M42T MaxxECU idle tuning

[retoropak]

I just started tuning my stock block m42. I have stock compression, ID1050xds, Bosch 68mm DB throttle, Custom intake, EFR6758

I am trying to get the idle to behave. I am tuning open loop for now. Engine at temp all enrichments and lambda control is off. Anything below 1.2k rpm and the idle start hunting and surging.
I tried anything between 6-12 degrees of timing without much difference. AFR wise I tried 13 to 16 and its still very unstable.

I must add that i have RHD flywheel and tilton twin clutch and whole assembly weighs around 14LB which doesn't really help.

I saw some m50/52 ignition maps with idle timing as high as 20 degrees.

What do you set the timing to in idle areas?


Thanks


Untitled by w grync, on Flickr

[retoropak]

I guess it took a bit more time to tune it. I had a lambda corrections turned on and it was messing up the mixture a bit. Also closed loop setting were not adjusted correctly. Took me a day of logging to see what happens.
Lambda corrections were trying really hard to get the mixture right and even though the AFR's were staying between 14-15 it was at the limit of the allowed correction and when it was going outside of the correction range it would either drop or rise rpms and get unstable.
Idle Ignition control was allowed to retard the ignition to far and was sitting at 2 degrees, to lower the RPMs to 950 and 2 degrees was not the best for the stable RPM.

So the fix was to adjust the main VE table so the lambda correction doesn't have to work as hard and limit the idle ignition control timing range.

I still have a little fluctuations +/- 50-75rpm but I haven't tuned the closed loop yet.

[varg]

With megasquirt I used 10-15° on my M42 depending on rpm and kept the VE table as flat as possible in the idle range. You may have issues getting a stable idle with such big injectors without idling rich and using a more advance. The smaller the pulse widths have to get to idle at or around 14.7:1 the more likely it is you'll have instability. I've tuned cars where the pulswidth was like a light switch. As soon as I dropped below 1.5ms for example it would immediately start hunting and randomly misfiring because the injectors weren't giving repeatable results at such a small pulse width. Random misfires also will make the AFR look leaner than it is because unreacted air and fuel get dumped into the exhaust every time there is a misfire.

[retoropak]

I swapped Tilton clutch and flywheel with stock m52 dual mass flywheel and 240mm clutch and idle sits at 850rpm and is smooth as glass. I think 30lbs difference in rotating mass makes a huge difference.