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

[DNHunt]

Ben

That silly little 0.2 ms pulsewidth change results in a change in an afr change of 4 or 5 parts air to fuel. In other words, tuning resolution just craps out. Thats why I am betting one injector may be quitting. The new injectors just arrived and I intend to change them for the ride home from work. Hopefully it will run better. I know my fueling map is close except for the area where it cruises on the highway.

I really want to avoid changing to smaller injectors as I would like to work out a program that everyone with a 2.0 L could use to get a running start in converting to Megasquirt. I doubt if I am alone in believing the D-jets days are numbred. For me, Megasquirt was the only choice because of cost.

I also recognize that the Bosch 280 150 019 is not a very good choice for this motor. I wonder what the people who designed this engine were thinking of. Was the belief at the time use the biggest injectors available, were their choices so limited that they had to settle for these injectors, didn't they know better. It sure is a pain in the butt. The engine designers stuggled with it too, why else would the ECU have a circuit to cut off fuel and why put in a decel valve except to lean out the mixture. I' m hoping that more modern brains can offer better contol and I can work around this problem. If not, I may have to choose between a compromise in the way the car runs or changing to smaller injectors. At any rate I committed to getting them as close as I can.

Dave