2 stroke exhaust questions

[savage1987]

Little 2 stroke motor I'd like to get running a lot better, it's attached to a vacuum of sorts and the exhaust needs to be re-routed. It's a 1/2 in diameter system, with one of those little boxy 2 stroke mufflers.

1. Is a 2 stroke the same deal as a 4 stroke, and a slightly larger pipe will help it out at the upper rev' range?
2. What are the options for muffling a 2 stroke, can a resonator type thing be added?
3. Is there any hardware similar to a catalytic convertor for a 2 stroke, given that when the thing is in use, depending which way the wind goes the operator is sitting in the exhaust cloud for half the time?

I don't know an awful lot about modifying 2 strokes, but I am interested if anyone has any info they'd care to share on the topic.

Sam

[one_and_only2004]

can't help you with much, but i'd assume a cat would probably just block up with all the oil and gunk that generally comes out of a two stroke exhaust?

[savage1987]

I did think that, was wondering if there was anything similar that worked for 2 strokes... but that's less important than the rest anyway. Main thing is getting new piping run somewhere sensible. Do I just extend off the current muffler in the same pipe size, or remove the muffler, add better ones(??) and run slightly larger piping?

[greenfoam]

Two stroke exhausts are very complex (if you want to build a good one) it's something you need to read about for a few weeks and do alot of math before you make one. As for mufflers straight through glass packed mufflers are what you want. Study this picture, the diameters, length and angles all have to match the motor size and port timings and rev range you want to run. Lots of math

[levymetal]

apparently 2 stroke engines actually need backpressure in order to idle. here's an interesting video i watched a while ago
YouTube - how back pressure in motors works

never bothered to confirm if it was actually correct (considering at the end he says it's important for 4 stroke engines, which is not true), but it's something to consider

[savage1987]

Thanks guys, shit jason that looks complex! Given I need to add a complete U bend to get it pointing the exact opposite way to where it exits now, I might just stick a fabricated pipe on the end of the existing crappy little muffler.

[Tree cutter]

Easiest way would be to just join a pipe to the existing muffler.
The length of the header pipe between the engine and muffler can be altered to change the performance of the engine.
You can get more revs out of the motor by putting an extra gasket under the barrel so the ports are higher but you will lose power in the low rev range.

[Sabbath']

The expansion chamber plays a pivitol role in the operation of the engine, performance wise.