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    • felooboolooomba · 7 days ago

      Pro tip: Show a message if WebGL is disabled instead of a blank space.

      • mrhottakes · 7 days ago

        Excellent animations.

        • misiek08 · 7 days ago

          You meant - awful knocking combustion in the first, main animation? I never catches any real bug is those great posts, but this one, especially as first animation on the page - weird.

          • Toutouxc · 7 days ago

            You might be misreading the animation. It's a direct injection engine, the thing that happens during the compression stroke is fuel injection. Ignition happens a few degrees before TDC, which is realistic.

            • lostlogin · 7 days ago

              One of the rare situations where someone wants a bit of retard?

              • HoldOnAMinute · 7 days ago

                That is often more advisable as opposed to doing it fully.

          • bob1029 · 7 days ago

            > Presence of oil is critical here as it creates conditions for hydrodynamic lubrication.

            You can hear this effect in some vehicles at initial startup time for a few seconds. I know of certain Ford engines where it actually causes issues over time. The model years with auto start/stop have the worst of the cam rattle disease.

            • Toutouxc · 7 days ago

              Note that that sentence is talking about the crankshaft bearings and their hydrodynamic lubrication, which is, well, elsewhere and separate from any cam rattle issues (including the cam phaser oil starvation that you might be referring to).

              • culopatin · 7 days ago

                Lifters also often drain while sitting and valve lash is greater at start until they get slapped a few times

              • LeifCarrotson · 7 days ago

                Auto start/stop isn't off for enough time for the oil to drain from the galleries and especially not out of the bearing journals.

                It's the first few seconds after an engine has been off for hours (or worse, for potentially years) that are the problem.

                • toxik · 7 days ago

                  I thought it pretty well established that auto on/off is bad for the engine, as is intermittently turning off some cylinders as some do. Is that wrong?

                  • vel0city · 7 days ago

                    It sounds like you're talking more about systems that supposedly disengage some cylinders while the car is cruising. Some engines with that kind of technology have been known to damage cylinders for multitude of reasons.

                    That's very different from the start/stop feature they're talking about. That's about fully stopping the engine when you come to a complete stop like at a red light and then automatically starting again when you get off the brake.

                    • Toutouxc · 7 days ago

                      I don’t think it’s pretty well established, there are cars that will happily stop and start the engine multiple times per minute, e.g. Toyota hybrids with their “HSD” drivetrain. It just requires some engineering.

                      • trhway · 7 days ago

                        I don’t think Toyota engine does traction from low rpm. Electric motor does it, and moments later already well spinning engine gets the load.

                        Hearing regular start-stop on intersection gives me sorry feeling for the engine.

                        • kube-system · 7 days ago

                          Hybrids generally command the ICE to run when under higher loads or cold conditions, but they do get a bit of a break under low load conditions when they’re warmed up.

                          But they also start and stop way more than a gasoline-only car with stop-start. Because they stop and start repeatedly while driving too. Series hybrids even more so.

                          • trhway · 7 days ago

                            >But they also start and stop way more than a gasoline-only car with stop-start.

                            they do it very differently. My Prius never does that coughing sound that the start-stop engines frequently do. The powerful electric motor in Prius spins the engine to at least 1000rpm before fuel is injected. That way it is much easy on the engine and much more fuel efficient too.

                      • gomoboo · 7 days ago

                        “While aggressive start cycles (>20 cycles per day) could lead to premature failure in the starter system of light- to medium-duty commercial fleet vehicles, modern fuel injection and engine control systems have eliminated any issues associated with drivers of typical light-duty vehicles turning the engine off while stationary for short periods and restarting the vehicles for <10 start events per day.” from https://publications.anl.gov/anlpubs/2015/05/115925.pdf

                        This paper seems to say that generally they aren’t a problem. I’ve only seen unsubstantiated claims that they are one.

                        • bob1029 · 7 days ago

                          This paper reads like a high school science fair project with zero treatment for the concern originally presented (oil system pressure transients).

