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PAIR valve removal. Worth it?


yycviffer

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Evening Gent's,

I am in the middle of doing valve clearances. As such I essentially have the PAIR valve system off the bike. My question is, is it worth removing the system from any kind of a performance spec? I bought the bike last year and the only thing I noticed was, that when I would dial on it, between 4500 and 6000 power seemed to drop off. (almost like it was fuel limited) After 6k it seemed to pick back up. I am going to do the flapper valve mod as that seems to be the "thing to do" also. Anyways I am looking for a general consensus among the high time 5th genr's as as to whether to leave it off or not. Weight is irelevent, its a VFR. Thanks for the input guys.

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Evening Gent's,

I am in the middle of doing valve clearances. As such I essentially have the PAIR valve system off the bike. My question is, is it worth removing the system from any kind of a performance spec? I bought the bike last year and the only thing I noticed was, that when I would dial on it, between 4500 and 6000 power seemed to drop off. (almost like it was fuel limited) After 6k it seemed to pick back up. I am going to do the flapper valve mod as that seems to be the "thing to do" also. Anyways I am looking for a general consensus among the high time 5th genr's as as to whether to leave it off or not. Weight is irelevent, its a VFR. Thanks for the input guys.

Performance-wise no, there is no reason to remove the PAIR system. It does however help with tuning the engine with a Powercommander (and Autotune in particular) as the PAIR system causes incorrect AFR readings to the Autotune when you close the throttle.

Oddly enough, my 2002 with PAIR disabled, Motad headers and a custom tune has some wicked exhaust popping when I decelerate, which is something that removal of PAIR generally stops.

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Guest MiddleTBabb

hmm....

you've got my attention about that power drain in those rpms....

I blocked off my PAIR valve and IMHO it greatly increased the accuracy of throttle inputs at low rpms (like a California roll through a stop sign)

...but...

is that what's responsible for the flat spot from 4-6k rpm? :comp13:

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I probably should have said driveability / useability stand point. I agree that its not going to make any more power. I was looking to solve that bit of flat spot in the rev range. It only appears to be at full throttle too. Bombing around town you would never know. I looked up some other posts re pair valves and didn't really find anything definitive on the advantage of removing it. Lots of how do it and a bit of its a dumb/waste system get rid of it, but nothing that said if you remove it you will see this result.

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The Pair Valve is a pollution control "Pulsed Air Injection" device, designed to "wash out" the purposely rich exhaust of metric bikes in order to pass U.S. EPA restrictions for import in the United States and other countries with similar restrictions. Many foreign designated models do not even come with a pair valve, although all other aspects of the bike's engine are the same.

The sole purpose for the Pair Valve is to passively "Inject" fresh air into the exhaust system at the exhaust port, to cause ignition of unburned fuel vapor *before* it leaves the exhaust pipes, or to thin out the mixture with enough air to fool the sniffer machines. Unburned fuel vapors enter the exhaust system whenever you back off the throttle, or gear down. When you close the throttle, as in gearing down or slowing down, the drop in vacuum at the intake port allows the Pair Valve to relax and open and allow air from the air filter box to be "siphoned" into the exhaust port by the negative pressure at the exhaust ports. (there are reed valves in the pair valve to prevent backflow from the exhaust to enter the pair valve and airbox during roll-on and subsequent positive exhaust port pressure).

On the rare occasions that the pair system is working as designed, there is no erratic popping or gurgling in the exhaust system. There should be either no additional sound at all, or a steady "afterburn" effect, similar to an eighteen wheeler's "Jake Brake", a compression release speed reducer for large trucks.

Many people who have replaced their exhaust system with louder, lower backpressure pipes, have experienced an increase in the rapid popping/gurgling noises when throttling back and gearing down. With less backpressure, the exhaust vapors tend to load up in the system, and ignition of these vapors is sporadic and annoying. This popping occurs further down in the pipes, and is louder because of more open baffles, or no baffles at all. The quick fix for this is to simply "plug up" the air tubes that go into the cylinder walls, thereby preventing the air from getting there in the first place, thus, no "in-the-pipe" ignition. You may still experience some occasional popping, set off by the intense heat, but it is much less frequent.

