Forum » General Tuning Discussion » Motec idle control functions.

Motec idle control functions.

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 


Page 1
Author
55 Views

Hey guys currently have some cold start/idle issues with my motec m150 on my gt86.

Basically just chasing some information on most of the idle control functions in a sort of dummed down way.

Most of them I have an idea of their function but I would like to be 100% certain on things im adjusting.

ok, so lets start with the (idle actuator) worksheet first,

-Engine crank idle mass flow and post start idle mass flow(I know what these are but, I want to know what the number i put in it is a percentage of) interested because of cold start issues.

-Idle mass flow integral max/min. (again what this percentage is off and how I utilise this)

-Idle mass flow feed foward main table. (How can I accurately calibrate this table or check that it is correct as im pretty sure my tuner did not calibrate anything other then the ignition and fuel tables)

-The idle activate functions in the idle aim worksheet. (throttle pedal threshold, hysteresis,Idle activate speed margin and throttle pedal offset limit)

Ill leave it at that for now as I dont want to annoy you guys with million questions, basically my issue is that my idle ignition control is constantly firing after TDC as its trying to get my idle speed down to 850. It sits at about 900 but I want to get it to the target but I cant seem to get there. Today I calibrated the DBW and it made it alot better somehow. Also sometimes depending on how you go back to idle it just sits at 1200rpm not moving down, so ive sort of narrowed it down to I feel the throttle body is slightly too open and I want to figure out how to close it a tiny bit to hit my target on the software.

Also I am not that experienced so it may not even be what I think it is, If there are any videos or links that you guys could supply for me to do some research on it that would be appreciated. I find motec webinars dont quite hit the spot for my application.

Again, thanks everyone in advance.

OK, here's the secret sauce. All the Idle Mass Flow values are the percentage of the value "Idle Actuator Throttle Aim Maximum". This applies to the Engine Crank Mass Flow, Idle Mass Flow Feed Forward Main. So one way to close the throttle is to lower the value of Idle Actuator Throttle Aim Maximum. Alternately, you can change the values (all or just some) in the Idle Mass Flow Feed Forward Main table. This table should be setup with a breakpoint at each RPM you intend to use in your "Idle Aim Main" table (where you set the target idle speed).

Before adjusting the Feed Forward table, be sure the Idle Ignition Timing Limit Advance Target has the target ignition advance you are trying to hit.

You can change Idle Aim Ramp Down Limit to have the idle control control the RPM starting at different values above your ultimate target, but that can define the minimum RPM you can control with the throttle pedal, so I find it better to leave this value fairly small (250 RPM).

When the throttle is hanging at 1200 RPM, what is the Idle Aim value? If it's 1200 or less, reduce the active cell in the Idle Mass Flow Feed Forward Main table, and begin to lower the RPM toward the idle target.

I suggest reading the help for "Idle RPM", "Idle Mass Flow Feed Forward Main", "Idle Mass Flow", "Idle Throttle Pedal Offset" -- they really are helpful.

I just leave the integral min/max % at the default.

One way to check/tune the Feed Forward table:

Change the value of "Idle Aim Main" to each RPM breakpoint in the Feed Forward Main table.

Watch the values of "Idle Mass Flow" (the Idle Actuator Throttle Aim will be this value * Idle Actuator Throttle Aim Maximum), "Idle Mass Flow Feed Forward" (this is the Idle Mass Flow Feed Forward Main plus any compensations like Post Start or A/C Feed Forward). You usually want the Feed Forward Main table to be close the the resulting Idle Mass Flow values with no compensation. Note this will change if you modify the Idle Ignition Timing Limit Advance Target, so set that first, or be prepared to retune the Feed Forward Main-- eventually the "Idle Mass Flow Integral" will reduce to zero and your Feed Forward value will equal the resulting Idle Mass Flow.

In the Feed Forward Main table, I find it helpful to set a Coolant Temperature breakpoint that equals the normal operating temperature of your engine. That way you are in the center of that cell when warmed up. During cold starts, you tweak the other values in in the Feed Forward Main table as the engine moves through those cells -- you don't have to hit every cell, the trend will emerge -- the integral PID makes of for any small errors you may have.

Hopefully some of these thoughts will be helpful to you.

Thanks heaps for the tips, I actually found the video on here which helped also. Got the idle a lot better but timing is still quite low. I've noticed downshifting in trafic with no accelerator makes the idle drop below target rpm by a lot. It's like it stays in idle control between downshifts with no throttle. Might have been doing that the whole time I just never noticed. But that's good, I'll keep trying to fix the idle first. Thanks again for the help.