UPP out there in Tony's neck of the woods does the polyurethane rubber stuff for me. When I had my 496cc Saber motor, the intake signal would nearly collapse the rubber intake tubes. I can do PU material (similar to stock), the issue I found is its not as cost effective as high density plastic or even Carbon fiber. With the plastic the filter can clamp directly to the tube, versus having some billet aluminum flange made. However, to work with stock airbox the PU would be the way to go off course. Thing to remember is this isn't just a stock replacement intake tube, this actually will give a big bump in performance. The one I've done for the yfzr was nearly 2-2.5hp improvement, and still finding more. I have my own dynojet dynamometer so I will know exactly what improvements can be made.
Also intake pulses are timed just like on the expansion chamber side. Key is getting the earliest intake pulse to return to the intake side of he cylinder around the same time as when the piston just drops past the intake ports, (volumetric efficiency). Again, just like the expansion chamber side, Length, taper and volume of the intake tube factor into this, and can change whether an intake is low, mid or top end range, etc... With that said, even with all the various methods or equations for calculating this it gets fairly complicated cause the intake tubes are rarely just a simple tapered pipe, they have kinks and bends and large transitions etc... Even with the engine simulation software I use, it assumes the intake is a simple tapered pipe. I've read some interesting papers on this topic where an oscilloscope and a microphone was used measure the pulse timing. I've thought about getting some of that equipment and trying it myself. For now I do "best" guess then hit the flowbench and dyno, but I'd like to have a more scientific approach to it. I do have a kickass Somat data aquisition computer, that I'm working on installing ultra high speed pressure transducers in the intake tube coupled with an analog rotary gauge. I'd like to be able to plot intake pressure vs. crank angle. This is very doable and I just need a little more time to get this all figured out.
