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Post by thetinker on Dec 1, 2012 18:21:35 GMT -12
What do u think would be the compression ratio of a seagull. It seems very low at about 4 to 1. Would be better at 9 to 1. Will burn the fuel better. Here is a great web site to help people to understand what is going on. www.torqsoft.net/compression-ratio.html
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Post by Rex NZ on Dec 2, 2012 7:23:00 GMT -12
Which is the better option?
Planing the head or planing the block?
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Post by chicken on Dec 2, 2012 15:28:55 GMT -12
Planing the block
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Post by thetinker on Dec 2, 2012 20:21:35 GMT -12
How can you increase the compression of a 102 then?
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Post by chillidog on Dec 3, 2012 20:11:31 GMT -12
If you where so inclined you could do it one of two ways , the object being to reduce the volume in the area between the top of the cylinder and the top of the piston head at tdc ,yet still provide an area for gas ignition and combustion . One way may be to make a higher cap piston , however that would change the relationship between the ports and could lead to more trouble than two wives . The other way is tricky,but do able I think, you'd have to cast an impression of the space at the top of the cylinder at TDC and fill weld the area at the top of the block then machine it out using the data from the cast to provide a squish area and a combustion area . I'd give it ago if I had a spare 102 head floating round . But I've got a couple of other builds on the go and having a crap year fiscally, so it will have to wait . I would also point out that this possible modification could easily end in tears due too the water jacket casting being thin in this area and considerable welding knowledge would help . It probably would push you into the modified class depending on your success with regards to the great race too.
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Post by thetinker on Dec 4, 2012 6:31:21 GMT -12
I have wondered about casting a plug to fit in the combustion chamber. I have seen this used on motorbikes.
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Post by chillidog on Dec 4, 2012 13:16:31 GMT -12
how would you expect to locate it , and would it transfer heat and cool ? I'd be concerned it might super heat and break up or the thermal expansion at a different rate to the cylinder could cause a problem . Still if has been done before , and it would be simple enough to make the casting .
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Post by thetinker on Dec 4, 2012 18:30:50 GMT -12
They screwed in, yes I agree about thermal efficiency. What about brazing them in
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Post by chillidog on Dec 4, 2012 19:07:17 GMT -12
don't know if I'd trust it Tinker , If I had good blocks and cranks to burn it wouldn't matter much. cutting a broken one up and having a practice with the pieces would give more confidence .
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ross
New Member
Posts: 31
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Post by ross on Apr 24, 2013 20:10:57 GMT -12
You have to be careful not to increase compression tooo much as this loads up the big end and mains which builds heat and then nips ! and if it doesn't nip it can evaporate fuel while passing through crankcase and engine will stop dur to lack of fuel reaching cylinder ! and this is one reason that engines went to needle and roller bearings that had high compressions.
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Post by gtfortie on Aug 18, 2013 12:29:22 GMT -12
I've built up my piston on an AD 102 buy pouring wax into the plug hole & lifting it out on the piston.It was about 5/8ths of an inch clearance, now its a lot closer to the plug but i can only get 55psi on the compression gauge.Idles @ 200rpm & peaks @ 6200 rpm!!GTfortie
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Post by Rex NZ on Aug 20, 2013 19:01:45 GMT -12
GT Fortie Sounds like a good bit of research & development works going on Can you post a photo or two Rex
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