How A Gasoline Car Engine Works
September 5, 2013 5:44 AM   Subscribe

Given the number of automotive related questions on Ask MeFi, this animated infographic should be useful for most of us. And even if you are a gear head you'll probably think it's cool. (It takes a few seconds to load - give it time.)
posted by COD (31 comments total) 48 users marked this as a favorite

 
Overall, excellent presentation, and I like how he hit about lubrication and cooling being critical.

I think it's funny that they have a modern fuel injection system depicted, as well as a dual overhead cam, but then have a distributor handling the spark. Modern engines use electronics to fire the cylinders, either via a central module, or direct ignition, where there's a high voltage coil on the plug and the single to fire is a low voltage pulse, again from a central electronic module.

It just stuck how how modern the engine presented was...except for that. Getting rid of the distributor is just one way that modern engines have become so much more reliable, in terms of both total lifetime and time between maintenance.
posted by eriko at 5:59 AM on September 5, 2013 [2 favorites]


It is a nice infographic; it simplifies some things (the exhaust valves stay don't actually close before the intake valves open; both sets of valves are open for a small overlapping period), but it really shows the main systems well and how they work together.
posted by Monday, stony Monday at 6:00 AM on September 5, 2013


Related: Animated Engines.
posted by entropone at 6:02 AM on September 5, 2013 [3 favorites]


As someone who, a few years ago, knew nil about cars and now can tear down and rebuild my Subaru's engine, this is a really great introduction. As always, though, the best teacher remains getting in there and breaking stuff, and learning things like the importance of always replacing O-rings, because you didn't when you took out fuel injectors and put a minuscule tear in an O-ring and now you're being sprayed with gas after putting your fuel injectors back in and your friend just left because you were "just about done" and now you have no safe, working car and have to walk to the auto-parts store and buy a big box of O-rings to replace that one.


Always replace your O-rings.
posted by InsanePenguin at 6:02 AM on September 5, 2013 [2 favorites]


Seems to have stalled.
posted by Kadin2048 at 6:10 AM on September 5, 2013


Wanna nip out and push, see if it bump starts?
posted by titus-g at 6:15 AM on September 5, 2013 [3 favorites]


I have a nit to pick about the hybrid engine. It's not that the engines in hybrids are more efficient, it's that smaller engines get used for efficiently.

IC engines are generally at their most fuel efficient at wide open throttle and low RPM. A big V8 would be producing WAY more power than you need to maintain a speed of 65mph that way so the throttle is partly closed most of the time reducing efficiency. A small four cylinder, however, will need a wide open throttle to produce the same amount of power (assuming both cars have the same weight and aerodynamics) at the same speed so it uses the fuel more efficiently. Now the problem is that it takes forever to get up to that speed so the electric motors are their to give it a boost.

It's not that the smaller engine is necessarily converts more of the chemical energy in the fuel into useful work but that the way it gets used allows it to work in it's most efficient range more often.

Also they weigh less and the engines are often tuned/designed with different goals and a host of other differences.
posted by VTX at 6:21 AM on September 5, 2013 [1 favorite]


They don't teach Auto Mechanics in high school anymore, do they? There were film versions of this kind of thing in all those classes 50 years ago, and I bet there are hundreds of others on the Web today. Here's a NASA one. Maybe the one in this post is the best one, I don't know.
posted by Kirth Gerson at 6:27 AM on September 5, 2013


Here's the Prius transmission interactive model. (scroll down halfway.) The planetary gear set itself is small enough to hold in one hand.

There's two electric motor-generators. (They can either generate electricity, or consume it as a motor) And the Internal Combustion Engine (ICE).

You can play with the sliders and see that low road speeds can have the engine on or off. There's no starter on the engine; it uses one of the motors to spin up, then injects fuel when up to speed, so the restart is very smooth.

The ICE can stay at it's most efficient rpms since the electric motors can change rpms to compensate. Even though there are power losses when the generators create and consume electricity, it still gets better gas mileage than a regular engine would.
posted by jjj606 at 6:34 AM on September 5, 2013 [2 favorites]


Can someone explain the pros/cons of different levels of compression and how it applies to various applications?
posted by mullacc at 6:35 AM on September 5, 2013


This is really cool!
I would have liked to have had a pause/forward/back control so I can better review each of the steps, but i guess that'll come in HTML6
posted by bitteroldman at 6:41 AM on September 5, 2013


Needs a rotary engine model.
posted by vuron at 6:46 AM on September 5, 2013


Borked :(
posted by Mooseli at 6:52 AM on September 5, 2013


Just about the time I started making enough money to pay someone else to work on my car, I was also, not coincidentally, able to afford cars that I could no longer work on...in fact, I just figured that basically nobody worked on their own cars anymore, since they are now--or so they seem to me--utterly inscrutable, and there's no damn room in the engine compartment. (shakes fist)

Oh and...are twin cams fairly standard now?
posted by Fists O'Fury at 6:52 AM on September 5, 2013


eriko: "It just stuck how how modern the engine presented was...except for that."

