A car engine basically has thousands of mini explosions happening inside of it, is has parts moving very fast and generating tons of heat, and experiences extreme temperature fluctuations on a daily basis. Yet it is the part that usually dies last in a car.
How do they make them last so long and why are we unable to make other parts of the car as long lasting, such as tires and brakes?
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Tires and brakes are designed to wear for them to work properly. An engine uses all sorts of tricks to keep it from wearing. Engine oil is probably the biggest but there are things like advanced cylinder liners and anti wear coatings to reduce wear. Engine wear is also a big problem with emission and warranties so extra R&D money goes into it.
Engines have oil flowing through them, lubricating and cooling the components. The oil gets used up and the debris from inside the engine gets stuck in the oil filter which also needs to be changed.
The fact that they are still alive is more down to simply physics: as long as you can spark fuel, the engine will run. Although the engine might not “die” until later, the components definitely wear down over time and old engines are significantly less efficient than they were when they were new.
Brakes work by turning motion into heat through friction and they lose material in the process. Tires work by pressing soft rubber into hard cement and lose material that way.
It’s not that they can’t make brakes or tires that last as long as a car, it’s that the most size-effective and cost-effective brakes and tires work through processes in which material is lost. You could potentially make tires out of titanium and brakes out of teflon but they wouldn’t work well at all.
You can just imagine the stress tires and brakes go through as you drive. Quick acceleration, sudden stops (maybe with tire marks on the pavement)?
Engines have stress, but it’s not close to the stress of breaking and actually making contact with the road.
If you’re thinking of the pistons, the things going up and down, they are machined to perfection sliding up and down an oiled chamber with relatively little stress.
Answer: Not all explosions are made the same.
Car motors are made of very strong steel, steel that can withstand temperatures far higher than that created by the cylindar combustion.
Combustion motors have also had over 150 years of engineering to root out and overcome production and quality issues. Throw two world wars and any number of regional wars in there and you’ve got a century or more of accellerated engineering to produce the most well designed devices on the planet.
So why is the motor always the last part to die? Becauze it is the most important part of an automobile. The body, the cabin, the seats and accessories are far less important, so are sibject to far lower standards of quality, and are far cheaper to replace. Vehicle manufacturers do all they can to keep costs low to maximise profits and sometimes keep vehicles affordable, so many parts have their quality reduced to the bare minimum, however the motor rarely skirts this line. **Some** car companies cut costs on some parts of the motor, but at that point, they’ve severely diminished the quality of the rest of the vehicle too.
Many parts of a car are also engineered to **intentionally** fail, too, for safety. The classic argument is that car bodies are made of rubbish materials that break and fall apart all the time. Sometimes this isn’t intentional, but almost every car body is deisgned to follow strict safety standards set by the largest markets in the world, so body parts are designed to fail in a way that absorbs impact damage and transfers forces away from the driver/passengers. This often means that they’re flimsy and less durable, but I know for sure what I would want in a car accident.
As much as I love classic cars, they’re death traps and should be treated like so. Sure, they were far more robust, but fatalities were way higher in thrm than before.
As for less important stuff like cheap and nasty trimming, as I said, thats cost cutting because those particular parts aren’t vital to the vehicle’s function like a motor is.
I mean – some of the best engineers of the past 120ish years have all worked on the problems engines have had. So many problems have been solved – and more will be.
The current combustion engine is a marvel of modern engineering. Every single part has been optimized and re-optimized, from what alloys are used for each part to efficiency of 4 large versus 6 smaller cylinders.
I know this and I am not even an engineer – I just watch obscure YT videos.
Really it boils down to incredible advances over the last ~50 years in:
* Oil quality
* Metallurgy
* Machining
* Control
Oil is just… oil to most people. Buy the cheapest stuff, match the numbers up to the cap, and let ‘er rip. But there are *so* many things that make oil good or bad at its job. The ability to withstand temperature. The ability to flow when cold. The ability to absorb pollutants and contaminants and still function. The ability to not break down over time or mileage. The ability to resist shearing forces at high RPM.
In the past oil was basically just crude pulled out of the ground, plus some chemicals and additives. Nowadays oil is incredibly highly engineered, to the point that Ye Olde Castrol GTX today is of higher quality than almost any oil in the 70s. We always hear “change your oil at 3,000 miles”, because when that phrase was coined that’s all the longer it lasted. It would start to break down and cause more problems than it started. Now, changing it at anything less than 5,000 is just throwing your money away; most oils last 7000-10000 miles.
