Here's an interesting article about the Lotus "omnivore" two-stroke engine, which is apparently 10% more efficient:
www.autoblog.com/2009/12/10/lotus-omnivore-engine-...e
This reminds me of something back in the late 80s or early 90s about two-stroke engines being the future, but nothing seemed to come of that. I think Ford were involved and even had a prototype car (not just an engine).
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I believe the Ford Ka was designed around the two stroke you mention and that there were quite a few test cars built. I am unaware why they decided not use the two stroke ,but they then had to shoehorn in the old tech 1.3 engine which was not the most refined or efficient unit.
It'd be good to know the real reasons for the last minute switch. Anyone out there know?
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Mmmmm, love a good two stroke engine in an old school motocross bike, cant beat the rush you get when it hits the powerband and you hang on for dear life!
But when it comes to cars I always thought the problem was that of emissions, in particular the hydrocarbons.
Shame really, because with one power stroke per revolution rather than half a power stroke on a four stroke, in theory there is the potential to have twice the power output for a given size.
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Ford were working with a company called Orbital in the early 90's on a 1.2 litre two stroke, three cylinder engine for the Fiesta and Escort. I recall reading a very complimentary review of a prototype Fiesta in one of the contemporary car mags. The tester reckoned it was gutsy, fuel efficient and very responsive. The only downside was that it sounded very noisy under wide throttle openings, and at high revs. It apparently delivered 10% better fuel economy and 10% more power than the 1.4 litre CVH that Ford were offering at the time, and due to its diminutive size and weight, the engine would have given a lot of interesting packaging options in terms of future model design. Can't imagine it actually sounded worse than a CVH either ;-)
I believe it was indeed emissions which killed off the idea, but in terms of what it actually did, it was very promising.
I always thought of two strokes as being highly strung things which would struggle to do a five figure mileage between rebuilds, but a friend flies microlights, and the club he belongs to has a few Rotax powered strokers on its fleet. The oldest ones have tens of thousands of reliable hours on them, and the maintenance bills are very favourable compared with the newer four stroke stuff. They need rebuilding every so often, but with no oil changes, timing belts or valve clearances to worry about, the overall maintenance cost is actually lower.
Edited by DP on 11/12/2009 at 15:17
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Two-stroke DIESELS still hang on by a thread, as in the class 59 and class 66 freight railway locomotives and in ships. They were once used in lorries and buses - Commer TS3, Detroit Diesels used in many US trucks, Foden's in-house engines (used in a minority of their vehicles) and last, but not least, the famous Deltic express locomotives.
Two-stoke diesels can be smaller and ligher than an equivalent power 4-stroke, but they tended to be less economical, more smoky and need a supercharger in order to work.
But I believe a small two-stroke diesel has been developed for light aircraft use.
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Even if the engine software could mellow the hallmark narrow power band that all 2-strokes have and even if someone could design reliable lubrication, the words "2-stroke" with its smoky scooter, difficult-to-start lawnmower and Trabant associations will kill any marketing effort stone dead IMO. It would have to be called a Day cycle engine or something.
Good luck to Lotus though.
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>>I think Ford were involved and even had a prototype car (not just an engine).>>
There is an Orbital Fiesta at the Haynes Motor museum.
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There were a fleet of police cars fitted with them-Suffolk I think-but they were useless on emissions.There was a firm in California working on a more promising two-stroke system where the crankcase and,hence,the bearings were totally seperated from the combustion process.Many two-strokes have pressure fed bearings but that oil still has to go somewhere.
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"hallmark narrow power band"
Only when designed that way, and/or with tuned pipes. Trabants and Wartburgs and most scooters are pretty flexible - indeed the torque from my old 3-cyl Wartburg was astonishing for a 1 litre unit.
The emissions problem has already been licked by Evinrude, whose direct injection 2-strokes have considerably better emissions than their equivalent 4-strokes (an order of magnitude better at low revs) but, as you say, the image still needs a little polishing.
Anyone remember the Norton Wulf stepped-piston 2-stroke..?
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