Ford Germany had built and raced a touring car version of the MKI Capri from their Competition Department at Ford Werke, Cologne in the early '70s, under the guidance of motorpsort boss Mike Kranefuss. These iconic blue and white cars are now fondly remembered as the "Cologne Capris".
The works MKI cars were withdrawn in 1975, following the introduction of the MKII and the closure of the Competition Department - necessitated by the crippling '73/'74 fuel crisis. However, Ford continued to be semi-officially represented in the German and international touring car world by Erich Zakowski and his Zakspeed team-built Group 2 and then Group 5 racing Escorts.
But by 1977, with the new MKIII version of the Capri going in to production for launch in the spring of 1978, it was decided to reintroduce the model to racing. Allegedly, this was because Ford felt that sales of the sporty model in Germany had never been as good as could be expected. However, with Cologne's technical facilities now closed, Ford was not able to build the cars 'in-house'. Thus, after developing an initial concept themselves, the company turned to Zakspeed to construct the cars and provide them with the extra horsepower that would be needed to compete against Porsche and BMW within the recently introduced Group 5 and 6 regulations. Ford correctly realised that Zakspeed would be able to draw on the wealth of knowledge gained from successfully converting the boxy Escort to Group 5 specification.
As the new racing Capri was to be aimed at invigorating sales in Germany, it would be entered into the German national series (Deutsche Rennsport Meisterschaft or DRM) which, from 1977 onwards, had been running under the prevailing Group 5 regulations. As this was ostensibly a silhouette formula, the Zakspeed Capri would naturally be a very different beast to the MKI Cologne Capris.
Although Group 5 was the natural home of Porsche 935s and BMW 320s, Ford motorsport boss Mike Kranefuss and Chief Engineer Thomas Ammerschalger - the engineer assigned to the project - believed that the MKIII Capri had potentially favourable aerodynamic characteristics. The steeply raked windscreen, long body and low profile would be a formidable package, enabling Ford to compete alongside more prestigious competitors in this "silhouette" formula.
With Gr.5 regulations, only the silhouette of the car above the wheel arches and a few other body parts need be maintained from the production line model. The engine had to be based on a production unit from the same manufacturer and located along the same axis. Also, the suspension layout had to be as per production model. Aside from this, pretty well any other mechanical or aerodynamic changes were permitted. This gave Ammerschlager and Zakspeed team chief Erich Zakowski the scope to produce a more pure-bred racing car than the MKI.
CHASSIS & AERODYNAMIC DEVELOPMENT
The design brief was devised by Ammerschlager at Ford Werke in Cologne in the winter of 1977. The racing machine would feature a huge flared front wing, massive rear spoiler and be much lower than its road-going counterpart. 16" front and 19" rear wheels and tyres would be accommodated by increasing the car's width and incorporating huge wheel arches into the body, providing extra downforce. Optimised weight distribution would be achieved by situating the engine and driver as centrally as possible. To develop the aero package, 1/5th scale models were produced and tested in the two wind tunnel facilities at Aachen University. Initially, the increase in downforce was estimated to be 50% above the road car, with the crucial surface being the overhanging front wing. Blueprints were then produced for Zakspeed to realise the full-scale car.
ABOVE: The ghostly wind tunnel model at Aachen University in 1978
As with most pure-bred racing machines of the time, the chassis was to be of space frame design, with a welded tubular roll cage structure forming the basis of the car to maximise torsional resistance. To arrive at a design that would provide the maximum stiffness and minimum weight that the Capri's slippery shape would allow, the Ford engineers hand crafted a scale model of the body shell and fabricated pieces of wire to fit inside. Lengths were removed and replaced until the optimum balance was found.
The initial phase of construction of the first full size chassis (ZAK C00178) began in the early summer of 1978 at Zakspeed's Niederzissen base with the construction of the roll cage. This took around five weeks and consisted of 80 metres of 30 to 40mm tubular aluminium. Erich Zakowski achieved much of this himself, along with his Chief Mechanic Helmut Barth and engineer Bruno Bunk, hand fabricating the tubular framework to fit inside the Capri's upper body, following the model produced at Cologne. Some square section was also utilised for the side rails at the top and bottom of the structure. The total finished weight of the entire tubular structure was just 75 kg.
LEFT: Thomas Ammerschlager said of the Group 5 Capri: "It's a big roll cage, really"
For the cockpit floor panel, thin gauge aluminium sheet was cut to shape and bonded to the bodywork using ultra-strong adhesive, mimicking the concept used in Formula 1 at the time. The gauge of sheet used was commented on by Zakspeed engineer Marco Fichter (the man who recently rebuilt Klaus Ludwig's 1981 car) in a recent interview: he noted that the sheet was so thin that light finger pressure would cause it to deflect - a dropped spanner would cause a permanent dent. And, with hardly any surface area on the bottom of the car to safely place a jack, four pneumatic jacks had to be incorporated into the lower chassis.
Group 5 regulations determined that the roof section, A-pillars and part of the bulkhead had to be the original steel work, so these parts were cut and welded to the bespoke spaceframe. However, for all the other body panels outside the steel cockpit area, cost considerations were cast aside and high-strength/low-weight Du Pont "Kevlar 49" Aramid fibre reinforced plastic was used as opposed to commonplace GFRP (glass fibre reinforced plastic). This handed the car a considerable weight advantage. The Kevlar doors, for example, weighed 65% less than a standard door - albeit at ten times the cost! All of the other panels were attached to the chassis with Dzus fasteners for quick removal.
