Is it impossible to run a type IV in closed loop?, Megasquirt Options

[DNHunt]

After about a month of tuning I have a fueling map that seems close. Most of the map yields air fuel ratios of about 13.8. From what I have read this is about where the motor was designed to run and it runs very well.

However, I continue to have problems with overrun. Between 2600 and 3600 rpms under very light load the air fuel ratio is much richer. This is quite disappointing as I would hope to gain some economy here. The solution would seem to be closed loop with the oxygen sensor leaning out the air fuel mix. The problem is that the pulse widths are so short that O2 correction leads to large changes percentage wise in pulsewidth and fuel mix and the car bucks. I have one more idea to try. I am waiting on some new injectors since it feels as if one cylinder goes dry.

If that doesn't help, it appears to be run open loop and send fuel ou the exhaust or run closed loop and suffer some loss of smoothness.

I'd appreciate any advice,

Dave

[airsix]

At any rate I'm getting a little frustrated. I want to do this right, I really believe in the megasquirt system,  but I'm not sure I have the expertise to get it done.

Dave

Of course you do! Don't let this get you down! Believe me I know how you feel. I had one little issue with my ECU install that almost made me throw it all in the trash more than once. Figuring out the problem took 3 months. Fixing it took 10 minutes. I've been all smiles and miles ever since. Keep at it. You will get this all worked out and it will be worth it in the end.

Ok, back to the problem. Are you saying that you can get it either too lean or too rich and that right now it just happens to be set too rich? Or is it always rich in that range? 2.3-2.5 ms seems like a really small window for a large change in mixture. Have you considered using different injectors? A lower flow injector should give you more tuning resolution. The d-jet injectors seem to be way overkill IMHO.
I am using injectors from a Subaru 1.8 turbo. $5 each at the wrecking yard. They are working very well for me. The longer pulsewidths make tuning easier, and they are nowhere near max duty cycle.

-Ben M.