Top end detonation?

[GTRookie]

Took my car to the track for the first time and made a half-dozen passes. Through the last part of the track I hear what sounds like bad detonation from about 5000rpm and up. It doesn't happen in first and second gear and only at the top end of the track. It doesn't happen when I rev it in neutral (while stopped) or lug it from low revs in too high a gear on the street. In fact, I never hear this sound on the street, only at the track.

My car is an 04GT five speed, 14000k, full weight (plus 300lb. driver), stock motor, stock Goodyears at 35psi, running on Chevron 87 octane fuel. I started at 15.5 at 80 (let off way before the stripe) and got it down to a 14.8 @ 94. The last three runs were all at about 93-94mph.

Any ideas? Things to check? Does the mph seem par for a stock GT?

I'm thinking its some type of detonation but can't say for certain. I don't want to wreck the motor but I'm hooked on running at the track. It takes a lot more skill than I thought (and got) to make a decent run.

Thanks

 

[Black2001GT]

Took my car to the track for the first time and made a half-dozen passes. Through the last part of the track I hear what sounds like bad detonation from about 5000rpm and up. It doesn't happen in first and second gear and only at the top end of the track. It doesn't happen when I rev it in neutral (while stopped) or lug it from low revs in too high a gear on the street. In fact, I never hear this sound on the street, only at the track.

My car is an 04GT five speed, 14000k, full weight (plus 300lb. driver), stock motor, stock Goodyears at 35psi, running on Chevron 87 octane fuel. I started at 15.5 at 80 (let off way before the stripe) and got it down to a 14.8 @ 94. The last three runs were all at about 93-94mph.

Any ideas? Things to check? Does the mph seem par for a stock GT?

I'm thinking its some type of detonation but can't say for certain. I don't want to wreck the motor but I'm hooked on running at the track. It takes a lot more skill than I thought (and got) to make a decent run.

Thanks

My 2001 Detonated really bad when I ran 87 Octane, try 93 Octane and see what happens.

There are a few tricks that will help you at the track. Take everything out of the trunk, lower the rear tire pressure to about 18lbs, loosen the Front Anti-Sway Bay and practice, practice, practice.

 

[Chopper1]

Try running the car on a dyno.This way you can listen to the engine while it's being ran and any detonation will leave a telltale drop in power output.

 

[GTRookie]

Thanks for the responses. I'm not sure there are any dyno's in my area. I'll try the higher octane at the track although the car runs better on the street on 87.

 

[02BlkStang]

04 GT at 93mph? something is wrong, that's stock 5.0 territory.

I've trapped 97-99 and I'm getting a dyno to see why it's so low.

 

[Mike97gt]

04 GT at 93mph? something is wrong, that's stock 5.0 territory.

I've trapped 97-99 and I'm getting a dyno to see why it's so low.

yeah he is either low on power. or he is running in very high DA. if the car is in colorado or other very high area you could see traps like that.

or a very very very very bad driver can do it too taking forever too shift

 

[Mstg05]

Try higher octane fuel and check out your air filter.