Modelled fuel - charge temp table - idle mixture leans out as IAT climbs

[Rozsko]

I know I am asking lots of questions nowdays and I am sorry for that, but I like to understand how things work and I like if things work as they are supposed to.

On the link below you can find a log I recorded today. Cold start and idling for quite some time so that the IAT can climb significantly.

As you can see the charge temp table at idle is pretty much 0 right now but previously I had that with various values, but so far I did not find the sweet spot. IAT comp table is 0-d out as I am running modelled fuel.

My IAT sensor is in the intake mani, just under the throttle body.

There are three issues I don't understand.

1) why the mixture leans out as IAT climbs if IAT compensation is part of the equation?

2) why is the idle more stable when the engine fan is on? This one seems to be caused by more ethrottle control, but the integral gain is 0.05 already and it doesn't really help if I make less or even 0.

3) why the mixture is more lean when the fan is offand less lean when the fan is on?

log: https://1drv.ms/u/s!Ale4oyMCOgLThMl2inBDi2JVMdozMA

current map is attached

Thanks a lot

Béla

2020.06.23 - WOT IGN.pclx

[Adamw]

1 hour ago, Rozsko said:

1) why the mixture leans out as IAT climbs if IAT compensation is part of the equation?

You need to bias it more towards water temp at idle as the air is moving through the port slowly it picks up more heat from the hot manifold and water jacket.  Typically charge temp approximation numbers will be up around 70-90% at idle.

 

1 hour ago, Rozsko said:

2) why is the idle more stable when the engine fan is on? This one seems to be caused by more ethrottle control, but the integral gain is 0.05 already and it doesn't really help if I make less or even 0.

You can see the E-throttle target is stable, but your TP is bouncing around a lot, this means your E-throttle PID needs work (not idle PID).

 

1 hour ago, Rozsko said:

3) why the mixture is more lean when the fan is offand less lean when the fan is on?

I suspect due to the throttle bouncing around as above, the throttle stablises a little when the fan is on so MAP is much more stable and therefore PW is more stable.  The unstable TP is also causing a little bit of accel enrichment to kick in.  

[Rozsko]

3 hours ago, Adamw said:

You need to bias it more towards water temp at idle as the air is moving through the port slowly it picks up more heat from the hot manifold and water jacket.  Typically charge temp approximation numbers will be up around 70-90% at idle.

Yeah, That's where it was, but even then the result wasn't pleasing. So this lean-out means that the engine is actuall breathing cooler air then what the ECU is accounting for, right? And if so, then if the table is biased towards the ECT, then the ECU will account for even more hot air hence resulting in an even leaner mixture. Or am I thinking to the wrong direction?

anyhow, I will set it to 100% ECT and record an other log to see.

3 hours ago, Adamw said:

You can see the E-throttle target is stable, but your TP is bouncing around a lot, this means your E-throttle PID needs work (not idle PID).

Thanks for the suggestion. I will take a look at that.

 

3 hours ago, Adamw said:

I suspect due to the throttle bouncing around as above, the throttle stablises a little when the fan is on so MAP is much more stable and therefore PW is more stable.  The unstable TP is also causing a little bit of accel enrichment to kick in.

I guess will see if the eThrottle PID will help. Thanks again.

[Adamw]

6 hours ago, Rozsko said:

Yeah, That's where it was, but even then the result wasn't pleasing. So this lean-out means that the engine is actuall breathing cooler air then what the ECU is accounting for, right? And if so, then if the table is biased towards the ECT, then the ECU will account for even more hot air hence resulting in an even leaner mixture. Or am I thinking to the wrong direction?

No, with charge temp approximation biased more towards air temp the ecu thinks the charge temp is varying more than it really is so it applies more compensation.  ECT is more stable so you need to bias more towards that so it gets less variation in the compensation applied.  You have to retune the VE table everytime you change the charge temp approximation.

[Rozsko]

9 hours ago, Adamw said:

No, with charge temp approximation biased more towards air temp the ecu thinks the charge temp is varying more than it really is so it applies more compensation.  ECT is more stable so you need to bias more towards that so it gets less variation in the compensation applied.  You have to retune the VE table everytime you change the charge temp approximation.

Understood. I thought this is really just a linear function between ECT and IAT.

Anyhow, yesterday I did an other session with 100%, which was overshooting a bit and then going to the richer direction (not much though), and today I have done one more session with 67.7%. This is not overshooting now, but it reaches the stable mixture later, so I'll have an other run once the engine cools down at 75% and see if it improves anything.

Here is an overlay of all 3 runs so far:

Also, wanted to ask about warm up enrichment.

Is that something that should be zeroed out in the modelled fuel? As you can see above (the yellow trace) I turned it off (zeroed out) but even with that, after start up there is a ~15% difference compared to operating temp. And obviously if I correct the current VE error at idle and apply warm up enrichment, the mixture will be considerable richer then it should be based on the numbers. (actually this is why I started to mess with the charge temp approximation)

Thanks

[Rozsko]

Not sure what's going on right now either with my browser or with the forum, but right now I can't attach pictures.

Anyhow, had the other session done and the 75% came out quite well in between the red(ish) and yellow trace on the screenshot in my previous post.

So I think I'll stick with that.