91 mustang tune

[loudexhaust]

I did some engine work on my 91 5.0 it seems to be eating through a lot of gas. gas smell in the exhaust is also pretty pungent. Where's a good shop to get a little tune? not looking to spend hundreds on dyno tuning or anything, just a little tweaking.

[orangefox]

Hitech in Elk River is the place to go!

[tim]

Good luck finding someone to burn you a new chip for less than a few hundred dollars.

Hitech will do a chip with all necessary dyno tuning for ~550.


What all do you have done to the car?

[mnstang]

put it on a dyno for 3 pulls with air/fuel readings and adjust your fuel pressure regulator.

you'll get hp and tq numbers, probably pick up pretty good hp and tq, and it'll only cost you about 50 bucks.

[loudexhaust]

$50 where? I put on gt40p heads, tfs stage 1 cam, explorer intake and throttle body plus exhaust.

[mnstang]

you can go to map and get 3 pulls with a/f for 50 bucks i think. it might cost 75 bucks at other shops like hitech/db/aps.

[loudexhaust]

Do I need a fuel pres reg for an a/f?
Also, my stock injectors are probably just cutting it with my mods. If i swapped injectors and maf would i need to get it retuned? I have injectors but don't have money for a maf quite yet.

[mnstang]

well you have a fuel pressure regulator, but you need an adjustable one to adjust the fuel pressure, which in turn changes your a/f ratio.

you can probably get by right now with stock injectors. if you swapped you wouldn't need a tune.

[loudexhaust]

Ok so looks like i'll need to spend about $100 on an fpr. Will there be instructions on how to set it up, at least well enough for me to get it safely to the shop? thanks a lot for your help, much appreciated.

[SDK]

You can put a guage on it. then adjust it

[Sweet35th]

well you have a fuel pressure regulator, but you need an adjustable one to adjust the fuel pressure, which in turn changes your a/f ratio.

you can probably get by right now with stock injectors. if you swapped you wouldn't need a tune.

Problem is that it changes your a/f ratio EVERYWHERE, not just at WOT. To correct the a/f mixture by changing fuel pressure you could be causing your part throttle a/f to go beyond what the fuel trims can compensate for. Possibly causing drivability issues, as well as poor fuel economy. Not too add the fuel pressure is a linear change. If your rich at 3500rpm, and lean at 5000rpm, bringing fuel pressure up to fix the lean conditions at 5000, is just going to make it richer at 3500rpm. Vice versa, bringing pressure down at 3500rpm to lean it out is just going to make it leaner at 5000rpm.

I agree with paying to get a baseline on it, cause it may not need any changes at all. The A9L/A9P computers are pretty damn good for keeping a decent a/f even after mods. Usually if they go lean its because of a faulty MAF, or other non computer related issues.

But if it is off....

An adjustable fuel pressure regulator was the way to do it back when there simply just wasnt much around for tuning software. But why spend $100 on a fuel pressure regulator, and then another $50+ on dyno time just crossing your fingers that its right. Save the money and do it right the first time.

[loudexhaust]

so are you suggesting getting a custom chip? If I brought it to get dynoed can the stock computer be programmed?

[Sweet35th]

so are you suggesting getting a custom chip? If I brought it to get dynoed can the stock computer be programmed?

I suggest you get it baselined, simply to see where you are at and if it needs a tune. If it does need a tune, then yes the stock computer can be programmed.

I know you said earlier that it seems to be eating lots of fuel, and the exhaust smell is strong. I assume you do not have cats? The exhaust smell is always stronger when there are no cats on the vehicle. As far as eating lots of fuel, what do you have your base timing set to?

[loudexhaust]

My base timing is 10 degrees. My compression ratio should be at 9.5:1 with these heads from what i hear. You are right about the cats, smog pump had to go too with the new heads.

[mnstang]

Problem is that it changes your a/f ratio EVERYWHERE, not just at WOT. To correct the a/f mixture by changing fuel pressure you could be causing your part throttle a/f to go beyond what the fuel trims can compensate for. Possibly causing drivability issues, as well as poor fuel economy. Not too add the fuel pressure is a linear change. If your rich at 3500rpm, and lean at 5000rpm, bringing fuel pressure up to fix the lean conditions at 5000, is just going to make it richer at 3500rpm. Vice versa, bringing pressure down at 3500rpm to lean it out is just going to make it leaner at 5000rpm.

I agree with paying to get a baseline on it, cause it may not need any changes at all. The A9L/A9P computers are pretty damn good for keeping a decent a/f even after mods. Usually if they go lean its because of a faulty MAF, or other non computer related issues.

But if it is off....

An adjustable fuel pressure regulator was the way to do it back when there simply just wasnt much around for tuning software. But why spend $100 on a fuel pressure regulator, and then another $50+ on dyno time just crossing your fingers that its right. Save the money and do it right the first time.

i know it's not the perfect solution or as good as a custom tune, but it can help and it sounded like he didn't want to pay 500+ for a tune.
it still can be the way for people not wanting to spend that kind of money, 500 bucks is alot of coin, especially for some of these cars that are getting old and barely worth that anyway. plus alot of custom tunes are not right the first time.