MicroSquirt.com read only forum (Jan.15,2018)

OK guys

I have 2off low impedence injectors and initial settings are 30% and 1.0 ms for the pwm setup.

I tried trimming these values down to find the optimum (1% and 0.1ms at a time spererately as in the manual) and didn't really notice much difference in "idle quality". I got down to 23% and 0.9ms. However I have no confidence these values are riht.

I did notice the afr's changing on my wideband when I pulled these setting down from 30% and 1.0ms but as the idle wasn't brilliantly steady - observing a deterioration in idle qulaity wasn't easy.

Can anyone guide me in terms of the changing in afr's whilst setting the pwm criteria. I'm just after a bit more advice about setting these, can the wideband make homing in on the optimum easier?

Also, what the disadvantage to staying with 30% and 1.0ms, I wouldn't have thought these settings are high enough to burn out an injector and wouldn't think they're too low for reliable opening as they're the starting points in the manual.

Any pointers for me guys?

Dan

Dan,

The AFR should not change at all if the PWM% and time are above the thresholds, in theory.

Theory and practice often don't agree completely though! There can be some interaction between the injector opening time and the PWM ttime threshold, so it would surprise me if there was a slight AFR effect. What I tend to do is move the PWM time threshoild and injetor oppening time together (keeping them equal), it eliminates a potential confounding factor.

With the PWM%, lower it until it has a noticeable effect (like you have done, then raise it a few percent). Make sure the engine still responds to 'blipping' the throttle though, because if you have the PWM time threshold a bit too long, that may be providing the fuel for idle, so you need to make sure the injectors stay open for longer pulse widths.

Leaving the PWM% too high (or the PWM time threshold) puts more heat into the injectors. However, a bit too long (or too high PWM%) is bet than too short.

Lance.

Thanks Lance,

I have a question though...

If I am idling at say 12.8:1 and keep decreasing the PWM criteria, surely the change in idle quality is due to a change in afr? WHat else would change the idle quality.

Because I am injecting a siamese port engine, setting this might not be as easy as the idle quality in general is not great at the moment so I was hoping the wideband might give a little more insight.

I appreciate that all injectors are different but if I'm under 25% and my time threshold is between 0.8 and 1.4 (let's assume I make it the same as the opening time at about 1.0) is there a rule of thumb to suggest the injectors are not being over heated? I've been down as low as 22% and there didn't seem to be any difference in idle at all.

ANy other pointers?