Ford's FWD rally Fiesta with a 4-WD secret
The 1979 Monte Carlo Rallye will certainly go down in history as a dramatic motoring event, but away from Darniche’s last night surge through the field to win by just six seconds there was another battle going on. A struggle that should also attract the attention of motoring historians. The fight within a fight was that of the major manufacturers with their front wheel drive hatchback designs.
The usual protagonists were there. In the Italian corner Fiat had sent along a pair of fuel-injected Ritmo 1500s. From France there came the defenders of the unofficial FWD crown, Renault. Last year La Regie had pulled off second and third overall! This year the same drivers were back with their Renault A5 1.4-litre machines.
The Germans were not directly represented, but they had an excellent chance of winning the FWD battle with the car most saw as the best the Golf GTl, one of which was driven very ably by Jean-Luc Therier.
Representing “Multinational Enterprises Inc.” and drawing on skills from Britain and Germany were Ford Motor Co. The Fiesta was making its rallying debut for the factory upon the Monte! That is a fairly harsh spotlight to enter the arena beneath, so we thought we would interview the men responsible at the Boreham end of things about the rapid behind-the-scenes development that made such a debut possible.
The Fiestas did not win first time out, but if it had not been for the Ford strike Ari Vatanen might well have finished eighth instead of tenth, and scooped the FWD honours from eighth-placed Guy Frequelin in the R5. How so? The Fiesta Vatanen used had to be built in a hurry in Germany and did not feature the same driveshaft spacer arrangement as the British entry; this made an effective cut in driveshaft length and led to a failure that cost Vatanen dearly. Without the road penalties he would have finished eight seconds behind the Renault, but since he was catching time hand over fist at the stage the failure occurred it seems reasonable to suppose that the young Finn would have won – neither the Golf (which was the fastest combination as well as the largest engined at 1.6 litres) or the pair of Ritmos finished.
Britain’s Roger Clark, MBE, finished 13th with very few problems encountered, though it was perhaps a little nostalgic for him to be back in a FWD car after so many years of Cortina and Escort motoring. They did have a problem with a fuel filter “O” ring failure on the road down, but otherwise the British entry had a pretty undramatic run. A fact emphasised by the photographs which came back, none of which show Mr. Clark in his normal sideways stance.
The reasons for the lack of drama were apparent when talking to Ari Vatanen about his first competition FWD drive. “The steering is very good, you just point and drive.” A slow grin spread over the young Finn’s face as he added, “it needs all kinds of trick to get the tail out! The Ieft foot is very important in this car, always breaking and driving to keep the engine working. They say I can use 8,500 r.p.m. but I don’t do this: it sounds enough at less, so why take a chance?”
Co-driver Richards added that:”The interior is very well laid out. A lot of thought has gone into making sure everything is where you want it. Noise? Much less than in a Group 4 car. Ari definitely needs to drive FWD more, I had the feeling he always had something in reserve.”
Both noticed that the engine needed quite a lot of revving to keep running smoothly and it seems that, with near-racing power output extracted from the 1,599 c.c. Kent cross-flow motor, an extra spread of torque might be more welcome.
For the 1978 season a number of low-key Fiesta development projects were announced or authorised by the factory. Russell Brookes took one out on a club rally; John Taylor looked at the rallycross and tarmac potential with a 150 horsepower plus version that featured the first of the Hewland gear sets within a modified production casing and Bill Meade, the Ford RS high performance parts engineer (as opposed to the competition engineer Allan Wilkinson whom I wrongly mentioned last month) produced a number of quicker Fiestas.
All this was peripheral to the Group 2 Fiesta we are discussing here. That really started with the homologation on May 1 1977 of the US Federal Fiesta 1600. That gave Ford a 1.6-litre pushrod engine base to build on.
Just about a year ago, in the early months of 1978, former Weslake engineer and well known member of the Boreham staff John Griffiths was assigned responsibility for the construction of a Group 2 Fiesta, utilising the parts already homologated on that May ’77 form.
The first step was to assign design responsibilities to Len Bailey (not Len Terry, as we had last month!), and Hewland. The latter were to produce a suitable pawl-type differential for the Fiesta, having already completed a perfectly satisfactory four-speed set of ratios for the competition Fiesta.
Bailey drew up the suspension for the Fiesta (which I will outline later), but there was sufficient doubt about the drive characteristics of the pawl-style differential to also investigate what Ferguson’s four-wheel drive experts could offer up in Toll Bar, Coventry. Why Ferguson? Remember those 4-WD rallycross Capris? They used the Ferguson system, and such a production car was put up as a serious limited-run project.
