Turbo LSJ tuning

[SuperCobaltSS]

Hey guys,

I just recently swapped my 06 Cobalt LSJ over to a turbo from Supercharged and im having some issues with tuning, I cant get the fuel trims to even out at all. Its either way negative or way positive. Im running 2.5" piping that whole way around and the maf is in a 2.5" pipe also. It seems to read just fine but the fuel trims are atleast -20 or positive 20 at some points. The only thing i could think of would be the 02 sensor being bad? unless i am doing something totally incorrect with the tune.

Running 80# injectors on E85 with a Precision 5531CEA turbo on 15lbs of boost. AEM320 Fuel pump

Any help would be greatly appreciated!

Cobalt SS Turbo Rev5.hpt
turbo run 1.hpl
turbo run 2.hpl

[CatnipG5Bandit]

Have you calibrated the MAF for the 2.5" intake tube using a wideband and error histogram?

[SuperCobaltSS]

Yeah i think im getting it figured out, It seems to be alot more sensitive to the numbers changing in the table vs the percent of fuel its adding or removing.

[SuperCobaltSS]

Did some more logging on the way to work. Tweaked the tune a bit. Fuel trims are still off. I edited the tune and will drive around on lunch see what it does. Kinda seems like the fuel trims are getting dialed in but not sure. Also it seems to idle surge really bad when its cold, Runs 14.7 then lean then 14.7 then lean until it gets about 100 degrees. Any ideas?

run to work.hplCobalt SS Turbo Rev8.hpt

[MarkTucker]

By the looks from you log, you are needing to dial in the MAF Calibration table. Fuel trims are pulling alot of fuel out in idle and cruising areas and are adding fuel in high rpms with low and medium boost levels.

[cobaltssoverbooster]

did you add 45% to your fuel tables for your stoich afr change? if you change stoich you need to add the percent of change to your fuel tables in order to even get close on first start. just telling it to run stoich richer will cause a massive offset.
14.69/10.1=1.454 or 45.4% positive increase.

turn defco off it will lean some cells out and mess with your cell averages. at a minimum you can filter out the tps threshold for defco to prevent those from showing up but when you do that you end up not plotting data on the low end of the tables.
defco is a shutdown feature so it doesn't care what the cells are valued to when its active, if it falls in the parameters it just shuts fuel off period. so tune with it off then turn it back on.

make your main spark tables match each other, you have two different idle and off idle timing values which allows the ecu to dance ignition timing.
and set your maf fail high under engine diagnostics to 16,385 (max value) when maf tuning. the maf likes to throw codes when it goes out of range. ive seen them thrown on factory setups with pulleys as large as 2.8" and the turbo swap is notorious for throwing the codes when not corrected for. This can also be avoided by placing it in a 3" maf tube to dumb the sensors activity into a lower hz range.

[SuperCobaltSS]

did you add 45% to your fuel tables for your stoich afr change? if you change stoich you need to add the percent of change to your fuel tables in order to even get close on first start. just telling it to run stoich richer will cause a massive offset.
14.69/10.1=1.454 or 45.4% positive increase.

turn defco off it will lean some cells out and mess with your cell averages. at a minimum you can filter out the tps threshold for defco to prevent those from showing up but when you do that you end up not plotting data on the low end of the tables.
defco is a shutdown feature so it doesn't care what the cells are valued to when its active, if it falls in the parameters it just shuts fuel off period. so tune with it off then turn it back on.

make your main spark tables match each other, you have two different idle and off idle timing values which allows the ecu to dance ignition timing.
and set your maf fail high under engine diagnostics to 16,385 (max value) when maf tuning. the maf likes to throw codes when it goes out of range. ive seen them thrown on factory setups with pulleys as large as 2.8" and the turbo swap is notorious for throwing the codes when not corrected for. This can also be avoided by placing it in a 3" maf tube to dumb the sensors activity into a lower hz range.

Thanks for the info, That definitely helps. I forgot to turn off DFCO for sure. I turned up the MAF Fail to 14K i can change it to 16 too. I did add 45% fuel too. I had it on E85 before just added a turbo over winter and got rid of the supercharger. Basically just tuning for the turbo now.

[SuperCobaltSS]

Well i got most of the issues ironed out. Ran a bunch of logs and got the fuel trims most of the way sorted out. One thing i cant figure out is on cold start it almost seems like its surging, The Wideband goes all over the place hits 22.4 then comes back a few times. once it gets to about 90 degrees coolant temp or so it stops.

EDIT: Looking at the log file maybe its my fuel trims?

Cold Start Lean Surge.hpl

[MarkTucker]

The fuel trims are adding around 25% fuel to get it to run right. Do you have a table setup in the scanner to scan fuel trims vs MAF Calibration in the histrogram. It might be able to help you out. And then you could copy and paste special(multiply by % or multiply by % - half) the scanner table to the editor table. And I don't believe it is a issue with your tune, but I have always set my E85 stoichiometric ratio to 9.87.

[SuperCobaltSS]

I have that table setup to show the fuel trims and how far off they are if thats what you are referring to then yes.


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[Area47]

the trims are horrid. you have a lot of work ahead of you. Are you using the afr error vs trims for the maf tuning? Reason I ask is very rarely will you see trims active above 6500 hz unless you're hanging the rpms up there.

[MarkTucker]

Trying to get the fuel trims dialed in a bit better and see if then if your cold starts are any better. Once you get trims closer and it still has a bad cold idle. Post up another log.

[SuperCobaltSS]

the trims are horrid. you have a lot of work ahead of you. Are you using the afr error vs trims for the maf tuning? Reason I ask is very rarely will you see trims active above 6500 hz unless you're hanging the rpms up there.

I never figured out how to setup a table to do that otherwise i would. Any help would be much appreciated!

[cobaltssoverbooster]

the formula is on the hpt forum in many places Just search afr error formula.

Iirc it should be 100* (actual afr-commanded afr)/(commanded afr)