his car idle right...
I am considering just redoing all the idle stuff completely...
his car...used to be my car...
and after seeing some other peoles tunes...I think the guy that did the tune on this car originally...didnt have any idea...
The original tuner told me that he did ltft tuning...but the table was still just the same as the stock table...and it was everything in mods list above except for lsx was ls6
