2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

Toroidal combustion chamber cut into billet SSO head - for Jorgen's well-developed classic Kawasaki H2 750 triple..

[Tommy Cookers]

glycerine is an ester
many synthetic 'oils' are esters
vegetable oils eg castor oil are esters (mineral oils are broadly olefins)

how would glycerine used as 'oil' avoid similar contribution to limits of what is for convenience called UBHC ?
legally ?
chemically ?
or not in any way ? - (as I would imagine)

[Pinger]

"Fully Synthetic" does not necessarily mean "non hydrocarbon."

http://www.synthetic-oil-technology.info/

Fair point. But, for 4T oils, when deviation from fully synthetic to semi synthetic occurs it will be by blending with hydrocarbon mineral oil. The reason that is done is that fully synthetic oils lack solubility which impedes their uptake and retention of the myriad additive packages required. So, while a fully synthetic oil's base may have a long service life, its real world life is determined by its meagre additive packages content which will deplete before the actual oil is spent and thus determines the oil's actual service life.

The above relates to 'sumped' lubricants. One pass oils such as 2T oils can omit much of the additives otherwise required and can therefore eliminate the addition of mineral oils there solely to add solubility.

Referring back to the Stihl 4-Mix engines. Stihl market three 2T oils. A mineral, a semi synthetic, and a fully synthetic. Stihl approve only the last one for use in 4-Mix engines.

[J.A.W.]

Forum member 'Uniflow' - shows us his (home-developed, 'sliding door'/variable port-area) - rotary disc-valve, 2T engine.

https://www.youtube.com/watch?v=v5jLX4KtpXs

[J.A.W.]

Many interesting 2T developments are due to inspired individuals, as a number of forum members here
have shown - in the course of this thread.

The link below features another such 'intuitive' mind at work, in Martin Heinrich.
One Heinrich design (made in metal) was a remarkable H8 2T, being 4 opposed-twin rotary valve units enbloc..

http://www.amsnow.com/how-to-tech/2017/ ... le-engines

[J.A.W.]

Recent science journal article examining finetuning a 300cc 2T cylinder running a low-pressure DI system, at "full power" level.
https://www.sciencedirect.com/science/a ... 0217337578

[Pinger]

Cheers J.A.W.. Found both articles interesting.

[J.A.W.]

Further evidence that basic 2T's are still amenable to 'backyard' tuning approaches.. such as.. 50cc/20ps..

https://www.youtube.com/watch?v=LIk71wFp1nc

[PlatinumZealot]

Been at the new job for a few months now. Power plant. 800mm bore two stroke MAN engines. Basically ship engines. But you get to understand why a two stroke "cross-head" design works best to get the high efficiencie and high reliabilty.

A cross-head design means almost zero blow into the crank case by and no side loads on the cylinders but the weight is heavy. Would be interesting if it were used in F1. How they could lighten it.

[gruntguru]

A cross-head design means blow by . . .

You mean "reduced blow by"?

[roon]

A cross-head design means blow by . . .

You mean "reduced blow by"?

Blow-by designed in, may be what he means. The piston doesn't need rings nor touch the cylinder wall. The volume beneath the cylinder can be used as a pump as a sort of forced induction. Blow-by would manifest as a sort of EGR, while being oil-free. The piston rod is what gets sealed from the crankcase, and also acts as the piston guide.

[gruntguru]

A cross-head design means blow by . . .

You mean "reduced blow by"?

Blow-by designed in, may be what he means. The piston doesn't need rings nor touch the cylinder wall. The volume beneath the cylinder can be used as a pump as a sort of forced induction. Blow-by would manifest as a sort of EGR, while being oil-free. The piston rod is what gets sealed from the crankcase, and also acts as the piston guide.

They do have rings actually. Combustion pressure is sealed to the space above the piston as in trunk-piston engines. The space below the piston is sometimes used as a scavenge pump.
http://www.marinediesels.info/2_stroke_ ... access.htm

[roon]

You mean "reduced blow by"?

Blow-by designed in, may be what he means. The piston doesn't need rings nor touch the cylinder wall. The volume beneath the cylinder can be used as a pump as a sort of forced induction. Blow-by would manifest as a sort of EGR, while being oil-free. The piston rod is what gets sealed from the crankcase, and also acts as the piston guide.

They do have rings actually. Combustion pressure is sealed to the space above the piston as in trunk-piston engines. The space below the piston is sometimes used as a scavenge pump.
http://www.marinediesels.info/2_stroke_ ... access.htm

Cool. I don't doubt some, most, or all, do. Just trying to make sense of the claim. Poorly worded on my part.

[J.A.W.]

Tech-transfer from our - currently tightly rules constrained F1 - might well yield viable efficency/performance gains..
..if a 2T/CI approach to turbo-compound piston engines was allowed/followed-up..in a number of usage areas..

(once again.. see below, this 1/4 century old.. NASA-Garrett helo-mill proposal.. as a reference)..

https://ntrs.nasa.gov/archive/nasa/casi ... 001160.pdf

[J.A.W.]

A cross-head design means blow by . . .

You mean "reduced blow by"?

Blow-by designed in, may be what he means. The piston doesn't need rings nor touch the cylinder wall. The volume beneath the cylinder can be used as a pump as a sort of forced induction. Blow-by would manifest as a sort of EGR, while being oil-free. The piston rod is what gets sealed from the crankcase, and also acts as the piston guide.

Roon, are you by any chance..somehow 'channelling' - the hype.. advanced earlier - in this thread.. for the "Ryger" mill?

(& we are.. still.. patiently.. waiting.. for the.. many times.. promised.. 125cc/70hp Ryger machine.. to 'arrive')..