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.

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.

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 at the top of the page for product information.

How we tested

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.

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

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

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

Recommended

SEAT Leon vs Volkswagen Golf vs Ford Focus
Family hatchbacks

SEAT Leon vs Volkswagen Golf vs Ford Focus

The Ford Focus, Volkswagen Golf and SEAT Leon are all long established hatchbacks - we find out which is best among the latest crop
11 Jul 2020
Volkswagen Golf review
Volkswagen Golf

Volkswagen Golf review

The Mk8 Golf offers cleaner engines, an updated interior and the latest on-board tech, but it can’t quite reach the top of the class.
7 Jul 2020
New Volkswagen Golf 2020 UK review
Volkswagen Golf

New Volkswagen Golf 2020 UK review

The new Volkswagen Golf will have to perform well on British roads to live up to its legendary name
5 Jun 2020
New 2020 Volkswagen Golf: UK prices and specs
Volkswagen Golf

New 2020 Volkswagen Golf: UK prices and specs

Volkswagen has added a new 1.0-litre three-cylinder petrol engine to the Mk8 Golf range, lowering its base-price to £23,300
28 May 2020

Most Popular

New 2021 BMW M3 launched with huge grille and 503bhp
BMW 3 Series M3 Coupe

New 2021 BMW M3 launched with huge grille and 503bhp

The new sixth-generation BMW M3 Competition saloon gets a 503bhp straight-six engine and four-wheel-drive
22 Sep 2020
New 2020 Volkswagen ID.4 electric SUV revealed with up to 323 miles of range
Volkswagen ID.4

New 2020 Volkswagen ID.4 electric SUV revealed with up to 323 miles of range

The new Tiguan-sized Volkswagen ID.4 electric SUV becomes VW’s second ID. model, rivalling the Tesla Model Y
23 Sep 2020
New Range Rover Velar PHEV launched with 33-mile electric range
Land Rover Range Rover Velar

New Range Rover Velar PHEV launched with 33-mile electric range

Land Rover has given the Range Rover Velar an update, with a new plug-in hybrid powertrain and an improved infotainment system
23 Sep 2020