Quote:
Originally Posted by SlideWRX
It hasn't gone anywhere because of miraculous claims that don't relate to what he is selling. Poppet valves work just fine; the claims of cleaner combustion and whatnot really don't relate to poppet valves. Claiming higher compression ratios from replacing poppet valves? makes no sense; diesel engines with poppets run 22:1 compression ratios.
The only possibly significant benefit I can see is lower friction from the valvetrain. However the typical valvetrain doesn't have combustion forces pushing on moving parts; the poppet is stationary against the head during combustion. The rotating valve will have combustion pressure pushing on it, and therefore on the bearing system. A good, honest study between the two styles would be needed to see where the benefits (if any) are from this valvetrain.
It *could* be better than traditional heads, but he is selling it as a miracle worker, and it isn't. It would take a while to point out piece by piece why each of his claims are pointless.
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Most of it makes perfect sense. There
are significant problems with poppet valves:
- Even fully open, they are in the way and restrict air flow. Race cars tend to have rediculously tall cam lobes to minimize the effect of this.
- They open into the cylinder and are shrouded by the cylinder walls. This restricts air flow.
- The exhaust valve is exposed to very high temperatures throughout most of the cycle and never really gets a chance to cool off. This hot spot can cause preignition in high compression engines. Preignition is not applicable to diesel engines.
- If valve seals leak, oil is either burned in the cylinder or in the exhaust, possibly increasing emissions.
It's pretty easy to see that these problems are all improved upon or eliminated by Coates valves. What isn't obvious is reliability and longevity, and I suspect that is the root of the problem.