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58 votes
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Why aren't electric forms of heating used in internal combustion engines

Because it wouldn't be very efficient. The main advantage of internal combustion engines is that the energy density of their fuels (gasoline, diesel) is very good. You can go a long way on a ...
raydowe's user avatar
  • 3,012
54 votes

Is revving the engine to redline on idle at morning bad?

If your engine even has a problem carboning up, you don't clear it at cold start. Nor do you clear it by spinning the engine to redline. "Revving" isn't meaningful to diesel engine performance the ...
Harper - Reinstate Monica's user avatar
51 votes
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What is the point of the exhaust?

Safety, comfort, noise and space are the things that come to mind. Safety Exhaust gasses are hot as hell. Hot enough that we put heat shields all over the exhaust line. In engines, we are actively ...
Becuzz's user avatar
  • 666
50 votes
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What are the benefits of a lightweight flywheel and why aren't they lightweight already?

The main advantage to a lower flywheel mass on race cars is that the reduced mass allows the engine to rev more freely. The overall weight loss to the car is really not the key thing, it's letting the ...
cdunn's user avatar
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47 votes
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Is revving the engine to redline on idle at morning bad?

Yes, this may be bad. The oil is not yet at the operating temperature, and the same is true for engine parts as well. I wouldn't redline a cold engine with cold oil. Your intention to clear carbon ...
juhist's user avatar
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46 votes
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Why is engine displacement frequently a few CCs below an exact number?

There are regional taxation and tariff issues associated with displacement Manufacturers will intentionally keep their displacement just under a limit that may increase their local/regional taxation ...
DucatiKiller's user avatar
  • 32.9k
44 votes

What is the point of the exhaust?

Well, we can have a pipe going out the front of a car as in this design here: or its heavier predecessor: Arguably, the aerodynamic properties are not optimal in both, but here is a similar approach ...
the-wabbit's user avatar
40 votes

Why are engines labeled as 2L or 3L?

When they put "3L", which stands for "3 litres", it is the approximate displacement of the engine. Displacement is the swept volume of all cylinders combined. Swept volume of the cylinder is if you ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
39 votes
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Why do manufacturers detune engines?

I'd be tempted to restate the question as "How do vehicle manufacturers decide what to tune for?" For the question as asked, there are a lot of possible reasons, and probably no way to know in a ...
dlu's user avatar
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36 votes
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Do cars consume less fuel when in Neutral?

If the car is equipped with a modern fuel injection system, it will likely use less if left in gear and allowed to run against the transmission with no throttle as modern fuel injection systems can ...
Steve Matthews's user avatar
34 votes
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We have fuel injection, why not air injection?

Simple reason: volume. @ 14.7:1 stoich, your input into the cylinder would need to be 14.7x bigger (or push that much more) through a nozzle than you would the fluid which is fuel. You state it would ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
29 votes

What are the benefits of a lightweight flywheel and why aren't they lightweight already?

cdunn's answer is spot on. To add a bit (especially for cars), in a race car you often want to be dropping from something like 7000 rpm to maybe 5500 rpm (or an even higher band, depending on the ...
J...'s user avatar
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27 votes

Why do we mostly use fossil fuel instead of a more reliable and larger sum fuel?

What you really want to look into is Energy Density. So called "Fossil Fuels" have a very high energy density, which is very important for a vehicle fuel since you have to load it and carry it around ...
JPhi1618's user avatar
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26 votes

We have fuel injection, why not air injection?

You have almost but not quite described the operation of either a Turbocharger or Supercharger. The idea of the air under pressure being injected from a common fuel rail would likely not work as it ...
Steve Matthews's user avatar
24 votes
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What is crankshaft grinding and why is it done?

Grinding a crankshaft is a process of removing material from the journals in an effort to refurbish and reuse an expensive, yet vital component of an engine. It is usually done during the process of ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
23 votes

Why do we mostly use fossil fuel instead of a more reliable and larger sum fuel?

While energy density is a rather nice property of gasoline and diesel, it's not the primary driver of their use. Instead, the primary driver is a rather practical one: they're cheaper. On the ...
R.M.'s user avatar
  • 331
20 votes

Will higher octane fuel improve towing power?

That is a great question. I believe the true answer here is "it depends". Like so many other things you can do with your vehicle, if your vehicle cannot use the higher octane fuel, it won't benefit ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
20 votes

Why do manufacturers detune engines?

Great answers, but there is also one more reason for manufacturers to detune engines: can the vehicle take the torque? A van isn't built like a sedan, and it's frame is built to handle weight (...
tlhIngan's user avatar
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19 votes
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Does stopping the engine while it is still moving/turning damage my car?

What will happen is dependent on the configuration of your vehicle. Automatic transmission - Due to the torque converter, the engine will just stop. This is bad for the transmission, because the ...
rpmerf's user avatar
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19 votes
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How do you get more horsepower out of a 1979 Mazda RX7?

I agree with your praise for this car, I had one back in the day and I have never loved a car as much since. To get more from this Wankel powered beauty, it's all about two things: Getting it to ...
cdunn's user avatar
  • 9,296
18 votes
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How do manufacturers detune engines?

There are several different ways a manufacturer can detune an engine: Mechanically: Cam profile can be changed. For instance, reducing the lift from one cam to another will not allow as much air to ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
18 votes

Why aren't electric forms of heating used in internal combustion engines

Although other answers provide good answers related to energy losses, there's an additional thing to consider. How on earth are you planning to heat the air in a tiny cylinder at many kilowatts? This ...
juhist's user avatar
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18 votes
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Engine comparison: How can a smaller/more efficient engine excel over its "bigger sibling"?

How can the smaller, more "efficient" (for a lack of a better word) option outshine the bigger, "hungrier" sibling in basically every category? In a word: Turbocharging Same ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
16 votes
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Why does GM still insist on push rod engines?

Car and Driver asked this very question to GM's Sam Winegarden, chief engineer for small-block V8's. The advantages of a push-rod valvetrain mentioned in the article can be summarized as follows: It ...
Zaid's user avatar
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16 votes
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Does a carburettor engine apply fuel at high speeds when the pedal is no longer depressed?

At a base level, carburetors meter the amount of fuel they let into the engine by the amount of air that is moving through them. Vacuum is created by the piston moving in the engine and creating an ...
Justin Lloyd's user avatar
16 votes
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What does a liter class engine mean?

The 1000cc is the displacement of the engine. That means the total volume of all combustion chambers which is the area of all the cylinders times the length of the piston travel in the cylinder. Here ...
cdunn's user avatar
  • 9,296
16 votes
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What's gonna happen if I disconnect 'single piston'

As you saw with your test, it is possible to disconnect the ignition on two pistons and still have the engine run. The vibrations have nothing to do with engine knock or detonation though. The reason ...
Zaid's user avatar
  • 39.2k
16 votes

We have fuel injection, why not air injection?

In many ways, you're describing a 5 stroke engine 5 Stroke engines are using a piston to provide a secondary means of compression for the AFR. Although, not injecting air they are compressing the ...
DucatiKiller's user avatar
  • 32.9k
16 votes
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What are the differences between a dual mass flywheel and a standard flywheel?

A dual mass flywheel (or DMF) is a flywheel that is split into two halves (hence the name...), with a spring or springs between them to dampen out sudden changes in torque and rotation speed, and thus ...
Nick C's user avatar
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16 votes
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Stainless Steel Fasteners

Stainless and aluminum are pretty far apart in the galvanic series of metals with aluminum at the anodic (corroded) end. This means that in the presence of an electrolyte the stainless bolt will be ...
dlu's user avatar
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