Removing or disabling the Pair Valve will have no ill effects whatsoever to the bike even if its is still stock. The pair valve system will likely clog with carbon after a year or so, and quit working anyway. Removal is simple, and will take less than an hour once you have all the "stuff" together.

The presence or absence of the Pair Valve does not affect your fuel mileage, power, or general engine running condition. It's purpose is solely to thin out the exhaust mixture so that it will pass all available emission control standards, and this "thinning out" occurs at the exhaust ports *after* the pistons and spark plugs have done their job. Basically it's a P.O.S. designed to make politicians look like they're environmentally concerned, and contributes more to driveability issues than lower emission concerns. So, yeah, yank it. (maybe "illegal" depending on where you are)

I'm running an '02 that's been de-PAIRed, de-snorkled and de-flappered with a PC-III (Cozye's map) and it runs smooth as glass with no popping on deceleration whatsoever. Hope that's useful.

I

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Thanks for the reply and very in depth system description dendron. I think I am going to remove the system as I forsee a PCIII in the future and it would have to be removed at that point anyway. Emissions isn't and issue in alberta yet so no worries there.

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I'm in the same spot as you. I really didn't bother with it until recently, as I am also in the midst of valve clearance adjusting. I've had the airbox off a couple time prior to this, and hated the bother of getting all the hoses routed properly, plus the dealie for the flapper that is on the bottom of the airbox. Just figured I'd remove a whole lot of messy crap while I am in there this time.

I've tried the quick and easy flapper disable in the past, and thought it may have been a little loud. I re-flappered it for a long time, but this time I guess I'm committed to flapperless operation.

All my track bikes have come de-paired, and my RC came de-paired and de-flappered with seemingly no ill effects.

This is what came out of my '99:

pair-flapper.jpg

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The Pair Valve is a pollution control "Pulsed Air Injection" device, designed to "wash out" the purposely rich exhaust of metric bikes in order to pass U.S. EPA restrictions for import in the United States and other countries with similar restrictions. Many foreign designated models do not even come with a pair valve, although all other aspects of the bike's engine are the same.

The sole purpose for the Pair Valve is to passively "Inject" fresh air into the exhaust system at the exhaust port, to cause ignition of unburned fuel vapor *before* it leaves the exhaust pipes, or to thin out the mixture with enough air to fool the sniffer machines. Unburned fuel vapors enter the exhaust system whenever you back off the throttle, or gear down. When you close the throttle, as in gearing down or slowing down, the drop in vacuum at the intake port allows the Pair Valve to relax and open and allow air from the air filter box to be "siphoned" into the exhaust port by the negative pressure at the exhaust ports. (there are reed valves in the pair valve to prevent backflow from the exhaust to enter the pair valve and airbox during roll-on and subsequent positive exhaust port pressure).

On the rare occasions that the pair system is working as designed, there is no erratic popping or gurgling in the exhaust system. There should be either no additional sound at all, or a steady "afterburn" effect, similar to an eighteen wheeler's "Jake Brake", a compression release speed reducer for large trucks.

Many people who have replaced their exhaust system with louder, lower backpressure pipes, have experienced an increase in the rapid popping/gurgling noises when throttling back and gearing down. With less backpressure, the exhaust vapors tend to load up in the system, and ignition of these vapors is sporadic and annoying. This popping occurs further down in the pipes, and is louder because of more open baffles, or no baffles at all. The quick fix for this is to simply "plug up" the air tubes that go into the cylinder walls, thereby preventing the air from getting there in the first place, thus, no "in-the-pipe" ignition. You may still experience some occasional popping, set off by the intense heat, but it is much less frequent.

Removing or disabling the Pair Valve will have no ill effects whatsoever to the bike even if its is still stock. The pair valve system will likely clog with carbon after a year or so, and quit working anyway. Removal is simple, and will take less than an hour once you have all the "stuff" together.