They even had direct injection!...but distributors.
posted by notsnot at 6:56 AM on September 5, 2013


They even had direct injection!...but distributors.

Might have just been some artistic license. With the mechanical distributor it's more visual interesting then a black box, and you can tell what it does.
posted by papercrane at 7:05 AM on September 5, 2013 [1 favorite]


Can someone explain the pros/cons of different levels of compression and how it applies to various applications?

Higher compression means more complete combustion, more power and more efficiency. So engines have as a high a compression ratio as they can get away with.

The more you compress the air/fuel mix the more likely it is that it will reach it's combustion temperature and spontaneously ignite. Since this might happen at the wrong time (like too far before the cylinder reaches the top of the compression cycle or while one of the valves are still open) it's bad.

The compression ratio you can reach is constrained by the fuel you intend the engine to use (87 octane, 81 octane, etc.), the design, and the precision of the manufacturing. IIRC, things like the geometry of the combustion chamber and some fancy tricks with the fuel injectors can allow for higher compression ratios. But these things increase costs and complexity

So generally, higher compression is higher performance and higher efficiency but also higher cost and more likely to break.

Turbo-charged and super-charged engines typically have lower compression ratios because the to turbo/super-charger has already compressed the air going into the cylinder. The pressure of the air/fuel mixture ends up being the same when it ignites but the ratio of the volume of the chamber with the piston at the bottom vs. the top is lower.

Diesel engines typically have higher compression ratios because they use a different type of fuel and they don't use a spark to ignite the air/fuel mixture. They compress it and heat it until it spontaneously ignites but it's designed in such a way that it will happen at the right time.
posted by VTX at 7:11 AM on September 5, 2013 [1 favorite]


I just figured that basically nobody worked on their own cars anymore, since they are now--or so they seem to me--utterly inscrutable, and there's no damn room in the engine compartment. (shakes fist)

I was actually surprised to learn that in many newer cars I thought overly complicated, despite a crammed engine compartment you don't have a lack of access to the important bits, you have different access - a lot of cars have you get at many of the important bits through the wheel well, not the hood, and a lot of the time you'll have to take sizable parts out of the engine compartment to get at what you want but it's made up for by those parts being much much easier to take off and put back on than they used to be. My beat up 2002 Saturn has you remove the wheel and the plastic flashing inside the wheel well and lower the engine cradle for about half of the important repairs. Plus some stuff is apparently vastly easier to get at nowadays than it used to be, when I told my dad I (with minimal auto repair skill) replaced the valve body on my transmission alone in the driveway he was dumbstruck, until I told him on my car it was just a matter of taking out the battery tray and there it was. Apparently that is orders of magnitude less effort than it used to be.
posted by jason_steakums at 7:33 AM on September 5, 2013 [1 favorite]


VTX: I have a nit to pick about the hybrid engine. It's not that the engines in hybrids are more efficient, it's that smaller engines get used for efficiently.
Perhaps you would be interested in learning about the Atkinson cycle, used in the Prius and many other hybrids.
posted by Western Infidels at 8:00 AM on September 5, 2013 [2 favorites]


No...no...now you've flooded it.
posted by TheWhiteSkull at 8:15 AM on September 5, 2013


I also recommend this video, an animation of how the parts of a modern engine go together.
posted by Multicellular Exothermic at 9:34 AM on September 5, 2013


"No...no...now you've flooded it."

How can you tell?

...well, there's gas shooting over your left shoulder.
posted by hearthpig at 9:43 AM on September 5, 2013


This was really cool! Now, do they have one for transmissions?
posted by ogooglebar at 9:57 AM on September 5, 2013


"...well, there's gas shooting over your left shoulder."

No, it always does that.
posted by Mitheral at 10:02 AM on September 5, 2013 [2 favorites]


Apparently that is orders of magnitude less effort than it used to be.

How cars are repaired HAS changed drastically. In the olden days cars were built to be serviced and individual parts of the mechanisms were designed/built in such a way that they could be accessed (eventually), repaired, and then reused, several times for some items.

