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Discussion Starter · #1 ·
well i got my new tune on wed and have been playing with it its great and no real problems except when im in 5th gear on the highway at low rpms if i mash the gas at say 55mph i can hear a small knock i figuer its just to low rpms with the new tune to do this so i downshift and no problems what you guys think this is.
 

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sounds like they played a good bit with your timing to get a little more HP out of it and its spark knocking... what octane gas are you running? and i agree with downshifting for that like everyone else...
 

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It's detonation, and it's bad especially with the stock hypereutectic alloy pistons--as others has suggested you should avoid "doing that", you may also want to talk to your tuner about backing off the lower rpm spark advance at WOT.
 

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Discussion Starter · #6 ·
im running 91 octane shell gas the tune was for 91 do you think i should run an octane booster with it to be safe i dont notice the knock in any othe gear other than 5th i just think it to hard on it at low rpm in 5th to go wot do you guys really think i need a retune
 

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im running 91 octane shell gas the tune was for 91 do you think i should run an octane booster with it to be safe i dont notice the knock in any othe gear other than 5th i just think it to hard on it at low rpm in 5th to go wot do you guys really think i need a retune
run 93 first and if that don't work back the timing off a degree
 

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Discussion Starter · #8 ·
im in california 91 is the highest i can get at the pump unless i want to buy 103 at the race track but its somewhat pricey for daily driveing lol.
 

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Yea def. on the 93. That knock can put a nice hole right through your piston one of those times.

edit: O that sucks you can only get 91. Are there any gas stations that offer ethanol? If so go ahead and add 1 1/2 octane to it, so 91 would be 92 1/2. Ethanol does that, and it smells better. Our Sunoco stations around here all have 10% ethanol.
 

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At 55 mph in my car, with 18" rims/tires & 3.55's, I drop it in to 3rd if I want to mash on it.

In 5th gear at that speed you are bogging the motor down and putting a load on it where it is not making much power.

It is also possible you need to run a higher octane fuel.

What tune did you put in? Was it set up for a specific octane? Was the timing advanced at all within the tune?
 

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It's not unusual to have an optimal tune that requires you to avoid certain scenarios--talk to you tuner and see what the trade-off would be for allowing you to "mash the gas at say 55mph" in 5th gear.

Personally, I would avoid the "mashing" at 55 (1500 rpm if you have a stock rear-end) and downshift to 3rd if you really want to go--it sounds like you have a fairly aggressive tune...
 

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Discussion Starter · #12 ·
it was a tune from jba racing around here there a mustang shop and i trust them it was for 91 octane im sure the timeing was advanced i really just think it was from me boggeing down the motor in 5th i listen carefully in every other gear and dont hear it. you think i should knock the timeing back one degree to be safe
 

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it was a tune from jba racing around here there a mustang shop and i trust them it was for 91 octane im sure the timeing was advanced i really just think it was from me boggeing down the motor in 5th i listen carefully in every other gear and dont hear it. you think i should knock the timeing back one degree to be safe
First I would try it from 55 again. Try downshifting in to 4th, and then getting on it a bit, and then down in to 3rd from the same speed and getting on it.

Do this a few times, each time getting on the gas a little harder as you listen.

If you don;t hear the noise again, chances are it was just because you were in to high of a gear when you smashed on it. :)
 
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