CyCloNe!

very interesting

bad_monkey

The interesting bit is that it would put the rod/stroke ratio at about 1.9:1 - apparently good for durability as it reduces piston/cylinder side loads.

The bore/stroke ratio would be ~1.3 - quite oversquare, reducing friction per RPM for the same swept volume (due to the reduced distance travelled during each engine rotation - one reason F1 engine have massively oversquare engines).

The more I read, the more I'm intrigued about the high RPM possibilities of this type of setup, given lighter/stonger rotating components. Michael Mount already showed us the possibilities of higher RPM with his awesome 16v build for
Henk.

To this end, could anyone add their experience of reliably increasing the rev limit of these engines? I'm particularly interested in the limitations of the stock 16v valvetrain - i.e. how high can you go while still getting reliable valve closure?

Getting power at higher RPM is another challenge - but first to find out what is possible, then determine what's practical.

944meister

regarding high rpm's with these engines, aside from head work and just lightening up the recipricating assembly, the biggest hurdle is supplying effective amount of oil and pressure. my understanding is that the stock oil pump starts to cavitate around 7200rpm, i personally would limit the rev's to a safe 6800rpm when using the stock oil pump. if you want to dump the $$$$.$$ on a dry sump system, micheal mount has proven 8500rpm, but thats just were the slippery slope begins. another thing to keep in mind is the location of the rod bearing oil supply hole, take a look at Henk's build thread and you can see a second hole strategically drilled through the rod journal. the angle of the hole is critical, i believe Henk's crankshaft has the ideal angle and hole location, it leads the critical point of the journal and allows the centrifugal force to work with the oil pressure. it is important that the drilling is done to all 4 journals and not just #2 & #3. i am not a veteran engine builder ,or an engineer, just something to consider.

bad_monkey

This is a good point about the oil pump - thanks. I wonder if there is sufficient excess pressure at low RPM to somehow under-drive the pump by 1/3rd. Might be a bit hard to achieve.

I've also seen some pretty interesting electric oil pumps in my wider research: http://www.rbracing-rsr.com/oilsystems.htm

The cross-drilled crank thing is a long-standing piece of knowledge - but I'll take a closer look at the angle in Henk's build - it makes sense that the angle etc make a difference.

This is exactly what I'm looking for - what else do we know about...

bad_monkey

I think I'm going to start a new thread regarding higher RPM - I'm OT in my own thread!