Vehicle Development Project - Interests

[MrPotatoHead]

I think it could work with more pedestrian rev ranges of around 5,500 - 7,000 rpm, engines with long strokes, but not at F1 speeds.

Very mundane and pedestrian indeed.

[Tommy Cookers]

[quote=J.A.W.]
[quote=godlameroso]I think it could work with more pedestrian rev ranges of around 5,500 - 7,000 rpm, engines with long strokes, but not at F1 speeds.
[/quote].........& one of the reasons F1 went back to forced induction was the overt inefficiencies of poppet valves..
..which showed in costly, short-life componentry, plus frictional , & gas flow-wise.. when used by ultra-high rpm N/A 4Ts..
reasonable engineering alternatives - such as 2T, or even 4T sleeve/rotary valves, were quickly proscribed, 'of course'.[/quote]

a wall-ported engine ie sleeve valves or usual 2 stroke is limited by simple geometry to quite low bore:stroke ratios and to corresponding rpm
ie it cannot use the high rpm potential allowed by high b:s ratios because the port area cannot rise in proportion
as port height determines port timing and so must reduce if the stroke is reduced

with head-ported engines eg poppet valves the port area (with b:s ratio increase) rises faster than the rpm potential
ie every time NA F1 engines shortened their stroke their relative port area improved and breathing was maintained or improved
the limits of this benign cycle were never reached as eventual limiting of b:s ratio (wisely ?) prevented further activity

fundamentally the stroke of an engine limits the rpm ie there's no great merit to a 22000rpm valve where the stroke limits to 18000 rpm
and similarly there's no merit to more port area than the engine can use

'F1 technology' can in F1 or in the real world can hide the downsides of excessive port area, whether from poppet or rotary valve
it's just unfashionable to see this as another compromise

[J.A.W.]

I think it could work with more pedestrian rev ranges of around 5,500 - 7,000 rpm, engines with long strokes, but not at F1 speeds.

.........& one of the reasons F1 went back to forced induction was the overt inefficiencies of poppet valves..
..which showed in costly, short-life componentry, plus frictional , & gas flow-wise.. when used by ultra-high rpm N/A 4Ts..
reasonable engineering alternatives - such as 2T, or even 4T sleeve/rotary valves, were quickly proscribed, 'of course'.

a wall-ported engine ie sleeve valves or usual 2 stroke is limited by simple geometry to low bore:stroke ratios and so to relatively low rpm
ie it cannot use the high rpm potentially allowed by high b:s ratios because the port area cannot rise in proportion
as port height determines port timing and so must reduce if the stroke is reduced

with head-ported engines eg poppet valves the port area (with b:s ratio increase) rises faster than the rpm potential
ie every time NA F1 engines shortened their stroke their relative port area improved and breathing was maintained or improved
the limits of this benign cycle were never reached as eventual limiting of b:s ratio (wisely ?) prevented further activity

fundamentally the stroke of an engine limits the rpm ie there's no great merit to a 20000rpm valve where the stroke limits to 18000 rpm
and similarly there's no merit to more port area than the engine can use
boosted F1 in the current style hides the real-world downsides of excessive port area, whether from poppet or rotary valves

Well, T-C, according to L.J.K. Setright in his 'Some Unusual Engines' book linked on Page 2 of the 'Crankshaft Config's...'
thread, Bristol ran one of their long-stroke 6.5in sleeves at 8,000 rpm in a single cylinder test engine..

"...Without anything going awry."

& the hugely over-square N/A F1 poppet valve 4Ts were unable to match the ~17 bar BMEP of the G.P. 2Ts..

As has been previously noted, Toyota tried to run one of their DOHC 4V engines as a 2T with external scavenging,
but it failed - due to port/time/area inadequacies, & inability to cope mechanically - with crank speed cams..

[Tommy Cookers]

@ J.A.W
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

[J.A.W.]

@ J.A.W
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..

[Mattchu]

Not sure where to post this, it`s pretty cool...

[J.A.W.]

Further to the discussions posted earlier on this page, some readers may find this
recent comparison test to be of interest:

https://motocrossactionmag.com/two-vs-f ... ur-stroke/


It serves as yet another example of - how super-restrictive technical regulations,
predicated by manufacturing-marketing ideologies - have cruelled motorsports,
not least by cost & complexity.

[J.A.W.]

&, here: https://www.researchgate.net/publicatio ... GDI_Engine

At the opposite end of the spectrum from motorsport engines, its a recent Ferrari-research built
2T hi-efficiency 'range-extender' mill, which utilizes electric-compressor scavenging for use
as a 'donkey-engine' to replenish batteries in electric vehicles, 'on-the-fly'...

[Will123321]

I don't always article the post on this forum often, but I just want to say that I think it's a great idea.