Zakspeed 861 - Engine and Transmission

Engine and Transmission

The Zakspeed designed 1.5 litre turbocharged engine shared its inline-4 layout with the Hart and BMW engines, of which by 1986 only the BMW (with the Benetton team) was still competitive (the Hart engine wasn't seen in F1 after the 1986 San Marino Grand Prix). Like both those engines, the Zakspeed was mounted semi-stressed in a spaceframe cradle. The year was dominated by the bespoke V6 engines of Honda and TAG-Porsche. During the 1985 season the team had worked on developing their own electronic fuel injection system, while using a mechanical injection system in races. For the 1986 season, the team reached an agreement to use a low pressure Bosch Motronic electronic fuel injection system, originally intended for Alfa Romeo's stillborn inline four turbo. This improved throttle response, drivability and fuel consumption. In race trim the engine was reported to exploit pressure of around 3.6 bar, roughly 3.6 times atmospheric pressure, which corresponded to about 850 bhp (634 kW; 862 PS). In qualifying boost could be raised as high as 4.5 bar, with correspondingly greater power (approximately 1,000 bhp (746 kW; 1,014 PS)). These figures are comparable to that year's championship winning McLaren MP4/2-TAG/Porsche, which officially produced 850 bhp (630 kW) at 3.3 bar in race trim, although the TAG/Porsche unit was far from the most powerful in Formula One that season (that title belonged to the special BMW qualifying engines which produced a reported 1,400 bhp (1,044 kW; 1,419 PS)).

The transmission was carried over from the 841, with an in-house magnesium alloy casing containing modified Hewland DGB internals.