Interpolation or Switching between cells ?

[gmh308]

Anyone have any idea whether the E38 (etc) simply switches from cell to cell on table lookups, or interpolates between two cells?

I understand that the ECM interpolates between the high and low octane tables based on the octane scaler, but on a regular table, for example the knock sensor sensitivity calibration (cyls A thru H) does it simply look up one cell until it gets to a switch point between two cells, like @ the 50% point on rpm/airflow axis?

Question arises out of the newer supercharger calibrations (LS9/LSA) where the 200mg and 300mg cell columns have been dropped to give two more columns to support the higher airflows up to 1300mg vs 900mg.

When looking for a number where these columns are missing at the lower airflows, does the ECM simply swap cells when it gets half way between 100mg and 400mg airflow number? At 250mg? For example .



Or work out the required number based on a linear calculation? (which would then apply for all intercell numbers).

Thanks for any feedback!

[swingtan]

My belief was that it interpolates.

The actual cells are anchor points for the actual data and the ECM will ramp between them as needed. This is seen in the spark tables like B5101, where the commanded spark will be blended between cells, as well as the OL fueling tables like B0141.

So I'd say that for this table, the same would apply with the values being calculated for the flow between 100 mg and 400 mg.

Simon

[gmh308]

My belief was that it interpolates.

The actual cells are anchor points for the actual data and the ECM will ramp between them as needed. This is seen in the spark tables like B5101, where the commanded spark will be blended between cells, as well as the OL fueling tables like B0141.

So I'd say that for this table, the same would apply with the values being calculated for the flow between 100 mg and 400 mg.

Simon

Thanks Simon. So there is linear interpolation in B0151 & B0141. Thanks for confirming.

Smart little ECM's arent they! Very powerful to get all this done in the blink of an eye.

Ian

[swingtan]

If they can calculate the VE on the fly, this would be pretty easy......

[joecar]

Ian, so what are you going to put the LS9 in...?

[GMPX]

Simon is spot on, it doesn't jump from one cell to the other, that is why there is no point getting carried away about your spark not being within 0.2 degrees of what you commanded at 'x' RPM and airflow.

Cheers,
Ross

[gmh308]

If they can calculate the VE on the fly, this would be pretty easy......

Good point!

Thanks Simon and Ross.

Joe.....Be nice to have that kind of folding lying around . For the price of an LS9 crate motor (US$30k list) we could buy a complete VE/G8 SSV out here. Or maybe two by the time the crate was shipped and taxed. , or at least an SSV and a Yaris for the missus!

Was looking at the ZR1 knock sensors to see how GM's knock calibration differs with the forged pistons. Searching for the Cadi LSA cal, but that is turning out quite evasive so far!

[GMPX]

2009 CTS-V Tune below (It's an E67 ECM).

It is amazing how much an ECM does in between firing events, of course it is nothing compared to say an Xbox360 or PS3, but when a computer is running an blown V8 it's a little cooler!

Cheers,
Ross

[gmh308]

2009 CTS-V Tune below (It's an E67 ECM).

It is amazing how much an ECM does in between firing events, of course it is nothing compared to say an Xbox360 or PS3, but when a computer is running an blown V8 it's a little cooler!

Cheers,
Ross

Thank Ross. Most appreciated. Different again from LS9. Cyl B (2?) has some knock really desensitized 3300-3800. Just gotta track down the T43 cal now and see how much different the 6L90 is set up. And yes a blown V8 gets my attention .

Have a good weekend all!

Cheers Ian!

[ScarabEpic22]

When anyone gets said CTS-V TCM T43 cal please let me know! Trying to figure out how to swap a 6L90E into a TBSS, its electronics...

And if someone has CTS-V ECM and TCM pinouts that would be great too!