povey
Part of things
Posts: 700
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Oct 29, 2011 20:37:23 GMT
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Alright all,
I'm trying to eek more power from my lil 1.8 8v golf mk3 and iv heard a GTI cam, manifold and raise the compression to 10:1 but how do I raise it? I'm confused
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mirafioriman
Posted a lot
My next project.......
Posts: 1,361
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Oct 29, 2011 21:55:02 GMT
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A cam and manifold won't raise the compression ratio unless they are attached to a different head if the combustion chamber is in the head.
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Oct 29, 2011 22:01:11 GMT
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Basically you need to make the combustion chamber smaller. This can be done in a few ways, the main ones being: Skim thickness off the head which is easy/cheep, but if you take much off you'll have to re-time the cam, and you'll need to keep an eye on the valve-piston clearances, althought they're good to start with on the 8v VW motors (they're non-interference when stock). Or you could fit taller/less dished pistons which will expensive/not so easy to fit, but probably technically the best way of doing it.
The mk2 golf GTI's had a compression ratio of 10:1, so it might be the case that a cylinder head and/or pistons from one of them would bring your's up to that, which would be ideal.
Edit, also, the cam you're after is one from a mk2 golf with k-jet (mechanical) injection, the ones in the later digifant (electronic) injection models are pretty similar to your mk3's.
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Last Edit: Oct 29, 2011 22:06:54 GMT by RobinJI
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mirafioriman
Posted a lot
My next project.......
Posts: 1,361
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Oct 29, 2011 22:02:44 GMT
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Sorry just re-read your post. The cam and manifold may help performance. To raise the compression ratio you need either different pistons or a different cylinder head with a different size of combustion chamber.
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Oct 29, 2011 22:53:39 GMT
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Take the plugs out and pop a few frozen peas in each cylinder. They occupy space in the combustion chamber and thus raise the compression ratio. Start out with 3 peas and if its not fast enough for you add another 1. Hope this helps.
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povey
Part of things
Posts: 700
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Iv only got kidney beans will they do?
So if I wanted to get it higher it's either skim the head or change pistons? Or peas lol
Could I use the mk2 cams if I don't change te C/R?
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