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Cars and Car Conversions - Technical: Engine Tuning Fiesta XR2
"Roadrunner"
September 1981
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Technical: Engine Tuning Fiesta XR2




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Roadrunner

Yes, he's on the road again, and this month, Ian Sadler continues our occasional series of motoring sense with a discussion of the merits of engine tuning - particular reference being given to Ford's new Fiesta XR2


This occasional series running under the title of Readability is definitely not a 'how to' feature. A 'why?' series would perhaps be a closer definition. CCC runs plenty of 'how to' articles-the backbone of the magazine, if you like.

Ideally, all that goes under this page top heading should work like a peacekeeper, columnist, crank and sometime downright eccentric. It isn't necessary to agree with it (well, perhaps some of it?) or to take any heed of it. But it will serve a purpose if, every now and then, a particular point strikes a chord and stops (or makes) you spending money for/to, little/good effect, or steers you down the next, more inviting, avenue.

Whatever, it is merely here as a mild palliative when all those facts, figures, crank throws and compression ratios begin to bear down threateningly; if, like me, you think that you prefer driving to poking about with lumps of engine or drivetrain.

This month, and with apologies to Playschool, we'll talk about engines in a most basic sense. Let's look through the square window. . . .

Petrol powered internal combustion engines come in a huge variety of sizes, weights and outputs to suit-one is led to assume - a similarly huge variety of motor cars. But in this world of increasing standardisation, just as there are fewer mainstream motor manufacturers, so there are comparatively fewer engine types around. Taken to the extreme, 99 percent of all cars on the road could be catered for with perhaps as few as three engine sizes, each designed in such a way that by altering various component sizes and mechanical timings, they could be made to provide an infinite variety of well suited applications. We'd be out of business overnight! That is the way the industry is heading, but thankfully, it still has a long way to go to achieve such a goal.

If we, as an editorial team, weren't so downright particular in the first place, we'd find that after a year of sampling manufacturer's test cars, a great many are hard to tell apart in several, mainstream, ways. So it is with the engines of these cars: unremarkable in a turn-the-key-and-it-goes style. I think that it would be equally true to say that most of the cars which CCC finds interesting also have interesting, or at least out of the ordinary, engines to match.

Generally, we find two distinct types. The first is the engine which spins harder and faster to deliver its horses. It has to be coupled to a lot of gears in order to operate effectively, but if it is so, then this type provides a great experience. Responsive, free-revving and breathing in an 'alive' way, it makes us sit up and take notice. It asks to be driven hard and that is all the asking we need.

The second type (and the sort I prefer) is the larger, lazier, no-substitute-for-horses mill. With torque from tickover to infinity, doesn't need five close ratios, but just the same, it, too, makes us sit up and take heed; even though we will probably tend to drive it less hard most of the time. Fortunately, a great many of both types are derived from the very same engines which, in cooking trim, are uninspiring and unremarkable.

Unremarkable they might be from the driver's point of view, but such an engine's design and operational capabilities, aided and abetted by the development of superior multigrade (and synthetic) oils, has improved enormously in the short space of time of just 20 years or so. Brake-horse-power-per-litre output has risen - and that 'per litre' unit is a much more telling figure than anything else (see accompanying table).

Of course, nothing alters the benefit of a low reciprocating mass to such figures, using engines with several small cylinders for high efficiency. The tiny 49cc (single) cylinder Honda four stroke engine fitted to Honda's cooking get-you-to-work commuter bike pumps our 4.5bhp-that's 90bhp per litre. Similarly it is no mere coincidence that Renault's 1.5 litre Formula One race car engine is a turbocharged six cylinder (vee six), with a brake horse power per litre figure (an incredible 360bhp) far in excess of a normally aspirated three litre F1 motor (just 163bhp per litre for a Cosworth), for the latter, without turbocharging would still give a better 'per litre' power figure.

More important for everyday motoring, the typical unremarkable power unit offers something better than greater operating efficiency, and the resultant increase in fuel economy when properly tapped. That something is called is reliability, both long and short term.

In the long run, the engine of today does not generally ever require a 'head job' or a 'rebore'......

Captions -

Middle - You'd be better off tearing up £10 notes than driving a car which shoots down the straight bits and then flounders on the bends.