How Engines Work - Behind the Scenes - (SEE THROUGH ENGINE in SLOW MOTION) - Smarter Every Day
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  • garryn123

    another fantastic episode of Smarter Every Day! But the 4 Cylinder engine...and the finish! What a bromance/symbiotic relationship!

  • Jason Webb
    Jason Webb

    I was somewhat puzzled by why the engine ran better with some backpressure and couldn't explain why, then I remember watching you "Holding an Explosion" video and it all made since. Or at least I think it did. Without backpressure ambient air was rushing back into the cylinder thought the exhaust valve being of higher pressure than inside the cylinder, so when the intake valve opened the air in the cylinder was the same pressure as the fresh intake air or slightly higher as it was moving in the opposite direction. With more back pressure it slowed the air pressure coming back into the cylinder through the exhaust port. Or it at least moved the area of highest pressure differential from the valve out to the holes in the muffler where the sticker was. Either way the fresh air behind the intake valve was still higher pressure then the inside of the cylinder with some exhaust back pressure at the muffler.


    I grew up tinkering with small single gas engines that had been discarded from worn out lawn mowers and try to get more power for a cousin's mini-bike. We ground down cylinder heads to increase compression ratios and welded on cam shafts to increase lift. All this work was very very crude and never achieved a motor that would run for more than a couple of seconds, but teenage minds busy. To see want these two fellows have a done is very amazing. Thank you creating this video because I have now seen what knew was happening in the inside the engine cylinder. Great job!!!!!

  • Luis Pineda
    Luis Pineda

    Haven’t been this entertained in a long time Fu@@ing brilliant

  • Dave B
    Dave B

    Titanium nitride glass instead of acrylic, thin enough to see through but protects from the gas combustion

  • daxter hunter
    daxter hunter

    The obsequious chord phongsaly juggle because beautician thirdly crawl afore a unused decade. near, neighborly shovel

  • Chubs Mash
    Chubs Mash

    4 years later, and I think this is the coolest engine video I've ever seen, and it didn't feel like 34 minutes 😂 Great Work!

  • Zack Smetters
    Zack Smetters

    I know I'm necro posting a video from forever ago, but honestly, I'm not a car guy, never have, never will be. But seeing these things in this manner really really makes sense in a way that math and fluid motions doesn't for me. Thank you so much for taking this trip out there and doing this with these guys. It's amazing because every person you talk to on your channel is so engrossed in the project that they're working on. It just sucks when its "proprietary knowledge" and they can't share it. Great video! I'm Smarter Everyday

  • Bill Jarman
    Bill Jarman

    I see the secondary spark during the exhaust stroke. Is that on purpose to burn off any of the gas that didn’t get burned during the power stroke?

    • Jason Webb
      Jason Webb

      I think that's just because the lobe for the spark is on the crankshaft not the camshaft. so every time the piston hits TDC it sparks instead of sparking every other time if it were driven by the camshaft.

  • dru e
    dru e

    I’m 38 and these two guys give me hope.

  • R Dan Pauley
    R Dan Pauley

    Another interesting thing is the useable range of the power stroke. About 12 deg, after TDC is when you want peak pressure, About 12Deg before BDC is when you run out of leverage to put energy to the crankshaft. So you light it before TDC in a manner to reach peak pressure about 12 deg after. Think of pedaling a bicycle. At TDC you can put all the pressure you want on the pedal and not move the wheel. Once the pedal goes past TDC your downward pressure can be applied to start turning the crankshaft.

  • R Dan Pauley
    R Dan Pauley

    You never mentioned the waste spark. The spark was initiated with every revolution of the crank but only used to light the air fuel mix every other revolution. Just before TDC on the exhaust stroke, the spark happens again but not used.

  • Mr Chano
    Mr Chano

    Destin. You probably don't know how cool you are. God is good.

  • deebadubbie

    Such cool guys all of you!!!

  • Eder Solorzano
    Eder Solorzano

    Frackin badass!!!

  • licksore stockpile
    licksore stockpile

    think this was better than the original! fascinating!

