2 stroke thread (with occasional F1 relevance!)

[Abarth]

Probably wouldn't need crankcase scavenging either - with an electric turbocharger.

What do you mean by crancase scavenging?

[Abarth]

With the exhaust pulse of a 2 stroke the energy recovery will be phenomenal, may be up to 50%

Sure it would be quite challenging to tune the scavenging so that it works efficiently over a certain rpm range.

Another interesting application of such a design would be a compact 1cyl. range extender for EV, running at constant rpm, having a scavenging compressor eg. attached directly at the crankshaft, as well as a compounding turbine. Startup would be with the generator which is there anyway, efficiency would be "generous". It would work only at one fixed speed, anything could be tuned for exactly one operation point.
Of course there would be losses from generating electicity to storing and consuming it (with wheel motors perhaps), but I think it still could be an efficient drive.

[gruntguru]

Probably wouldn't need crankcase scavenging either - with an electric turbocharger.

What do you mean by crancase scavenging?

Using the underside of the piston to pump fresh charge into the cylinder (the system used on most small 2-strokes)

[J.A.W.]

Or put another way, a system utilizing apparent ambient vacuum to draw air into the engine (crankcase) on the piston upstroke, ready for pressure-sonic pulse/timed-aimed duct transfer to the combustion chamber,
- in the latter part of the downstroke..

This seeming simplicity is complicated by the need for expensive rolling element bearings & discreet sealing
arrangements required by high output mills, but has shown itself to be robust enough in untold hard use applications
- from the likes of chainsaws to racing in everything from miniscule IC racers to F1-type powerboat machines.

Other 2Ts such as the venerable Detroit Diesel - used an external 'supercharger' pump for charging the cylinders,
& often operated with an additional exhaust driven turbo too..

I recall laughing when M-B advertised a 'first' for their diesel car mills as being pioneering 4 poppet valve per
cylinder units, when D-D had used such a set-up since before WW2..

[Abarth]

Probably wouldn't need crankcase scavenging either - with an electric turbocharger.

What do you mean by crancase scavenging?

Using the underside of the piston to pump fresh charge into the cylinder (the system used on most small 2-strokes)

OK, thats what I understood too, but since I ruled it out in my post anyway, I got confused.
It needs the MGU-H type compressor and has sump lubrication, so no charge going through crancase.

[Abarth]

Or put another way, a system utilizing apparent ambient vacuum to draw air into the engine (crankcase) on the piston upstroke, ready for pressure-sonic pulse/timed-aimed duct transfer to the combustion chamber,
- in the latter part of the downstroke..

This seeming simplicity is complicated by the need for expensive rolling element bearings & discreet sealing
arrangements required by high output mills, but has shown itself to be robust enough in untold hard use applications
- from the likes of chainsaws to racing in everything from miniscule IC racers to F1-type powerboat machines.

Other 2Ts such as the venerable Detroit Diesel - used an external 'supercharger' pump for charging the cylinders,
& often operated with an additional exhaust driven turbo too..

I recall laughing when M-B advertised a 'first' for their diesel car mills as being pioneering 4 poppet valve per
cylinder units, when D-D had used such a set-up since before WW2..

Uh no, I never meant to use crancase:

I'd go for a DI 2 stroke engine with classic Schnürle loop scavenging, and sump lubrication. Of course the MGU-H would allow for this, as no crancase pre compression would be needed.

Schnürle scavenging has nothing to do with crancase scavenging, all happens above piston. Instead of cross flow, it is a sort of loop scavenging.
But if you don't use the crancase, you'll ned to pressurize the inlet ports...which is possible with an MGU-H type machine.

[gruntguru]

I recall laughing when M-B advertised a 'first' for their diesel car mills as being pioneering 4 poppet valve per cylinder units, when D-D had used such a set-up since before WW2..

Was the Mercedes a 4 stroke?

[J.A.W.]

Yes, but 4 valve per cylinder 4Ts date back to before WW1!

[autogyro]

With the exhaust pulse of a 2 stroke the energy recovery will be phenomenal, may be up to 50%

Sure it would be quite challenging to tune the scavenging so that it works efficiently over a certain rpm range.

Another interesting application of such a design would be a compact 1cyl. range extender for EV, running at constant rpm, having a scavenging compressor eg. attached directly at the crankshaft, as well as a compounding turbine. Startup would be with the generator which is there anyway, efficiency would be "generous". It would work only at one fixed speed, anything could be tuned for exactly one operation point.
Of course there would be losses from generating electicity to storing and consuming it (with wheel motors perhaps), but I think it still could be an efficient drive.

Why bother with a crankshaft and crankcase for a range extender two stroke.
A linear generator through scavenged two stroke works far better.

[Abarth]

Yeah as long as you never have a misfiring

[riff_raff]

It might be tough to get a 2T poppet exhaust valve system to work reliably at F1 speeds. Plus there is the issue of having intake ports in the cylinder walls, which would require long piston skirts, long conrods, and oil rings located at the bottom of the long piston skirts. Even with an electrically assisted turbo, it may not be easy to obtain efficient scavenging over a wide speed range.

[uniflow]

Full circle, enter Ricardo's open ended sleeve system.

[J.A.W.]

It might be tough to get a 2T poppet exhaust valve system to work reliably at F1 speeds. Plus there is the issue of having intake ports in the cylinder walls, which would require long piston skirts, long conrods, and oil rings located at the bottom of the long piston skirts. Even with an electrically assisted turbo, it may not be easy to obtain efficient scavenging over a wide speed range.

& of course, neither forced induction nor 2T mills.. ..require the costly super-high rpm designs of N/A F1 4Ts..

[gruntguru]

. . . and of course 2T, sleeve valves (and anything other than poppet valves) are illegal in F1 anyway.

[J.A.W.]

For sure, the current set of F1 reg's would have to be the most prescriptive..
&.. proscriptive - in the whole history of international G.P. racing, AFAIR..

Not for the better, either, it so far seems..


What could a decent F1 budget bring to bear engine concept-wise, on something a bit like this ?

https://www.youtube.com/watch?v=v8zGov8Fn7U