How a Car Engine Works

Get a car (mine arrived as a pile of junk on a flatbed), some tools, and start turning wrenches. It's not that hard, and I (and a couple friends) had a heluva good time. I suspect an account of that helped me get into engineering college.

My only regret is I ran across a '68 Chevy SS for $600 that I passed on.

I learned entirely by wrenching on my own car. Engine internals and transmissions are hard simply because you often need specialized tools. But there are plenty of parts you can fix yourself with only simple tools.

The main challenge now is that newer cars have a lot more complex components. Back in the '70s you could completely disassemble and refurbish a carburator. Fuel injection systems are a lot more complex. However, a lot of the systems on newer cars are still pretty basic.

One of the benefits of knowing how to work on cars is saving money. I fixed my wifes car (emissions failure) with a $12 part from ebay when a garage wanted $150 just to diagnose. And if you do have a garage work on your car, explaining what's wrong in way that makes you sound knowledgeable goes a long way to prevent being ripped off.

All you need is the ability to read, the desire to learn, the courage to get your hands dirty and not be afraid of breaking things, and some mechanical aptitude. And a little money to spend at Harbor Freight for some tools.

I have removed every rolling part of my ATV. It's quite strange to go 65MPH knowing that you put all the parts together... I am still alive so far, ha. :)

Are you trying to teach theory or real-world mechanics?

No engine in any car in the world has electrically actuated valves, except for a handful of prototype test mules such as one by Koenigsegg in Sweden. Everyone's still using "mechanical contraptions with cams", so it's pretty important to teach that, because any engine you look at will be made that way, and the design of the camshafts (and any support components, such as a variable-vale-timing mechanism) is critical to the engine performance.

>The benefit of the computer controlled system is of course you have more flexibility and have the ability to integrate data from various sensors to achieve some kind of "optimal" injection volume.

Yeah, that's great, but you might as well be talking about Moon colonies. It's sci-fi at this point. It may come in the near future, it may not; we might end up just skipping it in favor of EVs.

However, distributors by now are truly obsolete. I don't think any cars have them any more; they've all gone to coil-on-plug systems. Distributors aren't quite that old; there were still cars being made with them about 15 years ago, but those were the last holdouts. So I don't see the point in showing the distributor as is done on this site: it's simpler and easier to just show the spark plugs by themselves firing at the appropriate time, perhaps with some wires shown connected to the ECU.

It's a bit odd too, because aside from the distributor, this guy's illustrations seem to show a fairly modern engine, though he's omitted the variable-valve timing system that most modern cars have now. Notice that the fuel injector is squirting fuel directly into the cylinder: that's called "GDI", or gasoline direct injection. It's become pretty common these days (I think some Kias and Hyundais have been holding out on it), but go back just 5 years and not that many cars had it, and go back 10 years and it was pretty much none. Of course, like distributorless ignition, GDI is simpler in concept, though technically more difficult to accomplish reliably (the fuel pressure is much higher for one thing), as the old way had injectors shooting fuel into the intake plenum before it got sucked into the engine.

My only other complaint about this site is that they left out the V-12 configuration. There's still plenty of Ferraris that have those.

"I’m obsessed with solid, hiqh-quality research and design presentation. If you’re gonna do something you might as well do it RIGHT. Right?"

This isn't as bad as you might think, because of the nature of springs. When the valve closes again, most of the energy spent compressing the spring is returned to the engine!

[0] https://en.wikipedia.org/wiki/Desmodromic_valve

The alternative is to just not design for high RPM; the most efficient internal combustion engines are huge low-speed two-stroke diesels used for ships and stationary generators.

Yes, reliability is probably the issue. However, the same could have been said about EFI back in the day.

Full camless engine design is something we may only see in high-end racing and supercar applications for while yet.

I was referring to full-on solenoid control of valves without needing cams at all.

> Back to four stroke engines: Momentum and the firing of other pistons keeps the whole thing cycling back around

The firing of other pistons helps, but really, momentum alone is sufficient. There are tons of single-cylinder, 4 stroke motorcycle, scooter, and off-highway engines out there.

The big advantage is center of gravity: their shape lets them sit basically flat, near the ground, and since engines are the heaviest part of a car, this gives the car a lower center of gravity, which is good for handling.

The main disadvantage is mechanical complexity: instead of all the cylinders lined up in a row, with the crankshaft on one side and the valves and dual cams on the other, you have two banks of pistons, each with their own camshafts. So now instead of two camshafts, two camshaft gears, and one timing belt/chain, you need double all those. This of course increases cost too.

Flat-fours also tend to have rather distinctive exhaust notes, which not everyone finds pleasing.

Another notable place flat-4 engines are used is in small aircraft. Lycoming and Continental engines for small (e.g. Cessna) airplanes and helicopters are all flat-4.