PROJECT CARS: K&N Deep Breathing


For a quarter of a century, I’ve been fitting “the world’s best air filter” to my cars – K&N – with great results.

And when you’ve got an engine as modifiable and up-for-it as the turbocharged gem that is the 1,985cc B202 T16 ‘Carlsson’ spec engine as found buried on a 45-degree slant under the long bonnet of Project Ruby – our beloved new retro ride Saab 900 Turbo – fitting a K&N was a total no brainer.

You see turbocharged cars love deep breathing. And it all starts at the air intake end, where Saab in their infinite engineering wisdom designed an absolute gem of an airbox, with a perfect cold air feed straight run into the engine and good distance from the heat-soak of the Garrett T3 turbocharger across the other side of the engine bay. Clever.

What Saab didn’t do though is fit a cracker of an air filter as standard – but a feeble, restrictive paper one.

Enter the K&N E-2450 – a direct replacement, high air flow & high filtration cotton gauze unit, that drops straight into the easily-unclipped Saab 900 Turbo airbox. It’s a 2-3 minute job, for a 2-3bhp gain… maybe even more (see on).

And at a very reasonable costs of just £47.99, and coming with a million mile guarantee and requiring no cleaning for 50,000 miles, it’s simple man maths, innit? As they say: “It’s the last air filter your vehicle will ever need… designed to boost horsepower and rate of acceleration.”

The genius of fitting the K&N – ahead of the forthcoming de-restrictive, turbo back pressure reducing gem that is the 2.5-inch Abbott Racing stainless steel exhaust system  – is that Ruby’s party piece ECU can immediately make the most of its new hardware. Ruby’s big brain is the end-of-the-line, top spec Carlsson ECU – the fabled (amongst Saab owners & ECU geeks) “red box” of tricks. Inside the red box is Saab’s ahead-of-its-time APC system (Automatic Performance Control) boost controller (on the cars from was early as 1982, paving the way for engine management systems to follow), which analyses airflow, boost pressure fuel and ignition timing etc. – allowing the engine to run at the limits of engine knocking, based on all engine and atmospheric conditions. Put simply, wherever it can, it gives you maximum power. So, the better hardware you fit – like the K&N – the more the APC system optimises performance.

So, with the fast flowing K&N in situ and some Shell V-Power super in the tank, the red box didn’t know what had hit it and immediately re-callibrated ECU settings to allow more boost pressure – visible and instantly noticeable on the lush, iconic Saab APC boost gauge, as Ruby knocked (reddit?!) on the door of the red zone. Boooooost! You could easily feel the difference with faster spool-up, greater mid-range punch and top end grunt and sharper throttle response. And you can hear the difference too, as Ruby took deeper, faster breaths and revved cleaner and louder. Go for it old girl!

Another (great) car, another (great) K&N fitted and enjoyed. And there’s only more gains to be had from the K&N, in conjunction with the high-flow Abbott Racing exhaust system (to come in the new year) and with the years of air filter maintenance-free K&N motoring to follow… Happy days. Cheers K&N.

Order yours here now!


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