ABOVE & BELOW: How the Group 5 car compares to its road-going cousin
|Production Capri 1.3L||Group 5 Ford Capri Turbo|
|LENGTH||4373mm (172.2")||5060mm (199.2")|
|WIDTH||1700mm (66.9")||1980mm (78")|
|HEIGHT||1351mm (53.3")||1140mm (44.85")|
The interior of the Turbo Capri is described as 'functional', at best. The bucket seat, covered with fire resistant Nomex material was located inside the bare shell housing constructed from aluminum piping, sheet metal and plastic. The driving position was moved as far to the rear as possible in order to improve weight distribution. The small three-spoke leather steering wheel (from the Granada) with a safety impact absorber, was adjustable as was the instrument unit attached to the steering column. The rest of the instrument panel, which was tilted towards the driver thus making it easy to see, contained a batch of instruments, automatic fuses and switches. Two additional knurled hand wheels were located on the instrument board with which the driver could regulate the brake distribution turbo boost.
Another clear demonstration of the commitment Ford and Zakspeed were making to the success of the project is the material chosen for the wiring harness - 0.435mm2 silver-wire cable, as commonly used in aerospace. This achieved a 50% weight reduction on standard cable even though the wiring harness would only ever have been a fraction of the total weight of the machine.
Back in 1977, the DRM series consisted of two divisions for Group 5 cars - those up to 2 litres (division two) and those above 2 litres (division one) - with turbocharged cars restricted to 1.4 litres in division two. For the 1978 and 1979 seasons at least, Ammersclager planned to run the new Capri in division two.
Regulations stated that the engine had to be from a Ford production model and the unit selected was based on the circa 1968 Cosworth BDA, originally used on the roadgoing 1600 Escort. However, rather than using the highly race tuned 2.0 litre version (as in the Zakspeed RS Escorts), they opted to reduce the capacity to 1427cc and boost it with twin KKK turbochargers, Garret intercoolers and Bosch fuel injection. With the agreed multiplication factor of 1.4, this would just allow the Capri to squeeze into division two (1427 x 1.4 = 1960cc). The in-line four cylinder had a DOHC alloy head with 16 inlet and exhaust valves, four per cylinder. This gave the first version of the car 380bhp and a top speed of 170 mph - with much more to come! Engine development was carried out by Zakspeed's engine man Ernst Hirsch, in conjunction with the Schrick company who helped with the manufacture of bespoke heads and crankshaft.
Squeezing so much power from the BDA unit was not without problems. Highly boosted, small capacity engines develop peculiar vibrations and the Group 5 Capri suffered initially from broken pistons, camshafts and cracked distributor rotors. A lot of work was required to iron out these teething problems and pictures show that various combinations of single and twin KKK turbos and Garret intercoolers were investigated. The problems were eventually resolved by fitting the engine with a single but larger KKK turbocharger unit with the twin intercoolers. By the 1980 season, the division two car was quoted as reliably delivering 450-460 bhp at 9200rpm - for a car weighing just 790kg.
|LEFT: Ford's Thomas Ammerschlager|
FAR LEFT: Citreon side radiator, skillfully heated and bent to fit in front the rear wheel arch
Heat was also a big problem, which led to many interesting additions, including a chrome-nickel alloy exhaust manifold capable of withstanding 800 Celsius. The car was also festooned with various cooling devices, notably the Citreon radiators skillfully 're-fabricated' to fit just in front of the rear wheel arches (see above). There were also three oil coolers - one each for the axle, gearbox and engine oil.
SUSPENSION & BRAKES
The design for part of the front suspension was based on a method that originated in formula racing: aluminium wishbones in the shape of isosceles triangles in conjunction with screw-adjustable ball joints to guide the front wheels. The rest of the suspension was taken care of by MacPherson struts which, except for the Bilstein shock absorber units, were made of light metal. The shocks worked according to the single-tube principal with gas padding, each holding a concentric titanium coil spring supporting a vertically-adjustable aluminium spring plate. Two Girling brake callipers were used on each front brake disc, these were also cast from an aluminium alloy. For temperature and weight reasons the brake discs were internally ventilated and horizontally perforated and could be water-cooled under extreme conditions.
As with the front wheel suspension, the rear axle was designed for substantial weight reduction. Here, where it could be most advantageous it was not only a matter of reducing the overall weight, it also had to do with the unsprung mass. This was kept as low as possible to allow for good road surface contact. For the above reasons, light metal was used in the rear wheel area wherever it was sensible and feasible. The rigid rear axle, representing a relatively large unsprung mass, was made of light alloy as used in the Gr 5 Escorts. However, it was initially found that the extra 100 bhp and high rpm torque caused too many problems and they temporarily switched to a stronger steel unit until an improved and strengthened light alloy one was developed in 1980.
The rear shock absorbers were similar in structure and operation to the principle involved on the front spring struts and also consisted of coil springs made of titanium. However, the Turbo Capris rear axle did present internally ventilated and perforated disc brakes of different dimensions. Due to better traction and a lower vehicle centre of gravity as a result of the 19 inch high rear wheels, the Capri was able to employ brake discs on the rear axle as had been used on the Escorts front wheels. Compared with the brakes on a conventional 16 inch wheel with a diameter of 285mm, their diameter was 302mm. On the rear axle the Capri could manage with only one brake calliper per brake disc.
The first chassis, ZAK C00178 was completed in the summer of 1978.