[peppercorn (OP)]

What has expansion rate got to do with it?

I don't know that's why I posted:

Am I right in thinking the rate of heat transfer is governed by specific heat capacity. Does this figure also define expansion?

a couple of days ago - as I was struggling with the concepts then (as now!).

...What's wrong with air? It's so readily available.

I thought:
An engine without nitrogen would have no chance to create NOx's.
Also a 'heavier' gas should, on the face of it, soak up the thermal energy more readily, turning it into expansion - hence less wasted energy & potential for removing cooling system completely.

CRAZY I'M SURE....

[lyner]

Also a 'heavier' gas should, on the face of it, soak up the thermal energy more readily, turning it into expansion - hence less wasted energy & potential for removing cooling system completely.

That doesn't quite make sense to me. Why would it work that way?
The bit about Nox's could be relevant tho. But there could be a problem with CO being formed?

[lyner]

Also a 'heavier' gas should, on the face of it, soak up the thermal energy more readily, turning it into expansion - hence less wasted energy & potential for removing cooling system completely.

That doesn't quite make sense to me. Why would it work that way?
The bit about Nox's could be relevant tho. But there could be a problem with CO being formed?

[peppercorn (OP)]

Also a 'heavier' gas should, on the face of it, soak up the thermal energy more readily, turning it into expansion - hence less wasted energy & potential for removing cooling system completely.

That doesn't quite make sense to me. Why would it work that way?
The bit about Nox's could be relevant tho. But there could be a problem with CO being formed?

Well, that's the thing - I must have a complete misunderstanding of how gases (or any material for that matter) act when heated.

I though heat would be absorbed by a denser gas more than a lighter one.
-Although, now, just picturing it in my head, I would also expect that the time taken for absorption with a dense would be longer - ie, too long with CO2 for the revs of an ICE.

I suppose I  have been getting two very  simple parameters muddled up: heat absorption by a molecule and heat transfer speed...
 

[lyner]

I never paid much attention to the Thermodynamics I did at Uni, I'm afraid, so I can't be too dogmatic about it but there are a lot of websites about basic gas laws and heat engine cycles.
Just search on Gas Laws and Gas Constant; you are bound to find something for your particular level of understanding - then work upwards!
Good luck.