Man Conducts Manual ‘Cylinder Deactivation’ Experiment By Strategically Removing Valvetrain. Here’s How His Saturn Drives On Just One Cylinder

Saturntop1

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.

Dfm
GM

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.

Screenshot (5)
Robot Cantina

 

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.

Sc1
Robot Cantina

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.

Screenshot (8)
Robot Cantina

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.

Screenshot (12)
Robot Cantina

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.

Slowsaturn
Robot Cantina

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?

And as we’re always looking for feedback, do you enjoy posts about videos?

(Top photo credit: Saturn and Robot Cantina)

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42 Responses

  1. Posts about videos are fine as long as the article adds something to the video (which you did here by explaining the theory behind cylinder deactivation). What I don’t like is stuff like Great Job, Internet! from the AV Club back at G/O, where you’d get 200-300 words of nonsense attached to a 10-second YouTube video or a single tweet. That was churnalism at it’s worst, and I’d hate to see it happen here.

  2. Mother Earth News had an article about turning a V8 into V4 in the early 70s. It may have actually been an I4 since that’s how monobloc air compressors work. Take a V8, replace one head with a special air compressor part and rework the intake manifold and carb on the other bank. IIRC a Ford 302 put out 100 CFM, just like an IR screw compressor with a Ford 2.3 liter 4.

    1. I remember my Dad once mentioning that he knew someone who tried disabling some of their cylinders during the ’73 gas crisis, but that’s the first independent verification I’ve seen that it was a thing that maybe more than one person attempted. Maybe that article is where the guy got the idea.

    2. Your comment reminds me of the emergency kit that came with my old BMW airhead. There is a hose/fitting that you can plug into the spark plug hole to turn one cylinder into an air compressor to air up a tire. Thankfully, I have never had the need to try it out, but it is kind of neat.

  3. I rarely watch car videos (or anything else) on youtube or whatever, so I for one am totally happy with this kind of article. Like at the old site, I always enjoyed the Garage 54 articles and never even once thought to go look at their youtube channel.

  4. The single-cylinder backout of the garage and then limping into motion was my favorite part. They should have had someone walk alongside it for a frame of reference. Absolutely sounds like a thumper motorcycle I owned.

    And I had to chuckle at the care he took to carefully wipe off/clean the swanky Saturn valve cover after reassembling everything. Our kinda guy.

  5. “If the entire GM staff can’t make it work who can.”

    Ahem!

    “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.”

    There’s a graphic and everything!

  6. Gm kind of doesn’t have it down, or at least very recently had huge issues with 5.3 and 6.2 engines shearing the lifter locking pins on DFM cylinders. The engines would then bend pushrods. AFIK it was 2021 trucks mostly but still, huge L

    1. Also, the Saturn OEM design was tuned to be fairly fuel efficient with all the stock parameters. Even if you DID happen upon an externally controlled method to get more efficiency with a leaner burn, you would also be likely to burn valves, or have some other part of the engine starved into malfunction. The choice of a single cylinder powerplant can work in a car, and even be made reasonably efficient. But if you really want to go down that road, a complete vehicle weight reduction (speed holes!), aerodynamic mods, skinnier high pressure tires, and a lighter, smaller motorcycle derived twin would probably be your best bet.

    2. Others gave good replies, but this is why GM and Dodge (or whoever) deactivate in cruising conditions.
      Getting to 60MPG, using all 4 (or 8) cylinders, once you’re at 60 it takes waaaay less power to stay there, so you can shut down 3/4 of your cylinders and that where the MPGs rack up. So yeah you got 14MPG on the freeway ramp using all the cylinders, but poodling along on 1/4 displacement you’re getting 28, 42, 56?? I mean no, it’s not linear, but that’s the idea.

  7. “…have you done something like this before? If so, why?”

    Yes, but not elegantly and not entirely by unfettered choice.

    In 2012, the first time I took my three-cylinder, two-stroke SAAB 96 to a Lemons race, the middle piston decided to come just a little bit apart towards the end of the race, destroying the spark plug and deeply scoring the cylinder wall. The team figured we had little to lose at that point so I took the car back on track and finished on the remaining two cylinders. Performance, already poor, was noticeably poorer.

