12-01-2005, 11:57 PM
.RJ Wrote:rod to stroke, not bore to stroke is important for higher end rev stability
I would ass-u-me the I4 has some inherent VE to it that the H4 does not have, in terms of cylinder filling (and evacuation).
Well yes, I understand that the rod to stroke ratio has more to do with it, but in a 10 minute post bore to stroke was a little easier to find. (Plus, people are always talking about the square of an engine, over under, etc)
Also, you may be correct with the cylinder filling, as the intake vacuum would have to fight for incoming air unless the intake manifolds were divided (which they aint, in the EJ motors...in the SVX's 3.3 they are...but I digress) but for evacuation I can only see H motors being *more* efficient, as there are only 2 cylinders fighting for exhaust space in the collector, not 4. (depending on header design, yaddayadda)
But again, I digress. In my K24 to EJ25 example, the EJ25 has 1.67:1 rod to stroke ratio and the K24 (by my calculation) has 1.68:1. Sooo....where did 1000rpm's go?
I was just curious. It always seemed strange the large amount of torque that the flat motors made, and the relatively low redlines, when on the surface they appear to be more apt to rev higher. Perhaps there's some other intrinsic nuance in the H design that prevents this kind of thing?
1987 Oldsmobile Cutlass 442