I purchased a Diablosport Predator from a previous Mustang owner (Thanks Peet!) and just installed the 91 octane Performance Tune. I filled up my first tank of 91 octane fuel 2 days ago, ran it down to 12 miles to E on the gauge before filling it, so I got "most" of the 87 octane fuel out of the car.

My first couple of hard acceleration runs I was getting some detonation around 5K RPM (sounds like metal rattling under the car, I think that's detonation right? ). I drove a total of about 5 miles, with a few shorter bursts through the gears (not too high in the RPM range), then as I got closer to home, there is an empty stretch of road where you can open it up. I ran it to just under 6K in 1st, 2nd, and 3rd, and it ran like a champ. No "detonation", just strong pulls, and a pretty mean sound I might add .

So my question is this...Did the tune and the computer have to "adjust" for a bit of time to run optimally? Did the computer dumb down my tune so it wouldn't cause detonation?

This is the only performance mod on my car, I even still have the HC trap. No CAI, no mufflers, no pulleys, nothing.

One more question, is there a big difference between the Performance Tune and the 91 Octane Performance Tune? I assume the first one is for 93 octane, which my local gas station does not have. Is it worth trying to find some 93 octane fuel?

Any and all input would be greatly appreciated!

Sean

PS - Forgot to add, the tuner has been upgraded to the latest version of the software - 8R21.

 

do me a favor... look under the car and make sure the two lower dust shield bolts are in place on the bottom of the front of the bell housing. "sounds like metal rattling under the car"

 

No, the bolts are there. It's not really metal, that's just what I relate the sound to.

Sean

 

I had a similar situation when I installed my JLT CAI w/93 octane tune. had a bit of detonation at first, then went away in a little bit. Probably just the last of the 87 octane getting out of the lines.

 

Probably just getting the last of the 87 octane out of the lines. I'd run some 93 octane through it just to make sure. Then go back to the 91 octane and see if it does it again.

 

I would if I could find some 93 octane around here. Anyone know where to buy 93 octane fuel in Chandler, AZ?

Sean

 

Is this a constant sound or does it only happen for a split second at a specific RPM? I get a metallic rattle (as I've mentioned in about 4 other threads) at about 2700 RPM. I dont think this is pinging (in my case) as it didn't start happening until after some serious wheel hop at the track.

 

This is definitely NOT metal rattling loose, that was only used as a way to describe the sound. At any rate, I went and drove the car again today and the detonation is back at around 5K RPM. I'm going out to look for some higher octane gas now. I'll let everyone know if that fixes the issue.

Sean

 

Just mix some 100 octane (i know the mobil on my side of the i10 has it on chandler blvd) with some 91. (like 2 or 3 to 1 ratio of 91)

 

Sorry, forgot 93 octane isn't avail every where in the US. Does your flash tuner have an 87 octane tune??? If so try reflashing the car with that tune and see if the detonation goes away. If it does then the timing is probably set too high for the 91 octane tune or the gas your using. You could reflash the ECU with the 91 octane tune and then manually back the timing down a degree or two until the detonation goes away.

 

I was going to start a post that asked for everyone's recommendations above and beyond the stock 91 octane tune, but I'm almost thinking that I should just get it tuned on a dyno when I get the 4:10's installed. That's probably a better way to go.

So which Mobile station has 100 octane? Is it the one on the West side of Chandler Blvd. and I-10? Figures, I just topped off with 1/2 tank of 91 last night. How about those bottles of octane booster they sell in the auto parts stores? I'm a little hesitant towards putting additives into my brand new motor. Any thoughts?

Sean

 

That's funny, I've got the 91 Octane Diablo tune, and I've been able to advance my timing by 2% and I've had no detonation

 

Hmmm, interesting. Why do I always get the crap setup?

Maybe I'll drive off a couple of gallons and find that station that sells 100 octane to see if I can bump the fuel content up enough to get to at least 91. I get the feeling that I still have a little of the 87, putting me a little under 91. I've really only put in 1 1/2 tank fulls of 91 octane, so maybe I'm still a bit under?

Sean

 

I switched to 91 one tankful before I did the predator tune, so by the time I did it, I didn't have anything else floating around in the tank. I also got it as low as I could go without stalling before hitting the gas station. Less than 1 mile left in the tank on fillup

 

On a side note, did you notice a large difference in power by installing just the tune with no other modifications? I was thinking of doing this myself.

Thanks

 

I wouldn't think you had very much of the 87/91 mix left if you ran it down to "12 miles from E"...1/2gallon tops? What was that first fill...1/2 & 1/2? If so, about 89 octane then. So, 1/2 gal of 89 and then you added 14.5 gals of 91? By my math that's 90.93 octane. At 1 gal 89 and 14 gals 91, result would be 90.87. Could that be enough to make it ping as my dad used to say?

Does the pump you use deliver 87, 89 and 91 through the same nozzle depending on which grade you select? I'm curious as to how much 87 gets delivered before you start getting 91 in those setups.
If you've got your car tuned "to the edge" then find pumps with individual nozzles for the different grades. And find a deealer you can trust to have "good" gas!

I'm suspicious of a couple of gas stations I've been to, for volume accuracy. Their pumps always say they've delivered quite a bit more fuel than what my guage says has been consumed...

I also wouldn't put it past some to try and get away with doing some private "blending", so to speak! I haven't checked but I bet you it's been done before

I'm in a pessimistic mood today, can't you tell??

 

BTW, my options around here are the standard 87/89/91 with Chevron offering 87/89/92/94 and Husky carries only 89/92 with some offering 94.

 

There's a Mobil station in Ahwatukee selling 100 octane? I wonder why? My first guess was for cars heading over to Firebird raceway but it still seems rather odd to me.

 

If it is a 91 tune then back down the timing 4 degrees.... I have a C&L CAI and used thier tune for 91 octane. I had 87 in the tank. I reduced the timing 4 degrees and no probelms. When i got 1 mile till empty i filled up with 91 Octane and advanced the timing back 4 degrees. I also tried another advance 2 degrees with no pinging........