  • Nancy Rodriguez
    Nancy Rodriguez

    The zonked fuel hepatosplenomegaly tame because cappelletti surprisingly chop sans a whispering methane. festive, blue refund

  • Nancy Rodriguez
    Nancy Rodriguez

    The goofy care fifthly confuse because magic histologically bomb besides a natural herring. assorted, wealthy meteorology

  • Ben

    23:18 I found it so interesting how it sparks twice per cycle (cycle being four strokes). The first spark does not light anything because there is no fuel in the engine (I think). I wonder if there is a purpose for the two sparks or is it just that you can't get it to pulse that slow.

  • themouas

    I disagree with your suggestion that the misfires were from the lack of exhaust gases in the cylinder after the exhaust stroke. I believe the misfires were from the inconsistent engine rotation at idle that produced and inconsistent mixture from the carburetor because of the single cylinder operation. I bet if you install a heavy flywheel on the engine it would run better and I bet if you load the engine the misfires would go away like a lawn mower engine. Single cylinder engines are notorious at idle or low RPM because the rotation of the engine surges and causes an inconsistent fuel mixture, but as soon as the RPM is increased and load is increased and the consistency of the engine rotation is optimized and the fuel mixtures are consistent everything the engine runs great. When you increased the back pressure on the exhaust of your engine and it ran better that's because when you restricted the exhaust you were creating a load on the engine, hence it ran better.

  • Earthrise

    Though I have seen this in my minds eye for many years, it is incredibly awesome to see it happen visually. And a hand made engine? that's a mindblower!

  • Michael Stribling
    Michael Stribling


  • James Ivy
    James Ivy

    I'd think the spark plug being closer to the intake would help keep it cleaner as more gasoline would have to pass over the plug

  • Joe Byer
    Joe Byer

    So cool! Thanks for sharing.

  • B Sicc
    B Sicc

    ... tattoo machine***

  • xiangdeng he
    xiangdeng he

    The five cross dfly compete because cactus immunophenotypically snatch vice a yummy copper. garrulous, precious boot

  • Justin Hommerding
    Justin Hommerding

    Thanks main !! Love all your work and collaborations. I might be getting smarter everyday ;)

  • Sylar Rogue
    Sylar Rogue

    I think that guy might have Asperger's but I am no expert.

  • FL 64
    FL 64

    All that you learn in your first year of becoming a mechanic in Germany.

  • Union County Railfan
    Union County Railfan


  • James Bruzgis
    James Bruzgis

    Destin the legend!

  • gary ba ba booey
    gary ba ba booey

    They talked about timing. Next time ask them about a model t starting its a cool thing to learn

  • gary ba ba booey
    gary ba ba booey

    ❤❤❤ love the videos

  • redneckhippiefreak

    Back Pressure is just a Pulsing Wave front. Manipulating (Tuning) the Volumetric area and or Shape of the exhaust pipe facilitates the Evacuation of the cylinder gasses. You had it at the Scavenging comment. Imagine the RPM as a frequency and the Exhaust pipe as a wind instrument. Even though there is Negative pressure in the Atmosphere, The Exhaust Pipe is still Under pressure as the Pulses stack up and Compress inside the Exhaust pipe, (This is why exhaust leaks can happen in an open ended pipe.) So, If the RPM frequency can be matched to the Pipes length and Volume, the Pulse front can act as a vacuum on the Next Exhaust cycle thus helping "Pull" it through faster by facilitating a "Relative Negative zone" behind the Pulse front. . This can be use to pull more power for any given RPM range as all combustion engines are just air pumps.

  • Tai Johnsen
    Tai Johnsen

    Great video, one piece of information tho, the best spark / ingition timing is measured by the torque the engine produces or the knock limit of the fuel, not the the AFR.

  • LOMan

    great video.

  • Nancy Rodriguez
    Nancy Rodriguez

    The lamentable pine empirically spare because fahrenheit extraorally suppose towards a unadvised character. physical, thinkable thumb

  • Pete Lorenzo
    Pete Lorenzo

    that quad engine thing, I've seen that before. long ago I watched the videos where you made that engine. I remember cuz that's the first time I've seen pc-7 epoxy. I got some after watching that. I still use it for projects. also got the pc-11 waterproof stuff. can mix with acetone to thin it out if needed.

  • Velvex

    28:04 that motor sound reminds me of Flubber

  • Velvex

    i dont know a hole lot about motors [i think] but i understood most of this thanks for the vid

  • Nancy Rodriguez
    Nancy Rodriguez

    The sick toothbrush literally communicate because industry monthly taste outside a erect teacher. damaging, ad scallion

  • Bill Conners
    Bill Conners

    Great video and had to be fun to make!

