Intro to Fuel Injection

[Music] so now it's time to take a look at fuel injection this method of getting fuel to our cylinders is incredibly efficient particularly so when we compare it to the well ancient technology of the early 1900's which is the carburetor carburetors have been around for well ever since the dawn of the combustion based engine and wasn't long before people start to realize that carburetors were fairly inefficient so what are we gonna do well we'll invent this fuel injection system and sure enough it was discovered that fuel injection is much more efficient yeah why is that so why are fuel-injected engines way more efficient than carbureted engines well in a few moments I'll go over to the whiteboard and draw a diagram and that's not uncommon with a carbureted engine to have a huge difference in terms of temperature between each of those cylinders that's because it's got different amounts of mixture in each one so as I mentioned that is also going to greatly have an effect upon the power output of each of those cylinders so what I'm going to end up with is an engine that isn't very efficient at setting its power I'm also going to have of course an engine that isn't very efficient at setting the amount of fuel that it's burning so those are some bad things with carbureted engines how do we solve this problem well here's what we'll do I'm just gonna erase this here you can just remember which cylinders are which but what we're going to do is we're actually going to take this carburetor here and we're gonna eliminate it entirely so let's do that let's just say good i carburetor alright there we go gone now notice we still have our throttle valve but what's gonna happen now is the induction system is actually going to end up being pretty much one-piece let's put that throttle valve back in here so now what I've got is exclusively air coming in through this system now so let's erase all of this fuel here in the induction lines because there's no longer any fuel going through the induction system it's exclusively air now alright so you're like well that's not gonna do any good to our engine if we've only got air going through the system now well here's what we do will actually take a distribution unit and put it up here what's going to happen now is this distribution unit up here will actually have a sending unit from the throttle valve that goes through so it will have a little sensor here that sensor will go over here to something known as a fuel control unit so right there so the fuel control unit senses the position of the throttle and it says okay here's how much air we have heading towards the engine it then sends a metered amount of fuel towards the distributor up here alright so the fuel control unit is actually sending from the gas tanks a metered fuel amount to the fuel distributor so I'll actually draw that line all the way I did it again so what I'll do is I'll just kind of like this keep it as tight as I can into here there that's a little bit better so here comes all of that metered fuel towards the fuel distributor so the metered fuel is sent to the fuel distributor and then from here what now happens is we will have right at the intake manifold point we are going to put a little notch in each one of these here now fuel goes here and through a nozzle remember it's going to be pushed into the intake portion now if I was to take this spot here just this little spot here and zoom in so I'm gonna pretend that I'm gonna do that what we would see is something like this we've got our fuel nozzle like that so here's the fuel line and this of course goes to the distributor then I've got the intake manifold like this going to the cylinder so this fuel control unit sends this metered fuel towards the fuel distributor but there's one more key piece to this and that is so what happens is this pump this fuel pump is going to force this metered fuel under pressure towards the distributor and towards these lines so what will happen is that fuel is going to come through the lines under pressure once it hits the nozzle of course it's going to be pushed out under high pressure into the air that is flowing right towards and just outside of the cylinder so pressurized fuel getting pushed through a constricted area is going to very very efficient at atomizing that fuel it's going to mix better with the air and it's going to be very close to the edge of the cylinder itself now because the fuel control unit has sensed how much air is coming in it can actually again as I mentioned tell the fuel we need to send this much fuel to the distributor we're gonna send this much fuel under pressure so what now happens is these ratios here actually can become much much tighter so let's say that you as a pilot set your mixture to the perfect Stokey okay stoichiometric value 15 to 1 so this cylinder over here might be actually running at let's say fourteen point nine to one this one here might be running at say fourteen point eight to one this one over here maybe it's still you know fifteen point one two one so now that we've got a more uniform mixture value guess what that's going to do to our power it's going to keep the power across all of these cylinders very much the same the other benefit to this is for the fuel-injected unit how about my temperatures well what's going to happen there well this one over here remember at fifteen to one we start out at say 1350 so that one will still stay at 1350 but this one is only a little bit leaner so we might now be at say 1375 so what I can now see is my change in temperature between each of the cylinders has been reduced significantly it's not uncommon for fuel-injected engines to be able to keep the temperature variation between cylinders at about a hundred degrees Fahrenheit or less as in the case that I've shown you here so as we've seen here more consistent power because of that consistent mixture and more consistent temperatures throughout each of the cylinders why because now we've sent a metered amount of pressurized fuel into a known air quantity that is the purpose of fuel-injected engines you [Music]

Channel: Harvs Air Service

Views: 55,392

Keywords: Fuel, Injection, Aircaft, Engines, Systems, PPL, CPL

Id: CFnxPhUMHOI

Length: 10min 0sec (600 seconds)

Published: Mon Dec 24 2018