Not too long ago there was a thread in the Back Room about two stroke motors, and particularly diesels. The latest edition of Practical Classics has a feature on two-strokes, and also an article about a magnificent vintage style car powered by a Commer opposed-piston two-stroke diesel.
One interesting point from the article - apparently the reason the Ford Ka ended up with the old all-iron crossflow motor which dated back to the Ford Anglia was that it was designed around a compact new two-stroke motor. When this project was canned at a very late stage, the faithful old crossflow was the only Ford engine which would fit in the Ka engine bay.
Richard Hall
bangernomics.tripod.com
|
Anyone know why the project was canned? I seem to remember Ford getting involved with unusual engine designs on several occasions in the past, and it's hard to resist the thought that they buy inventors out to squash them, although perhaps the charitable explanation is that their accountants can't stomach the cost of tooling up for anything too radical.
My idea, FWIW, is to have solenoid operated valves that would allow completely variable timing and lift. Desmodromic operation, too, if you want it...
|
If, in fact, Ford were contemplating a two-stroke engine I would guess that this would have been the Australian Orbital engine which has been under development for a couple of decades now. I don't know why Ford dropped the two-stroke engine but I am sure that they would not buy out inventors simply to destroy any competition. That is an oft repeated fallacy.
JBJ is much nearer the mark in his alternative suggestion regarding the take up of new inventions, i.e. Rejection on cost grounds. Complete production line re-tooling costs many millions of pounds and is not viable unless the new invention is sure to be absolutely reliable and more highly desired by the public than what has gone before. A manufacturer would be foolish to make a huge investment without a reasonable chance of a good return. Then there are the technical problems with two-strokes ...
For a two-stroke to meet current emissions legislation it would need to be radically different from the ones we are familiar with. For a start, having piston rings traverse ports in a cylinder wall sets up minute fluctuations of the rings which is known to increase undesirable emissions, so intake and exhaust control needs to be via valves as in a four-stroke engine.
Also, to meet modern economy and emission expectations, the inlet gas must be kept separate from the exhaust gas within the cylinder (some limited mixing may be useful but this must be very precisely controlled, like the exhaust gas recirculation (EGR) system in some four stroke engines). One idea, seen in a patent, was to keep the gases separated by a disc which rides up and down between the piston and the top of the cylinder under the control of a camshaft system. This is too cumbersome, complicated and expensive.
Another consideration is the heat output of a two-stroke which is likely to be similar to the equivalent power four-stroke, so the cooling system is likely to be as large. Further, the two-stroke will not produce twice the power of a similar capacity four-stroke, those in the past were not a great deal over 1.1/2 times and it will take a lot of innovative thinking to improve on this without pricing the two-stroke beyond what the market will stand.
So we end up with a two-stroke that is a bit smaller than an equivalent four-stroke but is likely to be complicated, expensive, possibly less refined and with unproven appeal to the new car buyer. That, I would suggest, is why Ford kept to four-strokes.
|
|
Ford ran a fleet of Orbital engined police cars-local area cars- not high speed pursuit-the engines were complicated-needed high pressure air to blow the fuel into the combustion chamber and had trouble meeting the emission requirements of the day and the fuel economy was nothing special-you also had to keep filling a little tank with oil for lubrication.However that was many years before the Ka was even thought of.There was a Californian firm trying to develop a two-stroke sealed from the crankcase which would do away with many of the problems but this would require an air-pump to get the mixture into the combustion chamber.Any motor manufacturer would be only to happy use any type of engine if it was reliable,economical and easy to manufacture.
|
|
|
I don't know why Ford dropped the two-stroke engine but I am sure that they would not buy out inventors simply to destroy any competition. That is an oft repeated fallacy.
I can't comment on Ford, or the motor industry.
But I know for a fact of a company paying a big six figure sum to eliminate a potential competitor.
Obviously confidentiality clauses apply, but I can confirm it wasn't to me!;-(
|
From what I can remember, the Ford project (which used the Orbital engine) was abandoned due to problems with nitrous oxide emissions, also durability problems with the roller bearing crank. Presumably Toyota's two-stroke straight six also failed to meet emissions - a great pity as I bet it would have sounded fabulous. I wouldn't be too surprised to see a small two-stroke diesel in the next few years, since the latest high pressure injection diesels must be pretty expensive to make, and manufacturers are bound to be looking for a cheaper way to get the same sort of power output.
Richard Hall
bangernomics.tripod.com
|
|
|
"But I know for a fact of a company paying a big six figure sum to eliminate a potential competitor."
Microsoft do this all the time. I wouldn't mind quite so much if they didn't keep describing it as their "freedom to innovate"!
|
|
|
|
|
|
