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How a Car Engine Works

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Re: How a Car Engine Works

#51

Post by stonemetal »

Gonzih wrote: post #37
Wingman4l7 wrote: post #25

Earlier quoted context omitted.

AFAIK we're still not doing it right. The best way is to make the electric motor the main motor, and having the gasoline engine be small and tuned to run at a consistent peak efficiency RPM, and only used to charge the batteries. This was figured out in 1979! http://www.motherearthnews.com/green-transportation/electric... (see the diagram in the fourth image).

Yes, that is exactly what I meant. There are already some cars that do it almost properly. http://www.fiskerautomotive.com/ https://en.wikipedia.org/wiki/Yo-Mobile Btw Yo-Mobile is interesting since they are using rotary engine to do power generation.

Thanks for the fisker link. I saw one on the road the other day but forgot to look it up later. They are as pretty as Teslas.

Re: How a Car Engine Works

#52

Post by maxerickson »

freehunter wrote: post #50
robin_reala wrote: post #15

93 octane is premium fuel in the US? Petrol in the UK starts at 95 and premium is 98. What’s the practical difference then?

My car asks for 91 octane fuel. I have no idea where I'm supposed to get that when all I see is 87, 89, and 93. Since it's an Italian-designed car, I was expecting that 91 is a common European designation. Perhaps not?

It's generally an 'at least', you probably don't need to worry about 93.

If it is modern and fuel injected, 89 or 87 will probably also be fine, it just won't perform quite as well (but the computer will notice and back off of the timing).

Re: How a Car Engine Works

#53

Post by freehunter »

maxerickson wrote: post #52
freehunter wrote: post #50

Earlier quoted context omitted.

My car asks for 91 octane fuel. I have no idea where I'm supposed to get that when all I see is 87, 89, and 93. Since it's an Italian-designed car, I was expecting that 91 is a common European designation. Perhaps not?

It's generally an 'at least', you probably don't need to worry about 93. If it is modern and fuel injected, 89 or 87 will probably also be fine, it just won't perform quite as well (but the computer will notice and back off of the timing).

Yeah, I put in 93 once and had a small but noticeable increase in power. From my understanding, this only really happens if your knock sensor is retarding your timing with 87 octane and 93 lets it advance the timing further. It's 87 minimum, 91 recommended with my engine.

Since I secretly wish my car was a small diesel, the slight lack of power with 87 doesn't bother me too much :)

Re: How a Car Engine Works

#54

Post by jcampbell1 »

sitharus wrote: post #4

It's worth noting that the engine illustrated is a gasoline direct injection engine, which are fairly common on new cars but historically not so. Until the early 2000s most fuel injected gasoline engines were multi-point injection - the fuel was injected in to the incoming air stream immediately before the cylinder, and before that indirect injection which injected where the carburettor was. Then there are carburetto…

Direct injection implies the fuel is injected at the top of compression stroke, but the animation shows the fuel being added during the intake stroke. This is just an inaccurate drawing showing the injector attached to the cylinder rather than the intake manifold.

Interestingly, this could be a drawing of a ultra modern gas direct injection system running in classic mode. Ford's EcoTech will, under certain conditions, operate like this picture, though I am sure that is not what the author had in mind.

Re: How a Car Engine Works

#55

Post by adolph »

Peroni wrote: post #43
elnate wrote: post #14

Earlier quoted context omitted.

The other difference is Diesel engines ignite the fuel by compressing it rather than with a spark. (Also Diesel is the engine type not the fuel http://en.wikipedia.org/wiki/Diesel_engine )

Well they both work on compression, diesels simply rely on it more than gasoline engines. Diesel engines work on what's called adiabatic compression heating. In other words, the compression causes the air to heat to a point higher than the ignition point of the fuel. Diesel engines usually use glow plugs to compensate for the lack of adiabatic compression heating when the engine is cold.

