This was subsequently replaced by an air operated three-position control on the steering column. Although it did not progress beyond the garage door opener battery stage, Foden subsequently built and tested an automatic transmission. Engines preceding the 1962 Mk6 Dynamic range had 85mm cylinder bores. Responding to changing marketplace appetites, it was decided to raise engine output.
Increasing the bore size to garage door opener battery achieved greater cylinder swept volume without having to alter the external dimensions of the engine blocks. This raised the capacity of the FD6 from 1 to 8 litres and the FD4 from 72 to 2 litres, resulting in 17% higher power and 20 percent more torque and a claimed 5% improvement in fiie economy. Alongside the FD4 and FD6 Mk6s, Foden unveiled the crowning glory of its automotive two-strokes, the 225bhp/6001b ft turbocharged FD6 Mk The blown, turbocharged Mk7 featured air-to-air intercooling, an innovation introduced years before other engine manufacturers. Apart from upping output of the FD6 from 175 to 180bhp to match Gardners new 6LXB, production Foden two-stroke truck diesels remained essentially unchanged until they were delisted as an option after 1972 But behind the scenes, the ambitions of Fodens engine design team told a different story. A pipeline of contemplated future developments included a further bore increase to 100mm , heads with four exhaust valves, associated with which were twin-cam operation and multi-hole injectors.
Based on the bhp per litre of the 92mm bore engines, extrapolated outputs were 210-215bhp for a blower scavenged six and more than 265bhp for a blown and turbocharged version. Straight-eight evolutions of the Mk6 and turbocharged Mk7 units were projected with respective outputs of 240bhp/550lb ft and 300-330bhp/800lb ft. And well before these, in the Fifties Foden explored the design of V8, V6 and V4 engines with an 5 degree bank angle. Outputs ranged from 160 to 400bhp. And it seems logical that a V-12 block, singlecrank version of the 450bhp, 6-litre FD12 Mk7 twin-turbo double-six marine engine might have been developed for automotive use.