BobGt

I currently have a 06 gt with a brenspeed 93 octane CandL intake tune. 1st off I must say his tunes are awesomeand never had 1 issue with it until i installed the mac axle back mufflers.. After the install the car would ping at wide open throttle under heavy load and also drone like an animal. I then reinstalled the stock mufflers basically cause of the drone but also noticed the ping was gone. I figured maybe i got bad gas or something so no big deal.I recently went to borla stingers axle back and the wide open throttle ping came back. I switched back to stock exahaust with the 93 tune and allis goodagain. I'm figuring variable cam time is used in place of an egr valve to intoduce exhaust in the cumbustion chamber to prevent pre- detonation. Now that you have removed some backpressure with these high flow mufflers the egr effect is not as effective.

ZZmustang

First, Make sure your getting 93 octane at the pump. and try to find gas that doesn't have alcohol in it. The alcohol is most likely your problem.
Go to Exxon. and if the pin is there, put in a couple 104+ octane boost containers. This will tell you that its the fuel or not. ( if the ping goes away)
If the ping is there after you ,for sure got 93 gas, then your program is advancing the timing to much for 93 octane. The program is probably not taking into account the low restriction mufflers. Get with the programmer and tell what you have,

BobGt

Yeah thats what I'm thinking. The program was meant for my stock exhaust. I remember him asking what exhaust i had when i purchased the tune ,so i guess backpressure plays a major role in the tune.

MrSandman

Exhaust should not make a bit of difference. There is probably little difference in flow between the stock GT muffler and the MAC. Have brenspeed email you the 91 octane tune. The only difference is the timing.. which is what is causing pinging.
Same thing happened to me....but had the pinging before I installed the MAC.

BobGt

I hear what your saying ,but I hear no ping with the 93 tune andstock mufflers. I have all 3 tunes 87,91 and 93. I've tried them all and rather have 93 tune then loud exhaust with the 91 tune.

mygt500

Let us know what Brenspeed says. I would contact them ASAP and get the tune with any new exhaust component taken intoo consideration.

MrSandman

Just let them know then. When I went from a single GT muffler to a single MAC, he said that he did not have to retune. When I said I had pinging, he said that he would send me the 91 tune.. and that should take care of it. I didn't mind.. because if I understand this correctly, the 91 and 93 tunes are virtually identical except for a little timing adjustment.
I would just email or call and see what he says.

ZZmustang

MrSandman
Yea, Back pressure makes no difference. and grandmas make bad cookies. Back pressure makes a big difference in wear the timming is set. The timming setting for openV8 headersvs a single muffler is major.