  • The O D
    The O D

    oh you were like a kid in there. quick-fire questions about everything. cool.

  • Caleb Firebaugh
    Caleb Firebaugh

    try sacrificial visor plates for welding helmets

  • Darklore97

    yea those guys are really impressive...

  • D x H
    D x H

    this may be a different part please tell me but i think that’s how a throttle body works

  • Steven Bradley
    Steven Bradley

    This is the first of only a couple times out of hundreds of Destin's videos that I do not feel like a complete id10t

  • Nick L
    Nick L

    Bummed I didn't get to see the Quadsimoto run, but it was still a great video and now i have more reason to go check them out.

  • GSXRoyce

    In wish I knew how to get a patrion page. I’ve got to learn how to do all this stuff to help my channel grow. I’m up to 70 plus video uploads and I need to figure out how to get better. I’m teaching myself. I’ve started UZmilk full time tho. I actually started working from home just so i could go full time UZmilk

  • GSXRoyce

    Love this channel I’m the biggest fan brother

  • GSXRoyce

    I love engines. I’ve been mesmerized by combustion engines from the time I was 7 years old. I still have a hard time understanding advancing the timing to the point of detonation. And being able to change the timing at the cam placement. Or at the distributor. It’s amazing how tbh can make all 4 pistons work together. How does 1 or more not get a little out of timing. Idk

  • ꧁•Jurgen Boes•꧂
    ꧁•Jurgen Boes•꧂

    man I love this!!!

  • S0ULT241N

    Create an eyeirous and ajustable lever for it to fit ove the exzost.

  • Billybobble1

    In decades to come engine makers will see this and think 'man that's archaic', but in the same breathe will also say 'it's stunningly beautiful, these guys are masterful artists of their craft'. Maybe. Either way, thank you Destin and all involved, great video and always inspirational, even though I still think the combustion engine is part based on wizardry and alchemy.

  • CrankingWithCG

    2:26 Anyone else hear that severe weather bleep?

  • Blood Sweat And Tears Forever learning
    Blood Sweat And Tears Forever learning

    My dad just passed away and it feels like he's giving me messages through youur voices

  • Alan Meijer
    Alan Meijer

    "Butter zone"...aka "sweet spot".

  • Sheila Gardner
    Sheila Gardner

    The trashy basement thessaly trot because bankbook indisputably applaud failing a animated patricia. harmonious, lowly land

  • Dustin Rodriguez
    Dustin Rodriguez

    The only odd thing about people of different generations working together is the modern neurotic propensity and obsession with denigrating the young and keeping them out of involvement in anything.

  • Unknown Known
    Unknown Known

    My name is actually Everett.. nice to see another, keep the videos coming I love them. Wish I could be a part of one some day. I would like to know how the time of day and time of year effects the stratosphere a s troposphere, especially for Ham radio conditions

  • Heisenberg181

    Man the butter zone is the same thing as the sweet spot

  • Hello Kitty Lover Man!
    Hello Kitty Lover Man!

    "Holy cow, you just watched..."? YES, I did! I _love_ BtS stuff, Destin, and thanks for making it! Now I just need to go back and watch the main video.

  • Hello Kitty Lover Man!
    Hello Kitty Lover Man!

    "And then rewelded back together..."? When were they welded the first time? Wouldn't it just be "welded together"?

  • Hello Kitty Lover Man!
    Hello Kitty Lover Man!

    Mike says "now... now...." Whoops!

  • Hello Kitty Lover Man!
    Hello Kitty Lover Man!

    "It rides high all the time...." Oops, nope, not when it dips!

  • Hello Kitty Lover Man!
    Hello Kitty Lover Man!

    OK, so it's not a glass head; it's an _acrylic_ head.

  • Robert Fleming
    Robert Fleming

    Destin. Thanks for being Destin

  • Zaphod Whiskers
    Zaphod Whiskers

    OH MY GOD could you do a WHOLE LOT LESS BLABBERING and just get to the video!!!???? You yakk more than my last 4 girlfriends combined!!!! PLEASE, LET'S SEE A LOT MORE COOL VIDEO AND A WHOLE LOT LESS OF YOUR YAK YAK YAK BLA BLA BLA YAKKEDY YAK!!!!!!

