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Well, I thought id post something to get some conversation around the all-important aspect of Compression in relation to turbo/supercharged engines (in particular the EA/AU 6's)
We all know a high compression and high boost don?t really go hand in hand (except in extreme conditions.) For my proposed application something around 8 up to 8.3:1 would be the aim, to allow for a possible 20lbs boost. Now the easiest way to achieve the compression would be custom pistons, but we are not all cashed up that we can ring Arial and order in some custom forgies.
I?m thinking the way to do it is with Head gaskets, piston dishes, and head chambers.
Its common knowledge that
1) EA has the largest piston dish (11.3cc iirc)
2) The EA head with the swirl port removed has the largest volume
3) The Au gasket is the thinnest allowing for compression increase
4) The EF==> heads flow much better than <==ED heads
So to achieve that compression I'm assuming EA pistons and deshrouded EA head would be the way to go (as stock compression is 8.8:1 and deshrouding may result in 8.5:1)
To use this will loose the possible benefits in an EF/AU head and its inherent flow characteristics however the compression decrease by using the EA deshrouded head may surpass the better flow of the EF/AU head.
Or, the following may be attempted. Use an EA piston set however use a ported EF/AU head which may result in around 8.9:1 compression. I?m assuming new (say ACL race) pistons would have a decent crown thickness which could be machined down slightly to reduce the deck height of the piston/rod/crank assembly. This method if possible could yield 8.0:1 compression quiet easily (maybe 7.5 if used with EA head).
Id like to hear peoples views on this topic, from research, experimentation or theory.
Regards
Daniel
We all know a high compression and high boost don?t really go hand in hand (except in extreme conditions.) For my proposed application something around 8 up to 8.3:1 would be the aim, to allow for a possible 20lbs boost. Now the easiest way to achieve the compression would be custom pistons, but we are not all cashed up that we can ring Arial and order in some custom forgies.
I?m thinking the way to do it is with Head gaskets, piston dishes, and head chambers.
Its common knowledge that
1) EA has the largest piston dish (11.3cc iirc)
2) The EA head with the swirl port removed has the largest volume
3) The Au gasket is the thinnest allowing for compression increase
4) The EF==> heads flow much better than <==ED heads
So to achieve that compression I'm assuming EA pistons and deshrouded EA head would be the way to go (as stock compression is 8.8:1 and deshrouding may result in 8.5:1)
To use this will loose the possible benefits in an EF/AU head and its inherent flow characteristics however the compression decrease by using the EA deshrouded head may surpass the better flow of the EF/AU head.
Or, the following may be attempted. Use an EA piston set however use a ported EF/AU head which may result in around 8.9:1 compression. I?m assuming new (say ACL race) pistons would have a decent crown thickness which could be machined down slightly to reduce the deck height of the piston/rod/crank assembly. This method if possible could yield 8.0:1 compression quiet easily (maybe 7.5 if used with EA head).
Id like to hear peoples views on this topic, from research, experimentation or theory.
Regards
Daniel