Topic says it all, how much would the MAF (with screeens removed) support?

 

MAF HP limit is determined by the model year computer you have. Removing screens or heat sinks etc will not change that. The late 80s Bosch MAF is good for about 340 before special tuning is required. The 94-95 MAF is good for about 560.

 

If that is due to the magic number of 255, is that the gm/sec reading seen with a scan tool, i.e. 255gm/sec?

 

Yes, the 165 computer has only a 1 byte variable for grams/sec, and 1 byte has a maximum value of 255.

 

Hi. I have an 85 with the 870 computer.
I try to get some hp out of the car in some mod stages over time.

Question:Is it,what is mentioned here, not possible to get more than about 340 hp out of an engine with a MAF and this computer. That means that it is stupid to pay alot for heads and other mechanical mods to get the engine to about 400 hp.

Would very much appreciate some comments
Have a great day

 

You can go above the 340 MAF limit with special tuning and getting rid of the TPI. Some of the guys with the 86-89 MAF got fed up with the tuning problems and went to a speed density 7730 computer.

 

so considering the package in my sig that i may go with, would i need more air to get the numbers where they should be?

a newer MAF, a better computer, or MAP system?

 

This is a great question i was going to buy that MAF in group purchase for my 86. Then eventually do the cam to a .460 lift i should get about 300Hp after running desktop dyno. If the CPU only supports 255Hp i'm beat.

 

At 300-350hp you'll be ok. He's saying that the MAF data is limited to 1byte or 255gm/sec of maximum measured mass air flow, which is about 350hp.

If the intake flows more air than this (at WOT at high rpm) you can use an AFPR to add some more fuel, within limits. Plus, the plot of hp vs air/fuel has a rather broad peak so there is some flexability for good power.

Beyond that you need to custom program the tables in your EPROM.

 

No, the ECM only supports 255gm/sec of air from the MAF.. not 255hp..

My 89 dyno'ed at 301hp running rich with a STOCK MAF.. only the rear screen was removed.

You can remove the screens and heatsinks and of course more air will flow through it and the MAF itself could probably support a decide amount of HP. The ECM is the restriction. as stated before there is only one byte in the ECM PROM to allow for MAF values which is 0-255. Although you can get higher HP #'s but it will be predetermined in the PROM since the MAF will be saturated. now if the ECM allowed 2 bytes and the MAF was calibrated for 2 bytes.. then you have more resolution from the MAF.

with the 7730 ECM you now are removing the MAF for the MAP. Again the MAP set-up (aka Speed Density) works off of the RPM and Load (measure in kPa) . The MAP system is not as forgiving as a MAF since the MAP is all Calculated values.. MAF is measured..

The later ECMs in the 94 and up vettes where they have both a MAF and MAP are the best, but I don't believe that anyone has adapted that system to an L98 car. I have always wondered if it could be done, but never looked into it. Maybe someday I will.

Another thought is if you were to get a MAF that worked just like stock but was double the size.. meaning if the stock maf is 0-255gm/s maesured by the ECM at 0-5volts.. use a MAF that is 0-511gm/s measured from 0-5volts.

The ECm would have to be reprogrammed to take in account the change, but I think then the ECM would not saturate as quickly. In theory it sounds like it would work.. but in reality it is a whole other story

 

You can program a 85-89 MAF car to do 450-500hp no problem despite the MAF limit of 255g/s.

 

94 - 96 ecms require an opti to provide the timing signals. It might be possible to adapt a distributor to make the signals but it would be a headache. The LS1 computer could work but it will also require some way to generate the timing signals that the LS1 motor makes.

You can do a similar thing with the stock MAF. There are enough locations in the MAF table in the ecm to go to 340 gps (around 500 hp). The values in the MAF tables would be scaled so that 255 = 340. The other change is to scale the injector constant so that it accounts for the change in MAF calibration.

I have looked into to doing this and using tuner cats ecm def file generator to make the scaling transparent to the user. The problem is that the ecm uses the MAF for a lot of stuff to run the engine. I think most of it is available in tuner cats software but theres no way to be sure if this idea will work without trying it. I don't have any way to test this idea.

If anyone wants to try this, email me. You'll have to have tuner cat or a way to program eproms and 87-89 MAF car.


[Modified by AquaMetallic94LT1, 1:31 PM 4/19/2002]

 

The ported MAF sensor can support mid 11 second ET's.

Vic

 

MY personal idea is run twin tubes and twin MAFs from the airbox to the throttlebody. Only hook up one of the MAFs. You are effectivly measuring exactly 1/2 the MAF.

Also. The only restriction to HP on the 84-89s it the airflow of the MAF. You can take advantage of your car and make it run strong up to that point (as evidenced by Beach Bum's #s). HOWEVER you will have to kludge it above the 255 gm/s limit in the ECM.