How GM's Variable Compression Engine Works - Patent Review


GM’s Patented Variable Compression Engine - How It Works
Sponsored by Skillshare -
The First 500 To Sign Up Using The Link Get 2 Months Free!
Internal combustion engines have a flaw. When the piston reaches the bottom of the power stroke in a traditional four-stroke engine, there is still a high pressure contained within the cylinder. This pressure is released when the exhaust valve opens, ultimately wasting energy. One potential solution is an Atkinson cycle engine, which increases the expansion ratio, relative to the compression ratio, resulting in greater efficiency.
The problem with the Atkinson cycle is that because it reduces the intake stroke length, less air and fuel are drawn into the cylinder, and overall less power is created. In this video, we’ll explore GM’s solution to this problem, which is to create a variable compression ratio Atkinson cycle engine. Check out the video to learn all about GM’s patent!
Patent Source:
Don't forget to check out my other pages below!
EE Shirts! -
Facebook: engineeringexplained
Official Website:
Twitter: jasonfenske13
Instagram: engineeringexplained
Car Throttle:
EE Extra:


  • Engineering Explained
    Engineering ExplainedÅr siden

    Hope everyone's having an excellent day! What do you all think about this style engine versus Nissan's VC Turbo? Thanks for watching and thank to Skillshare for sponsoring! First 500 to sign up get 2 free months!

  • 787brx8


    År siden

    @Marc Asposito I have helped out Japan A little more than the American automakers for quite A while now. I did the initial design work for many vehicles since the seventies. (child prodigy) Over time people have begun to think Japanese designs are superior but the reality is, they are American designs made in Japan. A few of my similarly named works... VTEC, Vortec, Voltec, Duratec, Ecotec and Ecoboost Of course there were many more designs that I have created. Some were for the military. On my page I have various videos with A few examples of different projects people can check out if they want to. One is for an anti-knock device that should make compression ignition gasoline engines fairly easy to do. On A regular engine it allows me to advance the ignition timing to the maximum factory setting. Which is something you cannot do, even with race fuel! Pause on the distributor part, if you wish?

  • Joel Leehy

    Joel Leehy

    År siden

    Nissan VC-Turbo is a whole world better

  • Marc Asposito

    Marc Asposito

    År siden

    Working as an Engineer I have developed over 100 1st Gen small block Chevrolet engines, and in technical inside sales at a U.S. engine remanufacturer taking calls from all over the country hearing from automotive enthusiasts, mechanics and the general car consumer gave me real insite of what engines are failing on large numbers call after call after call some people even crying in disbelief at the financial crisis a failed engine put them in. Mechanics telling me they see three of these a day, every day. Several engines with less than 100k miles. So what do I think....deveopment of anything and the long term reliability, that we who own and work on 1990-2010 pre-direct injected Japanese developed automobile engines, depends on several factors and most importantly the background of the Engineers the engine builders hire. GM can build some of the best pushrod engines, but they need the best seasoned Engineers from Japan if they are going to make long term reliable engines the likes of Honda, Nissan and Toyota, who are also not without their own errors in the last 20 years. Personally as an automotive enthusiast and not a car consumer, I would wait years to verify reliable technology. The shift I am seeing is not long term reliability, but rather a disposable mentality just past the warranty period. My advice stay away until it's proven, and stick with what is proven reliable. It's your money not the ignorant person who tells you what you should buy.

  • Oblithian


    År siden

    Nissan's is better.

  • eli oliver

    eli oliver

    År siden

    I've heard the skyactive x feels pretty powerful for the amount of fuel it uses

  • Guillermo Grecco
    Guillermo Grecco2 dager siden

    Nissan VC turbo ?

  • Curtis Grisdale
    Curtis Grisdale4 måneder siden

    You continue to blow my mind all the time!

  • aterack833
    aterack8334 måneder siden

    So the blue linkage is free moving at both ends and the red “linkage” crankshaft is of course only free moving on one right? But then GM went and made the position of the STILL free moving linkage change? Which is like taking a normal variable compression engine and adding an extra degree of free movement? Also what about having the blue part be a second crank type shaft with a gear ratio to the red one, or just different “lift” than it, would either of those options work and do anything or would the ratio thing just make it change once per cycle?

  • The Barking Mouse
    The Barking Mouse6 måneder siden

    I see a lot of points of failure... I can see this in a low power, relatively unstressed, all about economy engine. But in a high power application? Bits & pieces everywhere.

