When it comes to tuning engines, we’re all familiar with the understanding that the more air you can get in, the more power the engine can potentially produce. But it’s never quite that easy. For a start, in order to get that nice, fresh, cool air into an engine, we must first get rid of the hot, dirty, spent exhaust gases.
It’s easy to get hung-up on the inlet side of things, but we must remember that any restriction on the engine will hamper performance. They say ‘an engine is only as good as its most restrictive component’ so no matter how good the other bits are, the area you should always be looking at improving next is the most restrictive part.
That’s why you should never underestimate the importance of a good exhaust system. A well-designed, well-engineered exhaust system will make a positive difference to any engine, but the biggest improvements are found on turbocharged engines, especially tuned engines.
On a turbocharged engine, the most important part of the exhaust is the downpipe; the first couple of feet after the turbo outlet. A large turbo outlet and downpipe, even on a lower powered engine, can net surprising gains in turbo response and spool-up speed, even if the rest of exhaust diameter isn’t restrictive from a peak power point of view.
This is why Scorpion Exhausts have spent countless hours developing their range of performance downpipes for various fast Ford models. One of the most impressive is their large-bore 3in version for the Mk7 Fiesta ST. The fabled Fiesta is a tuner’s favourite of recent years, with many specialists now offering some really quite crazy power upgrades of 300bhp-upwards!
But, of course, none of this would be possible without the use of a free-flowing performance downpipe. Scorpion offer theirs in two versions; one with a 200-cell sports cat to ensure the car remains 100% fully street legal, and a de-cat version for ultimate power on track-day applications.
The downpipe may be the most crucial part of the exhaust system in terms of performance, but remember that an engine is only as good as its most restrictive part, so there’s no point in feeding those free-flowing exhaust gases into a tiny, restrictive cat-back system is there? Scorpion offer two different styles of cat-back system to complement their turbo downpipes for the Mk7 Fiesta; one in 2.5in diameter and one in 3in diameter.
The 2.5in version may not offer the full-fat performance advantages of the huge 3in system but is a huge improvement over the OE system. Just the cat-back alone has given 7bhp increase in Scorpion’s testing, so on a tuned engine where exhaust flow becomes more crucial it’s sure to yield even better results.
The 2.5in system is ideal for road use, thanks to the resonated system incorporating an additional silencer to keep volume within sensible ‘everyday’ limits. But even the larger 3in cat-back system, which is available in resonated or non-resonated versions, keeps cabin drone and boominess at cruising speeds to a minimum thanks to Scorpion’s clever ‘acoustically developed’ silencers.
Like all Scorpion products the Fiesta ST cat-backs and turbo downpipes are hand-made in the UK from T304 stainless steel to a high-flow construction. For more details, and to check out Scorpion’s full range of Ford products, head to the website.
01773 744 123
Turbo downpipe (sports cat) – £489.25
Turbo downpipe (de-cat) – £184.36
Cat-back (2.5in) – £513.97
Cat-back (3in, non-resonated) – £530.45
Cat-back (3in, resonated) – £565.47