It’s less of a careful spurt and more like a hose.
It’s rare that we get to see the inner workings of a high-revving engine as it reaches full tick. Most internal combustion motors in regular production cars don’t dare rev past 8,000 RPM, with many running out of steam at around 7,000. Ever wonder how much fuel is necessary to keep an engine running strong up to a truly monstrous 10,000 rpm? It’s a lot.
YouTube channel AutoTechnic posts all kinds of short informative automotive clips, but this one about testing fuel injectors is way cool. The simple rig in the video is built by fuel injection experts ASNU. Once eight injectors are installed, it allows for various RPMs to be tested independent of whether the injectors are actually installed in an engine. The result is that we’re able to visualize the fuel spray without any pesky internal combustion, something that is rarely witnessed so clearly.
The test starts at a measly 200 rpm, which is well below the speed most gasoline engines idle. It then moves up to 2,500 rpm, which is where most will start to make a little torque. After this, it goes up to 5,000, which is pretty impressive to watch. Then, it quickly doubles to 10,000 rpm. At this rate, the injectors are not so much popping off as pistons go up and down; they’re positively spraying fuel at an incredible rate. Might as well just leave them wide open at that point.
The last part of the clip shows an experiment to measure how much fuel is actually being sprayed, which even at modest rpm seems like a lot. We don’t get a measurement at 10,000 RPM, but we know what extremely high fuel flows look like. Just sample the single cylinder out of a top fuel dragster, and you can begin to understand just how much liquid hydrocarbon it takes to make thousands of horsepower.
The flows involved in the more conventional test aren’t so extreme, but powerful gasoline engines, as most of you will know, can be incredibly thirsty. Forget a car’s city fuel economy. When you’re wide open throttle on an engine with big displacement or one that’s running forced induction, you would doubtlessly be surprised just how much gasoline is being turned into horsepower, heat, and noise.
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