  • jwdickieson
    jwdickieson10 måneder siden

    So is this a 4 cycle engine or 2 cycle or something else

  • Juho Mäki-Petäjä
    Juho Mäki-Petäjä10 måneder siden

    Saab developed this in beginning of millenium. That time Saab was owned by GM and was testbed for new ideas.

  • Chris Corea
    Chris Corea11 måneder siden

    Hey Jason, have you done any videos on the koenigsegg free valve system Wouldn’t you be able to get rid of all this complicated mechanical issues by simply running the free valve systems. ? Or am I missing some advantage here?

  • Juan Martínez
    Juan Martínez11 måneder siden

    Imagine thinking you blew it up so you do a compression test lol

  • kevinvvn
    kevinvvn11 måneder siden

    Let's assume the crankshaft is rotating at steady RPM. The piston movement is almost 2 times during exhaust stroke than any other stroke in this design thus it may have some issues related to excessive wear due to piston being thrown around at various intensities.

  • Adamant Adam
    Adamant AdamÅr siden

    It would be really helpful to see a physical example of the Traditional Atkinson Cycle. Also maybe you should clarify that you a talking about an Otto cycle so people don't think you're saying auto (like automotive) cycle.

  • John Coppola
    John CoppolaÅr siden

    similar to the nissan design in a way.

  • 8000RPM
    8000RPMÅr siden

    Well done time, but sometimes, animation is needed, this is one of those times.

  • Joel Leehy
    Joel LeehyÅr siden

    Nissan VC-Turbo is way better

  • Ron Groove
    Ron GrooveÅr siden

    Insane emission limits leading to insane mechanical engineering. The end of the story is always the same: the ordinary person will spend A LOT on maintenance or even loosing all the value by junking the car after a couple of years. There was a time that a car was somthing popular and accessible by everyone. From now on, it seams to be the reverse.

  • Nick Amarit
    Nick AmaritÅr siden

    In operation, would there be an audible difference (with the difference in C.R.) like in old school VTEC's application?

  • fluffy1973
    fluffy1973År siden

    GM and Nissan, names not really associated with reliability making a funky system with more moving parts and more complexity... what a time to be alive...

  • matrix777able
    matrix777ableÅr siden

    Not sure with whom I’m more impressed with , the GM engineers or you for explaining this so we can understand 👍 lol

  • Micheal Stillabower
    Micheal StillabowerÅr siden

    10:40 area....wouldn't adding forced induction increase the compression in that cylinder though? i dont understand why high compression would cause knock either.

  • Andi K.
    Andi K.År siden

    The kinematics of this system looks awfull complicated compared to a normal piston rod and crankshaft.

  • rimsath poprio
    rimsath poprioÅr siden

  • wacio
    wacioÅr siden

    Waiting to see video of one of these grande on dyno...

  • fadetoblack2104
    fadetoblack2104År siden

    Yay, more moving parts! For reliability of course...

  • OZ D1983
    OZ D1983År siden

    I couldn’t even draw that, much less explain it.

  • Alofzico
    AlofzicoÅr siden

    America such an awesome country and highest tech of everything. But, why can't American cars have better tech than other makers?

  • Core
    CoreÅr siden

    Wankel engineer: there are too many parts in 4 stroke... GM: Hold my beer

  • Mustafa Aşkal
    Mustafa AşkalÅr siden

    Comparision with Nissan infiniti VGT

  • eyelid____
    eyelid____År siden

    Nice, but you don't need this. For normal passenger car you use as high compression ratio as possible, and for sporty car you lower it to get more boost, sporty car doesn't need to be eco-friendly and they're low volume products anyway.

  • Eric Valverde Rosado
    Eric Valverde RosadoÅr siden

    Variable compression Can work in v engines?

  • Keyur Bhesania
    Keyur BhesaniaÅr siden

    2:34 feeling when you say " Engineers are very clever"🤣

  • vetteboy1024
    vetteboy1024År siden

    Great simplified description. I think I learned something. Keep up the great videos.

  • alex leonard
    alex leonardÅr siden

    Vtec for camshafts

  • ed s.
    ed s.År siden

    This is the first time I watched one of your videos from beginning to end. I usually don't because i don't like watching you just write stuff on a white board. I actually enjoyed this video and I'm going to watch a few more now 🙂

  • HowManyTabsYouGotALot
    HowManyTabsYouGotALotÅr siden

    recall central

  • William Parker
    William ParkerÅr siden

    since the intake valve is going to stay open as the Pistons coming up I'm assuming that they're going to implement some type of supercharger to turbo turbocharger similar to of a Mazda Miller cycle engine that way that the air will be forced in as the Pistons coming up.

