Serious MAF problems

[XSRACING-GT]

I have problems since I installed my 30lb injectors and my 80 mm maf. The car is running only 30psi of fuel on the rail. I have adjusted it and it still shows only 30psi with the vacume line attatched at the regulator, but it shows 40 with it off. wtf??? when I drive the car it surges off of idle and at wot, the car just about dies. If I am 3/4 throttle, the car pulls all the way to the redline, but just not as hard as i think it should. Anyone had this problem? i know its running lean, just dont know why. i have stock heads and cam, and a tfs street intake.

[sedanman]

Do you have some form of forced induction? If not 30# are way to much injector for your car. The change in fuel pressure is to be expected when you unplug the vacuum hose. Mustangs have boost/vaccum sensitive regulator so they change the fuel pressure depending on vaccum or the lack there of, the less vaccum the more fuel pressure its should be about 1 for 1. For every one inch of vaccum you should have 1 pound of fuel pressure pulled. I think a stock mustang pulls 14" of vaccum but I am not sure since its been years since working on a stock cammed mustang. So basically it seems you have to much injector but post your entire mod list.

[XSRACING-GT]

I have tfs Street intake, msd 6al, 3:73 gears, cai, 80mm maf(calibrated for the 30#) pulleys, shorty headers, o/r h pipe 2 chamber flowmasters, 150 shot NOS, tremec tko 600, mcLeod clutch, will have f303 cam installed soon I hope, along with 1.6 roller rockers.

[Jeff Chambers]

Is this a Pro-M, C&L or Granatelli MAF? The calibration curves on calibrated mafs can be absolutely horrible. Nowadays, most tuners are trying to steer people away from the calibrated mafs and towards mafs such as the Lightning and SCT Big Air mafs. They are much easier to work with; tuning is done by operating on the maf transfer function directly like is done with a calibrated maf, but the curves are much more exact and usually take much less tuning effort. It sounds to me like you need to have the car tuned so that the calibration curve can be corrected.

BTW: I've seen a few of the new Professional Mass Air Systems meters come through the shop and their calibration curves seem to be quite a bit better than the others.

Off the original subject, but is the 150-shot wet or dry?

[XSRACING-GT]

JEFF-The maf is Pro M, which I thought was one of the better ones out there. Do I need to get a chip for my car? Other than that how should I have the car tuned? Could you get me some prices on some chips that would be good for my car? (I take it you sell chips because you have the link on your sig. whats the price on those new proffessional mafs? I have an 80mm btw. oh, The NOS shot is dry, I have a 255 lph intank pump. pressure is at 40 with the vacume line off.

[Jeff Chambers]

With the dry shot it is going to be imperative that you have the car properly tuned. If you're running at 14:1 now and hit it with a 150 shot, you could easily roach the motor.

If I were tuning your car, I would put a four-program SCT switch chip in it with a base N/A program, then a program or two for the NOS (say a 75hp and 150hp tune). You need to find a tuner close to your area since the car needs to go on the dyno for wide band A/F measurements to do the tuning correctly. In general, I think you'll find that a switch chip will run you close to $300 and dyno time anywhere from $75 to $150 per hour. I tell EFI people to plan conservatively for two hours on the dyno for a good tune.

[XSRACING-GT]

OK, thanks for all your help and advice. Do you think that the SCT and dyno tuning will solve my problem, or do you think its something with a part I have? MAybe because of the mods and all, the eec IV wont correctly judge the a/f ratio and screw up?