The presence or absence of the Pair Valve does not affect your fuel mileage, power, or general engine running condition. It's purpose is solely to thin out the exhaust mixture so that it will pass all available emission control standards, and this "thinning out" occurs at the exhaust ports *after* the pistons and spark plugs have done their job. Basically it's a P.O.S. designed to make politicians look like they're environmentally concerned, and contributes more to driveability issues than lower emission concerns. So, yeah, yank it. (maybe "illegal" depending on where you are)

I'm running an '02 that's been de-PAIRed, de-snorkled and de-flappered with a PC-III (Cozye's map) and it runs smooth as glass with no popping on deceleration whatsoever. Hope that's useful.

I

There was a point in which I thought, using the theory you mentioned above, I could use the same signal that activates the PAIR to turn off my Autotune on deceleration. I had removed my PAIR because Dynojet had told me that I needed to for the Autotune to work correctly. To test it's function to see if it would work for my new purpose, I connected a light to the PAIR plug and went for a ride. I found the PAIR circuit was only active when the throttle was closed and when the temp was below 168F. Once the bike hit 169, I never saw the light come on again. Since the bike doesn't go into close loop until it's up to temp, that would make since. The PAIR would never effect close loop operation. With further research, I found the PAIR is only to help reduce emissions during warm up. At the same time it helps generate heat in the CAT and also heats up the O2 sensor to help them both operate correctly. So what does removing it do? Well after the bike is at operating temp....nothing, however it my take the bike it's self a little longer to get to that temp. The reason I left mine off? One less thing to malfunction.

Side note: While the snorkel and flapper are there to lower intake noise, their main purpose is maintain intake viscosity at small throttle openings. The flap doesn't open until the bike can use the 'extra air'. Disabling the flap doesn't increase the overall volume for max power, at full throttle and a RPM at which it's needed, the flap opens anyway. Disabling it can only hurt low speed torque. The fact that the intake sounds louder, mentally tricks our 'butt dyno' into thinking we're making more power.

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I'm in the same spot as you. I really didn't bother with it until recently, as I am also in the midst of valve clearance adjusting. I've had the airbox off a couple time prior to this, and hated the bother of getting all the hoses routed properly, plus the dealie for the flapper that is on the bottom of the airbox. Just figured I'd remove a whole lot of messy crap while I am in there this time.

I've tried the quick and easy flapper disable in the past, and thought it may have been a little loud. I re-flappered it for a long time, but this time I guess I'm committed to flapperless operation.

All my track bikes have come de-paired, and my RC came de-paired and de-flappered with seemingly no ill effects.

This is what came out of my '99:

pair-flapper.jpg

Uhmmmm.... that's not too much off the bike.... What about the hard plumbing (metal air injection pipes going near the exhaust manifold exit point at the heads. I assume the 5th gen has them too. Did you just abandon those in place?? All you will need are some blocking plates and you can get rid of them for good.

Beck

95 VFR

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What about the hard plumbing (metal air injection pipes going near the exhaust manifold exit point at the heads. I assume the 5th gen has them too. Did you just abandon those in place?? All you will need are some blocking plates and you can get rid of them for good.

There's actually no hard plumbing as such. They are channels which run within the engine cylinder head. A picture might better explain things. I'm guessing 6thGen are similar.

PAIR.jpg

For those who have done this mod, can anyone tell me what the small piece is just below the reed valve, on the left?

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What about the hard plumbing (metal air injection pipes going near the exhaust manifold exit point at the heads. I assume the 5th gen has them too. Did you just abandon those in place?? All you will need are some blocking plates and you can get rid of them for good.

There's actually no hard plumbing as such. They are channels which run within the engine cylinder head. A picture might better explain things. I'm guessing 6thGen are similar.

PAIR.jpg

For those who have done this mod, can anyone tell me what the small piece is just below the reed valve, on the left?

