Automotive: why 2 stroke engines were not used, even in competition?

[Philippe Schutt]

I remember the Suzuki Gt 750, 8,5 liters of regular gasoline. Playing on the gas net in turns without risking a brutal engine brake can rub the pots all the way.
Later, a Kawa zzr 750 consumed just as much, at the same speeds (+ - 150), but super.
The engine brake argument is in my opinion a big pipe. Those who are used to it boast about it, but when you take the plunge to let it go, the driving is smoother and more economical, not only in fuel, but also in tires and chain kits.
I recovered 3 gt750 from the bottom of the barns, I hope to make a rolling one.

I have always wondered if combining the carburetor and direct injection systems would not be ideal. Pre-charge the intake air with insufficient fuel to start combustion, then inject just enough and just into the spark area to start the flame front. Then the increase in pressure and heat would burn everything. We would have the advantages of direct injection without the particles ...

[chatelot16]

The engine brake argument is in my opinion a big pipe. Those who are used to it boast about it, but when you take the plunge to let it go, the driving is smoother and more economical, not only in fuel, but also in tires and chain kits.

there is a big difference in engine braking between 4 stroke and 2 stroke ... 2 experience: French company tractor 2 stroke diesel ... downhill with a trailer at the bottom the engine brakes much less than with a 4 stroke similarly power

another experience or memory ... a trip in the alps in a berliet cruisair ... I heard the engine go up at high speed in the downhill as if it had very little engine brake ... I did not know 'epoque que c'est un 2 temps ... but it was only later that I understood that it made the same noise as buses in American films ... and today the internet confirms to me that berliet has used a detroit diesel engine in this model

for cars we avoid unwanted braking when we want to let it roll with long gearboxes ... 5th gear ... on a motorbike I understand the advantage: when you stop accelerating it does not brake suddenly

another remark on the 4 stroke: the exhaust valves are too small ... we prefer the size of the intake valve to increase the power but it brakes too much on the exhaust and it is harmful for the loss of energy ... with a smaller intake valve and larger exhaust we optimize performance and reduce braking

[Christophe]

There is also a big difference in engine braking when going from a gasoline engine to a diesel ... diesel have much less (since no throttle at least on most ... therefore no brake by "pumping ") which does not prevent diesel from outclassing gasoline ...

So I also think that the argument of the engine brake does not hold ...

Flytox according to you what is the valve used on the diagram that you posted?

Since there are still intake valves?
Aspirate more air when the piston goes down?
If it's an exhaust valve then we can no longer speak of a 2-stroke cycle ... right?

[chatelot16]

it is not the valve that changes the number of times

the problem of the 2 simple time is the scanning: intake light too close to the exhaust light!

one solution is to make the intake by light and the exhaust by valve: solution of the Detroit diesel and huge boat engine

other solution: 2 opposite piston no cylinder head ... intake light to one exhaust light piston to the other: junker and CLM diesel engine

I have a tractor of this type: CLM engine 1 cylinder 2 piston 3 rod

other 2-stroke diesel: 2-stroke diesel junker aircraft engine: 2 crankshaft

[Did67]

The opposing 1 cylinder / 2 piston diesel have had some success in agricultural machinery; I do not remember the brand, there was a formidable forest tractor well known in the East (maybe of Swiss origin ???) ....

[chatelot16]

I forgot to specify the brand of the tractor with clm engine: laborer (builder at mouchard jura)

these clm engine were mounted on several mark of agricultural machine at a time or the manufacturer did not have diesel of their manufacture

[Did67]

Maybe that's it!

I had always found it "brilliant", as a design.

A bit like the 2CV flat-twin, with platinum screws, dynamo at the end of the shaft ...

[Philippe Schutt]

And turbo engines have little engine brake too because they are smaller. By the way downhill I would like to have more on my C5.

If we divide the problems of 2T, we have:
1. pollution from burnt oil
2. the unfavorable diagram because symmetrical
3. wear of cylinders and pistons due to lights

Honda therefore had a good game for its lobbying

[Flytox]

I have always wondered if combining the carburetor and direct injection systems would not be ideal. Pre-charge the intake air with insufficient fuel to start combustion, then inject just enough and just into the spark area to start the flame front. Then the increase in pressure and heat would burn everything. We would have the advantages of direct injection without the particles ...

Not bad the idea . We are getting closer to the conditions of the HCCI engine with its homogeneous mixture.

https://fr.wikipedia.org/wiki/Moteur_HCCI

Can be a difficulty, for very low revs, to inject a really small dose of fuel.

[Flytox]

Flytox according to you what is the valve used on the diagram that you posted?

Since there are still intake valves?
Aspirate more air when the piston goes down?
If it's an exhaust valve then we can no longer speak of a 2-stroke cycle ... right?

+1 with Chatelot16. It works the same as a 2-stroke diesel.
The valves improve filling over a wide speed range.