6 stroke engine?

[jambo]

Torque is the force produced by the engine, generally bigger capacity gives more torque, and I believe 4 strokes offer more torque than 2 strokes for a given power stroke and capacity, but as 2 strokes have these more frequently they produce more power.

None the less I shall be intrested to see how the 6 stroke engine goes, definatly some advantages to be had, but transporting water and fuel may make it less useful for cars and bikes than you'd hope.

I am also waiting for pnumatic valves to take off as these can give great benefits to fuel economy with shutting down some of the cylinders on long journeys so they're not getting fuel (This is done at the moment) and crucially the pnumatic valve can make it purely induction / exhaust, meaning the engine isn't having to compress air in the unused cylinders...

[northwind]

Originally Posted by Scooby Drew

Unfortunately the cost of the technology is pretty high and this is what is stopping it from being used. A 2 stroke will always produce more torque than an equivelant size 4 stroke but they are very peaky and more difficult to ride. More kicks per mile if that's what you like

Yup... But then, once that was true of fuel injection. The reason it's expensive is that it's new and rare. Mass production would see that drop.

Lots of confusion about torque vs power in this topic Torque is a rotating force. The classic example is a wrench on a nut. If you have the wrench vertical and push downwards on it, you have exactly the same power, but you produce absolutely no torque, as the wrench will not rotate. To produce torque, you use your power to turn something, a crankshaft in teh case of an engine

An engine produces torque and power- using lb/ft and bhp, the amount of torque is the amount of power divided by the revs, multiplied by 5252. That's all it is- there's no type of engine that specifically makes more torque than power, or vice versa.

But slow engines that make 100bhp produce more torque than fast engines that produce 100bhp, as they do it at lower revs. And it just so happens that large displacement engines tend to be slower than small displacement, v-twins tend to be slower than IL4s, and 4-strokes tend to be slower than 2-strokes, so in each case the former will, all other things being equal, produce more torque.

Originally Posted by northwind

v-twins tend to be slower than IL4s, and 4-strokes tend to be slower than 2-strokes, so in each case the former will, all other things being equal, produce more torque.

Hence my question

I found it easy to relate to this quote -

"Torque is Chewbacca's ability to tear your arms off in one go. Power is a thousand Ewoks prodding you with pointy sticks."

[northwind]

Originally Posted by Flamin_Squirrel

Hence my question

Traditional 2-strokes make their power in a hysterical top-end rush that makes an R6 feel like a Rocket III... But that's not a hard and fast rule, some of the more recent attempts to revisit the format have used all sorts of interesting tricks to get the power down the revs, but more importantly to smooth the delivery.

Personally I reckon it's fashion that'll make that decision... The Big 4 spent years beating 2-strokes to death, they'd need a pretty good motive to go back- and they're really the only people with the investment funds to put into it, for biking at least. So I guess I'll have to wait a bit longer for my 80bhp, 130 kilo space-age 2-stroke

Going back to the original subject of recovering waste heat - BMW are in serious development of a steam turbine add-on, feeding water through a heat exchanger in the exhaust and using the steam generated to drive a tubine geared in to the crankshaft. They claim a significan boost to power / fuel economy.

see http://www.autoweek.com/apps/pbcs.dl.../60213002/1041

Just to throw a spanner in the works, but I think that in general 2 strokes rev slower than 4 strokes, which is not what those above have said. Not suprising when you consider that the piston rings run on barrels with lots of holes in really...
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