Running rich when hot

[Josh]

So I noticed this problem when tuning, it makes things very frustrating.

I start tuning after the car is warmed up. Set the idle, sitting right where I want it at 14afr. However after driving for a while I stop and the idle is in the low 13s / high 12s. So i corrected it back to 14. Shut the car off for a bit and when I fired it back up again the afrs are >16!

This all occurred when the coolant is at operating temperature, so WUE is not a concern.

What could be causing this? Im thinking potentially heat soak from the MAT sensor? But i have MAT correction turned off. I noticed the hose from the oil filler to the intake is collapsed, maybe this is another cause?

[opethmike]

I had the EXACT same issue with my car when I first converted. If you pay close attention, I'd be willing to bet you see similar but not as adverse swings in your cruising VE as well.

It absolutely is MAT heat soak; I permanently fixed the issue by setting up the MAT correction table with an "anti-ideal gas law", so it looks like this:

29 degrees, -8%
44 degrees, -5%
70 degrees, 0%
93 degrees, 5%
125 degrees, 10%
161 degrees, 15%

[Josh]

AWESOME!

I read a thread about putting in a curve to negate the Gas Law. Ill change that curve and see what happens.

Thanks Mike.

[opethmike]

Hopefully that works for you, it did for me. I tried EVERYTHING for months and months, and nothing worked until I set the MAT correction table.

[Josh]

Ill report back on what happens. The thing that is weird is it seemed to have gotten worse with time. When I first got my car running it would richen a little but now it is much more noticeable. Maybe the sensor is damaged? Im using a closed element sensor, as that is what I had sitting around.

[Spittybug]

I too was getting heat soak. My sensor was in the aluminum adapter between the manifold and my throttle body. I ended up moving it to be in the air duct that runs from my filter in the passenger side pontoon and the throttle body. Now sitting in plastic, away from engine heat. Voila, problem solved.

[Josh]

I too was getting heat soak. My sensor was in the aluminum adapter between the manifold and my throttle body. I ended up moving it to be in the air duct that runs from my filter in the passenger side pontoon and the throttle body. Now sitting in plastic, away from engine heat. Voila, problem solved.

That will be the next course of action if I cant fool it thru the software.
Glad this is a common problem!