Johannesburg - Ask any Sarf Effrican petrolhead for the simplest way to liberate some more voomah from a standard engine and he'll answer: "Uncork the exhaust!"
Which is true, as far as it goes, but we often forget that getting cold, dense air into an engine is just as important as getting hot exhaust gases out.
This is especially true of Ford's fire-breathing turbo-hatches, the ST versions of the Focus and Fiesta.
Standard paper-element air filters are cost-effective for the manufacturer and work well in the damp, relatively clean air of the northern hemisphere, but they're less than optimum after a few months of what passes for air in dry, dusty, high-altitude Gauteng.
Which is where washable oiled-fabric or foam air-filters come into their own, particularly for the Blue Oval's Ecoboost siblings; Automotive Technology Specialists now has K&N cold-air induction kits for both models, which it claims will deliver a more authoritative intake roar as well as more power.
HOW MUCH MORE?
All else being equal, about five kilowatts from the Fiesta ST and 7.5kW from the Focus. Rather surprisingly, the improvement doesn't come so much from letting in more air as from reducing intake restriction, smoothing and straightening the airflow, and shielding the engine from fluctuations in engine-bay temperature.
That also has a welcome side-effect, says ATS - lower fuel consumption. But, let's face it, ST owners are more likely to be interested in the additional - and more consistent - power.
The cone-shaped filter is designed to provide maximum surface area for optimum airflow without enormous volume, while the oiled cotton fabric sandwiched in wire mesh captures the tiniest particles of abrasive Highveld dust.
And when it gets dirty, you just wash it out and re-oil it with K&N's special filter oil.
The 69-series Typhoon system for the Focus ST has an intake tract made from aluminium tube, bent the expensive, old-school way on a mandrel so that it doesn't flatten out in the bends - which would restrict the airflow.
Which is why it costs R5995 excluding VAT, while the system for the Fiesta, with its intake tract cast in high-density polyethylene, sells for R5099 without tax.
ATS has similar cold-air intake systems for most popular performance cars, as well as a range of washable oiled-cotton inserts that fit straight into the car's original intake system in place of the standard paper element.
More information from the ATS website or call (011) 670 8400.