Gas prices are on the rise once again, which means that many Americans are going to feel some pain at the pump. Some folks might feel inclined to find ways to boost fuel economy and thus lessen the pain at the pump. A YouTuber has performed a silly experiment, manually deactivating cylinders in a Saturn to see what happens. Low budget cylinder deactivation may not save you gas money, but weirdly, it doesn’t seem to make things worse, either. Let’s watch this together.
Today we’re trying something a little different here at the Autopian. We (probably like you) watch a lot of car and other vehicle-related videos. Some of these video creators have some fantastic and pretty original ideas and we think some of them deserve a spotlight every now and then. Personally, I’ve watched countless hours of Vice Grip Garage, Mustard, and Bus Grease Monkey. My wife and I have this dream of being like VGG’s Derek and rescuing some old abandoned junker. Maybe a diesel something! So, every now and then, one of us will highlight something awesome happening in video.
Back at the ol’ lighting site, I used to write about a YouTuber called Robot Cantina. The host behind the channel works with some downright silly ideas, like pairing a Honda Insight with a Harbor Freight Predator engine and trying to have a working car out of it. On a recent night, I decided check in on what’s going on. The wacky host has gone further with the Harbor Freight Insight project, adding a supercharger and trying to hit 70 mph. And then he decided to power a Saturn with a lawnmower carburetor.
Recently, the mad scientist of a host decided to see if manually deactivating cylinders in a Saturn SC1 helps gas mileage:
For years, automakers have been offering cylinder deactivation. In concept, cylinder deactivation is a system that allows an engine to provide full power when it’s needed, and better fuel economy when it’s not. This happens through disabling cylinders, effectively making the engine have a smaller displacement. The Clemson University Vehicular Electronics Laboratory explains why this matters:
Cylinder deactivation systems selectively disable some of the cylinders in an internal combustion engine to improve fuel economy and reduce CO2 emissions when the full power of the engine is not required. When power requirements from the engine are low, the engine does not run at its peak performance level. The throttle air intake is minimal and the intake of air to the cylinders is more difficult. Not only is more force required to overcome the internal vacuum, but the cylinders do not completely fill with air. With less air in the cylinder, the combustion pressure is reduced. This situation is commonly referred to as pumping loss and can significantly reduce the efficiency of the engine.
Cylinder deactivation effectively decreases the displacement of the engine by closing the intake and exhaust valves and cutting fuel injection for a particular cylinder. The pistons in the deactivated cylinders compress the trapped gases and are pushed back down, thus expending zero net work. The remaining cylinders compensate for the loss in power due to the inactive cylinders by operating at a higher combustion pressure. As a result, for a given load on the engine, the throttle valve is more open allowing the cylinder mean effective pressure to be closer to the optimal level and increasing the efficiency of the engine.
General Motors, Honda, Honda, Mercedes-Benz, Toyota, Volkswagen and more brands going back a whole century have used some form of cylinder deactivation. For an example of how this works, let’s look at GM’s Dynamic Fuel Management. In this system, a controller monitors accelerator pedal input to determine the exact number of cylinders that the engine needs to run well. It does a calculation 80 times a second for this.
An electromechanical system controls the engine’s hydraulic valve lifters. The system’s solenoids use oil pressure to help activate and deactivate the lifters’ latching mechanisms. The lifters of a deactivated cylinder are then made unable to open valves. GM’s cylinder deactivation gives its engines 17 cylinder patterns to operate on.
But what if you’re a backyard wrencher working with a car that doesn’t have such a feature? Well, as Robot Cantina will show you, just remove the rocker arms and the hydraulic lifters of the cylinders that you no longer want to run. At first, Robot Cantina decided to deactivate cylinders 2 and 3 of their Saturn’s four.
Our host also 3D printed out plugs to fill the holes where the lifters came out of. The YouTuber also had to remove the fuel injectors for the selected cylinders.
Amazingly, upon startup, the Saturn SC1 and its 1.9-liter L24 engine appears to run smoothly. But that makes some sense, as cylinders two and three were chosen to maintain some balance. Around town, our host found that the performance felt off, but it still had enough grunt to get around town. The exhaust note also got louder and more raspy. You can notice the car’s panic as its check engine light flashes, which makes me giggle.
For a test, the Robot Cantina host did a zero to 60 mph test. It took the effectively 950cc two-cylinder Saturn 34.54 seconds to reach 60 mph. They then continued driving, putting 164 miles on the car with it running on two cylinders.
Next, the host reactivated cylinder two, making the car roughly a 1,425cc three cylinder. As a triple, the car sounded terrible and there were more vibrations. The engine also bogged down in certain gears.
However, it did reach 60 mph in a faster 22.96 seconds. Our host drove 140 miles with the triple set up, but the ride was apparently pretty annoying.
Finally, just for fun, Robot Cantina deleted all but cylinder one, effectively making the car a 475cc thumper. It just barely starts and hilariously, it sounds like a go kart. Running on just the one resulted in a slow, unresponsive mess.
In the acceleration test, the car couldn’t even hit 60 mph. The engine bogged down at full throttle, making somewhere around 80 percent throttle the new maximum. And after three minutes, it still couldn’t get above 51 mph.
Now for the data. Running normally without any tricks, the 1.9-liter engine should make 100 horsepower. And in the baseline test, the car reached 60 mph in 13.96 seconds. Slicing off one cylinder added on nine seconds, while the two cylinder took about 20 seconds longer than the four to reach 60 mph. And of course, the single cylinder couldn’t even hit 60 mph. All of that isn’t surprising to me.
What did surprise me a little was the fuel economy. Running on all four, the Saturn did 42 mpg. Running on three, that went down to 40 mpg. And running on two, that went back up to 41 mpg. The single ran so bad, the host wasn’t able to get gas mileage data. I’m honestly not sure what I expected, but it wasn’t that deleting rocker arms and lifters resulting in pretty much the same fuel economy.
In the end, Robot Cantina’s experiment was a bit absurd, but it looks like it was tons of fun. And the host was able to answer the question of how a Saturn SC1 drives after you mess around with its engine. I could see myself doing something like this just for the giggles. I’m also curious, have you done something like this before? If so, why?
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(Top photo credit: Saturn and Robot Cantina)