I had forgotten that pre-war, Germany’s Army staff had concluded that their synthetic fuel processes were not suitable for diesel production, and this was an important reason for selecting gasoline powered engines.
Later in the war it proved feasible to synthetically manufacture diesel, but there were no engine designs ready. However, the head of their tank design/procurement department, Heydekampf I think, still maintained in post-war debriefings with the British that gasoline powered engines were better for tanks because of the higher power-to-weight ratio.
Missing the value of the higher energy density of diesel fuel combined with the much higher compression ratio providing for better fuel efficiency and more power, though at lower revs (which suits a tank just fine as opposed to a race car.)
Dave
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
22
Did y’all notice how big the throttle butterflies are on that beast? You can see the guy priming the engine through the one on the camera side, presumably there’s another butterfly just like it on the other side. Barely larger than the butterflies on a Jaguar V12! I guess nobody in the design department understood the need for optimizing air flow into the intakes.
I’m no military historian but surely air-cooled engines are better than liquid cooled engines in the desert?
Heat shedding depends on heat gradient. If we say a hot radiator runs at 100 C it sheds far less heat in 40C ambient than, say, 0 C ambient. Air cooled fins get far hotter, so the change in heat gradient is a far smaller percentage reduction for the same change in ambient.
I never had a bike with fan cooled fins and rode many off-road air cooled bikes that would get plugged up with mud (zero airflow) and they never struggled from overheating.
A liquid-cooled engine can get more power per cc of displacement because of the more even cooling possible with liquid. One reason Porsche abandoned air-cooling - in their market, they can’t take a penalty in terms of hp produced. Most of us have heard the reliability stories of heavily hotrodded VW Beetles.
Liquid cooled engines can be more compact and creatively packaged - even on a tank that’s a big deal. But for a tank, the advantages seem to outweigh the disadvantages. The Continental diesel used in the U.S. post-war tanks maxed out at ~900 hp. That’s with 29 liters of displacement and a 3,000 rpm redline, aka 5.5x the displacement of a street Jaguar V12.
As I mentioned before, the strong bias of the German armor development branch helped ensure that no such engines were ever placed in their wartime tanks. Even if the war had gone on another year or more, they would have stuck to gasoline powered motors, instead adding supercharging and fuel injection to them. I named the wrong guy in my previous post - the head of the German armor development branch was Ernest Kneipkampf.
Even an absolute dictator was unable to overcome the bias of a bureaucracy. Air-cooled diesels were used in some smaller vehicles, but not the battle tanks.
I was chatting with an owner of a 1980’s 911 and he said he had none of the issues with a radiator boiling over in summer, and no danger of coolant freezing and cracking the block in winter. Fair enough. But I had the bejazus of a time trying to get the heat shield shrouding around the 4 cylinder engine in my VW camper van to work properly to supply warm air to the cabin. Sometimes the extra complexity is worth it. But in a war time tank - a controlled temperature environment? I don’t think upper management would care very much.
A buddy had a 1776cc engine. He said this was as big as you could go with any hope of reliability. If memory serves he had a 300 watt electric heater with fan plugged into cigarette lighter socket. It was probably rewired for the extra current. It would warm your face but your feet and beer stayed cold.
I believe that the best asset of air cooling is it’s simplicity indeed.
I once helped a friend to fix his air cooled 911.
But on the case of the 911 all that was gained in terms of “simple”, was negated by the extreme complex scheme to heat the cabin… An air to air heat exchanger taking heat from the exhaust manifold and a whole bunch of ducts to get it all the way from the rear to the front of the car…
Nevertheless, what a great car !! The way it handles corners is uncanny.
My 1977 camper van had a 2.0L engine as stock, no real problems with it once I had replaced the O rings on the push rod tubes. If you really want to go crazy then you can get adaptor plates that will allow you to fit a modern Subaru flat 4. Serious HP available from many tuning outfits.
The air cooled nuts in our local garage use SCAT or Pauter, ca 2.4-2.7 liters displacement. One 1950’s Beetle with such an engine, running on E85 (ethanol) and an intercooler the size of the rear seat and a turbo charger about the size of our lawn mower gives ca 650HP and over 500Nm torque which has resulted in a 8.0s timed run over 1/4 mile. It still has the original steel body but obviously a very sturdy roll cage.
The guy I got the Jeepster from put a 2-liter Soobie in his Syncro: utterly transformed the bus!
He labeled it a ‘Urabus’ (read it backwards!).
The VW “wasserboxer” may not be the worst production engine ever built… but it is in serious running for the honor!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
35
OK, I had to look that up. As I understand it, “Syncro” implies 4WD in a VW Vanagon. So, when he shoehorned a Subaru engine in there, did he manage to keep it 4WD?
VW Syncros are a very unique vehicle, reaching cult-like status and desirability long ago. The Soob engine makes it soooo much better a vehicle, it’s impossible to overstate it.
There’s a long grade, up eastbound I70, from Silverthorne to The Tunnel (@soothsayer1 will know it): in TOP shape, a Vanagon–air- or water-cooled one–is lucky to make it up at 30 mph, screaming along in 2nd gear.
Charly’s Syncro will now easily get up that hill at 65 mph.
It is a shame that Subaru gave up on the fast road car market. My Legacy 3.0 R Spec B is towards the tail end of their fast saloon car range. Synchronous 4WD, and as quick as my XJR-S. Not bad for an anonymous estate car.
When I was living in Berlin I was seeing them all the time, they were Police cars!
And when they accelerated it was impossible to catch them with a normal car. The engines on these must have been seriously beefed up.
