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What to Set idle spark?

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I’m currently in the process of tuning my 4.6 2v and I noticed I’m running between -3 and 5 degrees of advance at idle. Is there a target I should be looking to hit? I recall a video on a ls motor saying between 12-18 but I’m not sure if that applies to all motors or just ls based platforms.

I find out the max torque ign. angle MBT. The timing where the rpm is highest. ie. 25 deg

Then where it is fairly low but the engine still idles smoothly, ie. 5 deg.

I then set target angle and rpm at half the span = 15 deg.

This way idle ignition control has a decent range to work in.

To reach my target number I assume I need to reduce the idle airflow. What kind of increments is good to start with?


1. Set timing to 15 deg to start with.

2. Set mixture to a known good idle value. Ie. Lambda 0.98 everywhere in the possible idle areas of the fuel map.

3. Establish idle at ie. 1000 rpm and lock the throttle plate angle, not to be changed for the test.

4. Now advance timing in small steps, rpm will increase. Once increasing ignition angle does not yield rpm increase anymore you have reached MBT (25 deg in the above example).

5. Decrease ign angle until the idle quality starts to worsen. In the above example 5 deg btdc.

Personally, I aim for more idle advance as opposed to retarded in a non emission critical application.

To lock the throttle plate would setting min and max limits to the same number be fine (like somewhere around 4.3% as that seems to be normal under idle)? and due to me using hp tuners is writing a fresh tune every time the only way I have to make the changes? or is there a product I need to purchase to make live spark changes to speed up the process?

You could simply tr,y 10 or 15 degrees for idle ignition aim target and observe how good the idle quality is and how much the idle ignition swings.

Ignition angle for idle control can show quite large and quick changes and can seem erratic, but as long as idle quality is good such swings are considered normal, necessary.

This way you can get it done in a timely fashion.

We usually reply within 12hrs (often sooner)

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