Jumps in APCYL at Operating Zone Boundaries

[rhit_rs]

I'm in the process of tuning the VE maps on a e67 ecm'd solstice with an m62 eaton and am having issues with sharp drops in the calculated air per cylinder (APCYL_DMA) at the operating zone boundaries. The problem is, the VE map is actually smooth there. I'm using the 2 bar IMTV open table. I've attached screen shots of the VVE map as well as the data logs. Any ideas what could be causing this? Could the VVE table not be accurately depicting the behavior of the coefficients?

I've notice the IMTV closed table had a drop in VVE at one the the speeds I'm having issues at (4000rpm), but is relatively smooth where another drop in APCLY is happening (5500rpm), and the effect is opposite at the other point (2700rpm - VVE goes up, APCYL goes down). IMTV open is the proper table if no valve exists, correct? As a quick check I made the IMTV closed table the same as the open table and regenerated coefficients and a couple test runs yielded the same results as before.

Possibly relevant other threads I've started that give more background:
http://forum.efilive.com/showthread.php?t=10931

http://forum.efilive.com/showthread.php?t=10589

The operating zone boundaries are set as follows:

rpm: 1400, 2600, 4000, 5500
MAP: 25, 50, 80, 120, 150

Thanks in advance!

Josh

[rhit_rs]

Update: We went back to the original Cell boundaries and kept the map the same, best we could. With one region covering from 4200 rpm to redline and 87 kPa up to max boost (~160kPa), the upper region tune was waaay off, but unlike with the modified cell boundaries there were no sudden jumps in Air per cylinder.

Now we're wondering if it would be best to try to modify the VE table using stock boundaries and try to get the tune as close as possible then use other tables like B0148 (Open loop fuel load modifier) and B3618 (PE mode fuel command) to get the AFR dialed in, or modify the boundaries and try to adjust for the unexpected steps in air/cyl with either the VE table itself or some of the other tables. Thoughts?

Thanks in advance!

Josh

[joecar]

I don't know the answer, but I'm following along...

[scdyne]

To each his own. I have done it both ways with boosted E67's, but I'm currently doing what you described.

See my attached VVE, but understand that this is a Centrifugal S/C. We can get away with some assumptions when boosting with superchargers.
Also I have a modified intake cam for high baro.

--- My Modified B8021
27.00 52.75 78.5 104.25 130.00
27.00 52.75 78.5 104.25 130.00
27.00 52.75 78.5 104.25 130.00
27.00 52.75 78.5 104.25 130.00
27.00 52.75 78.5 104.25 130.00


Most of the other work is in the PE from there.

[GMPX]

Josh, just out of interest, when you look at the coefficient numbers, is the last column [MAP_SQ] all zero's?

Cheers,
Ross

[rhit_rs]

Josh, just out of interest, when you look at the coefficient numbers, is the last column [MAP_SQ] all zero's?

Cheers,
Ross

Yes, the last column is all zeros.

[Mileage]

Adam, Thanks for the reply. From your VVE graph, it looks like you have kept the rpm zones, including the large one from about 4200 to redline. I assume you have not seen the dips Josh describes and do not have a problem tailoring the fuel curve in this area. I think I will do the same on the rpm zones. Unfortunately my first attempt at copying the VVE back to the original rpm zones did not look pretty so for this weekend, I will just patch up the table with modified zones. Thanks again.
Ken

[GMPX]

I have to ask this, it states in the Zone settings:
"Note: If you make a change to the values you must save the file then reopen the file for it to take effect on the Virtual VE table."
Now it's probably safe to assume you have reloaded the file since you first started this, but keep it in mind if you do make that change.

The Solstice file I have here shows it has no IMTV, so the first IMTV Open table is all you should need to deal with.

Changing the MAP zones is not abnormal, GM did it on the ZR1 and CTS-V, the MAP5 column is at 135 kPa and MAP4 at 110.

Maybe what you could try is lifting the VE table up at the zone boundaries. I don't know what it could be but maybe there is some other things at play as it transitions the zones.

[Mileage]

Yes, it has been saved and re-opened many times.
It sounds like changing the MAP boundaries works okay but there may be a glitch when RPM boundaries are changed. Even though the VVE tabular values are changing very little at the zone boundaries, the ECM is calculating large changes in Air per Cylinder.