The link was Bill Meade and the others at Boreham, who had persevered with those rallycross Capris. Meade was not officially brought into the project until the recent strike pushed the development schedule way off, but once in he displayed his usual full-blooded enthusiasm for anything new (he was an integral part of the J25 Escort Twin Cam project, amongst others) and the Ferguson differential had an ardent supporter on its side. Since they had used it in the Capri, Ferguson’s transfer box had been notably refined by the deletion of mechanical clutches and the substitution of a viscous coupling. It was and is this component that gives the FWD Fiesta the snatch-free driving manner of a RWD car – though the handling is still FWD. The heart of the matter is a sealed canister to which both driveshafts are attached, but only one enters within. Inside the space is divided amongst multiple discs with small gaps between them and holes cross-drilled in the faces. The discs move through a silicon-based fluid. The faster the discs are turned, the more resistance is generated with attendant heat rise and pressurisation.
Therefore the effect is a very progressive locking one on the differential action, rather than the reaction to torque generated in most mechanical differentials with a limited slip action. In testing it was found that a mechanically limited differential was fine on tarmac, but on the loose the car became all but undriveable through snatching violently from side to side. With the Ferguson layout the limiting action starts as soon as one wheel starts to spin. This does not happen on fast tarmac use – “you would be better off with the normal differential rather than a mechanical limited slip on the loose,” Meade comments dryly – but when the differential is in action they reckon they can get up to 85 per cent. mechanical efficiency. “The closest parallel I can think of is a torque converter,” says Meade. From a Ferguson viewpoint the design is totally new for this Ford application, but the principles had been established by their 4-WD development.
Testing with the Ferguson differential layout was underway by August/September of 1978. The body that appeared as DHJ 500T for Roger Clark had actually completed a lot of work before it wore that registration plate, for the Ford facilities away from public eyes were extensively used. As per Ford’s normal practice in the UK, the bodyshell was prepared by Maurice Gomm at Woking. The 3-door hatchback received careful seam-welding, but the old Escort trick of re-mounting the rear shock absorbers in turrets is history on the Fiesta. The dampers remain in the production position and carry out the production job of locating the axle against modest torque forces through a strap that stretches over the top of the production dead axle and links down to the axle itself. Ugly, but effective enough for tarmac at present.
However, I should hate readers to think that Boreharn/Gomm ingenuity is to die with the Escort. Though the Fiesta looks a lot simpler than the Escort, there are aluminium wheel arches and a 6-point roll cage to consider. The interior cage picks up in the rear damper top-mounting area, also covers the centre (B-post) with side location bolts and runs down the inside of the front screen, culminating at the dashboard. It would be tempting to run the cage on through to the front suspension mounting points, but that is possible future development. At present those front mounting points are just thicker and carefully welded.
Inside the rear hatch the problems started. A large 12-gallon bag tank was deposited on the floor with a dry sump tank to the right and myriad pumps to the left. Because of the Fiesta layout as a hatchback the team had to seal off the new fuel tank with perspex and alloy sheeting internally, so there is a rear window within as well as outside! Alongside the factory Monte car another Fiesta, originally the recce machine, was having its floor space below the rear passengers removed totally. The idea is that the large tank may be squeezed in here in future, possibly even with twin tanks, and the rear sealed compartment will be unnecessary.
At first I thought the round Lucas headlamps were some Meade throwback to the Escort TC days, but the Federal version has them anyway: the normal foursome of Cibie ancillary lamps are as usual.
The rough road testing swiftly highlighted the need for restraining the engine. This was done by a two-part crossmember along Escort World Cup principles that holds the motor in secure tension with the aid of silentbloc mountings and a location link from body to the top of the transmission bellhousing. “If the engine does move it upsets the handling and snaps constant velocity joints straight away,” says Meade factually. “Anyone who is planning to do the same thing should note that the crossmember needs dowelling and Helicoiling into the engine assemblies.”
The front end of the car is where the money is spent. Apart from the close-ratio gearbox and the substitution of epicyclic and planetary gears instead of the normal bevel drive transmission (plus the Ferguson-modified differential action) there is a new suspension layout to consider. This revolves around a new bottom arm, triangulated in tubular steel with one Rose joint at the outer end, and rubber up front to give minimal compliance.
A freshly designed cast alloy upright houses the 2-row SKF new generation wheelbearings as well as having provision for calipers front and rear! It is possible that separate calipers will be used in the future.
Though this “bigger and better” upright pass replacement driveshafts (about an eighth of an inch thicker) which are attached to new, stronger, constant ‘velocity joints. Many of these components, including the wheel bearings, are actually supplied on other brands of production car, but this is incidental to their suitability for competition.
At the rear new suspension parts are confined to the lower tubular steel location rods with Rose joints at one end. Boreham have now reduced their use of Rose joints in general feeling that too much of a good thing leads to, at least, premature wear and service demands. Of course Bilstein gas-filled dampers are fitted to this factory Ford, but they are directly interchangeable with production components. Looking at the damper central shafts on the rear you can see they are doing some location work by the extra-sturdy diameter of the central tube. New coil springs were made up, this light car asking only 170 lb. front and 150 lb. rears to provide handling that was generally widely praised.
