How to go MAFless

[noesfacil]

Hi

I currently have a 2002 Z06 with LS6 engine I use solely for the racetrack. The car has custom cam with .600 max lift and a Haltech Air intake with about 460hp at the wheels.

I am considering running MAFless since the MAF sensor recently failed and we were unable to finish a race. My mechanic believes that is unnecessary for racing purposes and we can use MAP only instead.

Although I don't consider myself and expert tuner, I feel confident modifying the tune as I have modified the Timing tables the PE and some of the idle tables as well as other tables over time.

I've read some threads that address this issue and I am willing to give it a try but have the following questions:

1. Do I need to convert to a custom operating system or Is it a setting I can just set to ignore the MAF sensor using my actual OS?
2.If I go MAFless will this affect my actual timing and fuel mixture?
3. Once done, what behavior should I expect from the car that would be considered normal? Idle issues etc.
4. Can someone please provide a step by step of the process?

I really appreciate any help with this issue.

best regards,

NoEsFacil

[joecar]

If you get a MAF DTC, then the PCM ignores MAF and runs from VE... BUT you must make certain that the MAF DTC triggers immediately (you may have to edit tables C6001 and C2901).


If VE is correct then you will see no change (ignition timing is computed from cylinder airmass, which is computed from VE or MAF, whichever one is being used).


If VE matches MAF (i.e. is correct) then you won't notice any other behavior.



Read calibration from PCM and save to file.

Locate table C6001: set P0101, P0102, P0102 to A:1-Trip.

Locate tables C2901 and C2903: set both to 1.

Save to file, then do cal-only flash.


As usual with Corvette, before flashing, make sure other modules are not attempting to talk on the bus.



When PCM ignores MAF and failsover to VE, one of the MAF DTC's should be present (and MIL illuminates).

[noesfacil]

Joe

Thanks for you quick response.

I checked and all of my C6001 table was set to not reported. Does this mean that the computer never knew that the MAF had failed so it never went to MAP?

Where can I find some info about the different setting options on table C6001? What is the difference in behavior between A, B, C and X?

the mils on C6002 were all set to nomil too.

C2901 is set to 13500 and C2903 is set to 18.

I know my VE tables are all screwy because the PE commanded fuel is not close to actual AFR measured by recently installed serial WB.

So I should first validate that the MAF is actually not working by doing the changes suggested and next step is to do an autoVE so I can get that table corrected?

Thanks again for your time an patience 😊

Jorge

[joecar]

Joe

Thanks for you quick response.

I checked and all of my C6001 table was set to not reported. Does this mean that the computer never knew that the MAF had failed so it never went to MAP?

Correct... without a MAF DTC triggering, the PCM assumes MAF is still working, and if it is incorrect, the PCM calculates what it should be and uses that.

Where can I find some info about the different setting options on table C6001? What is the difference in behavior between A, B, C and X?

the mils on C6002 were all set to nomil too.

This is a touchy subject due to emissions laws (there are more to these two tables than what is visible), but in simplest form:

C6001: MAF DTC: 1-Trip triggers as soon as MAF fails (see C2901/C2903), Non-Emissions also triggers the same way.
C6002 MAF DTC: No-MIL prevents the MIL from illuminating when the DTC triggers.

C2901 is set to 13500 and C2903 is set to 18.

when MAF frequency exceeds the threadhold in C2901 the number of times in C2903, then fail the MAF (trigger P0102).

I know my VE tables are all screwy because the PE commanded fuel is not close to actual AFR measured by recently installed serial WB.

So I should first validate that the MAF is actually not working by doing the changes suggested and next step is to do an autoVE so I can get that table corrected?

Since your MAF may be incorrect, you can fail the MAF (cause MAF DTC) and run AutoVE to correct the VE table (use EQUIVRATIO * WO2BEN as the correction).

Thanks again for your time an patience 

Jorge

Jorge, no worries.


Note that AutoVE is a subset of Calc.MAFT (AutoVE being olde and using older wideband pids, Calc.MAFT being newer and more general and using newer wideband pids (Calc.MAFT can be tailored to skip correcting the MAF).

[noesfacil]

Joe

Since I haven't done either AutoVE or Calc.MAFT I guess I will go with the newer Calc.MAFT and skip the MAF correction. I will be doing this probably next week and post back how that goes.

What about the custom OS for SD? We are planning to remove the whole MAF assembly and put in a simple (two wire) IAT sensor instead (less air restriction).

From the COS LS1 Tutorial I gather I need COS 02030001. Will the COS take care of ignoring the MAF by itself without me having to fail it? Where Can I download it and is there any benefit from doing the OS swap?

thanks

Jorge

[joecar]

So you do have a 2002 (GenIII/LS1B) and not an E38...?

[IJ.]

What are tables C2091 and C2903: set both to 1 Joe?

My OS doesn't have these.

[ChipsByAl]

Try C2901 and C2903. They are in the Engine Diagnostics/MAF/Parameters
If you don't see them, post your file. There may be something compatible.
Al

[IJ.]

Nope don't have either of those

thanks Al!

Attachment 15815

[ChipsByAl]

Ok, looks like you have a 2006 not a 2002. Big differences but it appears as if you have the MAF fail mods done. The enclosed photo is from a 2002 OS.
Al