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 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.

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.

Bump

You can bump the idle up a little with Consult II or Cipher. That should help with stalling...

The jim wolf website has a vacuum hose "mod" to help with this issue with his S1 cams. Might help for you...

Idle is bumped as high as consult can at Nissan dealership. I would assume its the same for the others.

I did read up on the vacuum hose mod ages ago. I will have another read.

Do you have a link to this page?

I looked all through JWT's site, but couldn't find it.

.

the JWT vacuum mod is pretty simple stuff. there is a certain NA motor here recently we had to make a nice controlled vacuum leak to get it to idle stable here.

take the throttle body off and drill a small 1/16th inch hole in it. it will stabilize the idle for you as well.

/\ Do you mean to drill a small pilot hole in the butterfly valve in the TB? Or actually drill a small hole in the TB housing itself?

the throttle plate itself...

works wonders. ive done it to a few cars with the tomei 268's and 272's on big 1600's

Thanks for the input.