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Intro to Fuel Injection

Jun 17, 2021
So now it's time to take a look at

fuel

injection

. This method of getting

fuel

into our cylinders is incredibly efficient, particularly when compared to the old technology from the early 1900s, which is the carburetor. Carburetors have been around a long time. The dawn of the combustion based engine and it wasn't long before people started to realize that carburettors were pretty inefficient so what are we going to do right? We'll invent this fuel

injection

system, and sure enough, fuel injection was found to be much more efficient, yes. Why? Why are fuel injected engines so much more efficient than carbureted engines?
intro to fuel injection
Well in a few moments I'll go to the whiteboard and draw a diagram and that's not uncommon for a carbureted engine to have a big difference in terms of temperature. between each of those cylinders because you have different amounts of mixture in each so as I mentioned that will also have a big effect on the power output of each of those cylinders so I'll end up with an engine that's not very efficient to establish its power. Of course, I will also have an engine that is not very efficient to set the amount of fuel. which is burning so those are some things wrong with carbureted engines how do we solve this problem? well this is what we're going to do I'm just going to delete this here you can remember which cylinders are which but what we're going to do is actually we're going to take this carb here and delete it completely so let's just do it say alright , carburetor, ok, there we go, now off we go, let's note that we still have our throttle valve, but what's going to happen now is the induction system. it's actually going to end up being pretty much one piece let's put the throttle valve back here so now what I have is exclusively air coming through this system so let's just wipe all this fuel out here in the induction lines because there is no more fuel going through the ind The intake system is exclusively air now it's ok so that's ok that won't do our engine any good if we only have air going through the system. what's going to happen now is this timing unit up here will actually have a sending unit from the throttle valve that goes through so it'll have a little sensor up here that sensor will go over here to something known as a throttle control unit fuel so right there so the fuel control unit senses the throttle position and says ok here is the amount of air we have going into the engine then it sends a metered amount of fuel out to the distributor here above so the fuel control unit is actually sending from the gas tanks a metered amount of fuel to the fuel distributor so I'll actually draw that line to where I did again so what I'll do is something so a little bit better So here comes all that metered fuel towards the fuel distributor, so the metered fuel is sent to the fuel distributor and then from to Here, what happens now is that we'll have right at the point of the intake manifold, we're going to put a little notch in each one. of these here now the fuel goes here and through a nozzle remember it's going to be pushed into the intake part now if I were to take this spot here just this little dot here and zoom in so I'm going to pretend I'm going to do it which what we would see is something like this we have our fuel nozzle like this so here is the fuel line and this of course goes to the distributor then I have the intake manifold so it goes to the cylinder so this fuel control unit sends this metered fuel to the fuel distributor, but there is one more key part to this and that is what happens is that this pump, this fuel pump will force this metered fuel under pressure to the distributor and to these lines, so what will happen is that fuel is going to pass through the lines under pressure once it hits the nozzle, of course it's going to be pushed at high pressure into the air which is flowing in and just or out of the cylinder so pressurized fuel being pushed through a restricted area goes very very efficient at atomizing that fuel it will mix better with air and now it will be very close to the edge of the cylinder because the unit The fuel control unit has detected the amount of air entering. mentioned tell the fuel we need to send this amount of fuel to the distributor we're going to send this amount of fuel under pressure so what happens now is these ratios here can actually get much tighter so let's say you like pilot, you set your mixture to stoichiometric perfect Stoey's, okay, 15 to 1, so this cylinder here might be running at, say, fourteen point nine to one, this one here might be running at, say, fourteen point eight to one is in e here maybe it's still, you know, fifteen point one two one so now that we've got a more even mix value guess what that will do to our power it's going to hold power over all these cylinders almost the same. another benefit of this is for the fuel injection unit, what about my temps?
intro to fuel injection

More Interesting Facts About,

intro to fuel injection...

Well, what will happen there? Well, this one here remember that in fifteen to one we start at, say, 1350, so one will still be at 1350, but this is just a little thinner, so now we could be at, say, 1375, so So now I can see that my temperature change 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 to about a hundred degrees Fahrenheit or less, as in the case that I've shown you here, as we've seen here, more consistent power because of that consistent mixture and more consistent temperatures in each of the cylinders, because because now we've sent a measured amount of pressurized fuel to a known amount of air which is the purpose of the fuel injected engines you
intro to fuel injection

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