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).

[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!

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
15816

[limited cv8r]

A read through these may help you out as well.

[IJ.]

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
15816
Thanks!

[Taz]

At a glance, that tune is from an early E38 and is configured for a 6.5L engine, large injectors, and a 2.5 Bar MAP ... fairly far from an LS6.

[IJ.]

At a glance, that tune is from an early E38 and is configured for a 6.5L engine, large injectors, and a 2.5 Bar MAP ... fairly far from an LS6.
Correct Taz, was just curious about the C2091 and C2903 Joe mentioned as I'd never seen them before ;)
(still have my L plates on for all this)

[darcy]

Ian, for yours it's
C2901 = C0301
C2903 = C0303

[IJ.]

Ian, for yours it's
C2901 = C0301
C2903 = C0303

Thanks Mark!

I do have a Gen3 car as well just havn't messed around with it much ;)

[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]

Typo: C2901 rather than C2091, sorry my fat-fingered typing :doh:

[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 

JorgeJorge, 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).

[joecar]

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

[Taz]

Hello Joecar,

Looks like IJ. (Ian) has an E38 - and jumped in on noesfacil's (Jorge) post, who has an LS1-B. Confused myself ...


Cheers,
Taz

[joecar]

Taz,

Ah, I see, thanks...

Cheers
Joe

[IJ.]

Sorry guys, was looking at new posts and didn't realise what section it was in...

[joecar]

No worries, stuff happens.

[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]

Calc.MAFT:
are you going OL (wideband only) or CL (LTFT and wideband)...?
If you're going OL then you have to modify the Calc.MAFT procedure as follows:
- in calc_pids.txt edit CLC-00-315 to use CALC.WO2BEN instead of CALC.SELBEN, <-- you don't have to do this if you're SD/MAF-less.
- in your scantool VE map use CALC.WO2BEN as the pid on the Data tab;
and like you said, do the VE correction portion and ignore the MAF calculation portion.

COS:
yes run a COS because in SD (MAF DTC present) this retains the adaptive spark (sliding between HO and LO spark tables as knock is detected);
in OL it also gives you very good control over OL fueling.
You will still need a MAF DTC to trigger, and physically removing the MAF will do this, altho you may have to set C6001 P0101,2,3 to 1-Trip, and C2903 to 1 time.
02030001 comes with you're V7 software install...
the 02030001 file is "empty", you full flash it first, and then from your last tune file you do a cal-only flash to populate the flashed COS with your tables...
and then you have to edit B3647 and fix any out-of-range parameters in the Custom segment.

If you run SD with the non-COS then you lose the adaptive spark feature (i.e. with MAF DTC present, the PCM runs from the LO spark table).

[noesfacil]

Found the COS. I guess I am going that way. Thanks for all the info.

I will surely have more questions before I do the actual process but I want to read some first.

Best regards,

Cheers from Puerto Rico:cheers:

[noesfacil]

Joe

What do you mean when you say that the COS gives m better control over Open Loop fueling? Do you recommend this? I like the idea of dealing with one specific sensor vs 2 approximate sensors. How do I get the pcm to use the Wideband reading and ignore the ltft?

I have always thought that the adaptive spark is not an issue for me since I am using 104 octane fuel. So I have both HO and LO the same.

Thanks

[joecar]

COS has table B3647 "Open Loop Commanded Fuel" which has the form RPM x MAP...

compare this to table B3605 which has form ECT x MAP.

The COS replaces B3605 with B3647.

[joecar]

If you have HO and LO the same, it might be simpler for you to run the non-COS stock OS...

with the stock OS, when a MAF DTC is present, the PCM runs from the LO table.

[joecar]

...

How do I get the pcm to use the Wideband reading and ignore the ltft?

...

To do the Calc.MAFT procedure in OLSD (i.e. Open Loop and MAF-less):

a. set your tune to disable CL/LTFT/STFT (B3801, B4205, B4206);

b. make sure your MAF will fail (C6001, C2903);

c. in your scantool VE map use CALC.WO2BEN as the Data pid;

d. do the VE correction (using CALC.WO2BEN as the correction factor);

e. ignore the MAF calculation (i.e. CLC-00-315 does not need to be modified since you're ignoring it).

[noesfacil]

B3647 sounds very interesting and more intuitive to work with. I think I'll go the COS route because of that.

With regards to my question about the pcm reading the wideband values, what I was wandering is once you tune and get your ve tables right, does the pcm need feedback from the Wideband for operating the engine. But Now I think I get it. Use the Wideband to get the VE right using Calc.MAFT. Once calibrated the engine will only use the VE tables, RPM and MAP values to calculate comanded fuel while ignoring MAF and LTFT/STFT.

Is this correct?

By the way, thanks again for your patience :>

[joecar]

No, the PCM does not read the wideband...

The PCM reads the narrowband O2 sensors and calculates trims (STFT and LTFT) which it applies, and repeats in closed loop manner.

The wideband is read by you (via your FlashScan V2)... you use the wideband lambda to calculate and apply a correction factor to the VE table.



Yes, correct: fail the MAF (DTC triggers), disable CL/LTFT/STFT, use WO2BEN (calculated from wideband lambda) to correct VE using Calc.MAFT procedure.

Yes, correct, if you leave the MAF failed and leave CL/LTFT/STFT disabled, then PCM will run OLSD (OL = open loop, SD = speed-density/MAF-less).



No problem.

[noesfacil]

Got it.

Thanks for confirming. I'm definitely giving a try to OLSD using the COS.

I'll keep you posted on how it goes.

Thanks

J