Pulsed Air Induction Reed valve
What does that mean? It's just a valve that remains open on low rpm's to let some extra air into your exhaust stream, directly from the airbox. This is really just to make your exhaust emissions a little more friendly. Because the PAIR valve, under low throttle, allows a little more air to mix with your exhaust, you will ignite any unburnt fuel that is about to exit the bike. This is desireable not only for the environment, but because it will eliminate the popping that you frequently hear on a poorly tuned bike that allows unburnt fuel into its exhaust.
So having a PAIR valve in place neither harms nor helps the true performance of the bike, but it does help insure that you don't go spewing unburnt fuel out of the tailpipe. And I can tell you from personal experience that without a PAIR valve you get very prominent explosions (popping) on decel, and these are completely eliminated when you restore the PAIR system to stock. Add to this the fact that you're spewing unburnt emissions into the environment with no actual increase in performance, and I think you can tell what I think of this mod...
Under wide open throttle, the PAIR valve is snapped shut. It will no longer allow extra air from the airbox to go into the exhaust stream. Instead, all of this valuable cold air is sent directly to your combustion chambers, where you want it, so that you can get the most power possible.
Go to TOPA schematic of the stock PAIR setup is shown at left
A hose directly connects the airbox to the crankcase cover. This allows venting of crankcase fumes, and allows equilibration of pressure between the crankcase and the airbox, so if pressure builds up it can be relieved. In the stock setup, this host (all the way on the left of the picture) really has nothing to do with the function of the PAIR valve.
Negative pressure is produced by the Venturi effect of the engine exhaust. The outflow of exhuast "sucks" air from the two PAIR valve outlets as shown by the orange arrows. So long as the PAIR valve is kept "open", this "sucked" air is drawn from the air box, straight through the PAIR valve and out the exhaust stream (see orange arrows).
The "vacuum hose", shown in blue, allows a mechanism to shut off the PAIR valve. At high rpm's, with the throttle open, negative pressure mounts in the blue hose. This closes the PAIR valve, so that NO extra air from the airbox can enter the exhaust stream. This is a good idea because on the stock bike that extra air would come from the airbox, and when you're revving up you don't want the PAIR system sucking valuable air out of the air box and shooting it into the exhaust stream. Instead, you want ALL your precious RAM-compressed air to go to the intake ports of your combustion chambers. The PAIR valve accomplishes this task:
You can test the airbox yourself if you have a vacuum pump. Apply negative pressure to the vacuum hose, and you will verify that NO air can then be pushed through the PAIR valve. When you do NOT apply negative pressure to the vacuum hose, air flows freely through the PAIR valve.
This is the actual view of the stock GSXR-1000 with the airbox removed.
There's just one small difference here: the vacuum hose inserts into the FRONT of throttle body #3, rather than the back of throttle body #4 on a GSXR-1000. The arrow points to the insertion of the vacuum hose on TB3.
Well, some very clever people have looked at this diagram and have noticed a great opportunity to use that same Venturi effect vacuum to a performance benefit.
In the auto and bike racer world, racers spend big $$$ installing vacuum pumps to remove air from the crankcase. This makes it easier for all the gizmos to turn and spin, since air resistance is decreased in the crankcase. Not having to work against such resistance, the engine can operate more efficiently, sending more of its power to the rear wheel, rather than wasting it as heat caused by fighting internal air resistance
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The PAIR mod, or "PAIR sucker" mod, cleverly uses this negative pressure generated by the exhaust system to suck the air out of the crankcase. Rather than just sucking extra air from the airbox, the new connections reflect the negative pressure from the exhaust back to the crankcase as shown:
Go to TOPDon't make my mistake and buy too much stuff!!! This is absolutely ALL you'll need to do this mod, and before you do this mod, please read "Does it work?". If you're going to do this mod, you'll easily find everything you need at NAPA.
| Heater hose | A total of 3' of ½" internal diameter heater hose. This is much more than you'll need, and you'll have lots left over. Don't get 3/8" internal diameter hose, or you'll NEVER be able to fit it onto the Tee fitting and the elbow fitting. Cost: $1.50 |
| Hose clamps | You only need three hose clamps, two for the top of the "TEE" fitting, and one for the connection to the crank case. Cost: $1.50 |
| NAPA 660-1697. Two-pack of black end caps, for the airbox. Cost: $2.99 |  |
| NAPA 660-1671. Hose TEE Fitting. Cost: $2.99 |  |
| NAPA 660-1481. Hose Elbow Fitting. Cost: $2.99 |  |
| Total Cost: | $11.97 |
You can download a nice instructional write-up done by a buddy of mine at gixxer.com. [566kb]. It is a simple mod. I'll show my own pics below as well.
