Zuma airbox tuning project finished (Video Inside 😎)
Jun 23, 2021 20:14:49 GMT -5
90GTVert, 190mech, and 7 more like this
Post by na96ek on Jun 23, 2021 20:14:49 GMT -5
A few weeks ago I made a post about using the stock airbox and came to the conclusion that I would attempt to enlarge all the ports and attempt to “tune” the airboxes resonant frequency in order to allow the engine to make more peak HP at higher RPM’s vs using the airbox unmodifed or simply “de-snorkeled”. I did some research on the subject and found a formula I was able to use to roughly raise the resonant frequency ~ 4,000 RPM higher then stock. I don’t have any way to test the acoustics of the modified box, although it would be interesting to see what has been done but I can say without a doubt that the combination of my modifications have increased at least the peak HP over the de-snorkeled, un-modified box.
I started by enlarging the carb side port to accept a 36mm diameter aluminum pipe, the pipe I used has 1mm thick walls. It was made to fit snug and then plastic welded into place.
Then I moved on to the inlet side where I opened it up in the same way and used the same 37mm pipe. I went with a length approximately 66mm long for tuning purposes.
I oiled and installed my new UNI air filter. I will be attaching the airbox to the carb with a 90 degree 1.75” to 1.5” silicone coupler you see pictured. I had to trim the ends slightly to get it to fit with the correct spacing everywhere
I made some brackets to slightly relocate the airbox as the large diameter elbow changed its position slightly. These allow me to pivot it to get the placement just right to keep tension off all the boots.
The first test run was with my tune at 84main 36 pilot where it had been running fairly well on a de-snorkeled box, even slightly opened up. Right away this was way too lean. I was getting much more air then before. After lots of testing I wound up at 90/38, my peak temps are still a little high after a long run and I could maybe go up to a 92. I wish I had a dyno to actually be able to show some hard results but all I can use as a reference right now is a particular hill that I hit WOT after a turn that is traveled frequently by me and used as a reference for power. With the de-snorkeled and slightly opened up stock airbox setup I was reaching 38mph on the crest of the hill. When I was running a pod filter I was reaching 40mph. After these modifications I was reaching 41mph on this hill. I should probably state that I approach this hill at close to 50 but it’s a rather steep hill and I lose speed near the crest. So it slowed down ~ 3mph less. It’s possible my tune was not perfect with the pod filter and I may not have been extracting maximum power from the pod setup but even so I am very pleased with my results. I did this mostly to be able to retain the noise reduction the airbox allows and still keep as much of the power of a pod filter as possible (or even gain some?) Either way this to me was worth the time invested. I will continue to refine the tune and possibly even in the future attempt to alter the pipe length, which combined with the diameter is what affects the harmonics of the airbox chamber.
