Quote:
Originally Posted by 370Zsteve
Exactly! You are hearing something that was already there, just better muffled at the time. (Love the explanation btw vroom,grab,boof..ohmmmmmm).
I used to subscribe to one of those urban legends (for lack of a better term) that stated that if you change to a freer-flowing exhaust, you have to richen the fuel mixture to eliminate the backfire (mostly on deceleration) or else you will damage your exhaust valves from the detonation. Of course like most legends it was all BS.
On my BMW K1200RS, I installed a Staintune full exhaust, which eliminated the cat. It has a sweet, mellow sound, much louder than before (I like that on a bike, since the cagers can now hear me). But on decel, it backfires quite loudly. Fortunately it comes with an insert that screws into the tailpipe that muffles the backfire nicely while also giving it a sound that to my ears is not unlike a 911.
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My bike does it occasionally (Honda VTX1300-C) with the pipes I have on it. I don't remember if it did it with the OEM pipes, but with these pipes, if I nail it, then decel just right, it'll burp a few times then KABOOM...scares the **** out of the wife since she doesn't ride as much...when I hear it burp it becomes a game to try and get it to blast...lol
On my bike I still have the emissions control stuff on it - which is nothing more than a reed valve and a vacuum switch - where it'll inject fresh air into the exhaust port to burn off any unburned fuel. What I think is happening is that I'm getting a build up of unburned fuel in there, that would ignite if there was any O2...the burps are air going in and burning some fuel, the blast is detonation inside the pipe. Sounds just like a 12ga going off, and I'm sure it's gotta be shooting flames out the tips...lol...
As for what it actually is with the Z, I'm not sure, but I doubt it's anything like what it is with my bike - more like a backpressure pop...I guess...lol