Tuning Idle on Cam'd Motor
10-02-2008, 12:14 AM
#1
Tuning Idle on Cam'd Motor
How do changes to fuel, ignition and cam timing at idle engine speeds affect the idle behavior on a built motor with aftermarket cams?
What changes can be made to these parameters to improve idle performance? Either while stationary after startup or after coming to a quick stop with revs falling rapidly to idle speeds.
e.g. I have been told that an advance in ignition timing at idle can improve a weak idle somewhat.
What changes can be made to these parameters to improve idle performance? Either while stationary after startup or after coming to a quick stop with revs falling rapidly to idle speeds.
e.g. I have been told that an advance in ignition timing at idle can improve a weak idle somewhat.
10-02-2008, 05:11 AM
#2
What management are you using? Also what cams, and what is your idle rpm? And are we still talking about a DBW car - if so, the falling revs should be taken care of by the stock computer dbw control if the tune is appropriate.
On more extreme setups, you will generally find more fuel will smooth things out and more timing will raise the idle. You must be careful on a Z though because the factory computer uses the throttle body and timing together to target idle, so if you take timing control from it at idle you have to spend a little more time to keep it steady/happy. In Haltech we have the ability to pass through the stock computer's timing values at idle so it the rpms will start, idle and fall like factory.
On more extreme setups, you will generally find more fuel will smooth things out and more timing will raise the idle. You must be careful on a Z though because the factory computer uses the throttle body and timing together to target idle, so if you take timing control from it at idle you have to spend a little more time to keep it steady/happy. In Haltech we have the ability to pass through the stock computer's timing values at idle so it the rpms will start, idle and fall like factory.
10-02-2008, 04:23 PM
#3
Thanks for your resposne.
My car specifically exhibits the issue of revs falling too quickly for stock computer + UTEC to catch so its stalls when stopping quickly. It idles fine after I increased it to 900rpm with an advance of ignition.
I am currently using a UTEC+Tuner+WB+Map Sensor / Tune and have been investigating Haltech.
Running 10:1 compression with Tomei 268 10.5/10.5 (bit less lift in reality), full exhaust, no turbos.
Any increase in fuel within UTEC around idle seems to be removed by the stock computer as it tunes back to lambda.
My car specifically exhibits the issue of revs falling too quickly for stock computer + UTEC to catch so its stalls when stopping quickly. It idles fine after I increased it to 900rpm with an advance of ignition.
I am currently using a UTEC+Tuner+WB+Map Sensor / Tune and have been investigating Haltech.
Running 10:1 compression with Tomei 268 10.5/10.5 (bit less lift in reality), full exhaust, no turbos.
Any increase in fuel within UTEC around idle seems to be removed by the stock computer as it tunes back to lambda.
Last edited by mchapman; 10-08-2008 at 01:50 PM.
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