Braking is an area of continuing development on the Fiesta at present. The cars actually went to the Monte with AP 4-pot calipers that had to be removed to change pads, and that demanded some extra machining inside those four-spoke alloy wheels. A new Girling AR 5 caliper will be called into use on the front and this will allow pad changes in situ. Luckily Ford only had to change pads once on the Monte and that was in a 30 minute service area!
The factory Fiesta eventually used 4-wheel ventilated disc brakes some 10 in. in diameter at the front and around 9 in. at the rear: the handbrake was less of a problem than is often the case on Escorts because the rear wheels are so lightly laden.
Talking about setting up the Fiesta overall Meade commented, “anyone can set up an Escort reasonably, to set up a Fiesta requires a lot more knowledge. Some things are critical. You cannot play around with ride height readily because you alter the angles on the driveshafts with a consequent mechanical risk. Another inch on wheel offset can turn a good Fiesta into a right beast, twitching all over the place. That is because of the negative scrub geometry – thus the built up “hubs” inside our front wheels. Geometry is all important and that is one of the major improvements we have been able to make.”
Meade makes the point that putting wider wheels on a production Fiesta can upset the handling and also cause malfunction in the cross-linked braking system. The factory used a variety of Dunlops on five, six and eight inch alloy wheels of 13 in. diameter. “We had always expected to use wider wheels at the front than at the rear with FWD,” recalls Meade, “and that is how it turned out when we went testing, it’s simply the better way.”
One of the least satisfactory aspects of the Fiesta was the clutch operation. There is nothing wrong with the four-sintered panels on the clutch plate itself, but a bolt on the activating fork showed a tendency to shear (it can happen on the road cars too, but the extra loads involved on the competition unit obviously do not help!) and there was the need for changes during the rally.
As an old Boreham hand, Meade also looks at Fiesta gearbox removal with disfavour. The Escort has a quick release layout for its ZF five-speed, but on the Fiesta it would take three-quarters of an hour: “We’ll get it down to 20 minutes, you see,” Meade prophesied with a chuckle.
Incidentally there are four final drive overall ratios for the competition Fiesta at present. Together with the top speed they provide on Dunlop A2 tyres at 8,000 engine crankshaft r.p.m., they are: . 5.91:1 (87 m.p.h.); 5.31:1 (95 m.p.h.); 4.85:1 (105 m.p.h.) and 4.36:1 (114 m.p.h.). The first ratio was the one used on the Monte. Gear ratios no longer have to be individually homologated.
I have left the 1,599 c.c. four-cylinder engine until last because that is a familiar item from Ford’s past – when it was usually homologated at 1,601 c.c.! – and it amounts to a pushrod Kent crossflow in a trim not far away from the old Clubman’s racing specification. The motors were built by Brian Hart at Harlow for the event and, I understand from Ford, incorporated Cosworth pistons allowing 10:1 CR (approximate); “selected” connecting rods; a Gp2 iron crankshaft; Cosworth A6 camshaft profile and the assistance of twin double choke Weber 45 DCOE carburetters upon new inlet manifolding. New exhaust manifolding was also provided and the complete package was reckoned to produce 155 b.h.p. at a safe maximum of 8,500 r.p.m.
Since the Clark Monte car also tested with an 1800 BDA 16-valve engine installed, it seemed fair to ask what the engine future held for Fiesta. Surely it can only be a class-winning car with 800 kg. and around 160 b.h.p.? That has not been the Ford style since the advent of the Escort.
As far as I could gather the future does lie with the 1600 pushrod. It may grow fuel injection – the problem is where to mount the injection pump as the crossmember gets in the way on this transversely-mounted motor. They will also be tidying up the fact that the exhaust manifold has to be removed to get at the alternator: that component often needs to be reached in a hurry on a rally car….
The Cosworth Ford 16-valve engine is out for the Fiesta unless Peter Ashcroft can persuade the powers that be to let a special run of 400 road-equipped BDA Fiestas into limited production. When I wrote this it seemed unlikely: I even heard a rumour that Ford wanted to produce a rear or mid-engined Fiesta BDA to give Renault a run for their money with that R5-turbo we have discussed recently! That seems even more unlikely to happen.
One thing’s plain. The factory Escort is in its last season. They are talking about its final rally at the factory and the future in small Fords is about front drive machines. It is simply too early to tell whether this means the end of Ford as front-runners on international rallies – they could use other models in the range if overall wins are still the target and financially within reach. Alternatively a fuel-injection 1800 version of the Fiesta in pushrod form would be an effective weapon in the eighties when it is quite possible that only less-radically-modified cars of Group 1 and 3 will be permitted. Soon, say the prophets, you will not be able legally to run a Gp4 car on the road (an essential part of rallying of course) and when that day comes a Group Fiesta (currently under development) will be just the job!
Personally I’ll miss all the sideways motoring, but I expect Vatanen will have an answer with practice! – J. W.