M20B23 - idle - AFR and timing

[e30davie]

Hello all,

setup: M20b23 (9.8:1 comp ratio and different combustion chamber to the m20b25), MS2, LS1 coils in wastes spark (no dizzy), Closed loop idle control with PWM 2 wire idle valve.

In the interest of fuel economy I am looking to optimise my megasqurit tune further. I currently have it targeting 14:7 on cruise with wide band feed back on closed loop, works well.

What sort of idle AFR do you think i can get away with? when i first got the engine up and running on mega squirt i found that it seemed to want a bit more of a richer tune at idle, its currently targeting 13.8:1 which works fine. But this was before i deleted the oem coil and now have LS1 coils in wasted spark, unsure if this will help?

I am currently at 19deg timing at idle at 13.8 and it idle fine.

Do you think i can achieve 14:7 at idle and if so what do you suggest i do for timing? increase? decrease? up the dwell time a touch to help it fire on a leaner mixer?

[decay]

you say it's idling fine; if it isn't doing anything you'd call bad behavior, yeah, have it auto-tune for stoich in that part of the map is my opinion and if it isn't pinging or stumbling, your ignition timing is good.

[e30davie]

yer thanks for that. I should just give it a go hey.

I was just on the war path of optimisation, so interested to see what others had done.

I was even considering trying cruise at 14.9 or even 15, and see how it went. At the moment it gets great fuel economy (~9L/100km) and even better on the highway. but maybe there is more to be had. or maybe if i start cruising at these speeds i will lose HP in these load cells, and end up using more throttle, and using the same amount of fuel....

[digger]

Lean cruise is ok but timing may need to be advanced more to do it effectively as leaner mixtures burn a bit slower

[MikkoR]

Hello all,

setup: M20b23 (9.8:1 comp ratio and different combustion chamber to the m20b25), MS2, LS1 coils in wastes spark (no dizzy), Closed loop idle control with PWM 2 wire idle valve.

Do you still have this car or the tune available? I have similar setup except 3-wire Bosch ICV. It starts, idle is hunting etc. I'd like to compare the tunes.

[e30davie]

Do you still have this car or the tune available? I have similar setup except 3-wire Bosch ICV. It starts, idle is hunting etc. I'd like to compare the tunes.

yep, still got the car. Happy to compare tunes, however mine still hunts a little bit whilst its warming up. but once its at operating temp it is rock solid. Never bothered to refine it more than that as its not bothered me enough. I'm sure the PID values can be changed to suit, but i tried a fair bit a few yrs ago, never could get rid of the slight hunt completely during warm up, but as i said its rock solid once warmed up.

3 wire will operate differently to my 2 wired so our tunes might not be that comparable. 3 wire i assume you have one output to open it, and one to close it, and then the 3rd wire is common. maybe this is a better arrangement.