Quote:
Originally Posted by cRiPpLe_rOoStEr
Lower compression sometimes can actually make sense, since it's safer to run leaner and free of knock with a lower octane rating gas, even if that would be at the expense of some power and torque. There are also fewer pumping losses and heat rejection. Sure, there's some point when decreasing too much the compression ratio is not going to lead to an efficiency improvement, and the same goes for a higher compression ratio. For modern engines fitted with direct injection, Mazda has found the sweet spot to be around 13:1 to 14:1.
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Mazda's going even higher.
They reckon they've got the compression ignition problem licked, so the next generation of SkyActiv is going straight to 18:1.
On gasoline.
Engineers tell me they'll still have spark plugs for cold start, but they shouldn't need them. Even better, injection pressure should be less than current common rail diesels, which means a cheaper fuel system and less issues.
I hope.