Exhaust Exhaust Port- Muffler-Gasket

[BSA]

Thanks forumites,

BSA, that's the type of answer I was looking for, very good lead.

Researched:
Researched using Google and I came up with heaps of other answers and more leads using the word Coanda
However, Sparky's answers DOES have merit, the Chinese are probbaly trying to perfect the Coanda effect to, or they have and won't tell, or they are giving us all a clue to lead us to something else.

Some of the graphics show a basic explanation of air flow and Coanda Effect principles.
See Exhibit A.
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Then it gets rather interesting, it goes to magnets !
The Coanda effect in principle using magnets, an untested theory so far showing magnets moving a rotor !
Hmmm,
See Exhibit B.
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Other exhibits show flying saucer experiments using Coanda Air Flow.
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Another interesting find is here:More to the point, but not the actual answer, I think.
http://www.patentstorm.us/patents/4899698-description.html
In particular where it where it say's
The present invention relates to measures stemming from the above-mentioned study and from the Applicant's earlier patent, so as to delay the flow of mixture in the combustion chamber relative to the flow of the air contained in said chamber, thereby tending to avoid loosing mixture via the exhaust. The cavity constitutes a retention space because it reflects the air flow thereby setting up a flow in the opposite direction to the flow of mixture inside the cavity, thereby momentarily stopping said mixture flow at the top of the chamber.

Research is now ongoing...,
1.To modify Standard HT Exhaust Gasket and Muffler pipe to match engine's Exhaust Port ( as exported from China) or not to modify ???
As Kidd sugested, an Adaptor Plate.
Has anyone one gone and made a adaptor plate, did it make much difference ?

2. Why did they change from what's used in China to what's exported to everywhere else ? ( who cares really, we fix them anyway.)

3. Is this the basis for a ongoing "who dunnit conspiracy theory" on the HT Exhaust Muffler and Gasket Mismatch ?

To be Continued...! ( if time permits)

Well I wouldn't think that the Coanda effect would have a very large effect on these light duty engines but when engines are desighned it makes sense that the ports are shaped in such a way that gases can flow through it easily. I found out about this effect in Gordon Jennings two stroke tuners handbook, published in 1973, it discusses the theoretical and practical aspects of high performance two stroke engines. It is a very interesting read.

Perhaps a more pressing issue is the fact that the exhaust tube and manifold is smaller than the port.

When Ghost0 fitted an expansion chamber to hs build he created a copper intake manifold. Someone could basically redo the manifold and fabricate there own mounting plate, then it may yield a small reduce in back pressure, it wouldn't be worth doing unless you drilled holes in the exhaust baffle.

There is definately no point in porting on the exhaust unless you reduce backpressure and get the exhaust tube and manifold outlet exactly the same shape and size.


BSA

 

[BSA]

Ultimately the porting on these happy time engines is very conservative. Mores the point I wouldn't bother actually enlarging the port. One should always remember that idiots don't desighn engines. The Designer nearly always knows best, the reason this engine is ported the way it is; is to stop people from overunning these engines. There is a very Good reason why the engines don't get high RPM's compared to other 50cc's etc. They would wear out very quickly.

BSA

 

[fastboy9]

Yep, many of the experienced wild in the streets guys have come to the conclusion that without working on the ports and pistons, the engine will max out at a certain rpm, you could have direct injected nitrous oxide and the ultimate expansion chamber, but the ports ultimately will give you a maximum rpm. Like a terminal velocity. Modifying the ports to fit the round pipe I guess is a bad idea, unless you are going to compensate with better cooling and some very strong head bolts!

 

[Ghost0]

Just because something is wrong doesn't mean you have to live with it. I took a dremel and ground the pipe to match the exhaust port and modified the gasket accordingly. It was easy and improved performance.

 

[fastboy9]

Just because something is wrong doesn't mean you have to live with it. I took a dremel and ground the pipe to match the exhaust port and modified the gasket accordingly. It was easy and improved performance.

Was just about to pm you about that! So literally grind away until you now have a circle instead of rectangle? I think that will be my next mod, isn't the intake the same situation?

I guess theres two types of people
--If it aint broke dont fix it,
--If it aint broke, make it better

I'm the latter

 

[sparky]

I'm the "if it ain't broke, don't fix it" guy... but I think it's pretty crazy Ghost0 used a DREMEL to trim his muffler. C-R-A-Z- double E

 

[Ghost0]

It isn't rocket science guys. Don't change the exhaust port, change the pipe to match. See pics.

 

[caddymankc]

Unless you modded the port also yours looks alot diffrent then mine, mine is almost perfectly square.

 

[Ghost0]

I didn't modify the port but not all these engines are the same. You should be able to accomplish the same thing though. It might be a little tougher but as long as you can just make the transition from square to round as gradual as possible it will help.

 

[RedGreen]

I have wondered about this myself. My bike is that way. I suppose an enterprising soul could take about 1" long block drill the hole through that would fit the muffler side and then file away the port side into a square configureation. Should reduce blockage and increase flow. HEY! Maybe that's where all the unfound power is lurking!