How engines work

[dessiato]

I've got a working model V8 engine.

I'm hoping to add a flat 6 then a V twin to form a little collection of engines.

 

[weltweit]

The potential disadvantage of turbochargers is that you have to have enough exhaust pressure to make them spin and to then have their effect. Hence you can get what is known as turbo lag, where you don't get the boost until the engine is spinning at a good rate. Superchargers don't have to have that disadvantage because they can be geared to blow strongly at lower revs.

I believe Mercedes kompressor models have superchargers rather than turbochargers.

 

[existentialist]

I know the offside rule...
Not as sure about engines but if pushed I could possibly explain.

I was quite pleased to find out I could explain how (and why) a turbocharger worked.

The only bit I can remember about the offside rule is the bit with the goat and the lime jelly.

 

[Baronage-Phase]

I was quite pleased to find out I could explain how (and why) a turbocharger worked.

The only bit I can remember about the offside rule is the bit with the goat and the lime jelly.

 

[Mrs Miggins]

No - because for a given volume of air, you can mix a given amount of fuel into it, in order to get the ideal combustion ratio. Turbochargers allow you to add more air, and so more fuel, so power is increased.

Ah! So I got that completely the wrong way round. Thanks for explaining. Makes perfect sense.

Carburettors... In the picture in the OP, fuel is injected directly ('direct injection') into the cylinder, which is relatively modern. Before that, it was mixed in the intake port, and the air entering the engine was a fuel/air mix. How do you make the mix? Well, before direct injection, it was still done with electronically controlled injectors - same thing, just not direct. But before that, it was mixed with a mechanical device, and that was a carburettor.

This thread is most instructive!

 

[mauvais]

The potential disadvantage of turbochargers is that you have to have enough exhaust pressure to make them spin and to then have their effect. Hence you can get what is known as turbo lag, where you don't get the boost until the engine is spinning at a good rate. Superchargers don't have to have that disadvantage because they can be geared to blow strongly at lower revs.

I believe Mercedes kompressor models have superchargers rather than turbochargers.

Some cars electronically assist the turbo now - spooling it up before exhaust gases get chance to. This is sometimes called 'mild hybrid'.

Superchargers are less efficient because they can't be controlled - they're on the drivetrain, always absorbing energy.

 

[Mrs Miggins]

So with a jet engine - and a rocket engine - how does the expanded gas cause the forward motion? In a physics way. The colder air is more dense so - bear with me - is it kind of like if you had a balloon and you blew up the balloon against, I dunno, a piece of wood, the piece of wood would move cos you're pushing it with the expanded gas filled balloon? In this illustration, the balloon represents the engine and therefore the plane, and the wood is the air around it getting pushed out of the way.

 

[existentialist]

So with a jet engine - and a rocket engine - how does the expanded gas cause the forward motion? In a physics way. The colder air is more dense so - bear with me - is it kind of like if you had a balloon and you blew up the balloon against, I dunno, a piece of wood, the piece of wood would move cos you're pushing it with the expanded gas filled balloon?

Physics.

 

[mauvais]

So with a jet engine - and a rocket engine - how does the expanded gas cause the forward motion? In a physics way. The colder air is more dense so - bear with me - is it kind of like if you had a balloon and you blew up the balloon against, I dunno, a piece of wood, the piece of wood would move cos you're pushing it with the expanded gas filled balloon? In this illustration, the piece of wood represents the engine and therefore 5he plane and the wood is the air around it getting pushed put of the way.

Newtonian physics. Every action has an equal and opposite reaction. So if you're going to expel gas as part of this process, something has to happen in return, and that's moving the projectile through the air.

 

[Mrs Miggins]

Newtonian physics. Every action has an equal and opposite reaction. So if you're going to expel gas as part of this process, something has to happen in return, and that's moving the projectile through the air.

Yep. Got it. Thank you!

That's what I'm getting at with my balloon business. I have an odd way of understanding things

 

[existentialist]

Let us know when you want us to explain the ion drive, and nuclear pulse propulsion, Mrs Miggins.

 

[Mrs Miggins]

So the jet engine really was a great leap forward in imagining how to provide thrust. It's a completely different way of looking at the problem compared to a piston converted to rotary motion.

 

[weltweit]

Steady on mate! How about you tell me how a 2 stroke engine works first. Which are the stages missing from the 4 stroke?

A two stroke is arguably much simpler than a four stroke.

Two strokes don't have any overhead camshafts or valves, instead the fuel air mixture is let into the sealed crank case of each cylinder and when the piston is on its downward stroke it compresses the fuel air mixture that is below it.

