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Diesel manifolds

Discussion in 'The Coffee Shop ~ Chit Chat' started by 9191gmc, Jul 13, 2013.

  1. 9191gmc

    9191gmc Rockstar

    This is about 13-15 litre diesel engines in tractor trailers. Do the fuel injectors inject fuel down thru the head into the combustion chamber ....
    or into the intake manifold next to the head??Any mechanics know ????
  2. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    A diesel engine fires when fuel is injected into the cylinder; just before TDC, on the compression stroke.
  3. 9191gmc

    9191gmc Rockstar

    that isnt what I asked. Are the injector holes thru the head or into the manifold next to the head??
  4. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    Actually, I did answer your question, when I said the fuel is injected into the combustion chamber.

    The piston is at the top of the cylinder, I expect the "charge" would be injected from the top.

    All of this, of course, depends upon the particular engine we are talking about. Some diesels use a pre-ignition chamber which is adjacent to the combustion chamber. It is not part of the manifold. The reason for this chamber is to create a diesel engine that runs quieter than diesels of old.

    To the best of my knowledge, true diesels do not mix fuel with the incoming air.
  5. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

  6. 9191gmc

    9191gmc Rockstar

    any engine needs air to mix with the fuel. 99% of tractor trailers have turbos whose only job is to provide
    large amounts of air.
  7. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    You need an air/fuel mix to generate combustion.

    Some engines mix the air/fuel in the carb, or manifold. Some engines inject the fuel into the air which is already in the cylinder.

    Gas engines require a spark to explode the air/fuel mix. Diesel engines require compression temp to explode the mix.

    We seem to be getting off track, why the original question?
  8. 9191gmc

    9191gmc Rockstar

    I am wondering how big a deal it would be to add a natural gas set of additional injectors into a semi engine, myself... instead of a 20K shop job. I guess from what I have read that the nat gas can be injected before the
    combustion chamber like right after the turbo and mix with the air. I want a rig that can burn a mix of diesel and nat gas in any combination because of inevitable future restrictions on diesel exhaust particulate and just general pollution from diesel. I would have to source a ECM to handle the injection and amounts but there are such things out there.
  9. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Look around on the net some, theres a few companies that have DIY kits for CNG or LNG.
    4 years ago I put a CNG kit on my 2005 Duramax, I dont see the kit I used for sale anymore but it was designed with a Bosche injector that put the gas in right after the turbo, I used a stand alone injector controller from Bosche that allowed me to adjust the pulse and pressure.
    Just a word of caution before investing in any gas injection kits instal a Pyrometer to monitor the EGT and look into water injection kits too. When mixing gas and Diesel, then turning up the fuel control you can create very high EGT's quickly, high enough to melt manifolds and collapse exhaust systems.
  10. 9191gmc

    9191gmc Rockstar

    the CNG and LNG debate is interesting.It seems that there will be a need for both types of stations. It seems that LNG would be better for many long haul rigs.The tanks for those will be more $. Who does the conversions for LNG???

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