AFR change with temperature

[antonch]

I have the Webshop MAT sensor mounted in my intake tubing right before the TB. The sensor is located at the bend and extends down almost to the center of the tube (3" piping). However, I noticed that my car leans out considerably on warm restarts/just letting idle for some time. I changed the sensor calibration to the 1900ohm one and it helped [webshop recommends using this value]. But it still makes me nervous as this is a turbocharged vehicle.

Just driving around helps and after about 3 mins once the temperatures go decrease, the AFRs get back to normal.

What do you think it is?

[dnb]

Sounds like heatsoak.  The sensor is reading the tube temperature instead of the air temperature.

There's a parameter called "Fake airden low limit" that can be used to stop the lean out due to heatsoak - set it to something like 70 and it should be OK.

[Tcal]

I´m having same kind if problem too..
I have that fake airden set to 98.

[GintsK]

I have a lot of experience with Megasquirt where no afterstart enrichment possible if engine above 71°C.
There is additional factor! I think it must be fuel temperature. With locked airden to get AFR 16 or 17 after hot start, if engine was off some minutes, is common.

[antonch]

I just checked, my low density limit is set to 0, or disabled. I am sure changing this value to 70 will help on warm restarts.

I am just curious as to why it leans out even when I drive slowly [the intercooler gets heatsoak]. The sensor is located inside a 90* bend, so there should be plenty of air turbulance to match air temperature to one being read.

[dnb]

There are 2 curves to change when you change the IAT calibration - one for the temperature and one to control calculating the density.  Make sure you replaced both!

My car doesn't seem to do this, even when the IAT hits 50c (usually when idling).

Thinking about it a bit more, if you adjust the density curve a bit, you can get some interesting fuelling effects such as automatic enrichment with increasing temperature when it gets really hot.  Might be worth thinking about.

[Tcal]

There are 2 curves to change when you change the IAT calibration - one for the temperature and one to control calculating the density.  Make sure you replaced both!

So if i set those like tempsensor_upload16*14_2063_2063_256.bat, there should be more to change??? Or is this correct?
   

[antonch]

There are 2 curves to change when you change the IAT calibration - one for the temperature and one to control calculating the density.  Make sure you replaced both!

Thinking about it a bit more, if you adjust the density curve a bit, you can get some interesting fuelling effects such as automatic enrichment with increasing temperature when it gets really hot.  Might be worth thinking about.

Where is the second table located? Is this the table that can be adjusted in the upcoming experimental firmware?

[rob@vems.co.uk]

The format for uploading the files is air sensor followed by coolant so for 2252:

tempsensor_upload12x12 2252 2252 256

The webshop does suggest 2063 so:


tempsensor_upload12x12 2063 2252 256

This will patch the standard firmware with the IAT and CLT curves to represent the

[Tcal]

I just checked, my low density limit is set to 0, or disabled. I am sure changing this value to 70 will help on warm restarts.

Did that cure your AFR on hot restarts?

I´m having same kind of problem too.
I changed my slow IAT sensor to faster one. Much better now.
Haven´t bothered to try to change that Fake airdensity value yet.

[antonch]

I haven't had a chance to try it yet. What sensor are you using? Where is it?
I am starting to think that location plays a big role in this. I can get the car to lean out just by driving in heavy traffic (higher IAT).

I just checked, my low density limit is set to 0, or disabled. I am sure changing this value to 70 will help on warm restarts.

Did that cure your AFR on hot restarts?

I´m having same kind of problem too.
I changed my slow IAT sensor to faster one. Much better now.
Haven´t bothered to try to change that Fake airdensity value yet.

[Tcal]

New sensor is bosch 0 280 130 085, it´s from Audi 1.8T.
Location is about 20 cm before tp.