Adrian wrote:
Clive George ("Clive George" ) gurgled happily,
sounding much like they were saying:

Another example from a few years ago - PSA 1.9 16v engine, 1905cc, 160
bhp. So 84 bhp/litre, over 10 years ago.

Longer, even, than that - that engine was in the BX 16v in '87.

No variable valves, and it was a reliable engine.

Indeed. And seriously fun in a car that weighed not much more than a
ton...

Now obviously these are all at the quick end of the market. But they're
there, easy to get hold of, and reliable. Which sort of makes your
contention that 70 bhp/litre is rare a bit wrong.

Panhard were putting out 60bhp from 850cc in the '60s - with two valves
per pot, air-cooling, carbs and pushrods.


Its easer with little engines, cos the revs acan go higher. Its even
easier wit 2-strokes, cos they get two bangs to a 4-strokes one..


I can show you a .36 cu in methanol and nitro engine (about what? 6cc?)
that will do over 3bhp...normally aspirated, on a carburettor..at 18K
RPM plus..

I've seen an 8 liter drag supercharged racing engine that will do around
5000bhp..well for about 30 seconds..

It doesn't matter how you swing it, you need either forced induction, or
6kRPM to get 100bhp/litre out of a N/A 4 stroke running on petrol.

6K is where you start to run into material and wear problems on anything
above 1500cc or so. at 8K you are needing very good porting and valve
trains..much over 12K and valve bounce is staring to be a killer, and yu
need pneumatic springs to slam the valves shut and keep them there.

Sure, its all possible, but it makes for an expensive fragile engine.