                    • bluedino · 7 days ago

                      That's the timing chain tensioners losing oil pressure.

                    • fauria · 7 days ago

                      "in real running engines the rotating crankshaft should float completely on a very thin surface of oil" - I found this to be a great insight.

                      • arlattimore · 7 days ago

                        The bearing surfaces in an engine (ex: crankshaft main bearings) have very tight tolerances, usually in the 15-25 thousandths of an inch. The engines oil pump fills those tiny gaps with pressurized oil which allow the metal surfaces to spin thousands of times per minute without damage.

                        This is also why if you have any issue with oil pressure (ex: oil pump failure, cracked oil line) or oil starvation (ex: driving a regular car on a race track, cornering forces slosh oil away from the oil pickup in the sump) issues, you'll damage your engine nearly immediately.

                        • LeifCarrotson · 7 days ago

                          It's 0.0015, that's 1.5 to 2.5 thousandths, or 15-25 "tenths" as they're called.

                          That's not a particularly tiny gap in the machinist world, it's large so that you can pump viscous oil in it and deal with a wide variety of temperature changes.

                          25 thousandths would be sloppy, a nominal clearance hole for a 1/4x20 bolt is about that much.

                          • arlattimore · 7 days ago

                            Good catch, sorry should have corrected that. While not small for a machinist, I think by the average persons definition that is a pretty small gap for the oil to occupy ;-)

                            • cagey · 7 days ago

                              > 25 thousandths would be sloppy, a nominal clearance hole for a 1/4x20 bolt is about that much.

                              Isn't that 0.250 which would be 250 thousandths?

                              • teraflop · 7 days ago

                                No, they're talking about the clearance, which is the difference between the diameter of the bolt itself (1/4") and the diameter of a hole in which the bolt loosely fits (a couple hundredths of an inch bigger than that).

                          • WalterBright · 7 days ago

                            That's the point of all uses of oil, other than rust prevention.

                            • calmbonsai · 7 days ago

                              Some engines are also substantially cooled by oil, but those are either older designs (think “air-cooled” Porche) or industrial prime-movers.

                              • WalterBright · 7 days ago

                                You are quite right, the oil also serves to transport the heat away.

                                • nablaone · 7 days ago

                                  It's a solvent also.

                                  • dotancohen · 7 days ago

                                    Oil also keeps the gaskets (e.g. valve cover gasket, water pump) and seals (front and rear mains) pliable.

                                • xenadu02 · 7 days ago

                                  Most piston aircraft engines are still air-cooled which really means air and oil cooled. The oil is a big part of getting heat out of various parts of the engine.

                                  That also makes them harder on oil as the piston/rings have larger tolerances so they don't expand and bind up during operation. That means greater blow-by at startup and when operating at lower temps which puts a lot more combustion byproducts into the oil. Ultimately you want to run an aircraft engine in the upper part of its range (65% power) continuously and don't let it get too cold.

                                  This is also true because 100LL still contains lead and at lower temps the lead combustion byproducts precipitate out of solution, coating everything in metallic lead, lead oxides, and various other lead compounds all of which are really bad for engines. Converting to unleaded nearly doubled engine life in autos.

                                  Many modern engines have valve rotators and hydraulic lifters. Oil pressure is fed to a lifter that sits between the valves and the cam and automatically takes up for any variation in the system, ensuring valves operate correctly. If you ever wondered why car engines don't need to have their valves adjusted every 20k miles anymore - that's why. In some engines if these leak down after shutdown it can cause trouble starting because the valve timing will be off until oil pressure re-fills the lifter.

                                  Rotators are little spring mechanisms that compress and when uncompressing try to rotate the valve in one direction. This causes the valves to rotate a tiny bit with each cycle. Often there are hot spots and exhaust valves especially often have no good way to shed heat yet are exposed to extremely high temps - so they shed heat when they close and are in contact with the head. If they don't rotate the slightly hotter spots will continuously build up heat eventually destroying the valve. The rotator keeps that from happening. (Some engines use sodium filled valves to help transport heat away from the valve face).

