Crazy idea, Forced Induction 2 stroke implications.

Discussion in '2 smokers' started by Sp4rks, Jan 6, 2014.

  1. Sp4rks

    Sp4rks Been here awhile

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    Seriously, think about it, it's a theoretical quadruple displacement advantage over a naturally aspirated 4 stroke. 2 strokes already have a theoretical double displacement(125 2t=250 4t, in theory). Now, lets say, we add in one additional atmosphere of pressure(30lbs of boost, yeah, crazy number, just go with it). Now, instead of 125 2t=250 4t, it's 125 2tFI(FI being forced induction)=500 4tNA(NA being naturally aspirated). Here that KTM, get to work on it. I want my 160hp sub 200lb. Obvious problems are exploding engine(KTM 125sx makes peak hp at 12000RPM, I can't imagine that the engine could take much more), and carbs not being able to compensate(DFI, maybe?). And probably about a million other reasons that I didn't think of when the idea for this post popped into my head while I was watching a video about forced induction.

    But then again, the possibility of a sub 220lbs 160 HP motorcycle is kinda neat. Even in cars, a 2.0 liter car makes around 150hp, if it was a forced induction 2 stroke, 600hp. :deal

    Alright KTM(from the guys that brought you 100hp dirt bike, 180hp naked bike, 150hp Adventure bike, and hilariously aggressive 125 2 strokes) R/D, get to work. Time to show those 4 choking bastards whats up(I joke, I joke).

    Again, this is just an idea that popped into my head and I thought I'd share. Cheers.
    #1
  2. Chillis

    Chillis Long timer Supporter

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    The engine in the Aprilia SR50 Ditech is direct injection using an onboard compressor(crank driven piston) to inject the air and fuel into the combustion chamber. It is providing forced induction.

    High Gain Tuning did a turbo SR50.

    With direct injection and a turbo it would be extremely efficient and powerful.
    #2
  3. dhallilama

    dhallilama Long timer

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    check out some of the turbo'd two stroke snow mobiles... some crazy swedes and their drag machines.

    i've ridden one, it flat out scared the shit out of me.

    not a ton of turbo two stroke stuff out there, i'm guessing lots of tuning headaches and such... but i want to try it. i've turbo'd enough other things.

    [​IMG]
    #3
  4. WIsixfitty

    WIsixfitty rock and roll the bones

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    going back to the snowmobile world they have been turboing two-strokes for thirty years plus. Mostly western mountain riders as they need the help at altitude.

    To this day the applications are well made, make big power and are reliable.
    #4
  5. Twotaildog

    Twotaildog Old Poop

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    Interesting idea. Just wanted to point out that 30 psig boost is a little more than two additional atmospheres of pressure. Depending on your elevation, of course.
    #5
  6. concours

    concours WFO for 48 years

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    Turbo charging two strokes is like smoking in a Nitro Glycerin factory:deal. The whole design of a two stroke relies on exhaust having no backpressure, and rather pressure waves tuned (expansion chamber) to extract the gases. A turbo puts a BIG restriction, and adds pressure on the other side... It's a PRECARIOUS balance... I've towed a couple melted turbo's off the lake, heard of every one built melting down. SUPERCHARGE if you insist on force feeding.
    #6
  7. tHEtREV

    tHEtREV Encouragement award recipient. tEAM iDIOT.

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  8. Duck_Pilot

    Duck_Pilot Retired Roadracer

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    ....... little practical experience. You'll never get a 2-1 horsepower advantage over a 4T engine of the same displacement. 2 reasons:

    1 - Scavenging will not seal a combustion chamber as well as poppet valves.

    2 - The faster an engine spins, the more power potential. Even with power-valve exhaust, chamber tuning will limit powerband more than cam profiles/overlap will. Feeding that beast enough air and fuel for peak power will make that much worse.

    Reliability is the devil you are dancing with, trying to artificially aspirate a 2T engine. The entire system NEEDS to be sealed tight, from throttle valve to exhaust tip. Pressurizing adds more heat than cases, gaskets and seals are designed for. Expect short life and expensive repairs.
    #8
  9. joexr

    joexr Banned

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    With blown , forced induction and direct injection you wouldn't need typical 2-stroke cylinder ports. You could have poppet valves in the head and a FULL powerstroke. No premix or oil injection.
    #9
  10. Tim McKittrick

    Tim McKittrick Long timer

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    See Detroit diesel.
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  11. joexr

    joexr Banned

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    You mean the 2-stroke turbo-diesel?
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  12. concours

    concours WFO for 48 years

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    Nope. That would be a 2-stroke SUPERCHARGED diesel. Later in life, they added a turbo in ADDITION to the supercharger. Now, defunct, they were, at one time, a HOT new alternative to the pokey old diesels that came before.
    #12
  13. darmst6829

    darmst6829 Been here awhile

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    My buddy Herb super charged a Kawasaki Bighorn with a vacuum cleaner impeller and belt drive off the ignition flywheel. From what he told me it ran hard for about 60 seconds.
    #13
  14. chollo9

    chollo9 Screwed the Pooch

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    DKW, in the 1930s:

    [​IMG]

    [​IMG]


    A later version:


    [​IMG]
    #14