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► Modify message ( Re: Halfway To Thunder Stealth Air Intake Mod for 1500 Kawasaki )

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Ok, this is an easy question to answer. The air system Kawasaki uses is similar to the system G.M. used on the later non computer controlled Chevettes. That system was called PAIR for pulse air injection reaction. It was a passive system that relied on exhaust port vacuum to draw fresh air into the exhaust manifold to burn off any left over fuel on deceleration. The vacuum switching valve under the tank is like the valves that cars with air pumps have, except it's passive rather than being force fed air. The 2 square boxes on the cylinders with the 1/2" hoses on them are reed valves that prevent exhaust gas from entering the air system. There is a small vacuum hose that maintains a vacuum signal on the switching valve to allow small amounts of air to enter the exhaust during idle. If you close off the air intake to the valve with the engine idling, you can hear the exhaust sound change a little. The whole thing is necessary for emissions purposes to ensure "legal" levels of CO and unburned hydrocarbons at the exhaust pipe. When you close the throttle at speed, say to go down a hill, the air intake stops, creating a high intake manifold vacuum. Most systems use a computer trick called deceleration enleanment  (the fuel is actually shut off on decel) to prevent fuel in the system from trying to burn with a limited amount of oxygen, which gives a high unburned hydrocarbon and  CO content due to incomplete combustion). The combustion takes place in the exhaust system. When you marble the air system, or put on coasters, you are defeating the emissions hardware....I just removed the air tube from the switching valve and put a 1/2" cap on the nipple. Will it hurt the engine? NO...see I told you it was simple.

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Posted by Washbrook

- May 21, 2013, 18:26:52 PM

I decided to get a little more power out of my 1999 Drifter and after some research and recommendations purchased the parts for the "Halfway To Thunder Stealth Intake Mod for 1500 Kawasaki Engines" http://www.gadgetjq.com/thunder+stock_acmod.htm (I'd previously fitted V&H Longshot pipes). I installed the kit this week as I am dropping the bike off on Saturday to have a PC5 computer http://www.powercommander.com installed and and the bike put over the Dyno. Mechanically this was a very simple conversion but herein lies my ignorance.

I am not a mechanic and whilst I can follow install instructions quite easily [when they use the same terms as the service manual], I also like to understand the implications of doing things when I can. Through researching this forum and others I have managed to satisfy all my questions [such as removing the ISC values from the equation etc] about the install except for one:

Background, The kit requires that I remove the fresh air hose (which appears to be the Vacuum Switch Valve Air Hose in my service manual) and plug it with a supplied plug.

Question, Are these the same? What is this actually doing? Are there any long term issues with doing this? Any other comments?

Any helpful comments would be appreciated. Thanks in advance.

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