Mat correction formula

[Newsamo86]

Hello i have an m50b25 6 cylinder bmw with ms2 and turboed engine.
When i runnit at monza is tuned at 11.2 afr but after 15 20 minute of track day afr drops down to 10 and aem wideband lamp so afr will go lower than 10.

Is this can be cause because mat sensor is near engine (stock bmw position)?
Or i need single squirt to not hot injector?

ABOUT MAT CORRECTION:
PErcentage of correction is correction calculated on tot inj time....or is a percentage applied only to ideal gas law correction?

Inj time=inj time table×nn linear perc correction
Or
Inj time=inj time table x (gas law factor × nn linear perventage)

[jsmcortina]

Both the formulae you posted do the same thing.

Assuming you are running on a recent firmware, you can adjust the MAT correction however necessary.

EDIT: See also http://www.msextra.com/doc/pdf/html/Meg ... 4-104.html

James

[Yves]

Are there instances in which the mat correction (which is based on the gas law if I'm not mistaken) would not operate correctly ?

[Newsamo86]

Ok so if in non linear correction i put +10 percent is directly added ten percent to calculate pulsewidth directly?

So if cal is 20 ms and i put 10 percent on 40 degree of mat temperature when manifold raise to 40 degree of temp ecu enrich of 10 percent?

Or percentage mean 10 percent is only calculated on basis of reduced fuel at high temp of intake manifold?

[jsmcortina]

The MAT correction does whatever you ask it to do at the given temperature.

The percentage change is before the injector deadtime is added, so +10% does mean +10% fuel.

James

[Newsamo86]

Mayu thanks.

Another issue i have when engine is hot afr drop to 10 very rich.i am rumning on 25 ms at full load.
Does this can make injector hot and retard closing of it?
With single squirt can i solve?
Because in firt 10 15 minutes of track day afr is good 11.2 then drop down 10

[lagos]

If you're having a problem were the mat table seems like its not working correctly, check the injector settings. I found that if your injector battery voltage compensation is not tuned right (as well as dead time), the mat table will do odd things and you will just run around in circles trying to correct it by hand.

Are there instances in which the mat correction (which is based on the gas law if I'm not mistaken) would not operate correctly ?

Yes, when your injectors are not setup correctly. You can check this by adding 10% fuel to your ve table at idle (multiply by 1.10). If the AFR increases by 10% then everything should be working right, but if you get a higher or lower change then the injectors are not setup correctly.

[Yves]

If you're having a problem were the mat table seems like its not working correctly, check the injector settings. I found that if your injector battery voltage compensation is not tuned right (as well as dead time), the mat table will do odd things and you will just run around in circles trying to correct it by hand.

Are there instances in which the mat correction (which is based on the gas law if I'm not mistaken) would not operate correctly ?

Yes, when your injectors are not setup correctly. You can check this by adding 10% fuel to your ve table at idle (multiply by 1.10). If the AFR increases by 10% then everything should be working right, but if you get a higher or lower change then the injectors are not setup correctly.

I checked my injector dead times with an actual test and at several voltage levels. Should be close at least.

[Newsamo86]

Ok a question:

If inj dead time is bad....why afr is good until engime became very very hot?(15 min of track)

About number of squirt....can affect also this?

[Newsamo86]

Correction:

I have a dropping down afr to very rich ( less than 10 afr) from standard 11.2 tuning.

i have The droping down to 10 afr after 20 minutes of track day, so enrichment is Not based on water temp.

If i turno on car and wait engine is hot and then i use at wot i get correct 11.2 afr.

If i make 4 or 5 laps of monza track i get afr down to 10

[suberimakuri]

You need to do a datalog and then look at the change in AFR over time and what other factors (MAT/CLT/OTHER?) that are changing..
Then adjust the corresponding correction tables.

[lagos]

If you're having a problem were the mat table seems like its not working correctly, check the injector settings. I found that if your injector battery voltage compensation is not tuned right (as well as dead time), the mat table will do odd things and you will just run around in circles trying to correct it by hand.

Are there instances in which the mat correction (which is based on the gas law if I'm not mistaken) would not operate correctly ?

Yes, when your injectors are not setup correctly. You can check this by adding 10% fuel to your ve table at idle (multiply by 1.10). If the AFR increases by 10% then everything should be working right, but if you get a higher or lower change then the injectors are not setup correctly.

I checked my injector dead times with an actual test and at several voltage levels. Should be close at least.

Did you tune the battery voltage calibration (MS2), or the dead times at different voltage (MS3)?
I found that setting makes the biggest impact for incorrect MAT.

[slow_hemi6]

Without a tune file and log how are we supposed to help you?

[lagos]

Ok a question:

If inj dead time is bad....why afr is good until engime became very very hot?(15 min of track)

About number of squirt....can affect also this?

As the engine temp gets hotter, MAT compensation should start to compensate by commanding less fuel to the injector based on the idea gas law. If this is not obeying the laws of thermodynamics, than the injectors are not calibrated correctly.

[slow_hemi6]

Sensors can heatsoak and give false readings of the air temp. Can be especially bad on maifold mounted IAT's and turbo cars can blast them with some pretty hot temps and they can be slow to cool down when you go off boost.

[lagos]

Sensors can heatsoak and give false readings of the air temp. Can be especially bad on maifold mounted IAT's and turbo cars can blast them with some pretty hot temps and they can be slow to cool down when you go off boost.

Its true but a heat soaked sensor should read a higher temperature, and make the car run leaner.
I have found heat soak to only be an issue in the summer time when the car is at idle or has been turned off and restarted. Thats when IAT start to climb to unrealistic values above 120F. In those cases, you should adjust the MAT compensation table to avoid the engine running lean.

[Yves]

Did you tune the battery voltage calibration (MS2), or the dead times at different voltage (MS3)?
I found that setting makes the biggest impact for incorrect MAT.

Yes, tuned at different voltages according to ms although the difference had to be converted to %

[Newsamo86]

Is possible injector became too hot and not work good? On track day

Number of squirt can affect this?

[jsmcortina]

Very unlikely.

Look at your datalogs and tune the MAT correction curve.

James

[nathanhardy]

You track at Monza I'm so jealous