Thoughts on compression/build - ZR-1 Net Registry Forums

tpepmeie · 09-03-2007

In my opinion, valve size becomes the limiting factor (and with valve size goes port size, per my previous post). Using a stock stroke length, with the biggest valves known to fit in the LT5 chamber, the mean velocity at the valve head approaches 80 m/s at 8000 rpm. That is pretty inefficient, as even F1, etc. are typically 73-75 m/s.

To achieve the real big rpms, you would need a more oversquare engine (shorter stroke:bigger bore) and intake valves around 34% of bore area. And ports to match, of course. That would allow more reasonable air velocity as revs increase.

Then, finally, I am told that the ladder-frame sump allows the crank to "walk" in its journals at higher RPMs. Perhaps that is solved with studding the bottom end, though.

Todd

09-03-2007	#12
tpepmeie Join Date: Aug 2005 Location: Fishers, IN Posts: 815	Re: Thoughts on compression/build In my opinion, valve size becomes the limiting factor (and with valve size goes port size, per my previous post). Using a stock stroke length, with the biggest valves known to fit in the LT5 chamber, the mean velocity at the valve head approaches 80 m/s at 8000 rpm. That is pretty inefficient, as even F1, etc. are typically 73-75 m/s. To achieve the real big rpms, you would need a more oversquare engine (shorter stroke:bigger bore) and intake valves around 34% of bore area. And ports to match, of course. That would allow more reasonable air velocity as revs increase. Then, finally, I am told that the ladder-frame sump allows the crank to "walk" in its journals at higher RPMs. Perhaps that is solved with studding the bottom end, though. Todd