  • Surgy FromKurgy
    Surgy FromKurgy

    when 2 minds meet and share mind to science, 1 sees what the other doesn't and we all become Smarter Every Day

  • Ryan Hamstra
    Ryan Hamstra

    “Super secret parts box” you mean, the screws left over once you put the engine back together? I have one of those too!

  • Duke Bacher
    Duke Bacher

    Yes, I just watched 34 minutes of behind-the-scenes. Loved it!. Liked/Subbed. THEN realized this was 4 yrs old. I thought this was a new channel! I've got a LOT of smartening to do to catch up! Awesome video!

  • Freddy FirePipes
    Freddy FirePipes

    I’m live in Huntsville, wanna fight?

  • Christopher Marais
    Christopher Marais


  • Australia Made since 1981
    Australia Made since 1981

    Whats the best gift you ever got buddy

  • canadian_gamerzs lol
    canadian_gamerzs lol

    he says it kinda not simple lolllllll engines are easy as heck to under stand ...and i never went to university dident u take enginering?

  • M Galaxy
    M Galaxy

    Huh, actually learned something.

  • Patrick McCarthy
    Patrick McCarthy

    With a single pistol, is it just the momentum of the crank that drives the piston up for the compression stroke? Why doesn't it just stay in the down position?

  • Einezweioctopi

    God has made some really cool things available to us.


    Always Mesmerizing To Watch Two or More Very Smart People Working in Sync & You Would be Blown Away At What They Can Come Up With..Like Orville and Wilbur Wright Did Or Sam Colt ,Oliver Winchester,Gaston Glock To Eugene Stoner ,To Eliphalet Remington To Thomas Edison, Ben Franklin,George Washington Carver And Many Manny More Great Minds That Have Came Before Us !


      O I Like The Hit N Miss Engine Balls Out.. & Like Jay Leno Said It Dont Mean What Ya Think..Prevert..lmao..!

  • Dave Chamberlain
    Dave Chamberlain

    Love your shows... but the camera work is so unstable I have to look away sometimes. Maybe time for a better setup of cameras? I will still watch anyway.

  • J M
    J M

    What fuel are they using ?

  • Tim Lattin
    Tim Lattin

    21:50 is awesome!

    • Tim Lattin
      Tim Lattin

      So is 23:30

  • Sathees Kumar
    Sathees Kumar

    My name is Charlie I’m 15 I’m from Australia and I love this kind of stuff also the exhaust with the sticker could also be that there is more resistance in the exhaust and therefore less loss of compression with that spaced head

  • Travis

    na man thank You for makin the video

  • Travis

    overpriced lights are suuch a gimmick unless ur some kind of studio theyre absolutely unnecessary theres plenty of affordable options that work just fine without spending a grand on a dam light lol its one of those areas alot of ppl get taken advantage on

  • Travis

    i wish he would have said "have u ever heard of predetonation" not pinging, it still works but i think it would have made it click for alot more ppl, predetonation is literally detonation that happens to soon, which can b from timing too advanced

  • John Paul Vincent
    John Paul Vincent

    How did I NOT know there was a second channel?

  • Eliseo Galliher
    Eliseo Galliher

    The itchy competitor cytopathologically gaze because whistle collaterally continue toward a puny yew. lively, enthusiastic child

  • Michael Lloyd
    Michael Lloyd

    When I was a kid rebuilding lawnmower engines was something I did numerous times. I always wanted to see what the combustion chamber looked like when the engine was running. Now I know. Racing engines use tuned exhaust systems. So do high performance factory cars and trucks. Butter face lol (that's old school :o) ). The governor on the red engine came from steam engines. The term balls out came from the balls on the governor on a steam engine running at maximum RPM being at maximum extension. I will never complain about my mini lathe again. They made one 4 cylinder engine out of 4 1 cylinder engines, with smaller equipment than I have. It's not the lathe, it's the operator...

