Tuning test: Turbo Sierra XR4

Foretelling Ford’s plans?

Those who have survived 21 years in the business of making production cars a little quicker than their factory-fresh cousins are becoming British rarities, particularly if they have not only survived the recent recession but also expanded steadily. Such a business is that of Janos Odor, long-established fabricator of specialist exhaust systems and — since 1977 one of the largest aftermarket suppliers of turbocharging kits, and complete cars, under the familiar Janspeed name.

One might have expected the years and increasing affluence to have calmed Jan’s enthusiasm for all practical engineering aspects of the speed business, but still his large frame quakes with laughter as the anglo-saxon expletives flow to describe his latest wares, or the shortcomings of the standard product. Perhaps his main claim for this Sierra conversion — which proved to be the best car we have had from the Salisbury concern in terms of speedy sophistication — was the throwaway line, “this is quieter than my Rolls Royce at 100 mph! You just try it with a decibel meter and see what I mean.” Worried that janspeed’s priorities might have changed toward providing the soft life on silenced wheels, I forgot the decibel meter and set about thoroughly enjoying 0-60 mph abilities in the seven second bracket and a genuine 130 plus mph capability. Unfortunately my pleasure in such exploitation, plus the superb bias toward mid-range boost and a startling bonus from mild handling modifications, resulted in mpg figures that! have not dared whisper to Jan! Suffice it to say I was returning 17 mpg over roads that have produced 18 to 18.5 mpg in lighter traffic with the standard XR4i/Capri 2.8i five speed. This supports Jan’s claim that mpg is in the same league as the standard car, although those pursuing pleasure at the 8 psi boost maximum can widen that gap considerably. Less enthusiastic use should provide the independently measured 21-23 mpg with the still considerable power bonus in the 2,750 to 5,000 rpm band to provide safer passing, and an aviation feel to requests for extra hillclimbing speed. In fact it feels as though the 2.8-litre Ford V6 has grown two extra cylinders and expanded a couple of litres under such circumstances.

The Modifications

The intercooled Rotomaster RM60 turbocharger installation in conjunction with basically standard Bosch K-Jetronic fuel injection is extremely similar to the already popular Janspeed kit for the Capri 2.8i, which has earned respect from the variety of owners and drivers we have discussed it with. For example a saloon car racing driver for a commercial rival to Janspeed told us, when he first saw the car during its three day commuting sojourn at the British GP: “If that’s half as good as Jan’s Capri it’ll be one of the quickest and best conversions you’ll ever try.” Well, it was not the quickest converted road car; from memory that honour still lies with the 150-plus mph Alpina turbo BMWs, but it was certainly a machine we were loath to return.

Internally the engine retains a standard specification, including the usual 9.2:1 cr. Externally the turbocharger is attached to the righthand bank (looking from the front) of Janspeed’s cast iron top manifolding. A link pipe carries exhaust gas over from the left bank. The turbo inducts air via the standard flap, compresses it and sends it onto the intercooler via a shining tubular steel pipe. The intercooler is mounted in front of the larger water radiator in Sierra’s nose, and the cooled air is returned via another impressive shining tube to be passed through the throttle butterfly thence to the standard plenum chamber atop the injection stacks. Odor estimates: “Based on our test room results the air emerges from the compressor at 128 to 130°C, the intercooler knocks it back around 70 to 75C and the completed mixture is delivered around 60°C. That’s very good for power with reliability.” Janspeed offer a 12-month warranty to cover the reliability aspect and comment only on power in the context of what is shown at the back wheels of the car on a rolling road. Ford quote 150 bhp at the flywheel for the Sierra’s injected 2,792 cc, while Janspeed find 109 bhp at 5,000 rpm as the normal peak for 2.8i-equipped Fords. Fitting their own high performance exhaust system from top to tailpipe “always seems to bring another 7 bhp on its own,” according to Odor. “For the turbo Capris we found 137 to 142 bhp at the back wheels, but with the Sierra it was 155 bhp straight away. We think this is because of a new down-pipe design.”

Underbonnet the layout is particularly neat with heat shields around the turbo, strategic use of Aeroquip lines and the unobtrusive incorporation of the black-boxed microcomputer equipment needed to instruct the fuel injection equipment. Regular 2.8i Ford users will be slightly puzzled by the injection layout until they realised that Janspeed have turned the manifolding and top chamber through 180 degrees, placing the butterfly induction side closer the turbocharger.

The white Geoff Mabbs-supplied XR4i otherwise remained standard, apart from the fitment of a 0-5-10-15 psi boost indicator literally stuck above the main instrument panel, and some important handling modifications. Working on the standard coil springs, Janspeed lowered the front of the Sierra 20 mm/0.79 in and the rear 40 mm/1.57 in. Four new Compomotive wheels at £95.96 each filled out the wheel arches in more convincing fashion than the rather skinny, drag-coefficient-conscious, production 51/2J alloys. Tyres were BF Goodrich Competition T/R 205/50 VR at the front and 225 / 50 VR at the rear. Although there is an enormous improvement to the handling, particularly in sheer grip, it is to Janspeed’s credit that they acknowledge a 195 section front tyre might be better to avoid the camber-following traits of the present 205s. It is also evident that clearances around the front were marginal, and it was a squeeze to fit the larger wheels into position.

In Action

Although the non-factory electric windows, branded Super Lift, failed within hours of the car’s delivery during the heatwave this was not an omen of a troubled 500 miles to come.

Morning starts in such Mediterranean conditions were predictably prompt, and only a 15 minute absence in 92°F would lead to any need for prolonged use of the starter motor for a hot engine restart. From cold to warm, for the temperature gauge never crept even to halfway in the worst of Silverstone’s traffic, the turbocharged V6 pulled with charm, and increasing zest beyond 2,500 rpm. The boost gauge would flicker over 1 lb per sq in, then rapidly escalate to 5 lbs or so at 3,000 rpm in fifth (just over the legal limit), providing astonishing ability to jet from 70 to 120 mph in that gear. At an indicated 5,000 rpm and 130 mph in fifth the Sierra was still warming to its task, but the chief attraction lay in the extra power between 2,750 and 5,000 rpm, which allows fourth and fifth to be the most used cross-country ratios. Such flexible power demands third for 40 mph curves, perhaps, but otherwise you waft across country with Ford’s excellent ventilation (augmented by the equally excellent tilt and slide sunroof) and modified suspension complementing Porsche-style performance.

If the mood is for ultimate acceleration, the Sierra turbo will handle 3,000 rpm standing starts with a slight squeak, followed by a squirming take-off and all the 6,300 rpm allowed by the production limiter. The use of 15 in wheels and 50 section tyres in place of the production 14 in and 60 per cent aspect ratio seems to have effectively raised the gearing and corrected some of the enormous standard speedometer flattery (around 10 mph at 120 mph for production Sierra), for 100 mph could almost be reached in third gear. At £1,750, plus £262.50 VAT for a fitted turbo kit, the Janspeed Sierra XR4i turbo may well foretell the way Ford will develop the performance Sierra, although we are told that the Frankfurt Show in late September may see not only a turbocharged Sierra, but one with four-wheel drive. We shall see. Meanwhile the modified XR4i from Janspeed can look the Capri 2.8i in the eye on performance and handling, whilst providing considerably more accommodation comfort, and freedom from claustrophobia than the aged Capri body could ever manage. — Jeremy Walton