See also the awesome fire piston, a relatively ancient technology using the same principles:

https://en.wikipedia.org/wiki/Fire_piston

Re: How a Car Engine Works

#56

Post by plorkyeran »

freehunter wrote: post #53
maxerickson wrote: post #52

Earlier quoted context omitted.

It's generally an 'at least', you probably don't need to worry about 93. If it is modern and fuel injected, 89 or 87 will probably also be fine, it just won't perform quite as well (but the computer will notice and back off of the timing).

Yeah, I put in 93 once and had a small but noticeable increase in power. From my understanding, this only really happens if your knock sensor is retarding your timing with 87 octane and 93 lets it advance the timing further. It's 87 minimum, 91 recommended with my engine. Since I secretly wish my car was a small diesel, the slight lack of power with 87 doesn't bother me too much :)

Now that the price difference between 87 and 93 is typically under 10%, using 93 may actually improve your gas mileage enough to make up for the difference in price. If your drive enough that fuel expenses are meaningful, it may be worth testing if this is the case for your car.

Re: How a Car Engine Works

#57

Post by chiph »

Arjuna wrote: post #42

Hi fellow gear-heads... very cool engine graphics! On a related note, I wanted to add that, if you are not familiar with dual-clutch transmissions [1], they are pretty interesting. One example (many manufacturers offer this type of transmission) is the Porsche Doppelkupplungsgetriebe (or simply PDK) [2], developed by Porsche. It is essentially two gearboxes in one complete transmission package, where both gearboxes p…

The new Corvette does something interesting - there's a sensor on the manual gear shift lever that predicts what gear you're going to select, and will do the rev matching for you. Result is a perfect downshift, every time.

Re: How a Car Engine Works

#58

Post by chiph »

maxerickson wrote: post #30
Gonzih wrote: post #23

Nowadays hybrids are smarter. Combustion engine is used to charge batteries and provide power to the electric motor, it's more efficient way of using energy from gasoline. Using combustion with electric motor stands out to be much less efficient.

That isn't true, most hybrids still have a mechanical connection between the combustion engine and the drive wheels. That is, the Prius, Ford hybrids, GM hybrids, I'm sure others.

AFAIK, the Chevrolet Volt (and Opel clone, etc) is the only one where the engine just charges the batteries, and the drive wheels are run by the electric motor alone.

From a technical standpoint, it's a good design for a hybrid - you can optimize each part of the system separately. But GM didn't quite get the car as a whole correct -- it has some ergonomic problems, priced higher than the value (perceived and actual) the customer got, and so on.

Re: How a Car Engine Works

#59

Post by arjunnarayan »

techdmn wrote: post #45
sitharus wrote: post #36

Earlier quoted context omitted.

I just took a close look at it, and I think you're right. It's not the easiest thing to see due to the wireframe, but with a second look it does appear that the injectors are just behind the valve. So yes, it's multi-point injection, rather than direct injection which is the new hotness for gasoline. Formula 1 will allow it from next year with the new V6 formula!

V6 formula!?!? Validating my decision several years ago to quit following F1. ;-)

For me it was when they kept changing the rules (in 2005) just to ensure that Schumacher lost. Haven't looked back since. I hear they can't even refuel these days (the horror!)

Re: How a Car Engine Works

#60

Post by jcampbell1 »

mindcrime wrote: post #10
jacquesm wrote: post #5

How a gasoline car engine works, specifically a piston car engine with injection. There are lots of other variations on the theme of car engine. For instance, Diesel, Natural Gas, LPG, electricity (non-hybrid) and another configurations for the hot chamber, for instance a Wankel engine. Instead of injection there is carburation (an older, less efficient process for getting the fuel air mixture into the cylinders), an…

Indeed. It also assumes an overhead cam configuration, and ignores the possibility of a pushrod / lifter based cam/valve system. And showing a distributor glosses over the electronic timing systems that newer cars use, whereby they don't need a traditional distributor at all, just a crankshaft position sensor. Still, for an engine neophyte, that was a pretty decent explanation.

Even weedwackers have electronic ignition these days. That is why they are so easy to start. You don't have to fight the the preset advance.
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