Car runs better with maf-t and NO MAF?!!

[Tantrum]

Hello all.. Just as the title suggests, my 1990 gs-t was running fine with a full maf-t set up. After a night of hard driving it began running strangely (stumbling and cutting off). We checked under the hood and figured it was more than likely the maf. We removed the maf, reconnected the intake hose and when we started the car it began running smoothWTF. We were puzzled because the maf-t was still hooked up. I drove it home and the car was boosting and blowing off fine like there was nothing wrong with it. I did have a CEL on but it ran great. Can anyone explain why this is please?? Thanks in advance.

 

[4g63Powered]

I'm confused here. "Removed the MAF and connected the intake hose." Are you saying the GM MAF or do you still have the stock MAF on the intake?

 

[slipstream808]

If I am understanding correctly then you have no air metering for the car hooked up right now? Then in that case the car is locked in open loop mode and is basing fuel calibration off of safe "back up tables" based off of RPM.

 

[Tantrum]

...Yes 4g63Powered I had a GM maf hooked up, then we removed it for a straight intake piece and the car felt fine again.... Is it safe to run a modified car this way since it's in a type of "fall back mode"? Thanks for your input guyz I really appreciate it.

 

[DRAGIN]

As the other guy said, the vehicle likely falls back to a safe pre-programmed fuel and timing map. Although possibly safe to use (can't be sure without looking at a datalog) it surely is going to run with conservative timing and extra fuel enrichement which equates to lack of power. Certainly not beneficial. If you want to go from MAF to MAP you'd need to go stand alone like an AEM, Haltech, F.A.S.T. etc... the other alternative is to find an old HKS VPC with proper chip and preferably a GCC piggyback as well.

 

[->PrOjEcTGS<-]

As the other guy said, the vehicle likely falls back to a safe pre-programmed fuel and timing map. Although possibly safe to use (can't be sure without looking at a datalog) it surely is going to run with conservative timing and extra fuel enrichement which equates to lack of power. Certainly not beneficial. If you want to go from MAF to MAP you'd need to go stand alone like an AEM, Haltech, F.A.S.T. etc... the other alternative is to find an old HKS VPC with proper chip and preferably a GCC piggyback as well.

Or DS-Map! You use the stock EPROM ECU for this. No need for stand alone... DS-MAP.NET &bull; Index page

Though he probably doesn't have an EPROM since he's got a '90.

 

[talon_frost]

what is ds-map and i have a eeprom so i can use that for what ever this is?

 

[->PrOjEcTGS<-]

what is ds-map and i have a eeprom so i can use that for what ever this is?

DS-Map is way to convert your eprom ecu to run Speed Density. If you are not familiar with Speed Density it pretty much eliminates your MAF and you put an Intake Air Temperature, and Manifold Absolute Pressure sensor in its place. Then based on tables you have setup with the DS-Map program the ECU then calculates the amount of fuel needed by using these sensors referenced by RPM & Vehicle Speed. It's really basic and simple. But by god it works!!

There is more to it but that is the basic premise.

The only thing... is that, you will be forever tweaking your setup. Since the ECU now doesn't know exactly how much air is coming into the engine it now guesses. Therefore if you add something to your car that makes for a better Volumetric Efficiency (more air into the engine i.e. Big Cams, Turbo, Exhaust, Intake, etc.) you have to edit your settings to show for it.

 

[H82lose91]

MAFT-PRO will also allow for Speed Density and does WOT timing control without going full standalone.

 

[Tantrum]

Thanks guyz BIG time. I was thinking about a stand alone in the future anyway. I'll just have to sit the car down... ...AGAIN

 

[BoredDSM]

May I suggest trying to replace the maf first? A gm maf setup is a pretty good setup and for 30bucks or so you could get another one off the classifieds. I have a few laying around if you need it let me know. But I would change the maf out first and make sure. Before spending $xxx+ dollars on a new setup.