    I had driven the car to the track and hadn’t yet set things up for flat towing, nor did I have a trailer, so again figuring there was little to lose, I decided to see how far towards home I could get before needing a tow truck. After all, closer is cheaper. As luck would have it, much of the driving was in stop-and-go freeway traffic so I wasn’t actually impeding anyone even as the car grew slower and slower as well as noisier and noisier. It made it about 100 miles home and was within five blocks of my house when it stalled at a red light. Surprisingly it roll-started after I walked it with the starter over the crest of the slight incline at the intersection and then made it all the way into my driveway before stalling again. I never tried restarting the engine after that.

    Ten years and two engines later, with a bit more luck I’ll drive it back to the same track this weekend for another Lemons race, although admittedly this time around I’ll be working as staff.

    1. Interesting post, thanks for sharing. Not to derail, but incidentally, I’m looking at buying a ’65 SAAB 96 Monte Carlo. Would you be willing to give me your insight on general worthiness, durability, etc of the drivetrain and vehicle? Mine would likely be weekend and car show duty, but still, a person likes to know.

      1. I have no experience with any of the GT/Sport/Granturismo/Monte Carlo variants of the 96 but my secondhand understanding is that (1) some of the variant-specific parts are, not surprisingly, harder to find than regular 96 parts and (2) fakes of varying degrees of completeness are out there, so don’t assume it’s really a Monte Carlo just because it has the badges and other goodies. Sometimes this was done “back in the day” just to dress up a car, not to defraud a later purchaser, but with the passage of time this can be forgotten or overlooked.

        Having said that, the 96 in general is a solid car and parts availability is… fair to okay-ish for nearly everything. Some brake parts are very hard to find, so make sure all that is in order. When (not if) rebuilding the engine, Tom Donney Motors can supply new pistons and bearings that are significantly better than the original designs and are well worth it. I understand there are companies and/or individuals in Sweden who also offer improved versions of these items but I haven’t yet had to look into that.

        Treat the transmission with great care, as it is slightly more fragile than it should be. The freewheel mechanism in particular should never be abused by suddenly revving the engine into engagement, as this will break things. Ease into the throttle until fully engaged. Really, a light touch when changing and engaging gears is a good idea all around. Transmissions can be rebuilt but it is more of a struggle these days and/or a longer wait for one of the dwindling number of specialists to do it for you.

        Do, however, use the freewheel except on very rare occasions such as descending long inclines when there’s a concern about overheating the brakes. Otherwise, driving around with the freewheel regularly locked out is bad for the engine, as this results in engine braking without sufficient lubrication. Of course, driving around without engine braking is yet another reason to make sure the brakes themselves are good…

        Beyond that it’s hard to know what to say without knowing something about the specific car you’re considering. I like my 96 and most other owners like theirs as well, but at this point it’s very much a self-selecting crowd.

          1. You’re quite welcome. Mostly I find parts through a combination of eBay, Craigslist, the occasional auto parts website in Europe (case-by-case depending on who has the part in question, so I have no specific advice on which sites), and a couple of guys in the local club who have been hoarding cars and parts for even longer than I have. You know, the usual for old and/or obscure vehicles.

        1. I had a chance to visit Tom Donney motors and his Saab museum, then in Iowa, I think it is now in South Dakota. One of the best car days of my life, Tom was a great host, saw a Sonett I, something I never thought I would see in the flesh. Got to drive a Saab two stroke sedan, saw the land speed record car and some very nice cars, old and newer.

  8. “I’m also curious, have you done something like this before? If so, why?”

    Yes, but not by choice. The Renault was already running on 3 of 4 cylinders and only in second gear when I got it. How the rings got baked onto the piston to cause no compression is still a mystery to me. All issues were resolved with a trip to the junkyard for some parts, but even though the car ran correctly, that made it no better.

  9. Yes, I absolutely enjoy an article like this, so long I don’t need to actually watch any video. This is perfect, with the author taking the time to write out and explain everything (with pictures!).

