I suspect that ac-aero do not anticipate that their cylinders for the 4 and 6 cylinder Lycomings will be used in combat."the B-17 literally had a liquid cooled variant that greatly outperformed the air cooled in efficiency"
May be true but one well placed round or flack hitting a jug, engine may still run. Same hit on the radiator of liquid cooled, you have only a few moments before it stops. I like both cooling schemes. Air cooled appeared to be more robust for combat.
That applies to the SMA diesel engines, too. Much better BSFC. But the conversion for a 182 costs around $100K, negating the fuel savings. It has other drawbacks, too, such as a limited cold-weather capability.Maybe initial cost but operating costs and operating weights for a given range are lower. Just compare the range of the B-17 to the Lancaster. 25% difference in range with the same power and 65,000lb takeoff weight.
One of the limiting factors in aircraft engines is the onset of detonation. Large-bore, slow-turning engines are prone to it, as it takes time for the complex fuel molecules to break down into simpler, autoignitable molecules. Higher compression ratios increase the risk, and air-cooling takes it further. A liquid-cooled head is going to stay a lot cooler than an aircooled one, so I'd bet that liquid cooling would permit increasing compression or turbo pressures, producing more power. And if the oil was also cooled better, the piston itself could be kept cooler, though a liquid-cooled cylinder wall would be a big help. And leaner mixtures could be used, as the website stated. Getting the mixture leaned to best power for takeoff would save fuel over the typical full-rich techniques in aircooled engines. Rich mixtures don't just aid cooling; they inhibit detonation.From the bit I've read mostly on their website, this site and the BPF are that these are for the people that want to maximize power output. High Compression/High Horsepower. Airshow, Unlimited Competition Aerobatics and Racing engines.
Generally they are selling 4 banger engines at 409ci and the 6's are ~615. Longer strokes and Bigger bores.
Not saying they are not worth it, but must have a large purse to purchase.
Some years ago, I was optimistic that Henry Bouley’s “improved” engine would be a winner. Read about it here: Bacon QUESTAIR-VENTURE crash in Iowa (N4QV) | PlaneCrashMap.comSomeone needs to take the historically empirical goodness of a Lycoming and upgrade it by copying what Rotax did with the incredibly efficient 912is. Liquid cooled heads, air cooled cylinders, dry sump oil cooled block, fuel injection with dual electronic ignition.
I think you mean clearances, not tolerances...Dear Andy RR,
Air-cooled cylinders can never be built to tolerances as tight as liquid-cooled.
Cylinders bores don't really reject so much heat compared to the cylinder heads. The temperature that they operate is huge compared to the temperature differential radially around the cooling flow path. Most of the thermal gradient is axially also so the thermal expansion is largely diameter rather than ovalization which is why the bore on the cylinder barrels is (intentionally) not actually parallel. They also have lots of ribs which keeps them pretty stiff. Pistons, on the other hand, don't stay round at all, despite your claim! - they grow round from their cold ovality and they suffer most from lack of cooling - the majority of heat they absorb is rejected through the ring pack to the bore walls. The rings are also flexible enough to cope with any remaining bore ovality, but, in any case, the largest area of leakage of the ring pack is at the ring gap which is larger on an air-cooled engine to allow for worst-case cooling scenario.Part of the problem is un-even cooling at high speeds. Fins on the front and sides remove plenty of heat, but the backside always runs hotter. Cylinder walls heat to egg-shape while pistons remain round. This limits you to running your engine by limiting power to the best that can be produced before over-heating the worst-cooled cylinder .. usually rear. Air-cooled engines must be built to the worst combination of hot piston and cold, egg-shaped cylinder walls.
No! Not tolerances here either - clearances! Liquid cooled engines operate at more stable temperatures because of thermostatic control of the cooling system. However, unless you compare apples and apples, you'll mislead yourself. Much of what you propose here is heavily influenced by bore diameter so comparing a 4.125" Chevy with a 5.125" Lycoming will lead you to an erroneous conclusion.The primary advantage of liquid-cooled engines is that they cool more evenly and can be built to much tighter tolerances. No egg-shaped cylinders here. Tighter tolerances between pistons and cylinder walls mean less leakage in to the crankcase, cleaner oil, less frequent oil changes, etc.
Again, I think you mean clearances, but even so, there is no halving fuel consumption to be had at all! The lowest BSFC of a LS compared with a Lycon is closely comparable! Also the lean limit is more influenced by chamber charge motion and overall surface/volume ratio rather than the cooling method. The Lycons are terrible in regards to surface/volume with a bore/stroke ratio of 1.17 compared with 1.03 for Andi's LS7. The higher the CR the worse this gets too! A proper modern design with a focus on fuel consumption will be undersquare at around 0.9Tighter tolerances (liquid-cooled) allow you to lean the fuel air mixture much closer to optimum, halving fuel consumption.
No, again, there is no half to be had anywhere here! Andi's numbers above demonstrate that!For example, when you install a liquid-cooled Corvette engine in a Seabee, you increase horsepower by 50 percent (300 versus the original 195 hp.), while dropping fuel consumption by half.
I have no experience but I do think that they look promising, at least with the brief look that I had at their website.