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Fixed idle config?

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Hello I'd like to ask if someone knows how to config an ECU if you like to run a fixed idle setup! Is it possible using MAP on the load axis? Or is only for Alpha-N tuning? I'm running ITBs without an idle air valve I've adjusted the throttle to maintain the trottle plates a little bit open. But I'm having trouble setting it up on the ecu!

With no idle control valve or e-throttle control, you won't achieve perfect idle speed control. In particular the engine requires more air bypass when its cold to achieve a reasonable idle speed. You can achieve reasonable results with idle ignition control but it won't be perfect. You can see how idle ignition control works in this webinar - https://www.hpacademy.com/previous-webinars/101-idle-speed-control-tuning-link-g4/

I think your question is how do you do idle control if you don't have drive-by-wire or an idle air valve. Many ITB setups are like that.

Depending on the ECU model, look for a function called something like idle ignition control -- this will vary the ignition timing to maintain the desired idle speed. Normally you need to provide a lower target ignition timing, and provide the idle ignition ignition timing with a range of ignition timing it can use to control the idle. Sometimes this requires using less than MBT timing in the idle range of the ignition table.

If you ECU doesn't have an idle ignition control, you can make something similar with just the ignition timing table, by setting lower timing (like 0-5 deg) just above the idle speed (so the engine will slow down), and using values closer to MBT below your target idle speed to speed the engine up to the idle speed.

Looks like I was just short of MBT (Max Best Typing) on my reply....

@andre Sorry that i can't watch the webminar my internet access is a bit limited for the time being! I hope when i'll have more access it will be very helpfull!

@David Ferguson First the only ignition adjustments that i can do is shown on the attached pics and second you mean to change the values on the highlighted area i have on the attached table?

Attached Files

Since you have Idle Ignition, that is the table you should adjust. What that says is adjust the ignition timing based on how far away we are from the targeted idle. You may need to increase those numbers in the table, or change the values of the table axis if there isn't enough range to control your idle. I would start by changing the max _/- adjustment to something much larger like 20 deg. Also note that it doesn't take effect until the engine is above 51degC (you could lower that if your cold start isn't idling fast enough.

In your Ignition Time Base Map, you would only change the values in the first two columns of your highlighted area (ie, when the TPS indicates 0 - 2% If you have more throttle, the driver probably wants to speed up). Depending upon the state of tune, you may need to use timing numbers more like 5-10% around your desired idle speed control range.

@David Ferguson Sorry my late reply didn't have any time to check your suggestion until now! Thank you very much for the advice it was very helpfull! I checked both changing the timing in the map and the Idle Ignition control to check what works better for my application! What I noticed is that my Idle gets better when my table numbers go as far as 40deg BTDC! Isn't that a bit to far for ignition advance or because the engine RPM are very low there is minimal for detonation?

I should note that the engine is running a base ignition of 16deg BTDC and a comp ratio of 9.5:1!

I have some ignition maps that shows 80 deg of advance at very low manifold pressures and 3000+ RPM, there is no problem lettting idle control have 40 deg range. There should be no real load on the engine at idle anyway.

If you're just setting 40 deg below your desired idle to keep the engine in the idle RPM, that is OK.

If your standard timing at idle is 40 degrees, you may want to make sure that is the real timing of the engine. Verify your timing mark is actually TDC, and then using a timing light to verify that the ECU's commanding timing matches the actual timing.

Thank you very much David you helped me a lot! There is one little issue I have to solve and I believe I will be able to make a reliable a stable tune!