a4 2002 z28 ported 5.3 heads, lunati cam, 85mm truck maf, aero 340lph, and some 34lbers.

The pull starts off decent with a good AFR and then the computer starts throwing a ton of fuel at it and it wont make any power. It is really irratic. May do it sooner in the pull or a little later.

Only thing used in my combo is the injectors. They sat for two years. Any guesses on this one?

 

Remove the MAF, and run it it open loop SD. Once you get it running/tuned decent that way, add back your MAF and tune the MAF. I made the mistake of assuming that since I was using a factory MAF, and a factory calibration table for it, that it would be pretty close. I was wrong, and until I went back to basics, and got rid of the MAF, never could get the tune right. After I had the car running well on a SD tune, I went back and added the MAF with some significant changes to the table. While running the car in SD, I data logged the MAF vs dynamic airflow, and used that to calibrate my MAF correctly. After those adjustments were made fueling was accurate.

 

Did you load the MAF table to go with the 85mm MAF, or still running your factory configuration?

 

I didn't do anything. The car is being tuned by someone on a dyno.

I bought the 85mm maf and figured a realtune would fix it.

 

Is the tuner aware of the MAF change?

 

Yes he is. He is using hp tuners to flash my computer. It was having issues isling, staying running. It goes through the pull, but goes so rich. Put some 39lbers from a fox bosy in. The car idles on its own now. Hopefully it was a fix. Going back on the dyno this week.

Can the maf cause any rich issues? I have a stock maf there as well.

 

If the MAF transfer table isn't calibrated correctly for the new MAF it will cause problems w/ fuel delivery.

From your statement on the injector swap, either the old ones had issues or the tuner didn't configure the PCM correctly for them.

I'd be prepared to swap the old MAF back in.

 

Old maf will take two seconds to swap. The injectors came out of a 98 vette with a procharger. They were in there in 98 as well. So they were a little bit older than i knew. So i have strong feeling.

 

Is there a stock gm 39lb injector that will fit my car, or an aftermarket injector.

 

FAST has a 36# one, and Bosch has a 42# one. Best to ask your tuner which injector he has the configuration data for, there is much more to setting these up than just scaling the injector flow rate table.

 

The richness is probly from the maf. As said above the best way to tune it in is Sd tune then calibrate the maf in after.

 

Hmmm well if these injectors work the car will be tuned on them. They have an adapter clip to fit. I have to use zipties to hold them in ecausr the metal fasteners wont fit. I don't like that. I figured i would swap later. Fuel pressure is at 51, so im pretty sure it ia mechanical. I will swap the maf as well if the problem persists!

 

Would i literally run an open tb and tell the tuner to tune it like that, then once it is running put it back on and have him mess with the maf?!

 

No, you don't take the MAF out - just disable it. Your tuner should know how to tune the VE in speed density and then tune the MAF...

 

I will let him know.

 

You just unplug the maf and make sure the iat still works.

These tunes Ussually cost more. They are not the 300 - 400 dollar tunes Ussually.

 

I appreciate the info. The only thing I do not get is assuming the injectors werent the issue, or the maf wasn't the issue either. Why would there be such a hard time tuning this car. I'm new to ls stuff, but it is ported heads and big cam with some extra fuel?

 

A MAF based fueling error ought to at least be consistent.

Things that will act inconsistent include COT protection
(fuel dump under sustained load) and IAT/ECT based fuel
adders (responding to assembly thermal drift, or flaky
connections perhaps shaken by vibe).

 

What is cot protections? As far as the iat goes it is inside the maf, I have that casper 3 to 5 pin connector. Any known issues with that? It is 8 ft long (more like 10") and had to be zipties to the maf itself. I know the connections were good, but when I go back I can check. Everything else was nice and tight.

Thank you for your response.

 

COT - Cat Overtemp Protection - if your tuner didn't disable it, it will add a bunch of fuel on hard pulls...