Welcome back to Smarter Every Day! Remember in an earlier video when we talked about how carburetors work and made a see-through carburetor? We saw the bowl, the float, the needle, and the Venturi on top. Today, let’s go find the carburetor on this old tractor.
We opened it up and noticed that there was no carburetor-looking-thing; just pipes going straight into the top of the engine. It turns out this is a three-cylinder engine and each of the pipes is a fuel injector.
We visited my buddy Dean’s Cross Creek Tractor, which refurbishes parts from old tractors and makes totally new parts for tractors as old as the 1940s. We set up an experiment to explore some tractor fuel injectors. Dean explained that fuel injectors are a totally different system than carburetors; they create a forced fuel injection.
We saw different types of fuel injectors, including Kubota, Massey Ferguson, John Deere, and Ford. We were excited to explore the fuel injectors in slow motion to see their spray, just like we did with the carburetor. Jacob and I go way back. He was on Smarter Every Day’s episode 20 something: Vortex Shedding. We have a tester used to test fuel injectors here. It’s a hydraulic pump with a gauge on it, and it works sort of like a floor jack. You shut off the valve, attach the injectors, then you build up the pressure until it overcomes the spring tension in the injector. We then check the pressure and the pattern. We then hooked up an old injector from an international tractor to see if it was still working. We got a little leak but it worked. We set up a bucket to catch fuel as it sprayed out of the injector and dialed in the lighting. We watched the nozzle spray pattern in slow-motion and it was super smoky in a good way. The timing was in milliseconds and the event was extremely fast. We found that the pattern was not great, and that it could cause misfiring issues due to it not being a uniform stream. The pressure popped off at 2,250 PSI, and we would have liked to have seen a more uniform mist out of the end of it. D - All right, should we try a new one? J - Yep! D - How old would you say that injector is? J - That injector right there was probably from the late 60s or early 70s. D - Are you serious? So fuel injector technology is pretty old pretty old. J - Pretty old… D - Really? J - Pretty old. D - And this is the old injector you’re taking off? J - And the adapter to fit it to the injector tester. D - What is this from? J - That’s a Kubota. D - Kubota…D - All right, ready? J - Yep. D - Yep. D - So you’re having to put some force to it? J - Well, I mean you’re building three thousand…on this particular one uh looked like it’s about 3,100 PSI so you’re literally I mean you’re using hydraulic pressure so it’s not like you’re lifting 3000 pounds but yes you got to put a pretty good amount of pressure on it too… D - All right, let’s see that one (Slow Motion Squirting Liquid Sounds) D - How’s that one look? J - This one is a much better pattern than the one we saw on the last go around. There were more individual streams coming out of the other one so it’s going to give you incomplete combustion. As you can see in this one it’s vaporizing the fuel….atomizing the fuel more so you’re gonna get that more even combustion inside the cylinder. D - So this is going to burn more efficiently…. J - Yes, like all around you’re going to get that even heating in the chamber and that’s going to be a better better fuel burn. D - So this is an ideal….maybe not IDEAL but it’s much better. J - It’s good. D - Okay…So we filmed a lot more of these fuel injectors in slow-mo and it was amazing to see the different approaches to delivery and vaporization of the fuel in an attempt to maximize power and performance. A lot of these things have four streams that shoot out radially, which is really fun to watch. I love looking at these things knowing that this can happen up to thousands of times a minute inside an engine. This is fascinating. Thank you very much Jacob. Jacob - Thank YOU! D- Appreciate it!
💥 Pew! 💥 D - I didn’t blow it up! 💥 PEW! 💥 (Both Laughing) Alright this should go without saying but do not try what I’m about to do at home….Even if you have really cool safety glasses (Chuckles) All right….turns out……you can buy these fuel injector testers on the internet for pretty cheap.In true redneck fashion I have a propane torch duct taped to a stick.with that flame tip being right at the end of a fuel injector.This is one of those that’s got the four tips on it? …Like it has four streams of fuel.So let’s catch some slow motion…uh we’ll go 6,000 frames per second.One…..Two….Three …….. Oh!…Oh,oh….oh okay. (Gathering Composure) All right let’s look at that (Pleasant Music) Wow!!! Oh man….Okay! (Laughing) Okay here’s what I learned here.When I first started squirting it , it was just liquid…just like a solid stream but it wasn’t until the correct vaporization or the the cloudiness if you will…it was until that started that it actually lit fire so that’s key to combustion you got to have the right surface area of the fuel to the air and of course you gotta have spark so uh….Okay we didn’t light one of the streams so let’s try it again let’s see if we can get all four to light.I have a mega fire extinguisher just so you know (Giggling still).All right here we go…..One Two Three…Okay……….Yeah I’ve got to go get a better torch….Okay acetylene torch…I’m melting that ready One, Two, Three… Aw! we only got three! I’m starting to understand this. I can’t see the camera there’s so much light.It’s like the Stoichiometry is changing radially out from the center of the injector….and so uh it’s…yeah! Think about it! Boundary conditions! Right at the little exit it’s 100% fuel…WAY out into Infinity it’s 100% air.Somewhere in between there’s a boundary it’s a gradient. It looks like there’s an optimum mixture point somewhere between the nozzle exit and the air, creating a radial boundary that the fuel can’t backburn into. It’s like the fuel and the air have to agree that it’s time to burn, with the fire trying to run backwards but it can’t quite get there due to the Stoichiometry. I’m using a torch to light off the fuel on these diesel fuel injectors, but that’s not how this would work inside a diesel engine. In a gasoline engine, we have a spark plug that acts like the torch and provides the flame propagating from one side to the other. A true diesel engine requires the compression and hot gases being compressed to make it all explode. There are many different types of fuel injection, such as direct fuel injection that requires high pressures and port injection that requires lower pressures.
My buddy Dean at Cross Creek Tractor sells parts that are new, used, and top to bottom. If you have an old tractor and need it running, Cross Creek Tractor is the place to go! It all started with a bottle rocket and a brush pile 20 years ago! Jacob said Dean should have gone into entertainment with his presence, before they said something Destin didn’t want us to hear.