pipes with little or no backpressure will pop slightly and are tough to tune,exhaust leaks are the first thing to check for.

 

Too lean? I always thought a little rich and the pop sound was excess fuel burning off in the exhaust? Not a tuner just my own logic. If I'm wrong someone please explain.

Btw I think a little pop sounds cool and have no problem with it.

Sath

 

There are a couple different kinds of 'popping' from the exhaust. The easiest to think of is the mixture is too rich... rich popping... on a Harley this condition sounds like a 'blubber' with my D&D pipes, or with other pipes its a big bang then a bunch of little popcorn farts. Rich popping is due to unburnt fuel being expelled into the exhaust from a really rich condition. If the bike is kind of rich, and then you slam the throttle closed, there simply is more fuel than the bike can burn kind of deal. It burns what it can and the excess fuel is shot out with the exhaust mixture, meets more oxygen and HOT pipe....... OK, that one is easy. We use the DE table to remove fuel so only enough fuel is there to be fully burned in the chamber.... nothing left over.

Most of the time, one hears lean pops... that one big ka pow kind of deal. How that happens is if the mixture is already lean, and then the throttle plate gets slammed closed, the carb or injectors quit giving up fuel, the engine gets starved for fuel instantly. You can see that happening right? Well... it is SO starved for fuel, that the fuel it DOES have is not burnt in the combustion chamber... it doesn't light up with the spark plug, it just gets expelled into the exhaust, where it meets fresh oxygen and... HOT pipe, then ka pow! So, we ADD fuel with the DE tables to move the combustion back into the cylinder with a good solid combustion event..

ALL engines will exhibit a small amount of lean popping, but for the third kind of popping it is lean pooping WITH an exhaust leak. The normal, all engines do it kind of lean popping really gets lost in the noise of the normal exhaust... it's there just not well defined. But... once an exhaust leak is put into play, that normal lean pop becomes a LOUD lean pop, due to its ability to get fresh oxygen AND hot pipe right away... way before the exhaust tip.

This is really a 'quickie' but I hope it helps you Sath.

There is a bit more to it, like where the flame front is due to timing right when the throttle is snapped shut, etc. But this is just the basic...

And... I absolutely do NOT recommend this, but one can fix lean pops by using timing, too. One can retard the timing, when the throttle is slammed closed but there is some rpms left before idle. WHat this will do is ignite the mixture right when the exhaust valve opens and it shoots flame right into the pipe! This flame will ignite the mixture that was too lean to burn in the chamber Then right before the exhaust valve closes, the piston will start heading down and that whole flame will be sucked right back into the chamber. Problem with this is one HAS to be very precise, or the exhaust valves will end up being burnt. Been there... Done that! HAHA!!!

 

So what causes it to pop when at the end of engine braking? I mean if I down shift and let the engine brake from 3500 I will get a couple of pops when it get down to 2000 RPMs or when the engine is no longer slowing the bike down.

 

I have decel popping on my 2010 Road King with Fuel Motto head pipe and Rush 2.5's and TTS Mastertune....pretty much the same rpm range all the time.... like others have posted i was told if the tune was tweaked to add fuel it would have less decel popping... 2.5 baffles are pretty open and this allows more of the decel popping sound to be heard.... saw a post where Jamie at Fuel Motto explained it really well..but that was quite awhile ago.... my question is ... does decel popping affect the life of the engine in any way.... i dont mind what i have but need my engine to last ...

 

I was getting nasty decel popping when I installed my Python 3 1/2" slash cuts and V&H Dresser Duals. Also had the s/e a/c kit. Luckily the beauty of TTS Mastertune allowed me to eliminate the popping exactly as the manual suggests. By enrichening (lowering) the AFR between 1500 and 3500 RPM in the 20kPa column by 5-10%. I was pleasantly surprised that this actually worked. In my case it was from to lean a mixture as wurk truk explained in the earlier thread. Enrichening these few cells took care of it. As discussed manifold flange leaks or incorrectly torqued muffler clamps can also cause this.

 

I am running the Fuel Moto Stage 1 setup with Powervision and would get a pop once in a while when shifting from 1st to 2nd. I let Jaimie at FM know and he emailed back a revised map that I just downloaded tonite. Pop is gone! Nice!

 

So on the pcv just add 5% to the 0% throttle position across the board. Does that change idle speed?

 

I kinda like the decel popping..... Am I the only one?

 

With my slip-ons we could not get it to go completely away, the pipes flow so well that they still have a pop or two on deceleration.