                                  I always found it surprising how tiny variations in wear or even a few degrees of excess heat can end up destroying an engine.

                                  • Toutouxc · 7 days ago

                                    Fun thing about the sodium filled valves — these are also used in cars. The engine in my previous econobox, a 3-cylinder 1.0 TSI (EA211) uses them in the 81 kW variant.

                                  • dotancohen · 7 days ago

                                    Some engines, especially high mileage engines from Detroit, are also substantially fueled by oil. In a sense.

                                    • dylan604 · 7 days ago

                                      Then there's the ones with the puff of blue smoke

                                      • kube-system · 7 days ago

                                        That’s how you know it still has oil in it

                                        • dotancohen · 7 days ago

                                          Yeah, that's exactly what I meant.

                                • CraigJPerry · 7 days ago

                                  The thing that's missing here that really drastically changes the story is all the emissions control hardware that would exist on such an engine.

                                  This is a circa 1990s engine in the US market i think? Dual Overhead Cam didn't really become popular in the US market until then i think. 70s-80s for single overhead cam to become established.

                                  The diagrams are beautiful and informative as always from this author.

                                  • MarkusWandel · 7 days ago

                                    Wonderful but it irritates me that so many descriptions of internal combustion engines refer to "explosions" of the fuel. You don't want that. It causes knocking and pinging and engine damage. You want a controlled burn that generates heat smoothly.

                                    • stouset · 7 days ago

                                      You don’t want detonation, but you do want deflagration.

                                      • Toutouxc · 7 days ago

                                        Not exactly. You do want a deflagration and not a detonation, but "explosion" is more loosely defined and, depending on who you're talking to, a self-sustaining subsonic flame front and a sharp pressure spike are a perfectly valid explosion.

                                        • raffael_de · 7 days ago

                                          explosion/detonation causes engine knocking or pre-ignition which is both very bad. a properly working combustion engine is driven by controlled burning.

                                          • Toutouxc · 7 days ago

                                            You’re replying to a post that says that “explosion” doesn’t imply “detonation”.

                                            • raffael_de · 7 days ago

                                              and that is not strictly correct. it's called combustion engine and not explosion engine for a reason.

                                              • kube-system · 7 days ago

                                                But it is strictly correct. Deflagration is the definition of low (i.e. subsonic) explosive.

                                                Combustion is a broader term — combustion just refers to burning. And the reason it is called an internal combustion engine is to contrast it from its predecessor combustion engine designs - the external combustion engine.

                                                More precisely, the type of combustion happening in an ICE engine is (low) explosive.

                                                https://en.wikipedia.org/wiki/Explosive#Low

                                        • rootusrootus · 7 days ago

                                          Even more confusing to anyone who doesn't know the lingo, detonation in the context of an internal combustion engine means something specific. It is a synonym for pinging and knocking, and happens when unburnt fuel/air mixture explodes after the spark plug has already fired. It can damage the engine, but typically takes some time. Preignition is when the mixture ignites before the spark plug fires, and is typically much more damaging, often destroying the engine in just a few revolutions. It can pound through the boundary layer between the mixture and the face of the aluminum piston and melt it, or break something else in the engine like a rod.

                                          It's been a minute, but at one point GM had some pretty interesting videos up on YT where they talked about preignition testing on Cadillac Northstar V8s and how quickly it would grenade the engine. Fascinating stuff.

                                          • userbinator · 7 days ago

                                            There are videos on YouTube of what the combustion actually looks like in slow motion. It's fast, but far less violent than an "explosion".

                                            • 00N8 · 7 days ago

                                              I don't think it's any slower than the dust explosions that occasionally happen in factories or grain silos. Although those do appear more violent due to the scale & damage.

                                          • mberning · 7 days ago

                                            If you like this kind of stuff go and look up videos on the Rolls Royce Crecy engine from WWII. Absolutely insane engineering that died due the dawn of jet propulsion.

