MoTeC Global Forum

I'm experiencing an issuue with fueling on idle with closed loop fueling turned off.

If i tune the engine lambda 1,0 at 80 degrees on coolant and say 40 on oiltemp. My engine wan't like 52%.
When the temp rises to 85c and oil temp catches up to like 80c it starts to run leaner, like lambda 1,1x. I need to increse the fueling to 60%.

I have no idea why it does this. I can expect the engine to run with less friction on higher temps but would it really notice this much?

Fuel temp is about 20degrees when first starting and at about 30c when oil is warm.

Is there a compensation for this? I don't notice much on load. It's mostly at idle i see this difference.

Im aware that the closed loop lambda would regulate this im just curious if this is a normal behavior and if it can be corrected.

There's a Coolant > Temperature > Fuel volume compensation table

I don't know your setup, but the current table settings seem strange to me.

Sean wrote:There's a Coolant > Temperature > Fuel volume compensation table

I don't know your setup, but the current table settings seem strange to me.

It's done like that as a test to prevent the leanout on higher temps. But i feel more i would like to compensate this towards oiltemp. Because even on same temp on coolant engine runs leaner when the oil gets hotter. Atleast what it seems like.

This engine is an s54b32 with ITB, maybe its whats causing this trouble in the first place. Tuning the ITB against map is something i know is not optimal.

Throttle bodies also heat up when the egnine get really warm. Could effect how they flow since they are so close to the cylinder head.

I've noticed this on an ITB engine before. When the throttle bodies heated up the blades were sticking in the near closed position. Get it hot, loosen the screws holding the throttle blades and let the blades seat themselves, then retighten. Fueling will probably be off when cold idling but the engine is only there for a short time. The other option is to make an insulating plate for under the throttle bodies.