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Thread: The future is two stroke! Hurrah!

  1. #1
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    The future is two stroke! Hurrah!

    Lotus Omnivore at Geneva
    Lotus revealed its no-smoke two-stroke engine at Geneva
    By John Simister
    09th March 2009


    Lotus revealed its intriguing Omnivore engine concept at Geneva, hailing it as, among other things, a way of making large-capacity piston engines very efficient.

    It's a tri-fuel engine, able to run on methanol, ethanol, petrol or any combination of the three, but methanol is the greenest of the three because it can be obtained by combining hydrogen with atmospheric carbon dioxide. This still requires a hydrogen source, something exercising many industry minds in the thrust towards electric fuel-cell cars, but methanol is a much more efficient way of storing energy than hydrogen is. 'It shouldn't really be a liquid,' says Lotus engineer and Omnivore developer Jamie Turner, ' because it's such a low-mass molecule. But the polarity in the molecules pulls them together.'

    The Omnivore is a two-stroke engine, but not like two-strokes we’ve known in the past in which a chunk of the intake charge goes straight out of the exhaust port at certain speeds. There's no primary crankcase compression here; the intake port leads straight into the cylinder and the charge is forced in by a supercharger. A rotary cam operates an exhaust-port flap to keep the charge where it's supposed to be, its timing variable by means of an extendible hydraulic ram to suit speed and load.

    This is a direct-injection engine, and uses the HCCI – Homogeneous Charge Compression Ignition – principle. At least it does 75 per cent of the time; 'We haven't yet been able to make it idle,' says Turner. So a conventional spark plug takes over when needed.

    For HCCI an engine needs a variable compression ratio, which the Omnivore has by means of a movable 'puck' in the combustion chamber (a simple solution made possible by the two-stroke's lack of conventional valves). This can vary the ratio between 8:1 and 50:1, although in practice it will never need to go that high.
    The advantage of making fuel self-ignite under great pressure, as a diesel does, is that all the fuel ignites simultaneously so there's no flame front. And that means there's no knocking or pinking, so the engine can be designed to get the most possible energy out of the fuel. Methanol is best here, because it burns less violently than the heavier alternatives.

    Because this two-stroke doesn't use the crankcase for compression, the Omnivore can have a conventional wet oil sump. Two extra piston rings at the bottom of the piston ensure the oil mist stays away from the inlet port.

    So far, the Omnivore exists mainly as a computer model, but the first real, single-cylinder example will fire up in the next two weeks. 'It should be very quiet, unlike a normal two-stroke,' says Jamie Turner, 'and theoretically it can be more powerful than production engines are now. This concept might allow very large-capacity engines with good fuel consumption, so it would be good for premium cars. People still buy capacity, because they equate it with status.'
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  2. #2
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    aaaaaaaAAAAAAAAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUUUUU GGGGGGGGGGGGGGGGGGGGGGGHHHHHHHHHHHHHHHHHHHHHH!!!!! !!!!!!!!!!!!!!!!!!!!

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    Pah. Heresy. Who would ever want a two smoker that didn't smoke! I bet it doesn't even go ringa-ding-dinga either.
    Quote Originally Posted by skidmark
    This world has lost it's drive, everybody just wants to fit in the be the norm as it were.
    Quote Originally Posted by Phil Vincent
    The manufacturers go to a lot of trouble to find out what the average rider prefers, because the maker who guesses closest to the average preference gets the largest sales. But the average rider is mainly interested in silly (as opposed to useful) “goodies” to try to kid the public that he is riding a racer

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    Not to mention never oiling up spark plugs.
    And I to my motorcycle parked like the soul of the junkyard. Restored, a bicycle fleshed with power, and tore off. Up Highway 106 continually drunk on the wind in my mouth. Wringing the handlebar for speed, wild to be wreckage forever.

    - James Dickey, Cherrylog Road.

