07 GT/CS

I loaded the 93 Tune from brendspeed and my gas milage has droped alot. I used to get 26 to around 28 MPG cuising at 65 to 70 MPH with stock tune. Now with the 93 tune i get About 21 to 22 MPG cruising at the same speed, city milage has dropped quite abit as well. Just wondering if this seems normal to everybody with brenspeed's tune or if it might be a tune prob, power feels great, might be running rich though as it turns my exhaust tips black every day. Thanks fo any help/ advice

East87

After the addition of the intake and 93 tune, I reset my MPG counter on the dash computer. With about a 60/40 mix of highway to city, I'm currently averaging 20.2 mpg since mid-April. Many long 300+ mile trips along with hundreds of miles of city/light-to-light driving thrown in there.

I am now all of a sudden having the black exhaust tip issue like you, and I feel like I'm running rich as well. I'm going to start calculating mpg at the pump. My LM's are kinda permanently stained now, unless I find some miracle metal polish. The darkening just seems embedded in the metal.

zachcrosen

I have gone from about 20.4 MPG down to 19.4, but I have also added 4.10s and a JLT CAI with the tune.

dolint95

brenspeed tunes are very rich....had my car on the dyno and the a/f was anywhere from 10-11....stock is 13.8. Going next week to get a custom tune. They want to keep their cars safe from detonation so all these mustangs don't start to detonate and give them a bad rep. all you have to do is tell them you want a more aggressive tune, that should take care of your richness.

HaneyMotorsport.Com

Car should not run rich during closed loop ....idle/cruise. You need to datalog the short term fuel trims.

From my experience, if the maf-x function is on the lean side, fuel mileage will be down. The pcm is always adding fuel to bring it back to 14.64. (closed loop/feedback from O2s)

Casey

ski

If your locale is like mine where only a portion of the gas stations sell E10, and you're now buying 93 octane at a different station than where you had previously bought 87 octane, then it's possible that the 93 is E10 and the 87 was not. And since E10 reduces gas mileage, then that may be the cause.
If that's not the case, and you're also not driving more aggressively with the new tune, then see if a different brand of gas improves your car's mileage.

ski

The stock tune's WOT A/F ranges anywhere from 10.5-12.0.

Stoenr

I thought mine was a little high when I ran the dyno, so I sent them an email.
This was 3 years ago, and his reply to to my 93 tune with JLT.

Normally you can see a gain in .5 A/F richness when reading at the engine, not at the tails. So if you are running 13.5 at the tails you are most likely 13.0 at the engine. BUT normally people see 12.9 A/F at the tails with that same tune if you are running ours. There could be variation in your MAF size. If the MAF housing has any variation at all you will see the cars either richer or leaner than others. So if the MAF is slightly larger than original specifications you will see the A/F go lean.

RainsFather

That would have been awesome if the tune they sent me would have been like that. My 91 tune they sent I had to take out 6 degrees and make it 2% richer to not have tremendous detonation past 4k rpms. There are obviously quite a few people that swear by their tunes so it just goes to show that every car is different.

Also, I wouldn't totally trust the fuel economy in the computer, I recently took a road trip 400 miles and the computer said that I got 33 mpg and my normal everyday driving I get 24 mpg mostly stop and go. This is with HR cams, frpp intake, o/r x-pipe, and a bama 91 race tune. Something tells me that can't be right.

07 GT/CS

Well, went through 3/4 tank of gas in 149 miles used to be more like 220 miles. I haven't changed my driving style because there is to much traffic restricting me. I do know that the counter on the dash says 22 MPG when cruising steady at 65 MPH. So I may go down to the local dyno and have them check air/ fuel and maybe get a custom tune.