How To Tune Closed-Loop Idle

For people running FreeEMS to discuss it and ask any questions about using and adjusting it.
Locked
User avatar
Fred
Moderator
Posts: 15431
Joined: Tue Jan 15, 2008 2:31 pm
Location: Home sweet home!
Contact:

How To Tune Closed-Loop Idle

Post by Fred »

This brief guide describes something that isn't yet possible with FreeEMS, but will be soon. It's very easy, but the first premise of any closed-loop
system is a stable and fairly accurate open-loop calibration. Without this the control strategy CAN NOT WORK effectively or even at all.

Note: Closed-loop refers to ANY type of control strategy with feedback. Idle means the speed at which the engine sits during its rest
state. Closed-loop idle means controlling that speed using a control strategy with feedback. http://en.wikipedia.org/wiki/Closed_loop

Steps

Perform all of the below without headlights, aircon, large stereos, etc active. Such devices can be used to evaluate the PID setup afterward.
  1. Give your engine just enough air-flow to survive a cold start at slightly too low an RPM and hold at slightly too high of an RPM once warm
  2. Tune your engine temperature enrichment curve(s) to facilitate acceptable running during the cold start period
  3. Close off the fixed airflow such that the idle valve will do all of the work, especially important with big Bosch valves
  4. Setup open-loop idle control, and set a curve of duty/steps vs. engine temperature that provides a pleasant RPM at all temperatures (eg 1500 cold, 800 warm)
  5. Setup a target RPM vs. engine temperature curve that matches your unloaded reality as provided by the open-loop curve
  6. ONLY now should you engage closed-loop PID engine speed control and tune the PID parameters in the normal fashion
Notes
I'll put another post in with respect the extra settings, etc. I'll edit this one to update anything. A questions/comments thread is available: viewtopic.php?f=54&t=2238

Fred.
DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!
Locked