Exhaust Want to find a decent exhaust

[GreenMantis]

My weedwhacker doesn't have an expansion chamber I'm going to call them and let them know how inappropriate this is.

I am not sure but that looks a lot like a muffler that did a bad job at behaving as a good expansion chamber.

Actually, that square boxy looking exhaust on your weed eater is, in fact, an expansion chamber. Specially designed for that particular engine, I know, since I bought a performance exhaust for a weed eater type engine that was on a goped, once. It worked well enough, and was the same size and shape as the original one. It worked better, though.

I now know the best design of pipe for these china girls but I haven't put it on my site yet.

Well, don't hesitate to share that with the rest of us! Pipes are vary important to 2 stroke engines, the right or wrong pipe will make or break the performance of the engine.

 

[Frankenstein]

Actually, that square boxy looking exhaust on your weed eater is, in fact, an expansion chamber. Specially designed for that particular engine, I know, since I bought a performance exhaust for a weed eater type engine that was on a goped, once. It worked well enough, and was the same size and shape as the original one. It worked better, though.


Well, don't hesitate to share that with the rest of us! Pipes are vary important to 2 stroke engines, the right or wrong pipe will make or break the performance of the engine.

Where I come from that's called a coincidence, and coincidentally they have been installing expansion chambers on the 4 stroke equipment too, really strange.

 

[Steve Best]

Yes, the guts of the Banana pipe are all wrong. It looks like an expansion pipe but it isn't, however don't give up on the stock pipe. A careful examination of the pipe pictured below reveals it is closer to being a tuned pipe than it looks.

The header pipe is the right length for 6000-8000 rpm tuning, opens onto the rounded end which acts as a sonic reflector much as a tuned pipe's cones, the chamber is the right length and volume and the stinger is sized close too. This above is indeed a tuned pipe. At least this particular one is. The black catalytic pipes and the Banana and Poo-Poo pipes are not. The long header of the Poo-Poo pipe does help low rpm power somewhat but the pipe above works better than a straight pipe of the same length.

 

[GreenMantis]

Coincidence, what, that the aftermarket exhaust for the weed eater engine worked? Not really, if you cut one of those open, you'll see that it's got sort of a square nautilus thing going on in there, that first opens into a large chamber, then forces down into a smaller port at the exit. The performance one was cnc machined, so they just rounded the corners off so it would flow smoother.
All engines require a certain amount of back pressure to run good. I was taught to tune a car's exhaust by an old timer, the idea is to spray paint the headers, and a long section of the collector pipe (usually 3") before installation, then run the engine until the paint burns off, and cut the 3" pipe 12" past where the paint stops burning off, and that's where you put in the reduction to the final pipe to the muffler, if you have, race cars don't (2" usually). All exhaust systems generally start with a large size, and taper down to a smaller size, that speeds up the flow, as the temp comes down. Even a "straight pipe" race car's exhaust without a muffler tapers the size down.

I think you are right about that banana pipe being useless, I don't know what's up with that stuff they have inside there, that should be hollow to be an expansion chamber. I guess I'll leave the stock pipe alone, for now, there are too many other areas for improvement I can address, first.

 

[6blueoval9]

Ive seen a youtube vid of a stock exhaust being enough to hit 41mph...When it was so called "modded" ,speed dropped a few mph.

 

[Street Ryderz]

Ive seen a youtube vid of a stock exhaust being enough to hit 41mph...When it was so called "modded" ,speed dropped a few mph.

Don't beleive all that people say on the internet.A stock engine can hit 41mph when tunned perfectly with a good pipe or a modded stock pipe done right but most of the stock pipe's are not capable of flowing properly at 9,700 rpm witch is what the engine has to be turning at with a 26" wheel and stock gear.That would drop to 8,000 rpm with a 36t gear but a stock set up wont turn that to 8,000 so I wouldn't put to much faith in that theroy.And the video you reffer to he only hit 41 spraying it with an 02 cartridge that's only good for about 20 seconds and runs it lean.

 

[6blueoval9]

Not sure what gains he would benefit to lie about it.

The first run was a 32:1 fuel mix and ill assume a broken in motor based on ratio and a phone app gps showed 40mph...so that number was only possible with a fine tuned carb and a wizard on stock pipe mods?

The second run was a 40:1 fuel mix with all else the same for 41mph by gps...i can believe more fuel into the chamber would equal more power.

3rd run added the exhaust mod with still 40:1 mix and went 38mph...maybe not a very good mod hes been informed about or it just didnt work all that well with the stock carb settings and somewhat tuned for 32:1 fuel mix (maybe went rich?).

Ill have to assume the 4th run was still a 40:1 mix with the exhaust mod and he claimed to use the c02 but no gps reading to verify anything.

Maybe the app was crappy or wind was helping push him or that slight down hill grade helped, but it wasnt a tuned pipe none the less and i believe the 40mph and the 41mph runs both with the stock pipe.

 

[Street Ryderz]

Not sure what gains he would benefit to lie about it.

The first run was a 32:1 fuel mix and ill assume a broken in motor based on ratio and a phone app gps showed 40mph...so that number was only possible with a fine tuned carb and a wizard on stock pipe mods?

The second run was a 40:1 fuel mix with all else the same for 41mph by gps...i can believe more fuel into the chamber would equal more power.

3rd run added the exhaust mod with still 40:1 mix and went 38mph...maybe not a very good mod hes been informed about or it just didnt work all that well with the stock carb settings and somewhat tuned for 32:1 fuel mix (maybe went rich?).

Ill have to assume the 4th run was still a 40:1 mix with the exhaust mod and he claimed to use the c02 but no gps reading to verify anything.

Maybe the app was crappy or wind was helping push him or that slight down hill grade helped, but it wasnt a tuned pipe none the less and i believe the 40mph and the 41mph runs both with the stock pipe.

The benifit or gain is to bring in customers.And showing a screen shot after the fact instead of real time leads me to think some funny s**t is going on there.Also if you listen to the engine the rpm and burn doesn't sound that clean or high enough for 41mph only on the sprayed run does it sound right so yes it was a bit rich and therefore not likly able to hit that speed.

 

[6blueoval9]

If i cant hit 40 with a stock kit exhaust ill be surprised...of course ill have a little more refining done to the motor but it will have the stock kit exhaust it came with for the first attempts as well as the 14mm carb... A 44t is what i have planned to try first.

I suppose ill find out eventually..lol

 

[Street Ryderz]

The stock pipe that Steve showed above is really good and as he said can even give a true pipe effect but still needs tinkering with to work it's best the e.p.a pipe and the flat ended ones are total crap and very resticted not letting most engines fitted with them to rev past 7,000 even dailed in.I've hit 11,000 with the above mentioned pipe on a 26" wheel and stock gear but the two baffle plates inside were removed.