vroompshhtsi

I have a basically stock (exhaust and gears) 03 GT and was wondering what a 91 tune would do for my car.

1) How much will it help?

2) What exactly does the tune tell the computer to do? How does my car perform differently when I tell it I'm burnign 91?

defconfire

It advances the timing and leans the a/f.

avlon06

if you raced the exact same car with the same mods, but you had the 91 tune if both drivers were the same then you would win.. that was a mouthful

n0th1n2kn0vv

The tune advances the timing, since higher octane fuel allows it. If you would advance the timing with 87 octane, pinging would start to occur. Then comes the debate of retarding the timing or spending more at the pump.

35thAnni99GT

Nothing so huge you would notice. If you really want the "extra" octane I would invest methanol and just run your regular 87. I'm willing to put my money on being able to run more timing with methanol + 87 than just 91.

StriderTacticaL

My sniper tuner arrived yesterday and I tuned my mostly stock 04 GT. The only changes I made was to set the octane to 91, remove the speed limiter, and turn traction control off.

I felt a bit of power right off the bat. The car seems to accelerate a bit faster. In terms of a 91 tune leaning the A/F, is that good or bad? or doesn't matter?

I like the extra power but I keep thinking all the tuner did was use more gas to produce more power. Or does it not work that way? I heard my MPG if anything will be increased too from the tune.



Brandon

defconfire

Usually what it does is advance the timing timing and possibly lean the a/f out a little bit. So if anything its using less gas to make more power.

vroompshhtsi

Is there anything else I have to do manually after I use the tuner to set it for a 91 tune? Does the computer do the rest?

StriderTacticaL

What tuner are you planning on getting?

cliffyk

Creating a 91 octane tune, whether it's the Sniper Special Forces, Diablosport's Predator, Granatelli's Fuego, or buying an SCT with a few tunes created by a guru, is a lot more than just "bumping the timing and making the mix leaner/richer".

Each manufacturer of these things has there own ideas of how to create that 91 octane tune, and the actual tune created uses a number of algorithms (and tables) in closed loop mode, and a number of table and other dynamic considerations in open loop mode. These are multiple dimension tables that consider engine load, incoming air mass, rpm, throttle position, IAT, ECT, yada, Yada, YADA...

I had a Predator, it was nice. Sold it and bought a Fuego, it was also nice (much like the Predator, my brother is using it no on his '99), but grossly misrepresented*.

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* - JR is an arrogant ***, the product does not data log, is not "updateable over the Internet", nor will it "let you tune as many cars as you like, one at a time" (you get 5 vehicle swaps and then it locks up).

Anyway my brother got me the Sniper SF package as a late birthday gift, and after some teething problems (the first tune I loaded locked my car up over the weekend, Sniper fixed it in 20 minutes Monday morning), I have grown to like it. Unless you are racing or have some non-mainstream f/i mods there is nothing it cannot accomodate and let you tweak for a DD performance street tune...