Metallurgy is one of the lesser talked-about subjects, but it is also hugely important. In the past, cast-iron blocks and heads were the norm. Iron is a fine material, but in the past it was prone to irregular heat expansion and weak spots that couldn’t necessarily be detected by normal factory processes. We still use iron blocks, but our understanding of the casting process has gotten much better and we can better control these variables, resulting in a stronger block.
We’ve also generally gone to aluminum blocks and heads (in passenger vehicles, in any case), which is lighter but weaker; working with specific alloys over the years has resulted in a remarkably strong, light block.
Machining is probably one of the biggest ones. The advent of CNC machining allowed us to take parts that used to have tolerances of .01″ to .003″. It’s an order of magnitude closer together in places like rod ends, crankshafts, and other moving/rotating parts. The less you allow moving parts to move against each other (like a rod bearing against a crankshaft), the longer the engine will last. This also applies to cylinder clearance and other areas.
The last is control. In the past, controlling internal engine operation consisted almost entirely of rotating the distributor, and changing the jets in your carbs. I’m sure you’ve heard the old warning against letting your engine idle for long periods because it’ll cause build-up in your valves. It’s absolute bupkus now.
The computer (ECU) controls tens of *thousands* of parameters, several hundred times a second. It can control spark timing individually, it can control fuel injector flow-both pulse width and strength, it can control coolant flow throughout the engine, it can vary camshaft timing on the fly, and so much more. Every single cylinder, every single revolution, is precisely controlled to deliver exactly the power required – and most importantly, the ECU *will not* allow the engine to get to a place where it will be damaged. Many ECUs, if the temperature gets too high, will deactivate cylinders to manage temps, and heavily restrict the power (and therefore heat) the engine can generate. Really, just enough to limp home – thus the name.
So yeah that’s the gist of it. We’ve engineered the shit out of them, systematically identifying weaknesses and failure points and solving (or avoiding them). It wasn’t any one big innovation that did it – just years and years of continuous process improvement.
There are plenty of answers that address the question in the post title, but I wanted to address the use of the word “explosion”. It’s better to call what happens in an engine as a fast burn. The pistons are pushed down by the expanding flame front and not a shockwave. So the force of the burn, while definitely frontloaded, does get spread out for the duration of the stroke. This helps with the longevity of the moving components.
The line between a fast burn and an explosion is actually kinda vague so youre not really wrong to use the word, but when people think of an explosion, they tend to think of something like a bomb that causes damage by producing a shockwave, and that’s not what happens in an engine. Or at least, it’s not supposed to.
The simple answer is “built to take it”.
An engine isn’t much different to anything else, where as long as it is allowed to work within what the materials it’s made of can take, it’ll be (mostly) fine. Take something as simple as a chair you own. You can sit on it, stand on it, put things on it and do this millions of times and it’ll be fine. Have an elephant try and sit on it and it breaks.
All materials have yield points of different sorts. It’s why some metals can be shot with bullets and it doesn’t even leave a mark, while others the bullet goes through as if it wasn’t even there. Or why a broom stick works well for cleaning floors with a broom, but makes a terrible shovel handle.
This is basically what engineering is about. Know the limits of a material and using the correct material for the job, and trying to use just enough of it to make it work.
The more complex answer is when you start talking about how it works, as others have pointed out with oils for protection, cooling systems etc.
An engine is much more difficult to take out of a car and take apart and fix broken parts on the inside. Conversely, tires and brakes are relatively easy to remove and replace, hence money and tech is used to make production of these parts cheaper, therefore cheaper for a consumer to replace every year or 2 instead of companies spending money and technology to try and make them last longer. Because engines are much harder to repair/replace, manufacturers have spent time and tech on making them last longer such as the discovery and widespread use of synthetic oils in modern engines, using multi grade oils, using baffled oil pans, more efficient/effective oil filters, thermostats to optimise engine temperature, using cylinder sleeves, cylinder deactivation, variable valve timing, air fuel sensors and ecus to optimise combustion (as opposed to old fashion carbs)
The reason why engines can outlast tires and brakes many times over is simple. Almost everything in an engine is lubricated to reduce friction. Brakes and tires require friction to keep you in control and help you stop.
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