How do you tune for SD/Boost an E38 with no VE table? Can somone look at this tune?

[Blackbird427]

I just bought this 2009 Z06 with an LME 427 LS and twin turbos. Seems to run good, makes great power. I downloaded the tune and opened it up in the VCM Editor... and I cannot determine how this car was tuned. It appears that the MAF was disabled by altering the on/off coolant temps, to go speed density... but the VE tables appear to be all zeros? It has a 2 bar OS installed, and a modified 2.5 bar MAP sensor.

Ive tuned with EFILive with an LS1 in my past but I am new to HPTuners. Can someone take a peek and let me know this was tuned? Am I must missing the table?

Thanks in advance.

Turbo Vette Original Tune.hpt

[blindsquirrel]

It's in MAF-only... Dynamic Airflow disable 500/reenable 400. The min/max temps for P0101/106/121 is just disabling the diagnostics for those codes, not the sensors themselves.

Out of curiosity, do you know what MAP sensor it uses? Any part numbers/ID on it?

[Blackbird427]

So its MAF only... so one more dumb question.... is there the equivalent of a "Command AFR" table that would enable me to lpok at a STFT modifiers to determine where I need to lean and richen?.... or is the Low and High MAF response curves the only way to tune mixture (excluding modifiers and trims) ? I noticed the MAF curve is sort of curvy and not exponential so it appears like thats the only way I can tune and alter mixture in addition to boost enrichment. I have been tuning R35's for the last two years and its tough to remember the GM stuff. Thanks for the help!!

The MAP sensor is one of the DPE Corvettes modified MAP sensors: https://www.dpecorvettes.com/2.5-bar-map-sensor.html Plugs right into my LS7 intake.

It's in MAF-only... Dynamic Airflow disable 500/reenable 400. The min/max temps for P0101/106/121 is just disabling the diagnostics for those codes, not the sensors themselves.

Out of curiosity, do you know what MAP sensor it uses? Any part numbers/ID on it?

[blindsquirrel]

Ah, your tune file has the wrong Offset value, that's why I didn't recognize it. 13.21, should be 10.21. (actually, I fried my brain one night trying to calc the offset for that NXP sensor element (I am NOT a math person), and I think even 10.21 is wrong, by the math it theoretically hits 0v at exactly 10.00kPa... but I would change it to the specified number from DPE, it's closer to 10 than 13, at least)

It's using MAF only, and WOT is being 'tuned' by power enrichment and boost enrichment. People smarter than me tend to frown on doing it that way. More than that, like if the MAF curve looks like something typical for that combo, I'll have to leave to others. I'm a hardware/config/wiring guy.

[Blackbird427]

So basic old school MAF tuning (MAF cal tables, PE and BE) got it.

So... how is an AFR commanded on the E38? In the GT-R world there is an actual AFR commanded table and your STFT's leg logged, smoothed, and applied to your MAF curve via some complex math to get them within a few %. But here... if no Commanded table... how are STFT's used and referenced?

Ah, your tune file has the wrong Offset value, that's why I didn't recognize it. 13.21, should be 10.21. (actually, I fried my brain one night trying to calc the offset for that NXP sensor element (I am NOT a math person), and I think even 10.21 is wrong, by the math it theoretically hits 0v at exactly 10.00kPa... but I would change it to the specified number from DPE, it's closer to 10 than 13, at least)

It's using MAF only, and WOT is being 'tuned' by power enrichment and boost enrichment. People smarter than me tend to frown on doing it that way. More than that, like if the MAF curve looks like something typical for that combo, I'll have to leave to others. I'm a hardware/config/wiring guy.

[blindsquirrel]

The very simplified version because this is about as far as I really understand it: Assuming closed loop and trims are active, the trims add/subtract fuel to make the O2s read stoich. It always targets stoich except in open loop PE. The ECM goes totally blind in open loop, and it has no choice but to assume what's in the MAF/VE/VVE tables are the truth and then multiplies whatever's in there by your PE/BE. Any errors get carried over when it goes into PE. Thus, if you want a commanded EQ of 1.22 to actually result in an EQ of 1.22 you have to have the MAF/VE/VVE corrected first.

The lazy-tuner 'raping the PE' tuning method is assuming the trims will be able to correct whatever errors when in closed loop, and then adjusting PE/BE to whatever it takes to make it read the desired number on the wideband at WOT. If it takes commanding 1.43 to get the wideband to read 1.22, who cares as long as the check clears the bank, right?

[Blackbird427]

Yes makes sense. The guy who built the car had it "professionally tuned" but even with my limited experience I had a feeling something was up with what the tuner did. Thank you so much for the info. I really appreciate it.

So Im curious as to your (and everyone else's) advice regarding a boosted LSx.... stick with a MAF only tune, use a hybrid tune (MAF down low and VE up high and tune PE/BE), or use a 100% speed density tune with the 2 bar OS thats installed?

The car also has Alky injection but its not controlled by the ECU

[mbray01]

without looking at your tune, or knowing the vehicle. I tune both airflow models, then run the vehicle in maf only. gm uses sd for a sanity chaeck, as well as for torque modeling, so even for maf only, your ve tables have to be correct for things to operate properly. now this is all assuming your not backed against airflow limits, or table limits, which you will find in e38 ecms. I am not a fan of alky injection with the exception of air charge cooling, and only with a 50/50 mixture. I never use alky for fuel enrichment. correct the fuel system first, if thats what is happening