                                            • relaxing · 7 days ago

                                              Very interesting technology. Would be exciting to see a hardware startup build a product around this.

                                              • darkteflon · 7 days ago

                                                Hmm not sure about that. It seems like a lot of complicated effort to produce locomotion. I’ll stick with my reliable horse, thanks.

                                              • londons_explore · 7 days ago

                                                Worth noting the design of the internal combustion engine hasn't changed much in 50 years.

                                                The thing that has changed is the control systems.

                                                What used to be a primitive mechanical way of mixing fuel and air (the carburettor), is now an electronic fuel injection system, with the fuel air ratio very carefully matched to reduce pollution (fun fact: modern cars release so little carbon monoxide, you won't kill yourself by starting one in a garage (but don't try it just incase your car is faulty)). Catalytic converters use any tiny fuel air imbalance to reduce carbon monoxide and soot, and on the other side nitrous oxides, by slightly increasing and decreasing fuel air ratios.

                                                • pak9rabid · 7 days ago

                                                  There's also been advancements in cylinder head technology (i.e., VTEC, VVT, etc), which I guess also falls under control systems, but worth mentioning as these technologies are very cool. Honda's iVTEC has it down to a damn science with how to optimize valve lift & duration across the entire RPM spectrum.

                                                  • OptionOfT · 7 days ago

                                                    What I am surprised by is that cams are still used to operate the valves.

                                                    Given to how precise these need to be these days, I would've guessed they would've switched to electronically actuated valves.

                                                    • jballer · 7 days ago

                                                      I was going to point to Koenigsegg’s Freevalve system and, in the process of looking for a link, learned that it was cancelled.

                                                        • Toutouxc · 7 days ago

                                                          The very first image at the very top of the MultiAir article shows, prominently, a camshaft and the cams used to actuate the valves.

                                                          • left-struck · 7 days ago

                                                            It’s because of the good enough precision at low cost that we use cams, it’s extremely difficult to get precise movement and the forces and speeds required when an engine is operating at >5000 rpm. It’s not impossible but the trade offs are rarely worth.

                                                            The exact valve timing isn’t really a big factor in emissions as much as temperature control and exact AFR control. I mean valves need precise timing to avoid coming into contact with pistons but if you’re already at that level of precision then you gaining more precision won’t really reduce your emissions.

                                                            Of course being able to change the timing of your valves helps with both efficiency and emissions, but VVT does that pretty well.

                                                          • left-struck · 7 days ago

                                                            > fun fact: modern cars release so little carbon monoxide, you won't kill yourself by starting one in a garage

                                                            Modern cars still release as much CO2 as older cars… which is still incompatible with human respiration.

                                                            • rstuart4133 · 7 days ago

                                                              Another fun fact: the body's suffocation response isn't caused by lack of oxygen. It's caused by high CO2 levels in the blood [0]. If your car floods the air with CO2, you will respond like someone is holding your head under water.

                                                              Carbon monoxide kills you by binding more strongly to the hemoglobin than the O2. You don't notice, because the CO2 removal mechanism continues to work fine. You'll usually die before realising anything is wrong.

                                                              • jamwil · 6 days ago

                                                                I just read this fact in Hail Mary, but it doesn’t fully add up to me. If you fall flat on your back and wind yourself (phrenospasm) that triggers an immediate suffocation response which has nothing to do with CO2 and seemingly everything to do with a lack of oxygen.

                                                                • rstuart4133 · 6 days ago

                                                                  > has nothing to do with CO2 and seemingly everything to do with a lack of oxygen.

                                                                  If you lack oxygen because you can't breathe in, then CO2 will be building up because you can't breathe out.

                                                                  Neither sound like a good explaination for the suffocation response being winded causes, because most people can hold their breath for a least a minute with too much discomfort. It's more likely due to a primitive response to unexpected airway restriction - the same as choking.

