Here's what's going on.
So far I have a:
Gruppe-S V2 Manifold,
PDE flex uppipe
APS TBE
Highflow panel filter

The other day I filled with gas (which I believe to be bad) and did my LGT brake swap. All of a sudden I have a really loud hammering/ratteling sound at about 3000RPM accelerate through it and it goes away let off throttle and it happens on coast down. Highway speed you can maintain the sound. I filled with 1/2 tank of 100 octane last night. The problem is still there. I was supposed to have my tune today but because of weather (road tune) it's a no go. I have not heard a WRX detonate before and I have no Idea if it truly is detonating or not. I need some help here guys. Ted came over yesterday to give me a hand and we were unable to come to any conclusions. HELP ME!!!!

 

When mine used to do it, it would only happen when i floored it at higher Rpm's (boosting) and it sounds like bb's or small rocks hitting a tin can.

 

when my car was detonating it sounded like pea size gravel was in my exhaust.

I would seriously go get some octane booster, add that in, then drive down to the 76 on foxworthy & almaden and top it off with a couple gallons of 100 octane.

there is either water in the gas, or they put 87 in the 91. I would complain to the owner if I were you.

Mike or Ed could probably tell better then me about when the 04/05 open/closed loop fueling transition occurs, but I think it is right around 3K RPM. When that happens the car runs lean, and when you have exhaust components that make the turbo spool quicker then the ECU is expecting it runs leaner.

 

woops, didn't see you already added the 100oct. did you try resetting your ECU as well?

 

I'll give the ECU reset a try. I haven't since I added the 100oct

 

do this. Drain the tank. There are 2 drain bolts I believe. Have someone drive you to a gas station and fill a 5 gallon container with 91. Pour it in your car, reset the ecu, let the car idle for about 15 minutes to clear out old gas that may be in the lines, then go fill up with 91. Couldnt take more than an hour and is alot easier/cheaper than replacing a shortblock.

 

its not detonation if it does it coasting down in speed
detonation only happens under load
sounds like something when wrong when you did the brake swap

 

damn....I thought for sure it was the gas.

Seems like if it was a brake deal it would happen only when the brakes are in use. Or it would be a consistant sound......change with speed but always there...like if there was a rub or what not.

Jeff.....how's the power? Feeling any decrease in power delivery?

My car seems to be back to normal with the new gas.


Side note.....to those that don't know...jeff and I filled up at the same 76 station on the say day and both had problems....

 

cross that 76 station off the list then those bastards are prolly adding water to the tanks..... i got some bad gas from one by my house too i switched to a different station and now mine runs better too but i wasn't getting any crazy noise just lack of power. the reason i say its the brakes is because that was the only thing he did besides the gas and he said the noise happened on decel the engine will not detonate on decel only under load.