  • Bobby Wong
    Bobby WongÅr siden

    If you got longest stroke journey for each all 4 strokes, why don't GM retard the valve timing?

  • Inside Garage
    Inside GarageÅr siden

    This is great!

  • pixel fairy
    pixel fairyÅr siden

    how well would this work for a range extender? what kind of engine would be best for a serial phev? or whatver you call a volt style optionally serial phev?

  • DK Danis
    DK DanisÅr siden

    If this was a toyota people will clap "fantastic job toyota" but when gm makes that "it will bReAK ". WHAT ABOUT VTEC DO THEY BREAK NOOOOO. SO ADDING LITTLE ELECTRIC MOTOR TO MOVE CRANKSHAFT IS NOT A PROBLEM.

  • 992 TURBO S
    992 TURBO SÅr siden

    For the right application it has a place. GM’s Northstar seems to come to mind on GM’s specialty Engine Evolutions.

  • 303 Nitzubishi
    303 NitzubishiÅr siden

    Cool concept but I can't get my head around the fact that the drag from all the extra moving parts would offset some of the efficiency gains? Those complaining about reliability should really read up on cam in block and flathead engines. There were naysayers every time a major innovation like this came about. Reality is we now have overhead cam, direct fuel injection, hydraulic automatic transmissions, etc that last hundreds of thousands of miles without need for major overhaul

  • sasja de vries.
    sasja de vries.År siden

    Haven't you wondered why crankshafts have a certain size? Haven't you wondered why they don't make the bearing surfaces of crankshafts thinner? Have you looked at the reliability of engines where they did do that? Do you think this many links is gonna last? And now take into consideration that the conrod is not making a smooth motion but its getting thrown left and right. Every link in this mechanism has it's own inertia, and every link gets pushed back and forth by the other links, the slop adds up, the banging of the conrods changing direction adds up.

  • ericgent8702
    ericgent8702År siden

    Like the concept Don’t like GM

  • David Mann
    David MannÅr siden

    Thanks, great video, but I'm confused. It makes sense that you want ER > CR to increase efficiency. But then you say the exact opposite for the GM patent. Did you get your efficiency and power positions switched? It's difficult to visualize the difference throughout the cycle.

  • eivis13
    eivis13År siden

    So baisically gm is pulling a nissan and a toyota out of their hat. More parts = less releable || harder to repair || more expensive to repair || harder to spot bad parts.

  • malamri424
    malamri424År siden

    Holy mother of bearings

  • nikhil prajapati
    nikhil prajapatiÅr siden

    hello sir i'm big fan of your channel which helps to me lot of things to learn about to automotive .so thank you for sharing knowledge hmm , sir can you make a video on engine downsizing and what does it actually and why now a days an automobile companies prefer it first.....i humble request to you sir than you ......

  • to G
    to GÅr siden

    I dont like or trust Gm products.they are known for small vehicles that are over priced and far from fuel efficient.even if this engine of theirs would save me 90% fuel,i would not buy it.

  • BobbyG
    BobbyGÅr siden

    Over complicated and relatively unreliable way of getting around the use of solenoid valves which could give any ratio between compression and power strokes and would not introduce any more moving parts (Actually eliminates a lot of moving parts) and would make a much more reliable and more easily maintained machine. Exactly the same as every other piece of garbage that GM has produced since its inception. Obama should have just let these clowns go bankrupt.

  • Reasonable Speculation
    Reasonable SpeculationÅr siden

    More efficient at converting fuel to power, but less efficient at what you really need,,, moving the vehicle the maximum number of miles over the life of the engine. More repairs= inefficiency .. More maintenance=inefficiency.. Short engine life span= inefficiency

  • DavidRC
    DavidRCÅr siden

    And since GM is doing this engine it probably won’t last very long. If Toyota on the other hand was Perfecting this technology it would be bulletproof

  • Quail Chips
    Quail ChipsÅr siden

    I want a plug-in hybrid twin-charged dual-injected variable compression Skyactiv-X CVT manual side-wheel drive Toyota Civic

  • GoTech
    GoTechÅr siden

    Worrying about valves opening and closing with independent control wasn't bad, where exactly is our crankshaft's position...hmmm. I can't wait to throw a pressure transducer into something like this! So much to be learned. Amazing explanation man. Bring on the new tech! ~Mike

  • Chris Falcon
    Chris FalconÅr siden

    GM still rearranging the deck chairs on the titanic, I see.

  • Victor D
    Victor DÅr siden

    I have GM car before never again I will trust their quality.

