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Message: <blockquote data-quote="f8." data-source="post: 106579" data-attributes="member: 541">flamefox,the cam duration would obviously affect your overlap but even if you adjust your cam pulleys for different overlaps, the duration stays the same and so the effect you get is no where near the same as long duration cams, even for the same overlap as you have dialed in.vtecs try to extend the revvability of the engine by having 2 different sets of cam profiles(lift and duration) each optimised for different regions of the rev scale. when you add a turbocharger in, things become even more restricted in terms of optimality across the rev because a small turbo will be optimised for lower rpm and vice versa.if you build up a vtec turbo, immediately you must decide if you want the turbo to help boost your low end performance, or your high end performance and size your turbo accordingly. inevitably the rpm region in which your turbo was not optimised for will make your vtec performance worse than if it wasn't turbocharged.for race engines, because they operate constantly within a narrow rpm region, they don't need vtec at all. just simply high cams. i doubt any of the true track civics or nsx have vtecs still enabled, and even if it is, i doubt the rpm ever goes down low enough to engage low cam. so what for have the additional complexity of the vtec system?as for lowering compression with thicker gasket or pistons etc, yes, many people know that. but why? everyone just simply say you need to lower compression but no one bothers why. actually, even with a high compression ratio, you might get away with a reasonably high boost on normal fuel if you have really long duration cams because the net effect is that of lowering your compression. otherwise, high compression ratio, say 11.0:1 with 1bar of boost and reasonably streetable cams are achievable provided you use racing fuel. otherwise, you just retard ignition so much that you end up losing so much power you might as well junk the turbo and go na with more ignition and more power.</blockquote>

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