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This is an extended powerband pipe utilizing a new design invented by Michael Forrest (Aug 2011). Normal expansion chambers, designed for pocket bikes for racing and sold to Grubee owners, are not suitable to everyday street riding of motorized bicycles because they have a very short powerband. By "powerband" I mean the range of engine rpm in which the pipe enhances the engines horsepower. The Jaguar Pipe has a 50% greater powerband than other pipes. Most of it has been scientifically designed according to technical information provided by professor Blair. This pipe is made specifically for the Grubee engine which is a piston port engine (w/o reed valve). If you have adapted a reed valve to your engine then I can make a pipe for your engine that's slightly different. It is basically the same pipe but with a longer belly area. How is a pipes powerband determined? 4 ways; The distance to the end of the diffuser cone with a piston port engine or the to the beginning of the diffuser cone with a reed valved engine, the angle(s) of the diffuser cone, the distance from the engine to the beginning of the baffle cone, and the length/angle of the final "baffle" cone. Using my Excel file you can see the powerband of both the diffuser and baffle cones. A racing pipes large angle (10 or more degrees) and short distance of the baffle cone gives a short powerband but a strong supercharging effect and thus more "hit" (engine power surge). But it also causes less engine power during the 1000 rpm just below the pipes powerband. So it is really only suited for racing. The Jaguar Pipe has a 6 degree angle for a sufficient supercharging effect and has a mid-cone extension that breaks the return sound wave into two parts to effectively extend the powerband range into the lower rpm's. How is the powerband felt while riding? While the engine speed increases you can feel an increase of power once the engine reaches a certain rpm (crank revolutions per minute). With a racing pipe you can feel it even more because of the decreased power before the the engine comes "on the pipe". With the Jaguar Pipe it isn't as easy to feel because there is no strong lag/hit like a racing pipe has. It comes "on" gradually and you will accelerate quicker and go faster up hills. Does the Jaguar Pipe change top speed? For engines whose top rpm is 6500 or less, if the header pipe between it and the engine is the right length then it will cause a slight speed increase. The only reason it is slight is that engine speed is mostly determined by the size and timing of the ports in the cylinder. The correct pipe dimensions are that which match the cylinder porting to enhance its effects and give more power all thru the engines rpm range. I have suggestions for increasing power and top speed by port changes. But the beauty of this pipe is the extra down low power it gives for hauling fat butts and going up hills. It was developed by Michael because of his need for such in the hilly city he lives in. He didn't want to resort to a shift kit. For engines ported to rev higher than 6500 then there is a slight loss of top speed but that can be compensated for by going to a 41 tooth sprocket which the engines extra torque can easily handle at low speeds. Examples: an engine ported for a 150 degree duration for 7500 rpm will loose 400 rpm on top. An engine ported for a 155 duration for 8500 rpm will loose 800 rpm on top. (This pipe is not suited for engines ported for 9000 rpm and above.) How does it compare to the standard pipe/muffler? On my 48cc engine that I slightly ported for a bit more top speed I compared the two exhausts on a steep short uphill (#1), a medium grade long uphill (#2), and on a long flat street. Below are the comparison results. My test engine uses the Jaguar CDI, standard head, 110psi cylinder compression, standard intake manifold, Dellorto 12mm carb, and is ported for exhaust/transfers/intake durations of 140/110/123 degrees. All four tests are with the CDI optimized for best results. Click here to read more technical info. |