My car is detonating like a b*tch over 5800 rpm at full throttle. I had just removed my stock exhaust, and replaced it with a 3" Top Speed Pro-1 exhaust. It didn't detonate previous to the install.

Could the 3" exhaust have caused a leaning above 5800 rpm causing the detonation? This exhaust is a beast !!!

No flaming because I don't have my wideband installed yet. I know I should.



I'm going to buy some 100 octane. That should cure it till I can get my hands on a UTEC.

Respect
JET

 

By the time you "HEAR" detonation the damage has been done...

 

How do you know it's detonating? Is it something you can hear? I've never experienced it before, so I was just curious what it feels/sounds like. Thanks, and sorry I don't have anything constructive to reply with.

 

When a car detonates... deep rapsy noise... black smoke out of the exhaust... running to rich, to much fuel in, stuff like that. It doesn't sound good at all.

 

Ive got no answers for you unfortunately, but I have the pro-1 and would love to go with a turbonetics setup. so Ill be looking forward to someone giving you some feedback on this issue so I can avoid it in the future! I hope you get it solved without doing damage to your car! good luck!

 

Like metal clank! Your pistons have been devirginalized.

 

Detonation sounds like someone poured a bag full of marbles into your combustion chambers. Or like a diesel truck.

Detonation doesn't always cause damage, but can blow out a head gasket, and blow your pistons into little pieces if it's bad.

Detonation is casued by a lean A/F ratio, carbon deposits in the combustion chamber increasing the compression ration, and/or too low octane. Not too rich or too much fuel. Just the opposite actually.

I think the exhaust must have leaned the A/F ratio, either by itself, or in combination with carbon deposits.

Can anyone else corroborate my theory?

Respect
JET

 

Contrary to popular belief the A/F mixture in the combustion chamber doesn't explode. It should burn progressively causing a gradual increase in pressure. Detonation is when it explodes causing an abrupt change in combustion chamber pressures. Not a good thing. The higher the fuel octane the slower the combustion giving a higher resistance to detonation.

Respect
JET

 

What was your a/f when you tuned the car (before installing the exhaust)?

 

Here is my dyno run.



Respect
JET

 

My understanding of this is that normally, the flame front spreads from the spark toward the piston face in a predictable, controlled fashion, providing a smooth compression curve. In detonation, the fuel ignites both at the spark source and at the piston surface. The "collision" of the flame fronts (and thus pressure fronts) results in an almost vertically graphed pressure spike that causes the block to vibrate (ping) at a somewhat predictable frequency that a knock sensor can detect. This effect is worse than a spontaneous combustion of the entire AF charge.

.....or at least that's what I've read. I just hadn't ever experienced it first hand......

 

Much like a sledge hammer to your pistons. Oh and don't forget rods break.

I'm not sure if our engine gets false knock but better hope it is.

 

Wait so just the exhaust is causing you to ping? Thats VERY odd if you ask me. You have 10s AFR with the stocker. Are you SURE its detonation and not something else? I'm not trying to be a dick but thats a +2 increae in AFR from JUST an exhaust. How bout if you unbolt it COMPLETELY?

 

I was actually thinking the same thing. His afr was pretty rich, almost 10.0 except for the part at 6100 where it goes to like 10.5, but thats still a little rich. So its really surprising that a exhaust alone would lean it out so much for the engine to start detonating. Pretty weird...

btw, didn't you (Miaplaya) go from the stock exhaust to a 3 inch exhaust as well? How much did that lean out your car?

 

Well the exhaust is 3" and it's just as open as an open dump as reported by Sharif. As soon as I get some race gas in tonight I will tell you decisively if it's detonation. 100 octane would surely cure any detonation. But yeah I'd bet the house on it. It didn't do this before the exhaust. Keep in mind at 19K miles I may have carbon deposits increasing the compression ratio.

BAD *** exhaust eh?

Hey Jaki.. I was the car parked next to you Fri night in MIA at the meet.

Respect
JET

 

It could be vibrating against your downpipe causing false knock. I may be absolutely wrong but it's worth a shot to go back to stock.

 

Yeah thats a RETARDRD good exhaust if it can do that. Yeah I run a 2.85" Apexi and my AFR is in the 11s across. taurran AND 35ounces have 3" Nismo and Fuji and their AFR is perfect as well. SO are the Borla modified guys, pretty much every damn one out there. EVERYONE is retarded rich. Thats crazy...

 

the best way to exsplan what it sounds like is metal bb's in a can atleast thats what mine sounded like....

 

I can hear the engine pinging.

Respect
JET

 

Borla's, Nismo, Fuji.... they are not straight through like the Top Speed.

Respect
JET