wcgman

So I live in Denver (about 5300ft altitude) and it was probably between 70-75 degrees today. So I took my 06 GT that is stock except it had no mufflers, just bent mandrel tubing from in front of the axle back. Still has the cats though, everything else is still stock. I've been running 91 instead of 87 because a friend told me I'd get better performance. I doubt that, but I've been filling up with it stock tune for about a month.

I get to the dyno, they make 3 runs and get my AF ratio. I max at about 248hp at 5500rpm and torque was 261, 254, and 259...and the guy at the shop said that's about right because of altitude. However he said it's running rich. At about 1750rpm, looks like about 14.5:1 and from 4500-6500rpm it pretty much leveled out on all 3 runs at about 12:1.

Again - car is stock tune (as far as I know - I bought it with 3k miles and the muffler delete.) I am concerned about it running rich and I think it's because I've been running the 91 octane? However I am not a pro so what the hell do I know? I'll try to upload a scan of the run if I can ever get my scanner running again.

Here's what I am thinking. I am planning a CAI and tuner setup from Brenspeed. Should I tell them my concerns or am I making a big deal about nothing? Is the problem with it running too rich because I am running too high of an octane? What would be the ideal AF mixture and does altitude make a difference in where AF should be running at?

As always, thanks in advance everyone!!

06SaLeEn

If you are not tuned for 91 oct then you will see little or no performace increase, maybe just mpg. When you get a CAI and tune they will do a 91 oct tune, once loaded you will see it increase.

248 rwhp. Was it on a Dyno Jet or Mustang Dyno. Even though with you living in Denver your numbers sound right, but dont worry everyone else living up there as the same issue.

Not sure what your A/F should be since you N/A. I know on a F/I car WOT should be 11.2-11.7 range

GT Bob

What your seeing is normal for the stock tune. Ford made the stock tune VERY rich from the factory, mostly for safety reasons. It has nothing to do with the grade of gas your running what-so-ever. The reason the CAI's and tunes make so much power on these cars iis because your letting the motor get more air and cutting out a bit of the fuel to achieve a better AFR.

At WOT, your typically gonna want to shoot for an AFR between 12.8 and 13.2 on an NA car.. and maybe 12.5-ish on a Forced induction over all. Whoever does your tune will know exactly what to do, and I wouldn't loose any sleep over it.

AS for the higher octaine improving performance. In theory, it could. Your computer would be able to slowly over time add a little bit of timing due to the higher detonation resistance of the higher octaine fuel. Adding timing like this would help give ya more power, but honestly, its nothing that you would feel because it would be so slow and gradual over so long a time, no matter how finely tuned your Butt-o-meter claims to be

MusiccityGT

No worries. That is not overly rich for the "safe" stock tune. Just go on with life and stop wasting money on 91 octane until you get a tune done.

wcgman

It was done on a dyno jet. Thanks for the feedback guys and I feel much better now I'll quit wasting my cash on the higher octaine juice until I get the tune.