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sbc direct fuel injection

Discussion in 'The Garage' started by PeteH, Aug 16, 2005.

  1. PeteH

    PeteH 1/2 ton status

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    (lots a reading)
    Why hasn’t anyone modified their sbc to direct fuel injection? Could it even be possible?


    Injecting gas directly into a high compression spark-ignited engine should not only improve performance but fuel economy. Detonations probably a big issue and emission also. But I’m sure someone could be smart enough to fiddle with a mega squirt type of program and tpi……..and no emissions crap would make it easier(for us ‘75 and older rigs in cal :waytogo: )

    “Mitsubishi has the GDI. 35 to 40 percent better fuel efficiency than an indirect multiport injected engine, 10 percent more torque and meets all emission requirements, including the ones for oxides of nitrogen (NOX)(that’s the tough one)”

    “The GDI engine runs on an ultra lean (40:1) air/fuel ratio at idle by using special injectors that produce a "stratified" charge in the combustion chambers. Regular gasoline fuel injectors produce a fine cone-shaped mist that's necessary to create a homogeneous air/fuel mixture. The high pressure GDI injectors, by comparison, produce a very compact spray pattern that forms a swirling cloud of fuel particles. This, combined, with a "reverse tumble" air flow in the cylinders creates a layered effect (stratified charge) of air and fuel in the cylinder that is rich in the immediate vicinity of the spark plug but is progressively leaner further out.”

    “One of the keys to making this work is the way air is directed into the cylinders. Most engines have horizontal intake and exhaust ports so air and fuel enter past the intake valve, blow past the spark plug and swirl back around the cylinder in a circular path before being ignited. In the GDI engine, the intake port is almost vertical. Air flows down from the top, enters past the intake valve and injector, flows down the side of the cylinder until it hits a cup shaped pocket in the piston dome that redirects it back up towards the spark plug. This "reverse flow" arrangement combined with relatively late injection timing in the compression stroke allows the engine to handle very lean mixtures at idle without misfiring. When more power is needed, injector timing is advanced earlier in the compression stroke and more fuel is injected into the cylinder to create a more conventional fuel mixture.”

    So that being said. Why not have cuped pistons of some sort or just domed ones, drill and fab something in the heads for injector and use a diesel injector that can support gas. Then hook up a tuned mega squirt, tpi and wowza :woot: ! Better than tpi tbi, and even better than the basic sequential.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    I read that article on the Mitsu probably a year ago. (as I recall)

    Doesn't that article get into how hard it is to inject gasoline directly into a combustion chamber? They mention how they get away with it, but that's been the limiting factor for gas engines and direct injection as I see it. How are you going to isolate the fuel/injector from the combustion heat and cylinder pressure? A standard injector certainly won't cut it.

    The Mitsu design would require all the automakers to completely redesign their engines and probably vehicles (to make a new engine fit) so there is going to be some resistance there.

    I suspect along with that, at this point anyway, the cost of producing them would be ultra high with the new components and designs.
     
  3. PeteH

    PeteH 1/2 ton status

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    click here

    yea that was the mits article from 97 or so. but i know theres more companies doing it out there.

    I dont know much about injectors and i presumed a normal fuel injector wouldn't work..but i figured a diesel injector might. I thought they could withstand lots of pressure/compression and heat? I dont know if gas would flow through them the same way though.

    and i was thinking that theirs a lot of pretty good fabrictors out there..i would think some would have done it.
    and i was bored and thought it was pretty interesting.

    id be nice to have it on a sb but maybe it wouldnt be much different then getting sequential through tpi or even batchfire
     
  4. dirtwarrior17

    dirtwarrior17 Banned

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    Evinrude just spent alot of time and money building a direct injection 2 stroke outboard and it kicked every single outboards ass including the 4 strokes. It burns cleaner(because of the lean mixture), has more tq, and gets better gas mileage.

    The injectors aren't the hard part... they already exist. Its the redesigning and making new machinery to build these new designs that cost a sh1t load. Gm used the same motor for over 50 years... and people are still buying carbs :deal:. If it does finally happen it will be because somebody was selling alot of them. Mit hasn't done that so theres no reason to change.
     

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