                                                                  PS: pigs have the same CO2 response as us, maybe stronger as they can detect C02 at lower concentrations. I find that hard to reconcile with pig abattoirs killing pigs by lowering them into a pit of 90% CO2. N2 would do the same job without the pig realising what is going on, but CO2 is heavier than air so it stays in the pit, making it more economical.

                                                                  https://pmc.ncbi.nlm.nih.gov/articles/PMC11948533/

                                                              • DeathArrow · 7 days ago

                                                                And there are also other parts for reducing the pollution like DPF, EGR and Adblue systems.

                                                                Unfortunately they also reduce the reliability.

                                                              • jtwaleson · 7 days ago

                                                                I'm showing this page to my team and investors every couple of weeks. Visual, animated explanations are MUCH better than textual content for deeply grokking something. This is what we're trying to build for large software systems. I love the animations on this site so much, thank you for building them.

                                                                • nickvec · 7 days ago

                                                                  I hope Ciechanowski posts some more in the near future. He has some of the best "how does this work" articles I've come across.

                                                                  • drayfield · 7 days ago

                                                                    Always good to revisit his older work, though I admit I did get excited that it was a new post!

                                                                    • duped · 7 days ago

                                                                      This is a stupid question but I'm a stupid EE/SWE who knows very little about physical objects.

                                                                      In the all these animations of the pistons I see linear motion translated into rotary motion using the crank shaft - but how do you design the pison/crank to always turn clockwise or counter clockwise (based on how you view it, obviously)? Is it possible for the crank shaft to lock up if it's perfectly oriented at 0 degrees?

                                                                      • pjc50 · 7 days ago

                                                                        This is why the starter motor spins the shaft in a known direction.

                                                                        • aw1621107 · 7 days ago

                                                                          > but how do you design the pison/crank to always turn clockwise or counter clockwise (based on how you view it, obviously)?

                                                                          You can design the starter motor to ensure the engine always starts up moving in the right direction, and after that it's "just" a matter of timing (e.g., spark plugs controllled electronically in more modern cars, mechanically in older ones).

                                                                          > Is it possible for the crank shaft to lock up if it's perfectly oriented at 0 degrees?

                                                                          That's what the starter motor is for!

                                                                          • reorder9695 · 7 days ago

                                                                            The starter motor turns the engine in a defined direction, this acts as a turning force directly on the crankshaft so it doesn't matter where the crankshaft is. The pistons only start firing after the crankshaft is already moving.

                                                                            It is actually possible for an engine to turn the wrong way, this occurs on motorbikes with kick starts. When you don't kick start it correctly (or if the ignition timing is way out), a piston can fire prematurely before top dead centre and force the crankshaft against the direction that the kick lever turns it, this is known as kick back and is about as fun as it sounds when the engine's force goes through the kick lever.

                                                                            • jabl · 7 days ago

                                                                              Some engines, nowadays mostly large marine diesels, are reversible. Change the valve timing, and start it in the opposite direction, and off it goes.

                                                                              • trevithick · 7 days ago

                                                                                Sibling explanations are correct re: direction of rotation. As to your second question, the flywheel keeps things spinning so it doesn't lock up and has the momentum to compress the air/fuel mixture. BTW 0 degrees is called top dead center or TDC and is a useful point for calibrating timing and ignition.

                                                                              • gwbas1c · 7 days ago

                                                                                When I was a kid, pre-internet, my dad took me to the local library and checked out some books that explained how an engine works.

                                                                                These animations are so much better than what I had!

                                                                                • klaff · 7 days ago

                                                                                  When I was a kid we had a visible V8 model that let you see quite a bit!

                                                                                • vjvjvjvjghv · 7 days ago

                                                                                  This should probably be called “Four Strike Engine”. There are other types of ICE that work differently.

                                                                                  • yunnpp · 7 days ago

                                                                                    You mean stroke?

                                                                                    • vjvjvjvjghv · 6 days ago

                                                                                      Yes. I think the iPhone keyboard tricked me again. I remember having to work quite a bit to convince it to take "stroke" instead of "strike" and I guess it finally decided at submission to go back to "strike".