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    If it goes fast then its good in my books

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    Just going fast isn't anything. If it's not antisocial and irresponsible, it might as well be a four stroke , they go fast too sometimes. I suppose one could run it on premix anyway.
    Quote Originally Posted by skidmark
    This world has lost it's drive, everybody just wants to fit in the be the norm as it were.
    Quote Originally Posted by Phil Vincent
    The manufacturers go to a lot of trouble to find out what the average rider prefers, because the maker who guesses closest to the average preference gets the largest sales. But the average rider is mainly interested in silly (as opposed to useful) “goodies” to try to kid the public that he is riding a racer

  7. #7
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    This technology has been around for years. No one has put good use to it however.
    The Aprilla DiTech is somewhat similar and has very good petrol economy and bugger all emissions.

    All its basically doing is making a 4 stroke a 2 by forcing the gas in at high pressure via a supercharger.

    Hopefully we see something come off it. Of course no smoke and no big expansion chamber (No exhaust port leakage, no point) .

    http://www.speed-sports.com/motorsco...rs/ditech.html

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    the future has always been two stroke.

    the current four stroke love affair with some misguided souls is merely a temporary obsession.

    normal service will be resumed shortly.
    "more than two strokes is masturbation"
    www.motoparts-online.com

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    http://www.anarchadia.co.uk/2008/01/...arged-two.html

    This has been around a long time!
    DKW had it down to a fine art!
    Then super charging was banned
    (Check out pre ww2 super charged bikes,Ajs,Gillera,Etc)
    Check out any two stroke diesel
    (Comer trucks,any large container ship)
    Four stroke type lower end two stroke top
    Good idea with new metallurgy most things will work!!!
    Sleeve valves, Deltic engines..
    Napier Saber now that was an engine
    (christ i know all this off the top of my head)
    Anyway this stuff sort of got put away pre ww2
    just in case someone got an advantage during the war,
    You should see some of the inlet pressures on a top fuel
    Engine

    What ever its worth

    the art of diplomacy is saying nice doggie,
    until you find a big rock

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    mmmmmmmmmmmmm
    Napier Sabre!

    H24

    Not very reliable to begin with, but.
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    I may not be as good as I once was, but I'm as good once as I always was.

  11. #11
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    I'm tryin to get away from 2 stroke not go back ...
    I aint no vegetarian, gimme beefcakes!

  12. #12
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    You lot obviously can't read or are ignorant.
    Variable compression
    HCC Ignition (not Diesel by the way,as it is not initiated by compression heating,but by free radicals in the exhaust gas)
    Lotus Charge trapping valve (don't tell me YPVS as they only altered blow down angle)

    Show me a fucken DKW or opposed piston diesel that had those

  13. #13
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    Quote Originally Posted by Pixie View Post
    So far, the Omnivore exists mainly as a computer model...
    Aha.

    Direct injection can already reduce 2-stroke emissions hugely and is used in outboards. Its drawback, as I understand it, is an abrupt throttle response that's fine for an outboard but a big problem on a bike. Still, manufacturers could make high-performance 2-stroke bikes tomorrow, with technology that has been proved outside computer models, if they wanted to enough and thought there was a big enough market.

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    Arrow and Tyga have announced spannies for the 2010 RGV750 are now in development stage

    I don't care if it doesn't need them.
    Don't you look at my accountant.
    He's the only one I've got.

  15. #15
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    Quote Originally Posted by Pixie View Post
    You lot obviously can't read or are ignorant.
    Variable compression
    HCC Ignition (not Diesel by the way,as it is not initiated by compression heating,but by free radicals in the exhaust gas)
    Lotus Charge trapping valve (don't tell me YPVS as they only altered blow down angle)

    Show me a fucken DKW or opposed piston diesel that had those
    So what lets see i work!
    Variable compression has been around a long time
    how do you think they give Ron/Mon numbers!!
    they use a test engine that changes compression

    the art of diplomacy is saying nice doggie,
    until you find a big rock

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