VCR engines

[Sybarite]

As I don't get out much I'm not sure if this is a genuinely new concept or one that I simply haven't picked up before now. If so sorry.

OK - FWIW a variable compression ratio (VCR) engine is being developed in France with the objective of being cheaper to produce and about 30% more economical than a diesel engine.

eg : In a prototype Peugeot 407, a 1500 cc engine produces 217 bhp @ 4000 rpm giving 43 mpg, the equivalent of their 3 litre V6 model at 2000 rpm less. With direct injection and a cylinder head redesign this is expected to pass to 270 hp and 47 mpg.

A further axis of development relates to using the variable compression to be able to auto ignite as do diesels in which case the ignition is more efficient and would boost the consumption figure to over 50 mpg. The engine also adjusts automatically to the octane level of the fuel.

They are also developing a 600cc engine having the power output of a 1200cc engine and expected to be the champion in fuel economy.

Having smaller lighter engines must obviously have a marine attraction as well.

John

 

[elton]

I'd never heard of such a thing until you mentioned it. Very interesting. There's an article about it here on Wikipedia.

 

[DownWest]

Me too,
The wiki stuff is interesting, but, most seem to prize, tough, heavy, simple engines on boats on the basis that one can fix them on the go. Usually' modern cars have plastic covers over the engine with some sort of notice saying "See your dealer if it doesn't work"
The idea behind these new engines is better economy. Very good, but not so much interest to a sailing boat that just requires a reliable back up to the sails, and use a few gallons of fuel per year.
Not against any of this this, just prefer sailing...
a

 

[halcyon]

I'd never heard of such a thing until you mentioned it. Very interesting. There's an article about it here on Wikipedia.

See the first VCR was built by Harry Ricardo in the 1920's, another British design down the pan.

Brian

 

[30boat]

By definition these engines have to be two strokes and they are also direct injected.Lotus has been working on one,read something about it in Bike magazine.

 

[KenMcCulloch]

I remember back in the day there were 2 stroke model aircraft engines described as diesels which had a screw in the top of the cylinder allowing adjustment of the compression. A fuel-air mixture was heated sufficiently by compression to fire, I think adjusting the cylinder head affected the timing of the explosion.

 

[RedAdmiral]

By definition these engines have to be two strokes and they are also direct injected.Lotus has been working on one,read something about it in Bike magazine.

The Ricardo was a single cylinder four stroke with shaft driven overhead camshaft. The shaft was in two parts with sliding internal/external splines. The Ricardo was designed purely for research. You could work out octane values for petrol and cetane values for diesel - if you really wanted to!