Internal Combustion Engine (2021)
ciechanow.ski
ciechanow.ski
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.
Given to how precise these need to be these days, I would've guessed they would've switched to electronically actuated valves.
And here's an example of someone that retrofitted a Miata to use a similar [air-actuated valve system](https://youtu.be/E9KJ_f7REGw)
Kinda, it's all continuous variable valve lift now:
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.
Modern cars still release as much CO2 as older cars… which is still incompatible with human respiration.
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.
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.
Unfortunately they also reduce the reliability.
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.
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.
Hearing regular start-stop on intersection gives me sorry feeling for the engine.
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.
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.
This paper seems to say that generally they aren’t a problem. I’ve only seen unsubstantiated claims that they are one.
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 :)
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.
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.
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?
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!
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.
https://github.com/Engine-Simulator/engine-sim-community-edi...
These animations are so much better than what I had!
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.
Happy to find someone else who hates that infernal technology as much as I :)
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.
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.
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.
...something which has been the case for at least 80 years:
https://news.ycombinator.com/item?id=15397926 (the article in that link has now moved to https://www.web.imperialclub.info/Repair/Lit/Master/003/inde... )
Thank you!