LMM-commanded boost

[killerbee]

Is there a commanded or desired boost PID? I don't see one. My actual boost is not jibing with the tables.

[GMPX]

I don't think so, GM.BOOST2_DMA is the measured boost pressure, we only added that due to the usual boost pressure upper limit problem on the GM boost PID.

[killerbee]

I have too much boost. Don't know what to do with it all. The tables don't predictably reduce it.

[bballer182]

In BBL

DESTCBOST (desired turbo boost (kpa))

[killerbee]

Here is shot. Makes no sense really. B2206 and B2209 tables are asking for 19 psia, transient set to the same, and I am getting 30.

I have no idea what is going on here, but I am afraid of blowing up the turbo if I can't assess and fix this.

[GMPX]

Michael,

I think it's time for the dreaded DMA PID additions .The process the ECM goes through is as follows:

1. First determine if the EGR is on or off, then select the des boost tables based on that, lets assume it's off.
2. Get the values from all 3 boost tables (Low, Med, High).
3. Multiply each by the altitude factor
4. Add all altitude corrected values for a final base boost value.
5. Then it does the ECT & Intake temp correction and adds the result to the previous base boost value for the final des boost value.

I can only think that it might be an issue where the vane position is actually causing the mismatch, overriding the desired boost as it were. In fact, have you tried playing with the Vane position tables only to see if they are having the final say?
There is different strategies for when regen is active, but I am guessing this is not your issue.

Cheers,
Ross

[killerbee]

I am at 14.1 psia, so my factor is 1 for low, 0 for the others.

I did set all boost values in the 3 low tables to 14.1, and ran a test. Attached is the log. It was all over the map, at times looking like it was complying (low vane), and then it would shoot into space. Log attached.

I do get a sense that vane position is driving boost when this happens, but I can not narrow down what tables would be doing it, if any.

I did a controlled vane position test yesterday, and had equally inconclusive results.

[bballer182]

Have you tried using B2232 and B2231 to isolate the problem.
Setting the two tables with high mm3 values would eliminate the referencing of the vane tables and would only look at the desired boost.
Conversely setting the two tables with low to zero mm3 values would make the ecm go solely off the vane tables and disregard the desired boost.

(theoretically)

I've done this a few times to isolate boost/vane issues that have arisen.

[killerbee]

High? B2231 should be lowered, not increased, correct?

[Big D]

I think BB is saying that with high values this will tell the ecm to not reference the vane position, bypassing those tables and only using boost tables. So by raising B2231 it will not enable ecm control of vane pos.

I will test this on Sat to confirm. I am in the same situation as you KB with spikes in boost and no clear references to tables.

Good thread.