I am certainly no expert but the compression ratio I recall for my motor was 6.5 I think this or even a lower # is probably more likely as gasoline octane/quality is possibly not thAt great in some areas of rural Asia our motors would burn crumby gas more happily w/o knock thAn at 8 9 or 10 Assuming our gas to be good quality is the main reason I upped compression to start with. Are there real gains in power with the new angle plug head? ThAnks again duivendyk
backpressure: what are the facts?
- Thread starter ratty
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RMWdave
Member
im interested to know how many of you run with no base gasket?
also, to get the ports where they should be i am thinking about a spacer for the bottom of the jug a little less than a 1/4" thick. this will also require the piston skirt to be cut and the head and cylinder planed down to get the compression back.
what do you think?
also, to get the ports where they should be i am thinking about a spacer for the bottom of the jug a little less than a 1/4" thick. this will also require the piston skirt to be cut and the head and cylinder planed down to get the compression back.
what do you think?
Why not just buy two new base gaskets and double up? I would try again to see if you cant find some kind of bit for your dremel that will do the job. BTW, dremel makes an angle head attachment to fit on the tool itself, but I dont know if it will fit in there, I dont own one so I'm not sure of the exact size of it.
http://www.dremel.com/en-us/AttachmentsAndAccessories/Pages/AttachmentsDetail.aspx?pid=575
D
duivendyk
Guest
I'm quite sceptical about the 8:1 ratio,I think most likely they just made that up. 6.5/7.0 more likely,Know nothing about that head,except that it exists.Only way to find out really is to measure compr. volume somehow,one teaspoon equals 4.93 cc, and the comp. volume is 9-10 cc (66cc engine, 6.5 CR)
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So you mean the volume of the head's combustion chamber is about 10cc ? It seems rather large when you look at it......I wish I still had my burette. I bet it is a 6.5 CR, and they left out the head volume in their calculation. Especially if you factor in the volume of the head gasket and the top of the piston to the rings.
machiasmort
Active Member
Insofar as backpressure is concerned. If you asked this question, you have reached the age of mechanical reason. In the words of one of Buffalo's best mechanics!
The way it was explained to me, perhaps wrong, shoot it full of holes if you wish. Back pressure is the opposing force to the force that the motor is using to produce usable power.
Most 2strk setups have a bellow in the pipe that is tunned according to cylider size, there is a formula I believe somebody posted on the forum here. Basically the motor hits an RPM point where exaust gas builds inside the bellow and pushes back on the piston through the ports in the motor, thus increasing the RPM range!
The way it was explained to me, perhaps wrong, shoot it full of holes if you wish. Back pressure is the opposing force to the force that the motor is using to produce usable power.
Most 2strk setups have a bellow in the pipe that is tunned according to cylider size, there is a formula I believe somebody posted on the forum here. Basically the motor hits an RPM point where exaust gas builds inside the bellow and pushes back on the piston through the ports in the motor, thus increasing the RPM range!
RMWdave
Member
^ hes nothing but right. the point he is referring to is that of which resonance is going nowhere but overflowing out the easiest hole (the stinger)
its all about soundwaves man. even a 4 stroke can take advantage of a bit of backpressure like the two stroke
its all about soundwaves man. even a 4 stroke can take advantage of a bit of backpressure like the two stroke
rmwdave port timing
How would port timing be improved with a thicker base gasket? After reading wiki abt. 2strks maybe the port timing is already pretty good. I have. Removed the cylinder from my used motor and will do what I can to clean up the ports but they look specifically shaped so may not change them a lot. The top of the cylinder is rough cast and unmachined (!) and will be corrected.
How would port timing be improved with a thicker base gasket? After reading wiki abt. 2strks maybe the port timing is already pretty good. I have. Removed the cylinder from my used motor and will do what I can to clean up the ports but they look specifically shaped so may not change them a lot. The top of the cylinder is rough cast and unmachined (!) and will be corrected.
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