Jumo 211 J Specification
Inverted V12, 60 degrees, bore 150mm x stroke 165mm giving 35 litres or 2136 cu.in. One-piece silicon-aluminium alloy crankcase (unusual in large WW2 aero-engines to have the blocks cast integral with the crankcase as in car engines, cylinder blocks are almost always separate castings) detatchable heads with two inlet and one sodium cooled exhaust valve. Single overhead camshaft.
Gear driven two speed centrifugal supercharger, ratios 7.95 and 11.37:1 with automatic boost control.
Direct fuel injection via Junkers 12 plunger mechanical injection pump with automatic mixture control, fuel de-aerator and one closed-type injector per cylinder.
As with other German V12 practice, there is a bore running right through the engines "vee" and hollow propeller shaft to give provision for a cannon to fire through the hub. On Ju88s this was not employed, and the project engine here has a propeller CSU mounted on the rear casing covering the cannon aperture.
Rating, take-off 1350hp at 2600rpm
Low gear 1300hp at 2500rpm, 12500ft
High gear 1260hp at 2500rpm, 16400ft
Comparisons with the Merlin include the weight, which at 648kg is 10kg lighter than the Merlin XX but with a capacity of some 8 litres more, although power is the same. Weight-savings included thinner cylinder liners and the use of magnesium for the top and bottom covers and many smaller castings.
Fuel grade was only 92 octane, the Germans used synthetic petrol much of the time and certainly did not have 100 octane.
Earlier versions were all rated at 1200hp and some versions used an intercooler to aid altitude performance.
