Hi everyone! I purchased a 2014 break (previously owned a V-rod) out about a month ago and I loaded it up with all the goodies the first week I owned it. I have the power vision with pro autotune. I have pretty much learned the software inside and out but I got a slight issue I can't tune out, dreaded decel pop.

Let me first state that I’m running V&H Short shots. I figured these would be hard to get rid of all pop. First of all I do not think I have any leaks, but I would welcome any good test for this so I can be 100% sure. I’m getting one maybe two pops on in the 2700 to 2500 rpm ranges. I watch the AFR go above 15:1 in this range on the rear cylinder (the short pipe). Front stays steady at 13:1. I have maxed out my VEs in the 20kpa rpm range and AFR doesn’t drop at all!! What gives?

I have also reduced my decel enleanment to .1 and advanced the timing. Its going super lean on just rear cylinder from 2500 and over. Is this all due to the short pipe?

Here is a video of my bike:

 

I'm not quite adept enough with the PV. But I will explain a little using what would work with a TTS and maybe you can replicate. I'm in Ashland, so ya know, too.

Yes, those pipes will suck.

Don't worry about any kind of AFR when in decel mode. Fill out your histograms to get less than 5% delta all around, and THEN go and look at logs to make sure you actually are collecting data in all cells. If you are not collecting data, then it will LOOK like there is less than 5% change, because you never collected data. See?

OK, once you have a decent fuel map. It's time to work on timing changes. Did you try this? Did you work the EGRs? Hmmmmm... charge dilution?

AFter all of this is when to work popping. So, playing with decel enleanment won't work? What kind of pop is this? Is it a big bang kerPOW when you let off? Or is it more like popcorn farts? PuPuPuPu sound? Is it loud or muted a bit?

Big KaPow is a lean pop, and a PuPuPu is a rich blubber.

I am going to assume we are talking about lean pop. Lean pop is from fuel in the pipe that gets ignited by the 'next' ignition cycle. The fuel becomes so lean that the bike misfires and fuel is not ignighted and sent to the pipe... next go around the fuel DOES ignite and when the flame leaves the exhaust valve, it ignites the raw fuel from the previous misfire. The misfire happens because there is not enough fuel to ignite... way to lean. With me so far?

So, using the enleanment tables, we richen the exhaust, right? Problem with decel enleanment is it is very short acting. Some bikes/pipes will exhibit a series of loud pops when the tach is falling from a higher rev, which sounds like your issue, right? Decel from 3000 rpms and you get a spaced kind of series of pops, right? Pow... Pow... Pow... kind of thing. Right?

If that is the case, what is happening is you are getting lean misfire when slowing down every once and awhile and it lights up in the pipe one the next 'good' combustion event and that flame is igniting the unburned fuel.

Ok... there IS a fix, but my lack of PV stuff will limit me here. With a TTS, we have a table that is called 'closed throttle spark'. It consists of a table that one can insert override timing when the throttle of completely rolled off. Lower RPMs, like 1000 to 1500 rpms are used to smooth start up idle. 20-30-40 KPA on the main tables should be set all the same at 750 to 1250 rpms on the main spark tables AND the same timing should be matched in the closed throttle sections. This all aids start up when cold to stop an engine from 'hunting' when its warming up. WIth me?

Now ... the same closed throttle spark table can also be used to control higher rev decel pops. 2500 up, on this table should be set at like 30*. WHat this will do is suck the flame front back into the cylinder before it can ignite any raw fuel in the pipe. The raw fuel simply exits with the exhaust flow without being lit off.

My issue, NOT yours my friend, is my total lack of PV. TTS and SEPST, ok.. i know these and know TTS inside and out.

Is there a table for closed spark with the PV? I'm not going to look, I wish YOU to do so.

Here is a shot of that table in TTS.



The red circled area is what I have recommended folks match to that 30-40 KPA range thing for good idle, remember? My main spark tables all match at that 24* to aid in cold starting smoothness.

But... see that 4000 row? See how I have it at 29*? THAT is to stop loud decel pops when the revs are falling.

Since we are close enough. I will PM you my number. Maybe we could meet later?

I would be glad to help you. I have a dyno and a million kinds of sniffers, etc. ALso have sniffing blocks that can be used. Most pipes will have bad locations for the 18mm bungs.

I am VERY busy at work right now, though. This is my busy season and right now, I am solidly booked until March!

Don't call, but shoot me a text at first and we can go from there. WHat I would LIKE is there is a fellow member here that lives near Marion. He is quite good with the PV, but he doesn't have a dyno. Between the three of us???? See where I am thinking here?

I just saw I cannot PM you my number. You are too new a member. I posted my email addy as a visitor message to you. Go find your visitor messages and email me and we can go from there.