  • isocuda
    isocudaÅr siden

    For years I've been wondering why independent valve control like "FreeValve" and the Variable ratio systems (GM/Inifiniti) are not developed in parallel? They arguably go hand in hand while also being the likely final evolution of ICEs :(

  • boomer9900
    boomer9900År siden

    I can't even afford a new car already. Now this extra complexity, never going to work money wise and reliability wise. Interesting idea though.

  • Yaofu Zhou
    Yaofu ZhouÅr siden

    Your diagrams are so very clear!

  • Chris Moorhead
    Chris MoorheadÅr siden

    Isn’t that the same as Ford’s flat crank V8?

  • Justin Cui
    Justin CuiÅr siden

    I wonder what Nissan has to say about how GM gave this system an unoriginal name

  • J Yearr

    J Yearr

    År siden

    That's what I'm saying. Nissan had VC Turbo Altima prototypes 2 years ago

  • Bernie Nebenfuhr
    Bernie NebenfuhrÅr siden

    Sounds impressive enough EE but I wonder how you rate this when compared with Mazda's new HCCI/SPCCI engine in the Skyactive X cars?

    CROWWÅr siden

    And here i thought the mazda design was madness.

  • Niklas Wulf
    Niklas WulfÅr siden

    If there is no circular motion of the main crankshaft anymore, there must be unbelievably huge stress on the connecting rods every time the piston changes direction, because you always kill the momentum multiple times a second. That could work as a prototype, but is definitely not suited for 300k km +. No matter which brand builds it... change my mind.

  • Abdoo ECHIKH
    Abdoo ECHIKHÅr siden

    thank you MAN

  • Adrian
    AdrianÅr siden

    Why doesn't American car makers seem to focus on reliability anymore, bad business as can't sell more trash quick enough?


    only time will tell if this new engine will be reliable and last years. for those who forget to do oil changes regularly will destroy their engines 🤔

  • Alejandro Guzman
    Alejandro GuzmanÅr siden

    You sure are a great teacher! And take it from an Engineer that just learnt something today because of you.

  • bu kwok
    bu kwokÅr siden

    8:28 dont know why im automatically moving my body and dancing .

  • John Wade
    John WadeÅr siden

    Oh, it's an exlink engine like Nissan. It achieves the same goal with different details.

  • Flávio N
    Flávio NÅr siden

    That is already a FAIL.

  • Wyndham Coffman
    Wyndham CoffmanÅr siden

    four new parts, three new pins; seven new points of failure, and seven reasons to switch to electric.

  • taanneth
    taannethÅr siden

    I dont really understand the geometry behind it, but it looks like with this design a parallel "v" engine could be possible. What I'm looking at specifically is how the crankshaft is offset (vertically) from the cylinder. So it might be possible to mirror it over the crankshaft to make 2 banks. Then it would be possible to make it have a single head like VWs VR engines (but not as funky with angled pistons on the head)

  • tropicana Sister
    tropicana SisterÅr siden

    hi jayson. may i ask the pros and cons of deleting an egr system in diesel engine, theres plenty of vids out there but your explanations is the only one i trust. thank you

  • Tom Raptile

    Tom Raptile

    År siden

    Con: you hurt the environment and your health by releasing more nox

  • Necrodox
    NecrodoxÅr siden


  • Zoio Silva
    Zoio SilvaÅr siden

    IDK, seems kinda fragile. This "simplified version" seems to put a lot of stress in that electric moving part. What you guys think?

  • karioken
    kariokenÅr siden

    Funny how companies try to get the last drop out of a combustion engine. The money is better used for electric car development.

  • Andrew Mayes
    Andrew MayesÅr siden

    Another reason to just go electric. Interesting all the same.

  • Maas Morin
    Maas MorinÅr siden

    Next video: Top 25 reasons why GM's variable compression engine failed miserably (part 1 of 4)

  • Maas Morin
    Maas MorinÅr siden

    Most other car companies: hey let's use known techniques that are reliable to increase power and efficiency GM: let's develop something so overly complicated its doomed to fail and still not use multiple values or belt driven cams

  • Shahnewaz
    ShahnewazÅr siden

    Pretty clever but is this tested on any engine yet? Will the pistons and linkages handle 5000+ RPM in just a back-and-forth motion without causing too much wear? How will they balance this engine?

  • No Show
    No ShowÅr siden

    In 12 months, the video on how it didn’t work

  • Ozzstar's Cars
    Ozzstar's CarsÅr siden

    Interesting engineering. I wonder how well the components would last long term?

    be4t.nlÅr siden

    I still think the Saab solution is beter, because less moving parts

  • fan wei
    fan weiÅr siden

    Hallo Professor, can you make a viedo about the EVAP System?

