Pipe mods for low end power

[Deleted member 12676]

Here are the results of my testing different exhausts on my piston-ported 48cc engine with 6.9" long intake tract (carb slide to piston). From not being able to climb street1 it was finally able to climb at 17.5mph without losing any top speed. (The X signifies inability to climb w/o pedaling.)

Street 1 is a fairly steep incline. Street 2 has a lesser incline. "Flat" is a flat street.

length__street 1___street 2______flat
_10"_______X_______18.0mph____25.0mph (standard)
_16"____13.5mph____20.0mph____25.5mph (+6" pipe added before muffler)
_23"____17.5mph____22.5mph____25.0mph (+13" pipe added. 1.5" notch cut out of side of center exhaust tube inside muffler 1" after it enters muffler. disc baffles removed.)

It is unknown what the results would be without the longer intake tract but from my experiments everyone should have an extended intake anyway. The easiest way, what I did, is use the intake manifold that zig-zags off to the side which is longer than normal and is made for those whose carb and frame wants to occupy the same space. Sorry but I forgot who I ordered it from.

 

[AusDan]

Hey jaguar
Jus to clarify on your pics when removing the outer tube on the muffler once we have made the cuts do we reinstall the muffler tube? and also when doing the extensions what's the best product to use to lengthen without welding I intend to weld it when I've chosen my length but don't want waste time n effort welding n rewelding?
Many thanks
Dan

 

[Deleted member 12676]

To clarify; just cut the outer part of the muffler to access the innards. Cut off the baffles and then do two cuts at the beginning of the inner pipe to make an opening in it. Then weld the outer shell back in place.
I used a thick automotive hose for all my testing. It held up pretty well for all but the last test run. The new hose I put on only lasted a few miles before it bubbled inward and choked the exhaust flow. You could try doing the same or find some steel tubing you could use. You could use short sections of automotive hose at both ends of the steel tubing and use hose clamps to keep the hose on. That way the hose is not directly exposed to the exhaust gas and lasts longer. But it's best to quickly test and then weld the final version together.

 

[Nitropeewee]

hmmm, why not just get/make an expansion chamber? that is how you can really get some noticable power/performace increases.

 

[Deleted member 12676]

Expansion Chambers are for top end power, not low end.