Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.
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Engine oil does much more for an engine than lubricate. It provides cooling, cleaning, and a bunch of other chores. You already know engine function is degraded when you run out of oil. Let's see if we can run it down to make more sense for you how it happens. Let's say, for lack of argument, your engine is running with very little to no oil. The engine ...


58

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 relatively small, light tank. The drawback of them is that they aren't very efficient. Most of the energy in the fuel is lost to friction and heat, and only a very ...


54

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 way it is to sport gas engines and it doesn't help remove carbon. It's just a rationalization. To remove carbon, you want the engine working hard for 10-20 ...


52

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 trying to remove heat. Adding more from the exhaust goes completely against that and would increase overheating. Also, would you want a hot exhaust pipe near ...


50

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 engine vary RPM really quickly. Being able to change RPM quickly can mean faster shifts, getting to a power band more quickly, etc, etc. It also makes the ...


47

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 deposits is justified. But why don't you do this during a drive? That way, the engine and oil have had a chance to heat up to operating temperature. By the way, ...


46

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 where aerodynamics have been considered for sure: other designs (like trucks) do account for aerodynamics by putting the exhaust tubing behind the relevant ...


46

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 as well import/export tariff regulations in accordance with trade agreements, etc. It's easy enough to make an engine exactly 3 Liters. Math is exact if you ...


42

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 look at the cylinder bore (area of the bore) multiplied by the stroke (distance the piston travels from top to bottom of the cylinder) multiplied by the number of ...


38

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 specific case unless somebody involved speaks up, but in general: To match the engine to a specific use case (as you suggested here). To find a balance between ...


37

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 and do shut down the injectors completely thus use no fuel whatsoever. If the engine is at idle in neutral, the ECU will have to use a small amount of fuel to ...


34

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 have fewer mechanical parts, but is that true? You'd have to furnish a mechanical method to create the high pressure air as well as introduce it into the ...


32

It's just math, and is because horsepower is defined (in terms of torque) as 550 ft·lbs per second. A single HP is 33,000 pounds moved 1 foot in 1 minute (as per James Watt, that's the average of what an actual horse can do). An RPM of an engine moving the same 1 lb would travel ~6.283ft (the circumference of a 1 foot radius circle). 33,000 / 6.283 = ...


31

It isn't something restricted to old vehicles; my Lumina has fans like this, though not as irregular as the picture shown in the question. As far as I can recall, the chief reason cited for this by the manufacturer is noise reduction. You'll notice the additional weight on some of the blades to ensure that rotational balance is maintained despite the ...


30

Two of the useful features of this setup (I have no evidence to prove they were the design reasons) are: when braking in a hurry stamping down until you reach the bottom will leave you in first, NOT neutral. This is much safer in many respects than being left with no power in an emergency situation. when starting from neutral, there is no risk of ending up ...


29

What is a 5 stroke engine? They tend to consist of only three cylinders rather than the more traditional 4 stroke, 4 cylinder engines that many people are using today. There are two small small high-pressure cylinders and one larger low-pressure cylinder. This video has some good information and animations. Why aren't they using them in vehicles right ...


27

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 with you. This chart shows fuels listed in order of their energy density: So, the main reason we don't use X for fuel and everyone seems to be so in love ...


27

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 engine) in a split second to make an upshift. Especially at higher engine speed, that's a lot of energy to bleed (and goes as a function of the weight of the ...


26

Answer The technical reason that manufacturers have chosen to use a sequential shift pattern with their gearbox configurations is that a standard shift plate that allows the selection of any gear desired is too bulky to fit into modern motorcycles. The REAL REASON this configuration is used is that it's defined in the US Code of Federal regulations under ...


26

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 would be difficult to guarantee decent atomization.


25

tl dr: Cylinder heads (commonly just called "heads") are the big piece of metal which caps and seals the end of the cylinder bore. Types of Cylinder Heads: There are three basic types of cylinder heads: Flathead Cylinder Head - These cylinder heads were used on older engines such as the flat-head Ford engines (like seen below). The oval protrusion at the ...


24

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 rebuilding an engine when needed, but also has some performance aspects which come along with the process. Let's first off describe the anatomy of a crankshaft....


23

What does the power at different rpm mean? Does it mean Car 1 has better power than Car 2 because it is at lower rpm? It depends. Or does the rpm not affect the power comparison? tl;dr: The rpm of the power peak affects the engine's usability for different applications. The "peak power" number is just one point on the power band of the engine. ...


23

Lean ≠ More Air I believe the source of the misunderstanding is in how the term "lean" is being interpreted. A lean mixture doesn't indicate the presence of more air. It indicates the presence of a higher proportion of air compared to fuel (air-fuel ratio, or AFR). Quick example Mixture A has 1,000 g of air, 80 g of fuel. AFR = 1000/80 = 12.5 ...


23

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 consumer side of things, we don't tend to notice this, as most places price things volumetricly — so much per gallon. In order to see the "true" price, you have ...


22

Ok, let's start from the same picture so we're on the same page: These engines are four stroke engines, which means the piston goes up and down a total of 4 times, twice up, and twice down for each cycle. So to answer your questions: Of course I do realize it stands for revolutions per minute, but revolutions of what? As you stated later, it's ...


21

Wikipedia describes four-stroking as: Four-stroking is an undesirable operating condition of two-stroke engines, where they instead begin to fire every four strokes, rather than every two strokes. This firing is uneven, noisy and may even damage the engine if allowed to continue unabated. Four-stroking was often a cause of poor idling in two ...


20

Is there a theoretical equation that is used to define engine load? It's not theoretical, but real. According to SAE International SAE J1979 / ISO 15031-5 (dated: 2014-08-11), calculated engine load is calculated by the following equation: LOAD_PCT = [current airflow] / [(peak airflow at WOT@STP as a function of rpm) * (BARO/29.92) * SQRT(298/(AAT+...


20

You Asked What are the benefits of a dry sump? Simply put a wet sump crankcase has oil sitting in the bottom of the crankcase. It's affected by various forces as the car or motorcycle is driven. At times it is possible, during hard braking or cornering, that the oil pickup is not in oil, resulting in a low or no oil pressure condition that could ...


19

Let me lead off with an excellent book on the topic: Corky Bell's Maximum Boost. There is a sound treatment of the basics of turbocharger operation in addition to some dated and esoteric applications that are still interesting. For example, I find the discussion of turbocharging different types of carburetor to be of intellectual if not practical interest. ...


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