pair mod w/VH - VTXOA
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post #1 of 9 (permalink) Old 02-11-2017, 11:43 AM Thread Starter
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pair mod w/VH

So in the midst of my leaky radiator repair, being The tank was already removed I decided to pull the pair solenoid off and cap the covers. I bought some rubber caps off the help rack put them on. I finally got the Radiator, lindby bars, radiator cover fuel tank etc. back on. went for a ride no leaks, but wow the backfires!!!!...sounds like fourth of july....(my pipes are not loose or leaking) I have a dual cone K&N intake setup with Vance and Hines slash cuts.......With the pair installed it had a low rumble with very minimal decal pops, with it removed its just plain embarrassing and annoying......looks like ill be pulling the tank......again......and reinstalling the pair.....blah.....
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post #2 of 9 (permalink) Old 02-11-2017, 03:11 PM
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It is difficult to understand why desmog would cause backfire. Imo you should look for an air leak. Are those rubber caps that you put on really tight? You normally should use rubber plugs(or block off plates)
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Last edited by fastspek; 02-11-2017 at 03:13 PM.
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post #3 of 9 (permalink) Old 02-11-2017, 05:43 PM Thread Starter
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very tight.....no leaks I'm actually glad I didn't spend money on the block off plates ...I read a ton of threads here about the desmog and all the exhaust notes it does/doesn't cause.....im just going to put it back on, no big deal, you cant see all that junk under the tank anyway....I only removed it because of the threads I read and figured it would clean up the area.
Ill try and get some pics once I pull the tank.......I need to run it down on fuel first..
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post #4 of 9 (permalink) Old 02-11-2017, 08:41 PM
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There really isn't any way for blocking off the pair valves to increase decel pop. If you think about it, decel pop is unburned fuel igniting in the exhaust. This requires 3 things in order to happen. You need fuel. That happens because you have a closed throttle and very little air coming in through the throttle body. The charge is rich and with the lack of air unburned fuel is a byproduct of this. You need heat. This is obvious, the exhaust pipe is generally hot enough to ignite a burnable air fuel mix. Then you need air / oxygen. Where is this going to come from. With the pair functioning the valve lets in air specifically to burn off any unburned hydrocarbons. Block that off properly and no air from there. Leaky exhaust gaskets result in a lot of decel pop because in a decel condition air will actually get sucked in there, decel pop is a byproduct if that. Ultimately if you take away the air, no decel pop, or very little anyway. There certainly should not be more decel pop with the pair blocked off. No way should that be possible. It just doesn't figure.

You, my friend, have a leak somewhere.
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post #5 of 9 (permalink) Old 02-11-2017, 08:50 PM
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Decel popping is the result of unburned gas leaving the combustion chamber, mixing with oxygen and igniting brought on by the heat of the exhaust. To ignite, the fuel/air ratio has to be just right or it won't happen. Straight pipes with little or no baffles allow oxygen to get sucked into the pipes on each return pulse of the exhaust. This oxygen will then mix with the unburned gas and the result is decel popping. I'm guessing that when your PAIR system was in place the oxygen it passed into the exhaust port, mixing with the oxygen coming up the pipes, created a fuel/air ratio that was too lean to fire off. You'll soon find out when you reinstall your PAIR system.
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post #6 of 9 (permalink) Old 02-12-2017, 01:40 AM
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I have never heard of anyone getting more decel popping from doing the desmog/PAIR removal.
I know you believe you have no air leaks, but there are multiple points where air could be getting in.
If the exhaust headers were moved or adjusted, the exhaust crush gaskets have to be replaced.


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post #7 of 9 (permalink) Old 02-12-2017, 02:18 AM
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Quote:
Originally Posted by nate6966 View Post
I have never heard of anyone getting more decel popping from doing the desmog/PAIR removal.
I know you believe you have no air leaks, but there are multiple points where air could be getting in.
If the exhaust headers were moved or adjusted, the exhaust crush gaskets have to be replaced.
News to me too Nate. Just thinking outside of the box.
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post #8 of 9 (permalink) Old 02-12-2017, 07:42 PM
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Quote:
Originally Posted by Sojourner View Post
Decel popping is the result of unburned gas leaving the combustion chamber, mixing with oxygen and igniting brought on by the heat of the exhaust. To ignite, the fuel/air ratio has to be just right or it won't happen. Straight pipes with little or no baffles allow oxygen to get sucked into the pipes on each return pulse of the exhaust. This oxygen will then mix with the unburned gas and the result is decel popping. I'm guessing that when your PAIR system was in place the oxygen it passed into the exhaust port, mixing with the oxygen coming up the pipes, created a fuel/air ratio that was too lean to fire off. You'll soon find out when you reinstall your PAIR system.
I suppose that's possible but I doubt you get air back far enough where there is enough heat to ignite the mix. Again anything is possible but this scenario would be a long shot IMHO. Far more likely air is incoming upstream.


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post #9 of 9 (permalink) Old 02-13-2017, 01:51 PM
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Did your caps have the cut out (dimple) for the screw? If not, it didn't seal.
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