Not 100% sure about what part you are asking, but I think it is just the metal screen. You can see 4 of them in my pic. Two are on the floor beside the reed valve, and the other 2 are sitting on top of the reed valves.

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Uhmmmm.... that's not too much off the bike.... What about the hard plumbing (metal air injection pipes going near the exhaust manifold exit point at the heads. I assume the 5th gen has them too. Did you just abandon those in place?? All you will need are some blocking plates and you can get rid of them for good.

Beck

95 VFR

I think I know what you are talking about, I've seen them on other bikes. No such thing on mine.

And for coderighter, my bike has neither a catalytic converter or any oxygen sensors! Same with my RC51.

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I saw a guy building a custom Superhawk street fighter block the pair system in a totally different, more permanent way. He drove a metal dowel down the shaft until it came into the combustion chamber. Then he ground it flush with the top of the chamber, like it was never there! :fing02:

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Not 100% sure about what part you are asking, but I think it is just the metal screen. You can see 4 of them in my pic. Two are on the floor beside the reed valve, and the other 2 are sitting on top of the reed valves.

Yes, that's exactly what they are, cheers :fing02:

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What about the hard plumbing (metal air injection pipes going near the exhaust manifold exit point at the heads. I assume the 5th gen has them too. Did you just abandon those in place?? All you will need are some blocking plates and you can get rid of them for good.

There's actually no hard plumbing as such. They are channels which run within the engine cylinder head. A picture might better explain things. I'm guessing 6thGen are similar.

PAIR.jpg

For those who have done this mod, can anyone tell me what the small piece is just below the reed valve, on the left?

Not 100% sure about what part you are asking, but I think it is just the metal screen. You can see 4 of them in my pic. Two are on the floor beside the reed valve, and the other 2 are sitting on top of the reed valves.

Ooohhh...looking at the diagram of the 5th gen head and air injection system, it looks like Honda went ahead and just cast in the tubes into the cylinder heads to intject the air into the combustion system, The earlsier 3rd and 4th gens had chromed metal piping on the exterior of the engine to inject the air in the exhaust ports just before the exhaust gasses enter the manifold pipes.

My mistake.....

Beck

95 VFR

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I havent screwed with the pair valves yet, but at some point while I'm working on something else, I might as well do that too. Hey KPerham could I have that pair valve to use as a template to cutout/make some block off plates, before I do a teardown on mine?

Just some info on my '98 - when I first bought the bike, it had only the carbon slip-on and everything else was stock. It did the off throttle decel pop pop dance quite often and was a bit annoying. When I added a BMC air filter and PC, now the decel pop is rare. Runs better, no popping, I'll take it.

BTW - this thread is an example of why VFRD is great. Real technical excellence and intellegence.

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Ooohhh...looking at the diagram of the 5th gen head and air injection system, it looks like Honda went ahead and just cast in the tubes into the cylinder heads to intject the air into the combustion system, The earlsier 3rd and 4th gens had chromed metal piping on the exterior of the engine to inject the air in the exhaust ports just before the exhaust gasses enter the manifold pipes.

No mistake mate, you've learnt something, and I've learnt something. You will note though that the 800cc does share a similar location to the fresh air outlet (just after the exhaust valve).

I havent screwed with the pair valves yet, but at some point while I'm working on something else, I might as well do that too. Hey KPerham could I have that pair valve to use as a template to cutout/make some block off plates, before I do a teardown on mine?

Same Mello dude, however, why not just buy some off Jim... better be quick though: http://www.vfrdiscussion.com/forum/index.php/topic/64442-fs-pair-block-off-plates/

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Uhmmmm.... that's not too much off the bike.... What about the hard plumbing (metal air injection pipes going near the exhaust manifold exit point at the heads. I assume the 5th gen has them too. Did you just abandon those in place?? All you will need are some blocking plates and you can get rid of them for good.

Beck

95 VFR

I think I know what you are talking about, I've seen them on other bikes. No such thing on mine.

And for coderighter, my bike has neither a catalytic converter or any oxygen sensors! Same with my RC51.

