 |
||
 |
||||
| •
450 HP @ 4400 RPM @ 37in. Hg abs. • 12 water cooled opposed cylinders • Bore 3.5 in. • Stroke 3.85 in. • Intake valve 1.9 in. • Exhaust valve 1.75 in. • 2 valves/ cylinder 2 spark plugs/ cylinder • One inlet and one exhaust cam, with pushrod operated valves • Weight 650 lbs. Length 53 in. Height 21 in. Width 35 in. • Output gear ratio 2:1 Bore size is important. Consider that WW2 aircraft engines with >6” bore and 7-1 compression ratio required 130 octane gasoline. Also, present aircraft engines with >5”+ bore, require 100 octane gasoline. A modern motorcycle with a <3” bore will operate at 10-1 compression ratio with 87 octane gasoline. We are using a 3.5” bore and taking advantage of the powerful effect of bore size. The fact of having small cylinders offers many advantages. By virtue of being able to operate away from the conditions that cause combustion instability, (that is pre-ignition and knocking), it is possible to operate at any fuel-air ratio between rich and lean, including the hottest condition. This makes operating in the lean part of the fuel-air spectrum feasible. Although much talked about, not many hours are flown at lean conditions. The danger of having one cylinder operating at the highest temperature fuel-air ratio causes most pilots to stay safely in the rich range. Fuel usage is, of course, greatly reduced by lean operation. The 444 Twelve has a solid state ignition system using 12 coils. This, of course, eliminates magnetos and magneto drives. Ignition redundancy is obtained by having 2 alternators. One of these two alternators is small and is dedicated entirely to one ignition circuit and one set of spark plugs. The primary alternator supplies the other set of spark plugs. The familiar 2 spark plugs per cylinder design has been used. The possibility of making significant improvements in all aspects of this class of engines exists. Longevity improvements compared to existing aircraft engines available will be much greater than incremental. Consider that a 400 HP diesel truck engine piston, with the same material combination, can run 10,000 hours, at high turbocharged loads. If the piston in the 444 Twelve could travel the same distance in its cylinder, it would represent a life of 7700 hours. |
||||