Tommy Cookers wrote: ↑
Fri May 26, 2017 12:02 pm
nothing in your last post is material to any point I have made
your (previous post) point seems to be that a 125cc cylinder Aprilia makes c.440 hp/litre and so was kept out of F1
but you are comparing this with 300cc F1 cylinders (that made c.320 hp/litre)
not for the first time - simple geometrical considerations show that .......
whether 4 stroke or 2 stroke, a smaller cylinder will have more breathing potential relative to its needs (ie possibly even beyond)
also the 4 stroke's breathing potential relative to its needs will increase with b:s ratio while the 2 stroke's will reduce
comparing an Aprilia cylinder scaled-up to 300cc with NA F1 - the 300cc Aprilia can't beat the F1
it would have 34% more bore and stroke and so 80% more port area
but would need (to emulate the 125 in bmep and rpm) 140% more port area
of course at the 125 piston acceleration it would make 16% less rpm and these 2 factors imply 'only' c.320 hp/litre
comparing NA F1 scaled to 125cc with the 125 Aprilia's 440 hp/litre - 125cc F1 implies c.370 hp/litre
running 16% faster (than 300cc F1) at the same piston acceleration and having relatively better breathing potential
You assumptions are flawed T-C, you must take into account that very little development was put into hard
tuned 2T cylinders of ~250cc, since they were mostly used in MX engines..
Honda did build the NSR500V twin cylinder G.P. bike, but again, its tune was - at a mere 280 hp/Ltr - predicated
to be user friendly in a motorcycle - if used in a car, then a much harder tune with fiercer power characteristics
could be accommodated, & the engine could be constructed via suitable architecture, given the space available.
See here: www.sportrider.com/sr-archive-riding-mi ... on-nsr500v
The F1 N/A 4T poppet valve engines HAD to achieve those 'stratospheric' rpm levels to spin useful work from
the limited BMEP/torque due to time/port/area, & the extreme B X S ratios were essentially a technical dead-end..
The FIA had to resort to to bans on alternatives, & then a strictly mandated forced induction rule set in an attempt to get cost/TBO issues under control.. Of course, as it happens - high power with long TBO is per se costly..