What exactly does the pair valve do?
- Thread starter GeebMan
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Re-circulates spent exhaust gases. Removing it simply does away with the what the Government wants your syatem to do regarding emisions.
Yes, to your last Q. One of two options; either blocking or utilizing the pump as a 'Sucker Mod', routing the pump to the crankcase, ie., pulling the pistons along in, creating negative pressure, thus (theroratically) easing the travel/work. <Nutshell description
Yes, to your last Q. One of two options; either blocking or utilizing the pump as a 'Sucker Mod', routing the pump to the crankcase, ie., pulling the pistons along in, creating negative pressure, thus (theroratically) easing the travel/work. <Nutshell description
Actually, I think I was the source (at least on this site) for this bad information. According to cache, who knows TONS more about the busa than I do, the PAIR valve pulls CLEAN air FROM the airbox and injects it into the exhaust to reduce emissions.
I know I posted somewhere here that the PAIR recirculates exhaust gas back into the airbox to be recycled and burned again to reduce emissions. I got this understanding from somewhere but for the life of me I can't find it again. I think it was someone's personal site. My bad for taking someone else's word as truth without confirming it myself somehow.
To back up cache's explaination, if the PAIR pumped exhaust gas into the air box, the box would be nasty inside and smell like exhaust. When I removed mine for the exhaust install, it wasn't nasty and didn't smell like exhaust. I didn't doubt cache at all anyway. Just telling you what I saw, or rather DIDN'T see that re-enforces the correct info he posted.
Again, I apologize for posting the bad info. I never would have done that on purpose. From this point on, I will either quote the source for my info or I will confirm it before posting. Far be it from me to give anybody bad info on anything.
Sorry...
I believe that you are correct BT. The PAIR clearly exists to inject clean air directly into the exhaust to reduce the emissions by dilution, which seems like a dirty little trick by Suzuki to lower the ratio of "bad" emissions versus clean air.
But at any rate, the reason you must remove it with an aftermarket exhaust is because they all "pull" more air than stock which means it also pulls more unburned fuel. When this unburned fuel/air hits fresh air (with oxygen) injected by the PAIR system it can ignite causing nasty backfires. This tends to happen while letting off of the throttle and/or decellerating or at other points in the map where the bike will tend to be rich (ie: too much fuel/not enough oxygen to burn it all).
I guess maybe I am not explaining this very well but if you think about it, it all makes sense. You need fuel and oxygen to burn, if you have too much fuel versus oxygen (rich) it cannot burn all the fuel, but if the fuel in the exhaust gets more oxygen (from the PAIR) it can burn and will cuase backfires or worse. And remember the problem is that arftermarket exhaust pulls more air/fuel than stock so they tend to run rich, setting the PAIR up to cause backfires.
I'll shut-up now, sorry if I confused anyone, I am now rambling..............point is you do not need the PAIR in any case except if you are having your exhaust sniffed by a tester which never happens here in VA or most places, so get rid of it - dead weight and clutter.
One more point to further explain the PAIR system, the small line from the PAIR to the throttle body is the vacuum line that operates the PAIR manifold (I believe), the larger line draws fresh air from the airbox, and of course the 4 lines from the manifold inject air into each exhaust path directly before it enters the headpipes. Enough said?
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Reason for Edit: None given...|1068219408 -->
But at any rate, the reason you must remove it with an aftermarket exhaust is because they all "pull" more air than stock which means it also pulls more unburned fuel. When this unburned fuel/air hits fresh air (with oxygen) injected by the PAIR system it can ignite causing nasty backfires. This tends to happen while letting off of the throttle and/or decellerating or at other points in the map where the bike will tend to be rich (ie: too much fuel/not enough oxygen to burn it all).
I guess maybe I am not explaining this very well but if you think about it, it all makes sense. You need fuel and oxygen to burn, if you have too much fuel versus oxygen (rich) it cannot burn all the fuel, but if the fuel in the exhaust gets more oxygen (from the PAIR) it can burn and will cuase backfires or worse. And remember the problem is that arftermarket exhaust pulls more air/fuel than stock so they tend to run rich, setting the PAIR up to cause backfires.
I'll shut-up now, sorry if I confused anyone, I am now rambling..............point is you do not need the PAIR in any case except if you are having your exhaust sniffed by a tester which never happens here in VA or most places, so get rid of it - dead weight and clutter.
One more point to further explain the PAIR system, the small line from the PAIR to the throttle body is the vacuum line that operates the PAIR manifold (I believe), the larger line draws fresh air from the airbox, and of course the 4 lines from the manifold inject air into each exhaust path directly before it enters the headpipes. Enough said?
<!--EDIT|EAKbusa
Reason for Edit: None given...|1068219408 -->
Removing the PAIR with stock exhaust will not hurt anything and will remove weight and clutter only.
The TRE really is independant of the PAIR problem/solution and really has no effect on the other.
Adding a PC ONLY does not necessitate removal of the PAIR. But if you change the exhaust with or without a PC added you will have to remove it. I am not aware of anyone having success at having a custom map that allows the PAIR to be left on with aftermarket exhaust but you could check with Johnnycheese perhaps.
The TRE really is independant of the PAIR problem/solution and really has no effect on the other.
Adding a PC ONLY does not necessitate removal of the PAIR. But if you change the exhaust with or without a PC added you will have to remove it. I am not aware of anyone having success at having a custom map that allows the PAIR to be left on with aftermarket exhaust but you could check with Johnnycheese perhaps.
