Vance & Hines FP3
#11
08-09-2014, 05:46 PM
Outstanding HDF Member
Everything I've read over the years always points to exhaust leak or running too lean. Also, you put on pipes and air cleaner on a new bike and it instantly runs lean which is why all the complaints about decel popping after stage 1 is done. That's one reason why people get tuners or get it dyno'd.
Here's something I googled that seems to explain better.
>>
You start out with an engine that is turning high RPM with a carb that is open, flowing freely. Next, you close that slide. This has the effect of creating a tremendous vaccuum in the intake manifold (CHOKE!). This vaccuum does curious things:
1. It pulls air and fuel from wherever it can--including the idle and low speed jetting in the carb.
2. To counteract the vaccuum, air will take the path of least resistance--including sucking exhaust gases back into the combustion chamber during valve overlap (the brief period of time that the exhaust and intake valves are open at the same time.
So what does this mean? Well, now you have a disproportionate rich mixture heading for the cylinder AND what little oxygen is drawn in is further diluted by gases that are coming back into the chamber from the exhaust valve. The result is poor, incomplete combustion! Depending on the temperature of the exhaust pipe and gases, reignition is possible once this mixture is introduced into a more oxygen rich environment. This produces the "pop."
Why does a lean running engine have a tendency to excessively pop? The exhaust gas temperature of a lean engine is substantially higher than one that is running on the rich side ( an EGT probe will show this). Therefore, the high EGT serves to heat the pipe more and the gases themselves become a much better source of re-ignition. By richening things up, you are cooling down the exhaust temp and therefore reducing potential re-ignition sources.
<<
Here's something I googled that seems to explain better.
>>
You start out with an engine that is turning high RPM with a carb that is open, flowing freely. Next, you close that slide. This has the effect of creating a tremendous vaccuum in the intake manifold (CHOKE!). This vaccuum does curious things:
1. It pulls air and fuel from wherever it can--including the idle and low speed jetting in the carb.
2. To counteract the vaccuum, air will take the path of least resistance--including sucking exhaust gases back into the combustion chamber during valve overlap (the brief period of time that the exhaust and intake valves are open at the same time.
So what does this mean? Well, now you have a disproportionate rich mixture heading for the cylinder AND what little oxygen is drawn in is further diluted by gases that are coming back into the chamber from the exhaust valve. The result is poor, incomplete combustion! Depending on the temperature of the exhaust pipe and gases, reignition is possible once this mixture is introduced into a more oxygen rich environment. This produces the "pop."
Why does a lean running engine have a tendency to excessively pop? The exhaust gas temperature of a lean engine is substantially higher than one that is running on the rich side ( an EGT probe will show this). Therefore, the high EGT serves to heat the pipe more and the gases themselves become a much better source of re-ignition. By richening things up, you are cooling down the exhaust temp and therefore reducing potential re-ignition sources.
<<
#12
08-09-2014, 08:12 PM
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I'm no mechanic but I think if you can take fuel out of the decel portion then there is nothing to burn which means no popping. It's not rich or lean, there is just little fuel left. I think that's the theory behind it.
Worst case, get ahold of V&H and I'm told they will actually send a custom map to your phone. But I'm sure they are just doing the same thing you are.
Worst case, get ahold of V&H and I'm told they will actually send a custom map to your phone. But I'm sure they are just doing the same thing you are.
#13
08-10-2014, 09:49 AM
Outstanding HDF Member
Agreed, still playing with the enleanment chart on decel. Made a few more adjustments and did a quick test ride today. Nice crackling but no major decel pop. We shall see.
I watched a few good videos on adjustment but doesn't look like I can access the full map with throttle position on one axis and rpm on the other which would be a better way to adjust it seems.
Having fun playing with small mods though
I watched a few good videos on adjustment but doesn't look like I can access the full map with throttle position on one axis and rpm on the other which would be a better way to adjust it seems.
Having fun playing with small mods though
#14
08-10-2014, 10:39 AM
Fp3
I used the FP3 after I did a Stage One. The FP3 worked perfectly and I am a big fan. I know it has it's limits - but used in the right application (a straight forward Stage One upgrade) it is a good tool. I just used their canned map and the bike runs great - whole tuning process took 15 minutes at most. When I have time in the future, I plan on playing with the auto tuner - but in the meantime, I am just enjoying the ride.
#15
08-11-2014, 07:58 AM
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#16
08-15-2014, 10:40 PM
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#17
08-15-2014, 11:50 PM
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They only way your going change that is through gearing. either get a bigger tranny drive sprocket or smaller rear wheel one. Man i wish it was that easy to change the RPM's with just the tuner.
#18
08-16-2014, 07:20 AM
One more fan of the FP3 ..I installed FP3 on a 2014 Street Bob with V&H short shots and high flow air filter. Greatly improved smoothness of engine, more power, and eliminated deceleration popping. I also installed one on my 2014 Street Glide with same results. Highly recommended for Stage 1.
#20
05-23-2016, 05:06 PM
