MAT vs TPS

[AVP]

Since this is equally interesting i have this question:

people are sayng to use this as per ideal gas law. BUT i also suffer from heatsoak. So i have to increase the values on hot IAT to compensate rather than degrease them as per ideal gas law. So what is the best thing to do then and how? Cause if i do the VE table first and then the MAT/TPS table, then i will notice that on cold weather the EGO most likely will be taking fuel out of the equation to keep lamda still on cruising and perhaps on high boost i will be more rich than i want to. On the other hand, on hot weather, the opposite might happen. So should i fix somehow this table first and then the VE?

[mattias]

For heat soak issues the only cells that you need to raise the values for are on the 0% TPS line.
Once you use the throttle the problem goes away quickly and EGO correction takes care of any still lingering heat soak.

Preferrably, don't tune this table until you have tuned the engine with the car always moving. The heat soak value is dependant on ambient temperature too, so if you've tuned it at 20C and get heat soak problems the adjustment is made above that temperature.

[AVP]

so does that mean that i should have that table as you do in your config? using 94 for the hotter IATs and above 100 on the colder and then fix my VE table  OR first do the VE table while having the mat.tps all to 100?

[mattias]

OR first do the VE table while having the mat.tps all to 100?

No. Never set "all to 100" ever. That removes the whole relationship of IAT and the fuel calculation.

Tune the VE table first, before changing the 0% line of the MAT/TPS enrichment. Then tune the table at idle =  0% TPS,  by watching EGO correction and minimize it while the IAT (falsely) rises.

[AVP]

ok

but i should use your MAT/TPS table to begin with? with the 119-113-106-100-94 values from -40 to 60 IAT?

is that something that generically should be used on these firmwares and only make small adjustments for heatsoaks etc?

[mattias]

Yes, use my tables with those values. They should be used overall to follow the laws of physics. You have understood correctly.

My values are also available in the "defaultfirmwareconfig" directory for each firmware version, so just drag'n'drop one of those config files over the dialog for the table and go from there.

[mattias]

The normal ambient temperature column that the car is tuned in should be the reference. At idle = 0% TPS and higher temperature you need to increase the values - often to the same enrichment that is used in the column for the ambient temperature - because that is actually the temperature of the air that the engine consumes, so it needs that same enrichment.

Some engine compartments heat soak easily, and sometimes the temperature actually does increase and what you're seeing is not heat soak. On Audi S4 I've had to compensate just a tiny bit for heat soak.

[AVP]

ok thanks

For the heatsoak issue i must admit that my car was becoming leaner on all cruise areas and TPS up to 20-25%. For reference, motronic ECU does the opposite regarding IATs. ON hotter iats it enriches and on colder it leans out. This i have been told by a tuner of motronic ecus.

From my experience of my car so far:

Up to 20-25ish TPS on IATs above 25, the car starts to seem that it is leaner and the VE table is not enough to cover that area.My car heatsoaks easier due to an aftermarket inlet manifold which is thinner and it affects the IAT sensor. I have used a phenolic spacer now but the effects are still there when the IAT is above 25C.
Above that area, because my map was not using closed loop , i have never had a problem keeping mixtures to the targets i set. These were done with megatune.

Your suggestion is: use 94 on any temp above 20, compansate for heatsoak on lower TPS values, and let tune the VE on the reference ambient temp of the car is used at.

My question will therefore be: If i tune the car to 0.80lamda for 10C IAT, and this works fine, once the IAT goes to 30C, and the table there iinstead of 100 has 94 as a value, will my car go lean? or will it still be 0.80? Am i at risk of melting things?

Should i do a trial and error thing?Should i leave it 100(at the end of the day worst thing that might happen is to get the car richer instead of leaner) and wait until the summer time and retune those areas by changing the MAT/TPS table only and not the VE?

[mattias]

My question will therefore be: If i tune the car to 0.80lamda for 10C IAT, and this works fine, once the IAT goes to 30C, and the table there iinstead of 100 has 94 as a value, will my car go lean? or will it still be 0.80? Am i at risk of melting things?

To keep the same lambda the MAT/TPS enrichment needs to be lower at the higher IAT, it will be alright.

I recommend to move the IAT sensor away from the intake, to just before the throttlebody.

What Motronic does is quite different, as it directly measures air flow. The MAT/TPS enrichment table is a direct concequence of the fuel calculation (Speed-Density).

[AVP]

due to the way the engine is done, i cannot move anything at the moment. The IAT is at the same position as the original is, so with the phenolic spacer in place it should be better than what it was before.

I see what you mean. I will have to test and go i guess. I will make the necessary changes to the table and leave the 0-5TPS areas for heat soak purposes.