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rootusrootus 31 minutes 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 :)
tmh88j 3 minutes 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.
Not to mention how compact and lightweight they can be for their displacement. Here's a 6.2L V8 LS3 found in mid-late 2000's GM cars like the Corvette and Camaro beside a Mazda 1.8L 4 cylinder from a Miata. https://i0.wp.com/engineswapdepot.com/wp-content/uploads/201...
londons_explore 4 hours 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 3 hours 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.
bob1029 5 hours 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.
LeifCarrotson 3 hours 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 2 hours 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?
Toutouxc 2 hours 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 2 hours 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.
vel0city 2 hours 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 4 hours 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 4 hours ago [-]
Lifters also often drain while sitting and valve lash is greater at start until they get slapped a few times
bluedino 2 hours ago [-]
That's the timing chain tensioners losing oil pressure.
fauria 5 hours 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 4 hours 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 3 hours 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.
cagey 2 hours 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 1 minutes 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).
arlattimore 3 hours 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 ;-)
3 hours ago [-]
WalterBright 4 hours ago [-]
That's the point of all uses of oil, other than rust prevention.
calmbonsai 4 hours ago [-]
Some engines are also substantially cooled by oil, but those are either older designs (think “air-cooled” Porche) or industrial prime-movers.
xenadu02 3 hours 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 2 hours 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.
WalterBright 3 hours ago [-]
You are quite right, the oil also serves to transport the heat away.
nablaone 3 hours ago [-]
It's a solvent also.
nickvec 2 hours 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.
CraigJPerry 5 hours 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.
felooboolooomba 6 hours ago [-]
Pro tip: Show a message if WebGL is disabled instead of a blank space.
gwbas1c 1 hours 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 49 minutes ago [-]
When I was a kid we had a visible V8 model that let you see quite a bit!
vjvjvjvjghv 55 minutes ago [-]
This should probably be called “Four Strike Engine”. There are other types of ICE that work differently.
2 hours ago [-]
drayfield 2 hours ago [-]
Always good to revisit his older work, though I admit I did get excited that it was a new post!
MarkusWandel 4 hours 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.
rootusrootus 37 minutes 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.
Toutouxc 4 hours 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 3 hours 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 2 hours ago [-]
You’re replying to a post that says that “explosion” doesn’t imply “detonation”.
raffael_de 59 minutes ago [-]
and that is not strictly correct. it's called combustion engine and not explosion engine for a reason.
stouset 4 hours ago [-]
You don’t want detonation, but you do want deflagration.
relaxing 4 hours ago [-]
Very interesting technology. Would be exciting to see a hardware startup build a product around this.
darkteflon 2 hours 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.
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?
reorder9695 1 hours 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.
aw1621107 2 hours 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!
jabl 1 hours 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.
pjc50 2 hours ago [-]
This is why the starter motor spins the shaft in a known direction.
mberning 4 hours 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.
mrhottakes 6 hours ago [-]
Excellent animations.
misiek08 5 hours 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 4 hours 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.
4 hours ago [-]
lostlogin 4 hours ago [-]
One of the rare situations where someone wants a bit of retard?
HoldOnAMinute 3 hours ago [-]
That is often more advisable as opposed to doing it fully.
zuzululu 5 hours ago [-]
[flagged]
throw567643u8 5 hours ago [-]
Probably better for the environment too.
Sohcahtoa82 46 minutes ago [-]
The carbon footprint of producing an EV is higher than an ICE. Nobody disputes that.
But the lower carbon footprint of operating the an EV makes the EV have a lower footprint over the life of the vehicle. This is true even if your electricity comes purely from coal, as a coal power plant gets an economy of scale that an ICE doesn't achieve. If your power comes from a renewable source, then the trade-off happens even sooner.
rootusrootus 5 hours ago [-]
No
jtwaleson 2 hours 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.
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 :)
Not to mention how compact and lightweight they can be for their displacement. Here's a 6.2L V8 LS3 found in mid-late 2000's GM cars like the Corvette and Camaro beside a Mazda 1.8L 4 cylinder from a Miata. https://i0.wp.com/engineswapdepot.com/wp-content/uploads/201...
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.
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.
It's the first few seconds after an engine has been off for hours (or worse, for potentially years) that are the problem.
Hearing regular start-stop on intersection gives me sorry feeling for the engine.
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.
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.
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.
Isn't that 0.250 which would be 250 thousandths?
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.
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.
These animations are so much better than what I had!
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.
https://news.ycombinator.com/item?id=26991300
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?
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.
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!
But the lower carbon footprint of operating the an EV makes the EV have a lower footprint over the life of the vehicle. This is true even if your electricity comes purely from coal, as a coal power plant gets an economy of scale that an ICE doesn't achieve. If your power comes from a renewable source, then the trade-off happens even sooner.