A smoother blend
Now that turbochargers as a fashion have abated, a turbo is now more often employed where it is genuinely appropriate instead of as window dressing. At the same time, with the steady increase of expertise, such installations are incomparably better than they used to be, especially from a specialist such as Turbo Technics, which produces the twin-turbo Ford Granada 2.9 conversion we recently tried, courtesy of Bristol Street Motors (Worcester).
There was a period when a turbo was seen as an easy bolt-on tuning device which needed very little engine work to install — perhaps merely lowering the compression ratio with a thick cylinder-head gasket. Certainly the hours of work which once went into conventional tuning (fitting larger valves and bigger carburetters, and re profiling inlet tracts), suddenly seemed excessive for the modest power gains available, whereas the turbo seemed to offer a magical solution to large increases in power for less work. The result of this “short cut” approach by some tuners (and some manufacturers too) was that the turbo developed a reputation for poor power delivery, a reputation which was often justified.
With advancing knowledge, it has become clear that while the older mechanical complexities have been by-passed, a new field of expertise is equally vital to a successful system. Digital electronics has replaced trial-and-error carburetter tuning; time-switched water cooling systems are common, and turbine and tract sizing has become an exact science.
With 2500 conversions under its belt, Northampton-based firm Turbo Technics is perhaps the best-known British outfit, working directly with turbo makers Garrett AiResearch in developing new installations. The firm currently lists 24 different Ford conversions among the 50 or so packages it offers, and these make up the bread-and-butter work amongst the 10 or so cars dealt with each week. Cabriolet Escorts are a popular subject, but the Sierra 4×4 has proved the most prolific of the range.
Sharing the same four-wheel drive system, the heavier Granada 2.9 stands to benefit even more because of its sluggishness in standard form. Turbo Technics has had a great deal of experience of the Ford V6, starting with a blown 2.8i Capri and carrying on to the present 2.9-litre unit, and the system fitted to the Granada 4×4 blends in so smoothly that it would be impossible to guess that it was installed afterwards.
As in every such installation, the big objective is to reduce response times, and so two turbos are used, mounted on short specially-cast exhaust manifolds from each cylinder bank. The tiny blowers, the size at a couple of oranges squashed together, are water-cooled Garrett T2 units which have an integral boost control wastegate and an oil feed from the block. These cram the air through a large intercooler below the radiator, making it denser and more “nutritious” before it is passed back into the standard twin-plenum intake body.
Ford’s electronic injection system is unaltered, but to cope with the increased demand, extra fuel is squirted in by two supplementary injectors controlled by a separate digital black box. Compression is reduced from 9.5:1 to 8.7:1, while automatic ignition retard is tied in to the boost system. Looking under the heavy bonnet, the plumbing looks complex, but, as the turbos and intercooler are hidden from view, no more so than on most fuel-injection cars today. What is impressive is the look of quality; the manifold castings, brackets, pipes and hoses are all well made and obviously carefully thought-out.
Not surprisingly considering its complexity, this is the most expensive kit on Turbo Technics’ long list at £2950, plus the eternal VAT: twice the cost of boosting a Fiesta. Yet on a £20,000 executive car this forms a smaller percentage, and it really transforms the Granada. Where normally it ambles along on 150 unenthusiastic horsepower, TT pushes this to 210 bhp of a far smoother and urgent nature. It even idles more placidly, and spins right up the scale with all its usual roughness planed off, which would be an improvement even without the extra performance.
On the road, though, the added urge is addictive. Where the standard Granada needs a downshift or two to heave it past a truck, the TT car is brisk in fifth, and a revelation in fourth: on one of the A5’s long hills I was able to pick off two articulated lorries without strain where the unblown car would have been gasping. At the other end of things, the Granada would waft along in top gear as low as 1500 rpm with nary a shudder.
No hiccoughs or starting problems appeared, and the standard suspension proved more capable than I had remembered it. This was in fact the first time I have actually enjoyed driving a Granada, and it makes me wonder why Ford is happy to let someone else bring out the car’s good points; after all, the Cosworth engine would fit nicely in here. But this is an executive car, not looking for such a sporting engine.
There had to be a snag even to such on effective conversion, though it is actually a minor Ford problem highlighted by the extra power. There is a little slack somewhere in the drive-line, and even the gentlest nudge of throttle can send the whole affair into a kangaroo resonance at low speeds. But it is not enough to detract from the overall improvement to a worthy but stolid machine. GC