> Also, you are turbo-ing a non turbo engine I believe. I think they have > piston oil squirters, yes ? > And about compression ratio ?........................ 'normally' > ,..........or 'used to be anyway, before more evolved electronics' you had > to lower the compression ratio of any gasoline non-turbo engine to turbo it. The zetec was originally designed with a turbo in mind, it is a descendant of the YBT. the T was for turbo, but the YB is what went into production. The CR thing is a compromise.. a nice low CR means more safety from knock and higher boost levels, but also means poor off boost response(which in our case is only idle to 1500 rpm). The stock zetec is 9.6:1, although there is conflicting data that says it is 9.1:1 in the focus... in any case, running 8-9psi is pretty safe provided you have good fuel mapping, a robust fuel system, and aggressive knock retard. We've been pushing well beyond that in testing, but for customers it obviously has to be much safer. It was much harder to do this with poor engine management control or more primitive engine management systems, so the lower CR was a requirement unless you had expensive engine management. Remember we're only boosting 8-9 psi to make the numbers we're after, the majority of the time the engine will STILL be operating with no boost at all, but it's there when you need it. It's the simplest most robust form of variable displacement possible... don't vary the mechanicals.. squish the AIR. > I think the newest Audi direct injection non-turbo gasoline engines are > even up to .....as high as 12 to one I think I 'might' have read. the new VAG 2.0T FSi turbo boosts to 17.5 psi.. they're making 268hp with that two liter from the factory, that's loads of boost for a factory engine. Too bad it's so complex it needs it's own shrink to help it figure out if it wants to keep on running... and it's too tall. Jim Akiba |
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