  • Michael Lefebvre
    Michael LefebvreÅr siden

    This motor is way too complicated a good turbo engine will make more power than this motor because it has forced induction and will cost less than Parts when the thing breaks guaranteed prove me wrong

  • Michael Lefebvre
    Michael LefebvreÅr siden

    This motors way too complicated and is not meant for hundreds and hundreds of thousands of miles I don't know why GM is fighting it but they should make a V8 turbocharged it can make tremendous amounts of power and then driving around on 02 no boost be very efficient

  • Dosedmonkey
    DosedmonkeyÅr siden

    Fantastic explanation.

  • Psychologist Thomas
    Psychologist ThomasÅr siden


  • rkl08551
    rkl08551År siden

    SAAB tech...

  • KATETA Y00
    KATETA Y00År siden

    not only more failure points, but also more rotation mass, worse response and higher center of gravity. despite all that, I still think it is a fascinating idea

  • Lee Dress
    Lee DressÅr siden

    This will make a great vehicle to lease and get out before it turns 4 years old. Excellent concept though.

  • TheTravellingHobo
    TheTravellingHoboÅr siden

    Hey Jason @engineeringexplained, I was wondering if you could help me out with a question about DCTs? (Irrelevant to this video I know but I cant figure it out!) In a common manual/automatic transmission when up-shifting, after disengaging the clutch the human/computer must wait for the engine RPM to drop to the appropriate value for the next gear before re-engaging the clutch. How does a DCT function in relation? In other words how does engine RPM drop at a faster rate compared to a manual transmission to allow a faster up-shift? Many Thanks

  • Maas Morin

    Maas Morin

    År siden

    I dont have an answer for you but couldnt you have a computer actuate an engine brake that momentarily is applied to the flywheel to rapidly drop rpms while the clutch has the engine disengaged?

    BLK DNAÅr siden

    Repair + mpg = empty pocket. But the tech is great.

  • RyanCooper
    RyanCooperÅr siden

    is that weird connecting rod movement eliminates secondary vibrations or enhances it?

  • Tj930
    Tj930År siden

    I had a very similar idea in about 2003... Thinking of forced-induction engines... A couple of engineering buddies laughed at me 😐

  • Jason Moore
    Jason MooreÅr siden

    GM junk

  • Jack Radzelovage
    Jack RadzelovageÅr siden

    - i just dont trust the little motor at the bottom. something tells me thatll break every 40k miles and require the body to be removed to get to it... - i imagine this is wholly incapable of handling boost? - why would you need to adjust position at a worm gears pace on each individual cylinder? arent they all supposed to be running the same exact specs as each other all the time? - is it even worth salvaging if the thing ever gets hydrolocked? - the more complicated an engine gets in the name of efficiency, the more stuff oil has to touch, thus the more things have a chance of failure if you have anything happen to your oil at all. if you run small engines without oil and seize them hard, you can take them apart and slap some new rings on the pistons if even needed, hit them with some WD-40 and theyll run again. THIS will cause a black hole if any little thing goes wrong. 2000 subaru forester s, 2.5L N/A 5M... i dont like the complicated thingamajiggers because i cant fix them on my own, or the parts are too expensive

  • Green Bot
    Green BotÅr siden

    Jason, I love your channel - thank you for your work! I have a video suggestion - the theoretical ultimate efficiency if all patented engine designs were applied to one design (sharing of intellectual property between manufacturers). If only Christian Von Koenigsegg combined freevalve technology with variable compression AND direct injection AND port injection (with a bit of Mazda's spark controlled compression ignition) AND the Koenigsegg compressed air system for turbo spooling AND pre-heated catalytic converters AND hybrid energy recovery... the IC engine would maybe get close to an electric motor efficiency but with all of that complexity. If on a level playing field 2 engineers presented the electric motor from a modern BEV and the best possible IC engine. Nobody would think IC was better. I love IC engines and we'll want to use them for a while longer, but looking objectively I think the industry is moving too slow to compete with BEVs. We need to treat IC as a nice hobby in classic now. If solid state batteries happen, IC needs to die - regardless of whether grid electricity is all renewable or not.

  • John Gialampoukas

    John Gialampoukas

    År siden

    Or you can look the theoretical cycles and see how much would be a theoretical maximum efficiency.

  • Shock Diamond
    Shock DiamondÅr siden

    And after all that work they will use OHV heads.

  • Tyler Brown
    Tyler BrownÅr siden

    If it’s anything like every other GM product I’ve owned, it doesn’t work.