Now cars are built with 'assemblies' that are just replaced in whole when some small component in the assembly fails.

All these assemblies are the big reason cars are more reliable now also. instead of a bunch of parts assembled on an assembly line with large tolerances and varying skill levels of workers, each assembly is built in a dedicated factory with much tighter tolerances and a more highly skilled workforce (with a lot of reliance on robots/waldos) and then the whole shebang is but together at the main factory.

The original River Rouge plant Henry Ford built started with a steel foundry and built the cars from raw materials. Modern cars are usually assembled with sub-assemblies from all over the world, even if the raw materials pretty much come from the country where the final assembly is done (which is the case for a LOT of the cars 'made' in the USA).


There are several good examples of this-

Ball joints-(a small part of the suspension that allows it to move with the angle of the tire to the ground changing) used to be fitted with grease 'zerks' that allowed you to regrease them every x number of miles and then you could take apart the suspension and replaced just the ball joint when you either forgot to grease it or it just wore out. Now that same joint (pretty much identical in location and function) is a 'lifetime' item that you CAN'T regrease and to replace it when it wears out you have to replace the whole control arm (a much larger part of the whole suspension). The new way is better in that you only have to replace the ball joint/control arm (most modern cars go to the junkyard with good ball joints) much less frequently than you would regrease and eventually replace just the ball joint but when you do have to do it it is much more expensive.

Alternators-used to be the voltage regulator was separate from the alternator but now they are all one unit and usually only repairable at a large factory with special equipment. This is why there is a 'core' charge on a lot of parts now that you pay if you don't give the parts store the bad item.

Constant Velocity (CV) joints-what used to be called driveshafts and Universal (U) joints. It amounts to about the same thing as the Ball joint paragraph above.

and it goes on and on. Modern cars are much easier to replace broken assemblies on but can be harder to diagnose and parts tend to be much more expensive, but the amount of time needed to perform the repair is much faster once the proper diagnosis is made.
posted by bartonlong at 11:00 AM on September 5, 2013 [3 favorites]


You people with your pitiful camshafts need to embrace the glorious Wankel future.
posted by ckape at 11:31 AM on September 5, 2013


do they have one for transmissions?

HowStuffWorks has gone downhill (IMO) over the years, but one of the first really good articles I remember reading there was How Manual Transmissions Work. It's still a pretty good primer. Page 4 has an animation of a fairly-realistic 4 speed transmission with reverse.

Also, while we're on the topic of alternative-cycle internal combustion engines (e.g. the Atkinson Cycle, Miller Cycle, etc.), I've always been a fan of six-stroke engines. What Wikipedia refers to as the "Crower Six-Stroke" is an idea that I've always found cool (and I know for a fact that the idea was around a long time before 2006, when some guy got a patent on some aspect of it) since it's a sort of hybrid internal combustion + steam engine. Basically you eliminate the normal external cooling system in favor of using waste heat in the cylinder itself to boil water and product an extra power stroke.
posted by Kadin2048 at 12:29 PM on September 5, 2013 [1 favorite]


No love for the good old push rod engine? Also, my timing chain laughs at your puny timing belt.

Seriously, though, can anyone expand on how oil pumps work? Why have I never heard of one failing and needing replacement?
posted by InsertNiftyNameHere at 6:11 PM on September 5, 2013


Fun visual.

Modern cars are usually assembled with sub-assemblies from all over the world, even if the raw materials pretty much come from the country where the final assembly is done (which is the case for a LOT of the cars 'made' in the USA.)

Which is why I always LOL and snort when someone tells me how they always and only 'buy American.'
posted by BlueHorse at 6:45 PM on September 5, 2013


Seriously, though, can anyone expand on how oil pumps work? Why have I never heard of one failing and needing replacement?

That's due to several factors.They do fail from time to time, but in general it's recognized that if an oil pump fails the engine is going to be ruined a matter of minutes, and so they are designed to be simple and robust.
posted by Rhomboid at 7:03 PM on September 5, 2013 [4 favorites]


Which is why I always LOL and snort when someone tells me how they always and only 'buy American.'

The rules concerning "Made in the USA" products (PDF) are not trivial, and attempt to establish that the majority of the value-add inherent in the product's manufacture occurred in the US. That's nothing to sniff at.

However, people who are "buying American" based simply on brands -- Ford vs. Toyota or Magnavox vs. LG -- are certainly idiots.
posted by Kadin2048 at 10:19 AM on September 6, 2013


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