                                                                                    • dotancohen · 7 days ago

                                                                                      Four stroke.

                                                                                      And why not call it "Four cylinder four stroke ICE" or "Inline four cylinder four stroke ICE" or "Inline four cylinder dual overhead cam four stroke ICE"? Of course there are other forms of ICE, the description does not need to detail exactly which subtype is described.

                                                                                    • rootusrootus · 7 days ago

                                                                                      I still remember the first time I tore down a pushrod V8. I decided it had to be close to the pinnacle of elegant design. Nothing wasted, everything had a purpose, and it all came together in a perfect mechanical symphony. We have since made engines which are significantly more efficient and powerful, but all of that at the cost of elegance, slapping on overhead cams and machinery just to adjust the valve timing, etc. Fantastic technology in it's own right for certain, but feels tacked on, like an expensive optimization.

                                                                                      Reminds me that I want to get something for my kids to work on which will maybe show them some of that same elegance. I don't currently have any V8s in the garage to go tear down :)

                                                                                      • plasticeagle · 7 days ago

                                                                                        Who is this person. A beautifully written and illustrated explanation of a fascinating machine. A website filled with other explanations of other things, also wonderfully written and clearly explained.

                                                                                        An instagram filled with beautiful landscape photographs, an "X" page consisting only of links back to this blog, and a Patreon with hardly any more information that that.

                                                                                        I love this. Fantastic content. Zero ego. And if there was any AI use, it's invisible. Certainly there is none in the writing.

                                                                                        • yunnpp · 7 days ago

                                                                                          There is no AI use here. I'm somewhat offended by the suggestion even though I have no relation to the author. Bartosz has been shredding for a long time now. His javascript is also unminified and perfectly readable, making it a great reference for study despite not being advertised on his pages. The animations are all hand-made. The guy is cooking. To suggest that any of it is AI is an utter blasphemy. AI is for noobs, grifters, and low-effort content farmers and Bartosz isn't any of those things.

                                                                                          • plasticeagle · 7 days ago

                                                                                            I agree completely, and if you re-read what I wrote I didn't exactly suggest that it was used. But if he's reading this I'd hope he'd nevertheless accept my apology for even the hint of a suggestion.

                                                                                            Happy to find someone else who hates that infernal technology as much as I :)

                                                                                        • RecycledEle · 7 days ago

                                                                                          This is an excellent explanation!

                                                                                          Thank you!

                                                                                              • ggm · 7 days ago

                                                                                                Why does this show a 4 cylinder engine firing as two pairs? My ignorance is on display, surely it's more subtle and there are 4 distinct phased firings not two?

                                                                                                • edot · 7 days ago

                                                                                                  There are four distinct firings. Look for the little yellow poofs. The pistons move in pairs for balance (vibrations). Each piston is doing one of the four strokes (suck, squeeze, bang, blow is the crude way to remember) at a given time. None of them are doing the same thing at a given time.

                                                                                                  • ggm · 7 days ago

                                                                                                    Thank you. TIL!

                                                                                                • mcmoor · 7 days ago

                                                                                                  It's unclear to me, why would the compression stroke (the 2nd out of 4) happens? There's nothing pushing the piston upwards.

                                                                                                  • Gebees · 7 days ago

                                                                                                    It's being pushed up by the crankshaft which keeps moving because of the inertia of the moving engine parts, especially the flywheel. On multi-cylinder engines, other cylinders add torque at different phases of the rotation.

                                                                                                  • sscaryterry · 7 days ago

                                                                                                    This is what I think learning should look like. Interactive, high-definition, 100% functioning of something you are studying. If only we can use LLMs for good, to create stuff like this.

                                                                                                    • rclabs · 6 days ago

                                                                                                      I remember as a teenager trying to understand what made rally cars go bang-bang, by modifying the ignition timing among other things, those gases hit a hot exhaust manifold where they create a mini explosion that keeps turbo spooled.