Interesting info Special Tool, but I think your mixing two semi-connected outputs. The APE MAF may not be able to record any more CFM than is required to make 340rwhp (and thats good to know because I was wondering how far I could push mine) but your injector duty cycle comes from the data on the chip for that particular amount of air. In my case, my APE K27 chips go to 100% duty cycle at 4000 rpms and my air fuel ratio starts going leaner from there due to increased air but no more fuel...

 

Andy - I am "mixing" nothing.

The APE confuses the DME at 340RWHP. It is difficult to control your AFR past this point using an APE maf.
Because, once again, it reaches 96% of its 0-5 volt output at 340 RWHP - this is a FACT

 

Understand. I thought that's probably what you meant after I wrote that, but calling it duty cycle threw me off. And like I said that's good info, cause I might eventually change my turbo but should be able to keep the MAF.

 

Do you need chips that are actually burned for a MAF, or can standard GURU/Vitesse chips be used, with a MAF, then fine tune with a piggy back?

 

If you have a PB then any good aftermarket chips would do the job. If you do not have a PB, then you MUST custom burn chips on a dyno.

 

With a MAF you should use MAF chips. Even when using MAF chip, you must use the correct transfer function for a particular MAF. Not all MAF are calibrated the same, therefore not all MAF chips are the same.

Many use a PB (or signal massager) to fake the MAF signal to appear like an AFM signal to the DME. You might get AFR correct, but your timing will be off.

 

Not if you make a transfer function in the PB so that you get the same voltage to the DME as the VAF would have given, for the entire flow curve. But then on the other hand you don't get any bigger air flow capacity from the MAF compared to the VAF.
But in general I agree that PB:s should only be used for fine tuning as it is easy to mess up your timing curve.

Tomas

 

The MAF or AFM voltage is used to calculate "LOAD" in the DME. The Load value is used to calculate injector duty cycle as well as timing. (Part Throttle maps are 3D map where load is an index).
The LOAD is directly related to the actual air flow! The MAF voltage if massaged greatly to look like the AFM voltage, then the DME will use the "new massaged" voltage to calculate the "LOAD" value and as you guessed you will end up with the "incorrect Load", therefore you can pick up incorrect timing (remember now your index into the table is incorrect)..

 

I was told this by a vendor selling MAF kits for the 951 guys, that vendor's MAF kits do not include chips but do include a PB.

 

Of course he did, because he's selling the kit. This is a case of "first hand info" is best info. AFM based chips will work on that vendor's kit, but are not "ideal". He just couldn't figure out how to program the chips.

 

Then explain now why 3 MAF vendors keep telling me this after i checked once again with them?

These are big and popular vendors whom informed me, i doubt they are mistaken. Would it be possible that their MAF kits are calibrated in such a manner?

 

If you make a transfer function in the PB so that you, for every value of the air flow, get exactly the same voltage from the PB as the AFM would have given to the DME, then LOAD will be exactly the same in both cases. It does not apply if you just make the PB output an air flow to voltage curve with similar shape as the AFM, every flow value must give the same voltage output. But as I said, then you will limit the MAF's flow capacity to the flow capacity of the AFM.

Tomas

 

Tomas, from your description you are actually building a MAF that flows & generates the same voltage of a AFM. Few more things to think about, a MAF already compensates for changes in temp, while an AFM does not. The AFM chips read the temp and compensates for changes in temps..

So building a MAF that emulates a AFM is useless, and unless you account for changes in temps you still have an issue to deal with. So bottom line, MAF chips are needed for a MAF..

 

Yes, I agree that it's not a great idea to do that. I just wanted to point out that it's possible.
When piggybacks are discussed I always point out the advantage of having well tuned chips as a starting point and only fine tune with the PB.

 

IIRC Danno hit 296RWHP or something around there...



Then the turbo blew itself apart from what I remember