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