Radial vs liquid cooled engines

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Napier Sabre IV: 2240hp @ 8000ft, 4000rpm, +9psi boost, normal power.

Lumsden doesn't have a figure for FS gear. The Sabre V had 1930hp @ 15,750ft, 3650rpm, boost not listed.
 

On the F series exactly such a valve was installed enabling one half of the cooling system to be isolated from the other,hopefully to enable a damaged aircraft to return safely to base. The valves were not installed at the factory but delivered as kits to be fitted by the units.
According to Prien the system worked well but the number of available kits was limited.
The valves were not fitted as standard on the G series,neither were post production kits supplied.
Cheers
Steve
 
Here's one for the air cooled crowd. And a picture.............is worth a thousand words. Oh, and I realize I just kinda stuck this in here so I apologize for that but a friend asked me to post this here so......I did.
 

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To get a failure like that you need to have had one of several things happen. Poor maintenance with reused or faulty or over stressed bolts ( how many out of 12-16 of them?). Which in a mono block engine would cause the cylinder block or head to lift depending on location of the bad bolts. Having one end lift a bit may cause several cylinders to stop running properly.

And/or the cylinder suffered detonation, this can happen even to a properly maintained/built engine. Engine is over boosted for gas/mixture being used and/or over heated. The fuel/air will burn all at once instead of a flame front traveling across the cylinder. This can happen in lean cruise condition. In a mono-block engine instead of the cylinder going up (away from crankcase) the pistons usually went down, in pieces, into the crankcase along with a bent or broken connecting rod. Wither or not the flailing rod punches a hole in the side of the block is up to luck.

The mono bloc engine is much less prone to having a block come off but but that doesn't mean the mono-block cannot suffer some catastrophic failures.
 
I like them all no favorites. But I do like simple logic. A radial is potentially easier to work on in the field. You can blow off a cylinder like the photo and keep running, but it can't be a master cylinder. And cutting the rod off would be recomended as well as blocking off that inlet pipe. Way more involved in working on a bad hole in the LC jobs. Then there is the leak thing, oil is bad enough, don't need something else to leak.
 
There is a proposal for a fighter dated 27 July 1938 in Baubeschreibung 187,it was known within the company as Projekt I. This would become the Fw 190. It states that maximum reliability was to be achieved by the avoidance of complicated liquid cooling or hydraulic systems,which experience had shown were often a source of problems.
There was at least a perception that air cooled systems were more reliable,if not less vulnerable.

In October 1939 Heinrich Beauvais came from Rechlin to Bremen to fly the Fw 190 V1. The third sentence of the summary of his report shows what the Luftwaffe thought about the vulnerability of various engine types.

"The view to the rear is superior,and its BMW radial engine is less vulnerable to enemy fire." [compared to Bf 109]

Steve
 
You have to compare like to like.
Rather obviously a 2000hp air cooled radial needs more fuel than a 1400-1500hp liquid cooled V-12.

When at cruising speeds the engines are usually within 10% or so of each other in fuel consumed per HP per hour.
Engines needing a lot of boost use more power to drive the supercharger.
But even internal friction can play a part at cruising speeds. very roughly 80% of the internal friction comes from the pistons and piston rings sliding in the cylinders. So you have the number, type, and tension of the piston rings and the number of sq ft of cylinder wall scrubbed per unit of time at a given rpm.
Friction also increases with the square of the speed.

So yeah, there are a LOT of "it depends."

Too many to pick one type of engine over the other in all (or even most) cases.
 
Post war there were several attempts to improve economy. The CW R3350 turbo compound and the Napier Nomad turbo compound showed how complicated and heavy piston engines become when you try to improve economy without losing power.
 
Its really difficult to do a comparison without considering the installation. A pretty close comparison can be made with the air cooled P-36(Curtiss Hawk) and the liquid cooled P-40. The Hawk 75A-4 had 1000 hp at 10k and a top speed of 313 mph at 10k, cruised at 262 mph, and weighed 4541lbs empty. The very similar P-40 (no alpha character) had 1040 hp at 10k and a top speed of 357 mph at 10k, cruised at 277 mph, and weighed 5376 lbs. (note: load carried on on gross weight was about 100 lbs more for the P-40). It is apparent that the cleaner liquid fueled P-40 was much faster than the Hawk, but was also 800 heavier, which would have affected climb, though not verifiable. P-40 had no armor, Hawk may have had some.

The verdict of history? Air cooled radial wins. Almost all of the post war heavy hitters, DC-7, Stratocrusiers, Constellation, C-124, Brabazon, used air cooled radials. The Merlins, Griffons, Allisons, all went to collector planes and racers and record setters; autos, boats, planes. In1969, the Navy flew me to New Orleans for a flight physical in an R5D with, you guessed it, air cooled radials.
 
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