As the piston comes down it uncovers ports cut into the cylinder liner which let the compressed fuel air mixture get pumped into the combustion chamber. The piston continues upwards compressing this mixture and near top dead centre a spark plug ignites the mixture.

After the bang, or better said burning of the fuel, the piston is driven down (compressing the next load of fuel air mix in the crankcase), the exhaust is let out of the combustion chamber through exhaust ports which are cut into the side of the cylinder much like the intake ports.

A two stroke fires every second stroke of the piston, where a four stroke only fires every four strokes.

Billions have been invested by the auto industry into making four strokes as good as they currently are, two strokes by comparison are harder to make comply with emissions requirements which is why they mainly remain the preserve of small motorcycles, chain saws and the like. Trabbants had two stroke engines.

 

[Mrs Miggins]

Let us know when you want us to explain the ion drive, and nuclear pulse propulsion, Mrs Miggins.

Fuck yes please! Believe it or not, I was a real science kid and have a degree in chemistry. Physics I found very difficult but it's all absolutely fascinating. And I just love things like massive Victorian beam engines.

 

[cyril_smear]

Mine works when I turn the key and it goes brum, brum, brum

 

[mauvais]

Someone might as well throw rotaries into the mix.

 

[existentialist]

Fuck yes please! Believe it or not, I was a real science kid and have a degree in chemistry. Physics I found very difficult but it's all absolutely fascinating. And I just love things like massive Victorian beam engines.

Nuclear pulse propulsion - build a spaceship with huge shock absorbers and a massive chunk of steel on the other end of them, drop small nuclear bombs out the back, and accelerate to a significant proportion of the speed of light (eventually).

Project Orion (nuclear propulsion) - Wikipedia

 

[weltweit]

Yes, and a rotary / wankel engine'd Mazda once won the Le Mans 24 hour motor race.

I forget which year it was, but I was there!! The car made a sort of screaming sound which was very different from the other more conventional racecars that weekend.

 

[Mrs Miggins]

Nuclear pulse propulsion - build a spaceship with huge shock absorbers and a massive chunk of steel on the other end of them, drop small nuclear bombs out the back, and accelerate to a significant proportion of the speed of light (eventually).

Project Orion (nuclear propulsion) - Wikipedia

Cor! Say what you like about humans but we're bloody brilliant

I do like the way you casually say "build a spaceship"

 

[mauvais]

Yes, and a rotary / wankel engine'd Mazda once won the Le Mans 24 hour motor race.

I forget which year it was, but I was there!! The car made a sort of screaming sound which was very different from the other more conventional racecars that weekend.

Mazda 787B - Wikipedia

 

[weltweit]

Mazda 787B - Wikipedia

That brings back some memories

 

[existentialist]

Cor! Say what you like about humans but we're bloody brilliant

I do like the way you casually say "build a spaceship"

Well, it doesn't HAVE to be a spaceship, but with that propulsion method, it's pretty inevitably going to end up in space whatever you do

 

[Gromit]

What I learned today is what the V stands for in V8.

It's not Volvo after all!

 

[Sprocket.]

Excellent thread HAL9000 .
Expanding, explaining and helpful to anyone wanting some information on the machines that are so vital to our lives.

 

[Mrs Miggins]

Someone might as well throw rotaries into the mix.

Where are these things employed?

 

[Sprocket.]

Where are these things employed?

Car and motorcycle engines. The first car I saw with a rotary engine was a neighbour’s NSU back in the early seventies. A lad who was an apprentice with me had a Suzuki bike with a rotary engine.
As mentioned above Mazda are one of the car makers that utilise these recently.

 

[mauvais]

They've been pretty much abandoned in terms of cars because of a number of engineering problems. They do find some use in light aircraft. They might also work well as range extenders in cars, where the RPM and load isn't necessarily linked to the vehicle speed.

 

[pseudonarcissus]

..two strokes ... mainly remain the preserve of small motorcycles, chain saws and the like. Trabbants had two stroke engines.

and large ships!

Marine slow speed 2-stroke engines are the most thermally efficient heat engines there are.

...and next year they might start burning low super fuel

 

[existentialist]

Car and motorcycle engines. The first car I saw with a rotary engine was a neighbour’s NSU back in the early seventies. A lad who was an apprentice with me had a Suzuki bike with a rotary engine.
As mentioned above Mazda are one of the car makers that utilise these recently.

The Mazda RX-8 has two of them.

 

[weltweit]

and large ships!

Marine slow speed 2-stroke engines are the most thermally efficient heat engines there are.

...and next year they might start burning low super fuel

Oh interesting, I had no idea.