PAIR Block Off Plates

What PAIR Actually Does

PAIR — pulsed secondary air injection — is an emissions device. It draws filtered air from the airbox and admits it into the exhaust ports through reed valves in the cylinder head cover, so that unburnt hydrocarbons in the exhaust gas continue burning after they have left the combustion chamber. It lowers measured emissions without altering how the engine runs.

On the motorcycle it does its job quietly and causes nobody any trouble. In a car conversion it becomes redundant hardware — and, more importantly, an active nuisance.

Why It Has to Go in a Car

It corrupts your lambda readings. This is the one that matters. PAIR admits fresh air into the exhaust stream upstream of where a lambda sensor typically sits. The sensor reads that oxygen and reports a mixture leaner than the engine is actually running. If you are mapping on wideband lambda — and on a supercharged engine you should be — that is bad data going into the decisions that protect your pistons. Worse, if you are running closed-loop fuelling against a target lambda map, the ECU will act on it and enrich an engine that was already correct.

It feeds from an airbox you have removed. The PAIR system takes its air supply from the standard airbox. In most car installations the airbox is gone, which leaves the system either drawing from wherever it happens to be pointing or simply open to the engine bay.

It causes popping and afterfire on the overrun. Fresh air meeting hot, rich exhaust gas is exactly the recipe. Entertaining once; tiresome by the second lap.

It is clutter. Hoses, a solenoid valve and pipework routed around the top of the engine, none of it doing anything useful in your car, all of it in the way when you are trying to package a loom and a cooling system into a space that was never meant to hold them.

Fitting

A short job, and one that can be done with the engine in the car. Work to the Kawasaki service manual for removal of the original PAIR caps and valve solenoid, then:

1. Take the two screws and four reed valves out of each reed plate. The reed plates themselves are reused.
2. Inspect each reed plate around its outer gasket face. That is your sealing surface, it is off the engine anyway, and a marked or distorted plate is worth replacing while you are there rather than chasing a leak afterwards.
3. Refit the reed plates together with the block off plates, in place of the original caps, using the supplied stainless fixings. Torque to 10 Nm.
4. Remove the PAIR valve solenoid and its associated pipework from the engine.

One motorcycle problem you do not inherit. On a bike, removing the PAIR solenoid frequently triggers a fault light that then needs an ECU flash or a bypass plug to clear. In a car conversion the factory ECU has gone entirely, so the situation never arises — one of the few places where the wholesale electrical rebuild makes life simpler rather than harder.

Some applications also need the airbox port plugging. On the Ninja H2 that is not required, and in most car installations the standard airbox has been removed in any case.

Do It Before You Map

If you take one thing from this page: fit these before the engine is calibrated, not after.

A map developed with PAIR still active is a map developed against lambda data that was wrong the whole time. The correction is not a small trim — the mixture the sensor reported and the mixture the engine was actually running were different figures, and every decision built on top of that inherits the error.

It is a cheap part that protects an expensive process. Our MBE 9A9 systems run twin wideband lambda inputs with closed-loop target lambda mapping, and that capability is only as good as what the sensors are actually seeing.

Engine Fitment

Supplied for the Ninja H2 and Z H2. If you are running an H2 SX or an H2R, ask us before ordering and we will confirm — secondary air provision varies between variants and we would rather check than send you something that does not fit.

If you are unsure which variant you have, our H2 engine reference explains how to identify one properly. The engine number prefix will not tell you, because it is shared across the whole family.