When running at or near redline WOT and you shut her down my engine will decel pop. I think thats normal.

 

Yea I had some pretty good popping around the time I got my big city thunder monster baffles, and decided to go ahead and get some of those rush 1.75's, and still had pop, grrrrrrrrrrrrrrr. But that's when I noticed my crossover pipe was 3/4 way cracked through, dohhhhhhhh. Bud of mine welded it up and I reslapped it back on, 90% of pop was gone, and after fuel moto had me tweak the pcv a touch, I now have NO decel pop. Sounds good.

 

The Science of popping on decelleration is really quite simple. As you decelerate (engine on the overrun), unburnt fuel passes along the hot exhaust tract - it's unavoidable on a correctly tuned engine because even with the throttle fully closed small amounts of fuel will still pass down the exhaust. Introduce oxygen into the equation via a leak in an exhaust joint and that unburnt fuel will then have all that's necessary for it to ignite in the pipe - i.e heat and oxygen. This is what causes the popping - you're hearing small explosions taking place within the exhasust pipes.

So, if you fit a new exhaust and you get popping on the overrun that wasn't there previously, quite simply you have a leak somewhere along the system. Tuning may well get rid of it but only because the air fuel ratio has been set so weak that the amount of fuel present is reduced to levels where it won't ignite, weak running engines overheat - fact. Tuning out deceleration popping is fixing the effect, not the cause.

Derv

 

Is it a Harley? They tend to pop on deceleration. It's normal. If you want to stop it you have to stop the exhaust leaks so air can't ignite the fuel in the pipes. Just forget it.

 

unburt gas getting into too hot pipes,2 fixes,either take all fuel away in first cell,or put more fuel in first cell to bring down ex temp,if you have no way of tuning theres nothing you can do(really should get some way to remap)
kirby

 

I think in my case the tech over at fuel moto had me increase slightly the fuel demand at either a certain throttle pos or rpm, not positive but, he had me bump the numbers up slightly and I presumed it was due to a lean mixture, so additional fuel spanked it. Pretty cool, all via laptop hooked up to my bike out in the garage.