SUB4 115 hp
These engines are designed specifically for the recreational aircraft market and are manufactured in Hamilton, New Zealand. Subaru EA81 engines are a favoured option for many recreational aircraft builders, however although these engines are light, rugged and dependable, they suffer a number of shortcomings which limit their true potential in this environment. For example, Subaru designed the original EA81 engine with siamesed inlet and exhaust ports. This, coupled with a long and poor flowing inlet manifold, significantly restricted the engine's output (115hp@5500rpm).
The SUB4 company have addressed this issue by designing and manufacturing new dual port cylinder heads which feature two sparkplugs per cylinder. These high flow, high compression heads utilise larger inlet valves which when used with SUB4's revised camshaft design and tuned inlet manifolds, combine to significantly increase the engine's BMEP (brake mean effective pressure), delivering a wide, smooth torque band and 60% more (dyno proven) horsepower. SUB4 engines are also supplied with a full electronic dual ignition system and a compact 4 into 1 exhaust manifold. These modifications make the SUB4 engine in the recreational aircraft market with an excellent power to weight to cost ratio.
After 2 years R&D, the company was at Sun N Fun 2000 with their SUB 4. While the basic block from the EA81 is used the rest of the engine has undergone extensive changes and or modifications.
The SUB 4 Port heads have been modified to give "one port per valve for both inlet and exhaust to allow for tuned length of induction and exhaust. The heads are cast in ASTM 356 aluminium alloy, which is heat treated and CNC machined. The heads come with bronze valve guides, 42 mm inlet valves x 7 mm valve stems. Performance valve springs, match cam and h.p. option. The water outlet fitting accepts a standard automotive water hose. Each head set is supplied with a camshaft ground to match the h.p. option.
The rocker covers are cast ASTM 356 alloy, with a finned design to aid cooling. A "O" ring is used for sealing. One cover is set up as the oil filter while the other as the breather.
The SUB 4 reduction drive has three cases cast in ASTM 356 heat treated aluminium. The intermediate case can be rotated 180 degress to allow for props in an up or down installation. The reduction gears are manufactured from EN39B case hardened to 60 Rockwell C. They are 11 degree helical, and 40 mm meshing width incorporating a radiused oil relief groove. The PSRU can be geared to 0.455 or 0.556.
The Propeller Speed Reduction Units (PSRU's) suit the EJ-20, EJ-22, EJ-25, EG-33, and EZ-30 (H6) series of Subaru engines.
An aluminum flywheels incorporating a high tensile steel ring gear is used, with a rubber cush drive on the flywheel. Ratios of either 1.8 to 1 or 2.2 to 1 are available.
All of the components are available complete or as separate units for the do it yourselfer!
This version can be retrofitted to Sub4 125hp specifications.