Quote:
Originally Posted by serialk11r
Hey arghx7 if you see this, I was wondering about the thing you said about direct injection being very reliant on charge motion.
The 2GR-FSE paper has a chart that went something like "tumble ratio" vs. "flow coefficient", and they explained that they used a high flow port on the 2GR. From context, it seems like they're telling us the 2GR has high flow, low tumble ports. It has a little blurb about "consequently the tumble ratio of the high flow test engine was reduced by one third at the valve-lift divided by valve-diameter of 0.3".
Is this to say that the ports are still a compromise between tumble and flow? Is this why you were questioning the viability of increasing revs (intake port flow)?
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Couple points to consider.
When they say 'tumble' it is probably in the context of low-rpm/intake velocity.
Also it's not tumble specifically that's important, but maintaining charge motion as the combustion chamber squishes approaching ignition.
One reason F1 cars were 'only' 12:1 CR was for room for this motion.