Pmas 85mm for 24lb injectors issues

[AntiFederalist]

Just rebuilt my t45, put in a upr k member and long tubes. Had 24lb I bought years ago so I thought now would be a good time to throw them in as well. So I ordered the pmas maf part# MH85F-MT724. Car will hardly idle at all, maf count readout on the sct which i can't tune the car with because the car came with a tune on it, reads 4 to 550 and everywhere in between constantly. The paper that came with it says it was calibrated for 02-04, my car is a 96. Pmas said the calibrations are all the same. Don't know where to go from here besides try to send it back.

 

[95opal]

Your tune is for 19# injectors hence why your having issues with the 24s.

 

[AntiFederalist]

Your tune is for 19# injectors hence why your having issues with the 24s.

I know it's not the right way but the maf is supposed to trick the ecu to compensate for the bigger injectors. It's calibrated for 24s. And the weird thing is the stock maf it runs just fine with the bigger injectors, definitely rich, but runs great. Stock maf readout stays right around 150

 

[96blak54]

I remember the old OBD1 trick to run bigger injectors was to get the maf that had the correct calibration for injector size. Thats not the case with obd2. The computer must be tuned. I have a MAF extender that interprets the maf reading from the maf into what you want the computer to read. Its works as it should, but still complicates the cars tune and isnt consistent

 

[95opal]

I know it's not the right way but the maf is supposed to trick the ecu to compensate for the bigger injectors. It's calibrated for 24s. And the weird thing is the stock maf it runs just fine with the bigger injectors, definitely rich, but runs great. Stock maf readout stays right around 150

The MAF transfer rate for your stock unit is different from the PMAS. The ecm can't interpret an unknown transfer rate. This is why the stock unit may run Ok but on the rich side because of the 24s, while the PMAS unit is not able to run because the elm has no clue what it's transfer rate is.
Why the 24s anyway? If the car was tu ed and ran fine on 19s leave it. There is nothing to be gained with the pmas unit

 

[AntiFederalist]

I remember the old OBD1 trick to run bigger injectors was to get the maf that had the correct calibration for injector size. Thats not the case with obd2. The computer must be tuned. I have a MAF extender that interprets the maf reading from the maf into what you want the computer to read. Its works as it should, but still complicates the cars tune and isnt consistent

What brand is that extender? Im just trying to get it running decent until I can save up for a holley or megasquirt

 

[AntiFederalist]

The MAF transfer rate for your stock unit is different from the PMAS. The ecm can't interpret an unknown transfer rate. This is why the stock unit may run Ok but on the rich side because of the 24s, while the PMAS unit is not able to run because the elm has no clue what it's transfer rate is.
Why the 24s anyway? If the car was tu ed and ran fine on 19s leave it. There is nothing to be gained with the pmas unit

I don't know why pmas claims it's the same calibration then. I bought the 24s years ago and have been waiting to get a ecu, they are a newer generation, have 6 ports instead of 4, and aren't almost 30 years old. Figured the car would run better. It's a full pi engine and intake from a bullitt with every bolt on avaliable, still don't need them but I would like to have them.

 

[ttocs]

back around 2008 I had heads/cam installed on the car and took it to a dyno for tuning. When I told the tuner I had a calibrated MAF I will never forget the look he gave me of "EEEEEW WHY!?". He gave a small speech on why he didn't like them and why they were bad and because I had the stock maf in the trunk he actually took it apart and put the thermistor/sensor from the stock in the larger sized maf holder and said that would be better. He described the calibrated maf "It is like going on a diet by starting to measure yourself on a new scale and suddenly you lost 10 lbs! Or did ya?????? you never really know."

 

[96blak54]

I totally get it! You have spent money on parts and you want them to be in use.....but your head will hurt a lot less if you revert back to the stock maf sensor and stock injectors for now. Then when you are ready for the car to be tuned, swap out the parts in favor of what you want and get the tune. Youll be miles ahead doing this instead of trying to figure out the "whys it wont, when it should" scenario. Any engine management associated sensor that deviates from stock scenario is not liked and the computer must be retaught. Its not your sensor thats the issue, its the computer. Our OBD2 years are now where near as finicy as the 05-up years. They get real touchy with any modifications like exhaust or cold air intakes.