:Just read through this and now I have a question. I understand that the PAIR valve is adding air to the exhaust for dillution of the emissions, but I'm now confused on the air/fuel ratio aspect.
The way I understand it is: If you change to a high performance exhaust with better scavenging, then it increases the air flow through the engine. This higher air flow should give you a lower air/fuel ratio which would cause you to run lean, not rich. The problem with running lean is that you create a lot more heat with a lean mixture which could cause overheating, valve damage, and head damage. On carburated bikes/cars, you always have to increase the jet sizes when going to a HP ehaust, and it help to install a HP air filter. On fuel injected bikes/cars, you have to get a new fuel map or have a fuel injection system that will account for the extra air flow by using the MAP sensor and O2 sensors.
I don't think you'll run rich changing the exhaust. The heat is due to running lean. Backfiring is usually due to an improper fuel map or jets that are too large, or improper ignition/cam timing.
Please correct me if I'm wrong. I just got really confused reading the previous replies.
Jim
The way I understand it is: If you change to a high performance exhaust with better scavenging, then it increases the air flow through the engine. This higher air flow should give you a lower air/fuel ratio which would cause you to run lean, not rich. The problem with running lean is that you create a lot more heat with a lean mixture which could cause overheating, valve damage, and head damage. On carburated bikes/cars, you always have to increase the jet sizes when going to a HP ehaust, and it help to install a HP air filter. On fuel injected bikes/cars, you have to get a new fuel map or have a fuel injection system that will account for the extra air flow by using the MAP sensor and O2 sensors.
I don't think you'll run rich changing the exhaust. The heat is due to running lean. Backfiring is usually due to an improper fuel map or jets that are too large, or improper ignition/cam timing.
Please correct me if I'm wrong. I just got really confused reading the previous replies.
Jim
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A bit of paraphrased info from our Ontario Drive Clean inspectors manual (yes, I'm a certified inspector);
"The function of an air injection system is to prevent hydrocarbons from escaping into the atmosphere. In most engines, the intake valves open before the exhaust stroke is complete, and the exhaust valve are kept open past TDC. This is refered to as valve overlap. By keeping the exhaust valve open, the fresh intake 'charge' is drawn in and displaces what remains of the exhaust gases out the still-open exhast valve. This fuel/air mixture 'charge' contains a high concentration of hydrocarbons (HC). The problem with this is that hydrocarbons can escape unburnt. By injecting fresh oxygen into the exhaust tract at the valve, the surrounding heat ignites and burns the remaining HC and reduces emmisions."
<span style='font-size:8pt;line-height:100%'> ... funny thing is, it took the government manual about 3 pages to say that :blush:</span>
So, the backfiring that we hear is the ignition of fuel that made it through the engine without being burnt.
Why does adding an exhaust cause backfiring?
Adding an exhaust leans the mixture for the above noted reasons. A lean mixture will not burn completely because the flame 'goes out' in the cylinder. Gas at the outer edges of the cylinder does not get burned, exits through the valve, and gets burned by the surrounding heat and the supplemented oxygen provided by the PAIR system.
Cheers,
"The function of an air injection system is to prevent hydrocarbons from escaping into the atmosphere. In most engines, the intake valves open before the exhaust stroke is complete, and the exhaust valve are kept open past TDC. This is refered to as valve overlap. By keeping the exhaust valve open, the fresh intake 'charge' is drawn in and displaces what remains of the exhaust gases out the still-open exhast valve. This fuel/air mixture 'charge' contains a high concentration of hydrocarbons (HC). The problem with this is that hydrocarbons can escape unburnt. By injecting fresh oxygen into the exhaust tract at the valve, the surrounding heat ignites and burns the remaining HC and reduces emmisions."
<span style='font-size:8pt;line-height:100%'> ... funny thing is, it took the government manual about 3 pages to say that :blush:</span>
So, the backfiring that we hear is the ignition of fuel that made it through the engine without being burnt.
Why does adding an exhaust cause backfiring?
Adding an exhaust leans the mixture for the above noted reasons. A lean mixture will not burn completely because the flame 'goes out' in the cylinder. Gas at the outer edges of the cylinder does not get burned, exits through the valve, and gets burned by the surrounding heat and the supplemented oxygen provided by the PAIR system.
Cheers,
Hi, i just registered here to mention de importance of pair valves on catalyzed exhaust systems as it helps to keep the temperature of the catalyzer up, and prevent HydroCarbons from hurting the catalyzer... So in that kind of systems is a very bad idea to disable PAIR valves without removing the catalyzer too.
As the last post mentioned, it basically allows fresh air into the exhaust to burn excess of HydroCarbons by the surrounding heat in presence of fresh oxygen. Also, afaik, remaining oxygen improves catalytic conversions itself..
As the last post mentioned, it basically allows fresh air into the exhaust to burn excess of HydroCarbons by the surrounding heat in presence of fresh oxygen. Also, afaik, remaining oxygen improves catalytic conversions itself..
Sooo in reference to a marble mod on a gen 2. Blocking off the intake of fresh air from the air box could actually hurt the bike. Now I'm curious what if the amount of air was to be restricted down a bit rather than cut off completely....?
A little info I have a 2015 with two brothers slip on. Before doing the mod I only suffered mild pops. Engine braking, slight aggressive acceleration and shifting. Marble mod definitely cured it. But I swear Im using more gas and it don't like to idle smooth.
A little info I have a 2015 with two brothers slip on. Before doing the mod I only suffered mild pops. Engine braking, slight aggressive acceleration and shifting. Marble mod definitely cured it. But I swear Im using more gas and it don't like to idle smooth.
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