Decel Popping...What exactly is the problem with it?
Cruiser
Joined: Dec 2006
Posts: 211
Likes: 4
From: Florida
RE: Decel Popping...What exactly is the problem with it?
BoomSoon
I have an 07 Lowrider and after I put on my Rush 1.75" slipons I had the decell popping but it wasn't bad. I had been readingforum posts on the Nightrider XIED's and many reported the decell problem was gone after they installed the XIED's. I ordered some and it cured the decell popping but still sounds great. They are primarily used to cool down the heat from the new lean engines and they work. I'd check into them if I were you. Most folks don't need to do anything in the way of AC or Serts after the XIED's are put on. I agree the bike runs great now.
RHJ
I have an 07 Lowrider and after I put on my Rush 1.75" slipons I had the decell popping but it wasn't bad. I had been readingforum posts on the Nightrider XIED's and many reported the decell problem was gone after they installed the XIED's. I ordered some and it cured the decell popping but still sounds great. They are primarily used to cool down the heat from the new lean engines and they work. I'd check into them if I were you. Most folks don't need to do anything in the way of AC or Serts after the XIED's are put on. I agree the bike runs great now.
RHJ
Road Master
Joined: Jul 2007
Posts: 1,101
Likes: 2
From: The Left Coast
RE: Decel Popping...What exactly is the problem with it?
ORIGINAL: grandpawmoses
Decel Popping 101
Either (1) air is entering the exhaust system or (2) you're out of tuneon deceleration.
(1) On deceleration there is actually a momentary vacuum in your exhaust pipes after each cylinder fires. This vacuum helps extract the exhaust gasses of the next cylinder when it fires. That's why 2 into 1 exhaust systems are the most efficient. Even the tiniestleak in the gaskets of an exhaust system will suck in fresh air which will combine with the hot gasses containing the smallest traces of unburned fuel and immediately explode. Fix: Always use new crush gaskets on header installation and use new clamps & sealer on slip-on installation. Re-torque bolts after a few hours use. Short pipes are problematic, see #2.
(2) You can have a terriffic tune on your bike for performance but it pops on decel. The fix would be to richen up the mix on decel to the point that it's too rich to explode. If you have a tach, note the RPM range where (on deceleration) itpops. Go to your tuning software & richen up the VE values (both cylinders) at zero percent throttle for the approximate RPM range that you noted the popping. I prefer to increase them one unit at the time & try it. This can take several attempts,each time getting better.
GPM
Decel Popping 101
Either (1) air is entering the exhaust system or (2) you're out of tuneon deceleration.
(1) On deceleration there is actually a momentary vacuum in your exhaust pipes after each cylinder fires. This vacuum helps extract the exhaust gasses of the next cylinder when it fires. That's why 2 into 1 exhaust systems are the most efficient. Even the tiniestleak in the gaskets of an exhaust system will suck in fresh air which will combine with the hot gasses containing the smallest traces of unburned fuel and immediately explode. Fix: Always use new crush gaskets on header installation and use new clamps & sealer on slip-on installation. Re-torque bolts after a few hours use. Short pipes are problematic, see #2.
(2) You can have a terriffic tune on your bike for performance but it pops on decel. The fix would be to richen up the mix on decel to the point that it's too rich to explode. If you have a tach, note the RPM range where (on deceleration) itpops. Go to your tuning software & richen up the VE values (both cylinders) at zero percent throttle for the approximate RPM range that you noted the popping. I prefer to increase them one unit at the time & try it. This can take several attempts,each time getting better.
GPM
I might add, don't overtighten at the heads, the crush gaskets can be compressed too much. And, if you have clamps on your mufflers/slip-ons crank those down to spec, ride it until hot and crank them down again, use NEW clamps if you have changed mufflers, I learned this the hard way!
Road Master
Joined: Feb 2007
Posts: 967
Likes: 3
From: Eastern Massachusetts
RE: Decel Popping...What exactly is the problem with it?
Part of the problem is that "popping" is a subjective term. There's a sound that we used to call "burbble" which is normal for a well-tuned engine that is being driven slightly by the wheel (as in a downshift situation or throttle roll-off.) Then there's backfiring which is just plain bad and stressful on the whole engine/exhaust system. My bike burbbles -- I like the sound. Every sports car I've ever owned burbbled. When I ride into a parking lot where there are other bikers and someone comes up to me and tells me I have decel popping I smile, nod and keep walking. On the other hand, the once or twice my Harley has backfired on me (happens sometimes in a hot start)it about scared the snot out of me. If I heard that when I decellerated, I'd be angsty.
Road Master
Joined: Jul 2007
Posts: 1,101
Likes: 2
From: The Left Coast
RE: Decel Popping...What exactly is the problem with it?
Snap, burbble, pop! It's a Harley
I know what you mean, I live on the top of a hill and it is a steep decent about a mile into town, my bike burbbles down the hill, but when my muffler clamps were loose, it was a definite popping sound..hard to describe.
Good way to check for popping is a steep hill and wind 'er up and downshift, if it's gonna pop it will then[8D]
I know what you mean, I live on the top of a hill and it is a steep decent about a mile into town, my bike burbbles down the hill, but when my muffler clamps were loose, it was a definite popping sound..hard to describe.
Good way to check for popping is a steep hill and wind 'er up and downshift, if it's gonna pop it will then[8D]
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