CC...Cubic capacity of what?

[BillyW124]

yes but in essence regardles of turbo etc,

cc by my understanding now is how much volume (whatever it is) it can hold to combust?

 

[camerafodder]

Size is but one variable. Not all 2 litre engines have the same output. It depends on fuel, turbocharger, supercharger etc.

You are of course absolutely correct. I was just trying to stick to basics whilst Billy got his head around the problem without clouding the issue with forced induction, fuel types, doping etc....

 

[camerafodder]

yes but in essence regardles of turbo etc,

cc by my understanding now is how much volume (whatever it is) it can hold to combust?

Yes, but remember what is in there is not liquid, its in the form of fuel vapour and air mixture, imagine it as glass that you've just squirted an aerosol into.

 

[finisterre]

yes...

and the volume of mix is the same when you are using a supercharger or turbo, but there is more oxygen and fuel crammed into the cylinders by the higher pressure.


If you think about it though, with turbo smaller engines a bigger explosion will make your exhaust gasses leave at a higher pressure so you shouldn't be able to be quite as efficient as a normally aspirated bigger engine.

oddly though it doesn't seem to work that way?

I expect it all gets a bit complicated.

 

[renault12ts]

why is it strange?

good question no?

Apologies. I found it interesting that you didn't know. But that's just me.

For instance, the volume of air/fuel mixture taken into the cylinders during the intake stroke depends upon how much it has been compressed. Thus both turbos and superchargers, provide more power because a greater volume (uncompressed) is pulled into the cylinders.

The more mixture you can get into a given size of cylinder, the greater the power. That's why smaller turbo engines can produce the same or greater power than much larger normally aspirated engines.

 

[finisterre]

fair question

I think the ladybird book of the internal combustion engine has been out of print for thirty years.

 

[BillyW124]

Apologies. I found it interesting that you didn't know. But that's just me.

For instance, the volume of air/fuel mixture taken into the cylinders during the intake stroke depends upon how much it has been compressed. Thus both turbos and superchargers, provide more power because a greater volume (uncompressed) is pulled into the cylinders.

The more mixture you can get into a given size of cylinder, the greater the power. That's why smaller turbo engines can produce the same or greater power than much larger normally aspirated engines.

I knew i would get found out. LOL,

but yes finding this very interesting. It seems there is no clear cut definitive answer to this as there are important factors to consider..

 

[renault12ts]

I knew i would get found out. LOL,

but yes finding this very interesting. It seems there is no clear cut definitive answer to this as there are important factors to consider..

The answer to the size of the engine is absolute. But that's only the start.

 

[Mactech]

yes...

and the volume of mix is the same when you are using a supercharger or turbo, but there is more oxygen and fuel crammed into the cylinders by the higher pressure.


If you think about it though, with turbo smaller engines a bigger explosion will make your exhaust gasses leave at a higher pressure so you shouldn't be able to be quite as efficient as a normally aspirated bigger engine.

oddly though it doesn't seem to work that way?

I expect it all gets a bit complicated.

If the gas escapes when the explosion happens, then the exhaust valves are open at the wrong time!
The higher the rpm, the higher the exhaust gas speed....given a similar valve effiency etc.etc....

 

[finisterre]

there is a clear cut definitive answer, - swept volume.
what it means is slightly more complicated

 

[renault12ts]

If the gas escapes when the explosion happens, then the exhaust valves are open at the wrong time!
The higher the rpm, the higher the exhaust gas speed....given a similar valve effiency etc.etc....

Exactly, not because of the size of the bang, but because of the greater number of rpm and thus piston speed.

 

[finisterre]

If the gas escapes when the explosion happens, then the exhaust valves are open at the wrong time!
The higher the rpm, the higher the exhaust gas speed....given a similar valve effiency etc.etc....

I was thinking about efficiency

1 compress
spark
2 push
3 exhaust
4 input

You must lose some (power) efficiency with a turbo because the pressure at the end of 2 should be higher than in a NA engine, yes?

 

[camerafodder]

I knew i would get found out. LOL,

but yes finding this very interesting. It seems there is no clear cut definitive answer to this as there are important factors to consider..

Stick to the basics to understand it Billy. The other stuff is just tricks that are used to increase the output.

1) CC of an engine remains constant
2) We can force more air in using a turbo charger (driven by exhaust gasses) or super charger (usually driven from the crankshaft), more air = better burn = more power
3) Another trick is the intercooler, this cools the air before it enters the engine, cool air has more oxygen in it than hot air, more oxygen = better burn = more power.
4) Different fuels
5) higher compression ratios
6) combine any or all of the above to increase engine output

There's more but you get the idea.

 

[renault12ts]

^ Succinctly put.

 

[renault12ts]

I was thinking about efficiency

1 compress
spark
2 push
3 exhaust
4 input

You must lose some power with a turbo because the pressure at the end of 2 should be higher than in a NA engine, yes?

Don't know. But if a similar power turbo engine uses less fuel than a v8, then the turbo is more efficient.

 

[finisterre]

cool air is denser, you get more molecules of oxygen in a pint.

 

[BillyW124]

WOW thanks guys,

 

[renault12ts]

cool air is denser, you get more molecules of oxygen in a pint.

Which is why most/many turbos have intercoolers.

 

[camerafodder]

Don't know. But if a similar power turbo engine uses less fuel than a v8, then the turbo is more efficient.

You tend to find that you still need a similar amount of fuel to get the power. Turbos allow you to get greater power from a physically smaller unit. The apparent efficiency comes when you are cruising steadily along not using the full output of the engine/turbo combination and therefore the base fuel consumption of the smaller engine is less than the big one.

I hope that makes a crazy kind of sense!

 

[finisterre]

Don't know. But if a similar power turbo engine uses less fuel than a v8, then the turbo is more efficient.

Yes, we are probably (guess) normally in some sort of high performance land and the trade off only really applies to marine diesels where weight is an asset?

I base all my knowledge on ladybird wisdom and extrapolation