Blow-Thru 42lb MAF

[speedytang]

I installed a Pro-M meter and converted to the new 6 pin plug to match on my '89. When the harness is plugged into the meter it idles perfect and runs great to 3k rpm then breaks up like a rev limiter. So I figure the meter is not working correctly. Well I unplug the meter harness and it revs to 7k rpm and does not break up but will not idle since the 42lb injectors are not getting a correct signal from the computer and is flooding itself. Am I in the correct thinking that the meter is calibrated wrong or is bad. The next thing is has anyone in the past years seen someone offer to burn a chip or internally modify a Speed Density computer for 42lb injectors. I rather go SD and junk the MAF if possible and use a custom Fuel Table instead.

 

[RatStang]

I'm rather amazed that the car ran at all on the preset fuel tables since you did not mention a chip of any kind. I'm also suprised that it idled with just the meter installed and no chip. You consider that even though this meter is supposedly calibrated to run on the stock EEC with 42 lb injectors, I can't say that I've ever seen this work first hand. The injectors minimums and break points are ALWAYS going to be wrong until you get that thing tuned. It makes no difference whatsoever what meter you decide to toss in with 42 lb injectors. The differences in the injector pulse minimums and breakpoints are WAY outside of the EECs adaptive ability when comparing 19 lb injectors with 42s.

The only alternative would be a chip, hand-held tuner, etc.


As for chipping SD... Good luck man. If you find a place, be sure to post it up. Roughly 10 or so years ago, I knew of such a place and chipped one for an aftermarket cam. It worked great! No luck since then though. Call around in your area and see if anyone still has any of that old software lying around.


Good Luck


P.S. I've heard mention that the TwEECer can be used to tune the SD EECs. You'd have to confirm. IMO though... TwEECer = HUGE PITA

Others have more patience than I though.

 

[speedytang]

I have tuned it with a PMS and it does not matter now since I am sure the meter has gone south for the winter. LOL
I took the PMS out just to make sure it was not the problem and used this meter for years when I was Supercharged without a PMS and with a PMS and never a problem till last year and then winter came and I parked the car. I think I will put the stock meter back on and 19lb injectors with a FMU just to see if it runs correctly. I just never seen something run better or at all with the meter unplugged. Been doing this for 20 years and this is just kinda weird compared to my issues of the past.

 

[RatStang]

So there's a PMS in the mix!

The reason it's probably running alright with the PMS plugged in then, is because when you're in open loop, the PMS reverts to piggy back mode, correct?

If so... then the open loop fuel tables it's using are the ones you've already programmed into the PMS (along with any pulse modifications for the injectors).

Any time you pull the MAF, the EEC reverts to whatever prebuilt fuel table is present in the EEC. Whether its the one from the ECU or the one in PMS though... you'd have to tell me as I've no idea how you've got everything built and/or triggered.

 

[speedytang]

What I was saying is it runs like crap with or without the PMS. I am really sure it is the meter. I will change everything back to 19lb injectors and run the FMU for now and just switch it out to a Megasquirt and be better off.