Performance air filters

If you're not breathing easily, you may need a new air filter to help stop the wheezing!

Just like us, engines need to breathe. Restrict the supply of air and they won’t work as well as they should – something that’s usually reflected in an increase in fuel consumption. But although your power­plant needs just about all the air it can get, it doesn’t want all the debris which is normally carried in it – and this is where the filter comes in.

Tiny particles held in the air are trap­ped by the filter and prevented from attacking the pistons, bores and valve seals. Ignore the filter, however, and these particles can start to restrict the air flow, and in severe cases cut the engine’s power output by up to 10bhp. The key to keeping the airways flowing is regular servicing. Inspection schedules will always include a filter check, and usually recommend replacement – although you can renew it yourself in between normal intervals.

Subscribe to evo magazine

Subscribe today to have every issue of evo delivered straight to you. You'll SAVE 39% on the shop price, and get evo for its original cover price for a whole year!

Your car’s handbook will point out where to look, and getting to the part often involves the simple loosening of a couple of fasteners. Original equipment filters are made from a material similar to tissue paper, and look grubby when they need replacing.

To renew a filter, all you have to do is pop in the replacement. However, you don’t have to use a paper filter as a replacement, as there are other options to choose from. You could fit a sports filter, which simply slots into the original housing and will never need renewing.

Advertisement
Advertisement - Article continues below

Alternatively, you could go for a complete induction kit; this replaces the original system, including most of the ducting. Both additions improve a vehicle’s driveability, throttle response and power – with some set-ups boosting the output by as much as 10bhp and around 14Nm of torque.

Many motorists ignore induction kits and sports filters because their image is tarnished by boy racers, but that can be a mistake. The improvements these add-ons give in performance and fuel economy are well worth the money.

What’s more, this is a modification you can make on any car, whatever the age, and it shouldn’t affect the warranty – although it is still worth consulting your dealer about cover and notifying your insurer of the change.

Click on the images in the right-hand column for product information.

Rating the performance gains

To see how well cars respond when the standard filter is replaced by a sports set-up, we took a Vauxhall Signum 1.9 CDTI diesel and a VW Golf GTI to tuning specialist Regal Autosport in Southampton.

Here, we hooked the models up to a rolling road and logged power data with a standard element in place, then with a sports filter and a full induction kit. We used K&N sports filters (£48) on both cars, a K&N Apollo induction kit (£190) on the Signum and an Evolution V-Flow (£249) on the Golf.

Advertisement - Article continues below

Vauxhall Signum CDTI Standard*/Sports filter/Induction kit: 150bhp/152bhp/156bhp

VW Golf GTI Standard*/Sports filter/Induction kit: 218bhp/219bhp/224.5bhp

*As tested at Regal Autosport (023 8055 8636, www.regal-auto.co.uk)

Advertisement
Advertisement

Most Popular

Visit/features/202640/bmw-m4-competition-vs-mercedes-amg-c63-s-coupe-german-coupe-twin-test
Features

BMW M4 Competition vs Mercedes-AMG C63 S Coupe - German coupe twin test

The F82 BMW M4 is about to be put out to pasture, so does AMG’s recently fettled C63 S Coupe finally have its number?
18 May 2020
Visit/jaguar/202404/jaguar-project-8-evo-reader-experience
Advertisement Feature

Jaguar Project 8 evo reader experience

The Jaguar Project 8 is a 200mph marvel of engineering designed with one purpose in mind: to deliver the thrill of driving. We put some lucky evo read…
14 Apr 2020
Visit/features/18127/the-best-six-cylinder-engines-ever-we-pick-our-favourites
Features

The best six-cylinder engines ever – we pick our favourites

Six-cylinder engines can be found in cars of all kinds, good and bad. We collate the very best
13 May 2020
Visit/porsche/911/202636/porsche-911-carrera-to-be-turbo-only-as-manuals-stay
Porsche 911

Porsche 911 Carrera to be turbo only, as manuals stay

Porsche confirms the 911 Carrera won’t be available with a naturally aspirated engine again, but manuals stay. For now
17 May 2020