The getting the CAT and O2 hot fast is a side benefit, a bonus. It still serves the purpuse of cleaning up the left overs hydrocarbons while the bike is in warm up and the mixture is rich. Once the bike is up to temp, it should no longer be needed.

My point is, it's only needed during warm up and is not a part of 'normal operation'.

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[

I havent screwed with the pair valves yet, but at some point while I'm working on something else, I might as well do that too. Hey KPerham could I have that pair valve to use as a template to cutout/make some block off plates, before I do a teardown on mine?

Same Mello dude, however, why not just buy some off Jim... better be quick though: http://www.vfrdiscussion.com/forum/index.php/topic/64442-fs-pair-block-off-plates/

Well, them's nice, all pretty and machined. 26 bucks? Aw, dunno, my labor is free, and I can cut, file, and sand out a set with some AL sheet I have lying around. I like little detail stuff like this to do.

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Side note: While the snorkel and flapper are there to lower intake noise, their main purpose is maintain intake viscosity at small throttle openings. The flap doesn't open until the bike can use the 'extra air'. Disabling the flap doesn't increase the overall volume for max power, at full throttle and a RPM at which it's needed, the flap opens anyway. Disabling it can only hurt low speed torque. The fact that the intake sounds louder, mentally tricks our 'butt dyno' into thinking we're making more power.

Agreed. I have left both mine on and had the bike tuned on the dyno. It has excellent midrange punch!

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Great snabbling quoting, Batman! Making a short thread into a needlessly long one.... :blink:

Here's a contrary view (didn't actually bother to read all the quotes of quotes, just assumed the were all saying how wonderful flapper valve and PAIR removal mods are...

I actually prefer the flapper valve working - gives a nice burst of acceleration when it opens and the mapping on the PCII kicks in. As for the PAIR valve - I tried disabling it, and the bike's performance was WORSE.

But what do I know - this is obviously flying in the face of conventional VFRD wisdom and Common Practice. For all I know, my Yurpeen spec bike doesn't run right anyway, seeing as the Coriolis Forces are the right way round here in the Anti Podes.... :bliss:

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I havent screwed with the pair valves yet, but at some point while I'm working on something else, I might as well do that too. Hey KPerham could I have that pair valve to use as a template to cutout/make some block off plates, before I do a teardown on mine?

Just some info on my '98 - when I first bought the bike, it had only the carbon slip-on and everything else was stock. It did the off throttle decel pop pop dance quite often and was a bit annoying. When I added a BMC air filter and PC, now the decel pop is rare. Runs better, no popping, I'll take it.

BTW - this thread is an example of why VFRD is great. Real technical excellence and intellegence.

Yeah, if you really want them.

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After so many years thinking about it, I finally removed the snorkel on my 4th gen. I was hoping it might do something positive for performance even if it's infinitesimal. I figure, in the least, I still get rid of what could be another useless bit of weight of the fat bike and at most get some sort of nice induction noise out of it and better breathing............Frankly, after having it off for over a year already,.................... I don't seem to feel or even hear any difference at all. :blink: ......and maybe by removing it, I just put out the welcome/vacancy sign for mice to move into my airbox in the future.... :blink:

I figure it will be the same effect if I take off the PAIR system on my bike....... :dry:

Beck

95 VFR

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  • 1 year later...

I'm in the same spot as you. I really didn't bother with it until recently, as I am also in the midst of valve clearance adjusting. I've had the airbox off a couple time prior to this, and hated the bother of getting all the hoses routed properly, plus the dealie for the flapper that is on the bottom of the airbox. Just figured I'd remove a whole lot of messy crap while I am in there this time.

I've tried the quick and easy flapper disable in the past, and thought it may have been a little loud. I re-flappered it for a long time, but this time I guess I'm committed to flapperless operation.

All my track bikes have come de-paired, and my RC came de-paired and de-flappered with seemingly no ill effects.

This is what came out of my '99:

pair-flapper.jpg

On this picture, the round almost golden metal piece on the right, what is that part called?

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