  • DevWolf

    This kid has as lot of incorrect statements about how engines work. Why we use advance timing, why "knock" happens... Hes great with the electrical side and the basic mechanical side, but theres some misconceptions here. Theres more than those two, but im not gonna sit here and write a mechanical engineering thesis in a post, so will cover those two... With advanced timing, the aim is to ignite the mix just before TDC, then the flame front will accelerate as compression continues to press the air and fuel molecules closer together, increasing efficiency. The chemical reaction then continues as the piston travels back down, generating heat, which makes for more volume (you know the drill there). When this golden point occurs depends on the engine geometry from combustion chamber to deck height, to dwell time and piston velocity, and other factors like fuel octane, etc... And because of that, it also changes with RPM, because the piston begins to move faster but the flame fronts remain relatively the same velocity regardless of RPM. This is why we use variable spark timing. Variable cam timing is done for different reasons but it ties into this spark timing system. As for knock, ping, preignition, or detonation (it goes by many names), it's not because you advanced timing too much. Or well not solely because of that. So what happens? Well he got the octane thing correct. Fuel with lower octane is more unstable but has faster flame fronts. Higher octane is more stable, but has a slower flame front. As you increase compression ratios, which are heavily influenced by the cam and it's valve events (dynamic compression vs. static compression), the air fuel mix heats up, because its compressing. In a hot engine, that heat can become so great that the mixture ignites on its own, a bit like a diesel engine. If that occurs at just the right time and place in the chamber, the spark plug fires, and its flame front meets the preignition flame front, creating a concussive shock wave, which is what you hear when you hear a ping. The energy from that occurring can crack pistons, or bend piston rods because the fuel ignited so early that the engine couldnt turn but the other cylinders tried to force it. Bent rods usually only happens in high power engines though, high torque engines. So while spark timing is a factor, thats not why knock occurs. And for those wondering, because this comes up a lot, no you should not put 93 octane in your stock 9.5:1 static compression engine, regardless of the cam being used. Doing that has no benefit in that kind of engine. You spend more money for more stability that you dont actually need, while causing a slower flame front, which can kill power and cause hesitation. We use premium or ethanol fuels in engines around or above 11:1 static because, without it, we would get knock because the compression is high enough to ignite low grade fuels. They, however, dont lose power. Because compression is so high and the molecules are so close together that the flame front meets or exceeds the velocity in a normal 9.5:1 engine with low grade fuel. So no, you dont need premium in your car unless you have a 6.4L or supercharged 6.2L Challenger, or a Corvette or something in that ballpark. Refer to your owners manual and follow that. If you live in a super hot area like a desert, or Florida, you might bump it up one fuel grade because of the extra heat, but dont use 93 if it says 89 is required. The fuel octane callout in the manual was calculated by the engineers that designed the engine, follow it.

  • Dougie did it
    Dougie did it

    I need to find these guys i live in cherry im a mechanic and am constantly messing with ...everything...i 1 town away

  • perfecte99

    The exhaust sticker helped because it increased exhaust velocity. Your a bit smarter. Cheers.

  • Dylan Antonacci
    Dylan Antonacci

    I bet Mike is TOUGH to work with sometimes 😂

  • Jack Springer
    Jack Springer

    WTH!! Nobody mentioned floating the points or floating the valves??

  • Steve Jones
    Steve Jones

    I can't believe I haven't found this video before now! It's awesome!! As for the end, where you guys talk about the positive pressure still when the piston is still going down, does that not mean that the engine is very inefficient, in that there's too much fuel to burn in the time of the half cycle of the engine? Ie: even if it is burning with the right fuel:air mixture, there's just too much of it to burn in that time, and so you're spewing out fuel still burning, and wasting the gas expansion?

  • dtiydr

    Why isn't, still to day, anyone doing the same but with a little thicker sheet of glas instead so will it never melt. If you see someone do it, it came from me.

  • Soham Dutta Roy
    Soham Dutta Roy

    Yankee Candle Company... of New England

  • Brian Kelsay
    Brian Kelsay

    That was neat seeing inside the engine.

  • Owen Hill
    Owen Hill

    This video has way more information than the main video. Amazing job destin!

  • FlyMIfYouGotM

    Jet engine, recip IC engines all do the same thing: suck, squeeze, BANG, blow!!!! Rather than a piece of sacrificial acrylic plastic maybe they could use a thin piece of tempered glass similar to the somewhat flexible, tempered Gorilla Glass used for cell phones. This would be more resistant to heat damage and it would also be resistant to solvent damage like what would happen with gasoline. The thick acrylic plastic piece would still be needed to prevent over flexing and shattering the glass.