  10. I don’t mind posts about videos, but chances are I’m not going to watch the video the post is about so I appreciate all the description in this article. For me reading a website and watching a video are two very different experiences, and I generally don’t feel like spontaneously switching from one to the other.

    If I’m chilling on the couch with my sweetheart and a beer for instance, I’m not going to suddenly subject her to the dulcet tones of a four-cylinder engine running on only one cylinder. Likewise if I’m hanging out in bed, or casually browsing while I eat my breakfast. Most of my internet consumption is like that, so unless I’ve intentionally set out to watch some videos, I’m probably not going to.

    That said, the article was fine and I enjoyed it. The fact that it was based around a video didn’t bother me. I don’t spend a lot of time watching car videos on YouTube unless I need to know how to change the timing belt on a Subaru Outback or something, so I would not have known about this had you not written it up.

  11. I know for a fact that at least GM and Honda have had major problems stemming from the cylinder deactivation systems. Many people have been advised by technicians to defeat these systems to eliminate the issues. I have a Honda Odyssey with cylinder deactivation. On forums, the problems, leading to engine failures have been well documented. Also, the active motor mounts wear out from compensating for the engine running on less cylinders. And replacing them is expensive, like a grand.
    Several engineers have come up with an electronic item that prevents the system from activating. You may lose 1 or 1 1/2 mpg. Big deal. It prevents the damage to engines and wear to the pricy motor mounts.
    These systems all seem to cause loss of reliability and engine damage. Not on my van. Oh, and the start/shop system causes wear on starter and battery. I turn it off at every start up. Losing maybe .5 mpg if that.

    1. I tried using a VCMTunerII in my ’16 Accord V6. The engine was slightly more responsive, but after a few months, I would have really long crank times if the engine was between 150 and 210 degrees. In the end, I removed it. I figured I would wear out starters more often than engine mounts.

  12. In the 70s Car and Driver did an article on DIY fuel economy modifications. I think it was a Chevy Monza, but not absolutely sure. As I recall they tried weight reduction, tire pressure, and adding aero aids, then testing. Believe they made a big ass spoiler and front air dam out of sheet metal and it actually improved highway MPG by a mile or so.

  13. Should have kept the exhaust valves open somehow, it sounds better than leaving a spark plug out.
    Then the pumping losses would be greatly reduced and it might have seen more power and better economy.

  14. Man there is nothing like age to make you look smart. Cadillac about 4 or 5 decades ago came up with the Cadillac V8-6-4, it supposedly would give the 8 cylinders on acceleration and 6 and 4 to provide better mpg. Took forever to be available, only available for 2 years, think pay back, and then disapeared. If the entire GM staff can’t make it work who can. Mercedes if you want more information on a car produced 3 decades before you were born feel free to contact me.

    1. I’ve been a loyal Chevy/GM customer most of my life, 5 new pickups in the past and a 2015 Yukon Denali that I just sold. I had been advised to defeat the AFM system be a trusted shop, I studied the failures on various forums and YouTube and realized how deficient this previous highly regarded engine was prone to failure. The poor GM warranty relieved most corporate liability and placed the expensive repair obligation on its customers, of which I was one. This was the situation that caused me to regard GM as an unacceptable source for myself and family, who regard me as an authority, for future vehicles.

    2. The V8-6-4 exceeded the capabilities of what the processors of the time could handle. It worked fine in testing, under GM’s laboratory conditions, where the cars were carefully primped and fussed over by a team of engineers, but turned out vastly different in actual use with regular consumers. Cars would get stuck in 4 or 6 cylinder mode instead of jumping up when required under heavy load, or the engine would just stall and shut down completely while the car was in motion. At least the “fix” was as simple as unplugging the whole mess and just running the car as a reliable old 368 V8 all the time.

      1. Apparently when GM debuted Cadillac’s V8-6-4 in 1981, technology was lagging behind. It was quietly discontinued after a year. Perhaps GMs engineers in later years looked back at this configuration and determined it to be unmanageable to revamp it with better technology to bring it up to date.

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