Decel popping can happen for a number of reasons, and there are a number of tuning strategies to alleviate it. Lets say there are absolutely no exhaust or intake leaks and you are getting popping on decel, this can be caused by a lean or rich mixture and here are a couple of tuning strategies to help resolve this phenomenon primarily related to exhaust gas temp (EGT). The most common technique is to add fuel thru a combination of the AFR table, VE tables, and decel enleanment table; a slighly lean mixture will hyper ignite any hydrocarbons in the exhaust stream, by adding fuel you are lowering EGT and in many cases this will take care popping that is present. Note that because injector duty cycle is so small during decel it may take a pretty big change to see results, this is normal and what appears to be a big change in a tuning table is a small amount of fueling under decel. If richening the fuel does not resolve the popping we will try to remove fuel in the same table(s), this will simply put less ignitable elements in the exhaust, however many times the popping will get worse due to the raise in EGT. Another tuning parameter that can be used are the spark tables and closed throttle spark, adding timing will many times reduce decel popping as well. To make things more complicated many bikes use a decel fuel cutoff (DFC) where the ECM turns the injectors off under certain parameters under decel, when DFC is causing popping you need to work the various tables to tune what we call the "landing" when the injectors come back on, and also note that even when the injectors are shutting down it is still possible to get residual fuel causing popping.

In the end while an exhaust leak or tune issue can be the root cause by far the biggest issue and contributor to decel popping is exhaust and muffler design. This all varies by combination however large, open, enormous mufflers & baffles can/will lead to issues. They also "greatly" affect low/mid RPM performance and tunability, an effect of the loss of velocity. Hope this info helps

 

Hrmm. Only thing I can think of - and this is a stretch- is maybe you have the throttle cable too tight and it is holding the throttle open slightly, which would introduce more air and maybe contribute to popping. Double check the cable free play adjustment and make sure it is within spec.

If you have a PV-2 you can experiment with eliminating decel pop. Go into the PV-2 Quick Tune menu, Tweaks. Add +10% to Decel Fuel, save and give her a spin. If that quiets the pops or gets rid of them, then you know you need to richen up the VE's in the decel area of table or richen up the Decel Enleanment table. I'd adjust the DE table first if the Quick Tune setting makes a positive difference. If you need guidance on adjusting the DE table, post your current values here and one of the "smart guys" can give you an idea on what and how much to adjust.

This is just based on my own learning the past week and dialing out the decel pop.

 

Holy crap Jamie- I really like reading your posts, because you actually know what you are talking about and can explain it concisely. Can I have a copy of you here at my house? LOL

Admittedly I know my VH 2-2 pipes are far from optimal, they came with the bike. I have a RB Racing LSR 2-1 pipe on my (heavily modified) 107 Evo, putting out 120hp/130tq, and the pipe was a huge factor in getting those TQ numbers. I will be putting on a better, 2-1 pipe on the Breakout next spring when I do the cam and head mods.

But! Optimizing DE, VE, AFR and closed throttle spark have all but eliminated the decel popping from the VH 2-2 pipes, so I'm very happy with the amount and depth of adjustments offered by the PV-2.

 

I want to send a huge THANK YOU to member ke5rbd for helping me on the side, with tune examples and detailed learning instructions on what does what and why. This guy knows his stuff. Again, thank you for taking the time to help- You are part of what makes this forum GREAT.

This, and the info / pointers here in the forum have given me a massively better understanding of how the various table parameters work within the Delphi tuning system, importance of VE, how to properly datalog and enable QT, etc. - I thank you all for your advice and help as well.

I still have a long way to go of course, but at least I have the ability now to actually do something meaningful with the PV-2. I have had some very positive results on my bike over the past couple of days.

 

My bad, I've lost a whole decade of memory lol.

 

Understandable. I used to know all the year to year changes too and that's all lost lol.

 

Hey Jamie. I have never thought about running a data log while in AT mode. I didn't think it would be any useful data since timing and afr both are changed during AT. I usually run data logs after I complete an AT to see what affects it had on my tune only.


So the question is, what benefit could you get from data logging during AT? Even after 7 years of fooling with the PV I am still interested in learning...LOL.

 

That is an EXCELLENT question (on AT Basic) and I wanted to take it one further. Let's say you already have a reasonably decent tune - could you go into Quick Tune, add 4 degrees to overall Spark, save, then run AT? Would this give more accurate results since adding the 4 degrees makes up for AT's subtraction? Or does it botch things up since AFR is set to a fixed value across the map table or QT's math accounts for the subtraction?

 

My understanding is you can add the 4*, but you run the risk of the timing being too far advanced and as you say mucking up the tune. Others has posted about this in here in the past, I think.

 

Thank you for your reply Jamie, If i try to run AT basic, the bike will run like crap, i assume because it's not getting enough fuel when AFR is 14.6. When i tried AT Basic, the bike idles very harsh and stalls and hesitates on acceleration.
I didn't have the Monster Ovals, it was the older style ovals. with the double lips.
do u think i made mistake going with the 4.5 V&H Monster rounds ? i wanted to quite the sound compared to my V&H ovals. Yes, i agree, the 4.5 rounds are a lot less restrictive towards exhaust flow... will this hurt the motor ?