The stock setup, with the airbox still on. You can see the crankcase breather hose here, the only vertical hose on the picture. It connects the airbox to the crankcase. We'll be getting rid of that. First, you'll have to take of the airbox to get access to all the goodies we're going to alter!
Again, the stock setup, you can see how all the hoses run. The PAIR valve is the gizmo between A and B. That's the valve with 4 total hose segments attached to it. This will be removed.
Just assemble your heater hose with the T fitting and the 90-degree elbow as shown. You'll want to cut off some very small pieces of heater hose for the top pieces of the "T" that lead to the reed valves. By this I mean the two short segments you need at letters A and B. Then just cut your heater hose so that it reaches the crankcase, but no longer.
Secure with one hose clamp at A, one at B, and one at C. No other clamps are necessary, since the fittings to the T and the elbow are extremely tight.
Now open your two-pack of end caps and put one at each arrow as shown, to plug the old holes on the airbox. I used some leftover stock wire clamps , as you see, to secure them.
As a last detail, you have to block off the place where the vacuum hose enters throttle body #4. I thought it was just too difficult to pull the hose off TB4 and then would be impossible to reach in there to put a cap on the throttle body opening, so I just cut the vacuum hose about 4" away from the throttle body, and inserted a tight-fitting screw, as shown, to block off the hose. Then tie it out of the way with a cable-tie, so that this isn't just flopping around.
If you choose to try the PAIR mod, you'll probably have to adjust your idle speed, since the idle commonly drops below 1000 rpms when the PAIR mod is active.
Here's how to adjust your idle speed:
First, un-do the bolts that hold the gas tank down. Lift and support the gast tank. The picture below shows the view from the left side of the bike with tank lifted up.
Look for these two screws on the left side of the bike. You'll see that the throttle cables end on a pulley right next to these screws.
Turning the top screw (yellow arrow) adjusts the idle rate when the engine is cold (< 100 F). Set this rate to about 1800 rpm . Turning the bottom screw (purple arrow) adjusts the idle rate when the engine is warm. Set this rate to about 1200 rpm
Go to TOPNo.
I think that's the straight answer here. Ok, the PAIR mod DOES result in the negative crankcase pressure, as claimed. But the negative pressure is not enough to cause any noticeable improvement in the ride of the bike. NO ONE will ever claim that the PAIR mod will increase the actual top horsepower of your bike. There is some claim that perhaps the "time to top horsepower on the dyno is improved", but I'm not sure that really holds water. If what you care about is FEELING a difference in the ride at speeds under 100 mph, then this mod will accomplish nothing for you. That's my conclusion.
Why doesn't the mod work? It just does not establish ENOUGH of a vacuum to amount to any meaningful benefit on your bike. One rider, cagixxer750 at gixxer.com, actually measured the vacuum created, and found the following:
Keep in mind for a reference frame that normal barometric pressure at sea level is 30 inches Hg. Pulling 5 inches Hg of negative pressure in your crankcase will help reduce engine work, but not in an amount that you can feel. If there is any benefit in acceleration at all, it will probably only be felt by racers at speeds above 100 mph, because the higher the RPM's, the more vacuum you'll create. At usual street speeds, any benefit you feel is probably in your head, not in your ass where it counts.
After trying the PAIR sucker mod myself for 6 months, I took it out in order to get my custom mapping done, and never reinstalled it because
As soon as I reinstalled the stock PAIR valve, the popping ceased.
An unwanted side effect of this mod is popping on deceleration. You'll now have loud popping and crackling of the exhaust whenever you rapidly let off the throttle. That's simply because without the PAIR valve opening on deceleration, much unburnt fuel exits into the exhaust stream, and ignites part way out of the midpipe. So your bike will sound like a badly tuned Hardly-Ableson, something I really did not find desireable.
Finally, remember that you must disable the PAIR mod, and set the bike back to stock if you want to get a custom ECM mapping done on your bike. This is because the PAIR sucker mod will alter the exhaust fumes. Set the bike back to stock for your mapping, then if you like the Sucker mod, just hook it back up later. It only takes 15 minutes to do / un-do after you get used to it.
So if you're really lazy and don't just like to change stuff in your bike, my advice is : don't do this mod. If you like working on your bike, and you just want to try a harmless mod that is EASILY reversible and costs next to nothing, then my advice is : DO this mod and decide for yourself if there is any benefit. If you don't like it you can undo it easily and no harm is done to the bike.
Go to TOPThis is a great concept, and learning this mod helps you understand some of the physics behind the function of your bike, and theoretically how you might boost it's power. Unfortunately the PAIR mod just doesn't produce enough negative pressure to have any useful impact on the bike. It also has some minor disadvantages which I've outlined above. It is a mod best left for the text books. Waste your time drinking beer or riding 100 mph wheelies instead... and move on to the TRE mod, where you really CAN make an impact on your performance for $5.
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