Do 'performance' air filters actually do anything?

[Dudey Head]

They claim to increase air flow by about 30%, but there must be a downside. I've heard tales of people finding fine grit on the wrong side of them, which obviously can be pretty detrimental to your engine!
If they are that much more efficient, why aren't they fitted as standard?
And what about full induction kits? Some create a vacuum to force the air in quicker & keep it cooler which makes sense, but others are just cone filters in the engine bay which surely just sucks in hot air?
Has anyone fitted one (either filter or induction kit) & noticed much difference? Or none at all? Other than the noise they make!!

[paul b]

My mate swears by K&N air filters. He used one on his VW Golf V GTI and claimed it was making a difference to the mpg. He didn't notice a particularly large increase in power, but he reckons the gain was around 5mpg.

He had it chipped, and was pleasantly surprised to see that after the chip was removed that the mpg didn't drop off at all. It would seem that the chip made no difference to mpg for him, just power, and the K&N air filter was increasing the mpg.

My T5 van needs a service, I am soon to buy a K&N air filter and find out for myself if they work.

[macmillions]

My mate's fitted a K&N panel filter to his Fiat Brava 1.6 16v, he noticed at high revs there was a slightly different engine note, but no performance gain at all.

After the "disappointment" of getting no power increase, he fitted a K&N 57i induction kit. Sounded immense, looked pretty cool, as it was designed for the car. Made very negligeable power increase, but drank his fuel like no tomorrow, I suppose his ecu was compenating for the extra air being forced in and therefore added more fuel? His range went from 500 miles per tank to 350-400.

3 months later he ripped it out and stuck the panel filter back in. £140 well spent!?

[clive30v]

If set up correctly yes. The s70 T5 that was the old family car had a Pipercross foam filter fitted and made a nice sound but just sucked in hot enginebay air. then a massive blitz sus air filter was fitted to it. I then fitted with a cold air feed. By taking in cold air from the side of the rad rather then engine heat in made a sizeable difference. On my A4 b5 V6 30v I have fitted a panel filter. Without a before and after dyno run I cant say it has added any power but I can say throttle response has noticeably improved. And it pulls easier.

[Dudey Head]

A mate of mine is an MOT tester & said that he had an emission problem with a car with an induction kit on it. They put it back to standard & it was fine! Don't know whether that was a one off oddity though.

[Col]

On a modern 'open loop engine management ' equipped car, i.e. one which relies on various sensor inputs to govern fuelling, ignition advance and boost, there is nothing to be gained by one of these things unless it is mapped to take advantage of the increased airflow.

What is more important is cool air getting to the engine as the key sensor in all of this is the MAF or Mass Air Flow sensor. The key word being mass. Cold air has more mass than warm. The MAF tells the ECU how much air is coming in and the ECU then decides from it's mapping how much fuel to inject, boost to apply etc.

All that a high flow oily air filter is likely to do is ruin the already weak and terribly un-reliable MAF sensor by coating it in oil ! It might flow slightly better but the ECU will knock back the fuelling so your back to square one effectively.

Also, the stock intake on every modern VAG vehicle I've seen has a very well designed cold air intake.

I could go on but would summarise by saying they are a waste of time unless you get the car mapped to suit and even then the gain would be minimal, especially on any car with a turbo.

Far better to save your dosh and fit a bigger intercooler if your turbo'd. If normally aspirated, I wouldn't bother doing anything at all.

[macmillions]

Well said.
I tried telling my mate to not bother as it's normally aspirated (and a Fiat), but he insisted, bought one, realised it was a waste of money, but was too late.

Now he wants to supercharge it. God help us.

[andy pen]

Yeh been there and done that wasted about £100 on filters all to no avail.Best mod I did was a larger bore stainless exhaust from manifold back and that really did improve power.Now got a couple of expensive filters on the shelf doing nothing real wast of time and money.

[brown]

This one is such a common question on all car forums i've been on!
My two pence, older cars with very restrictive breathing systems can see actual gains.
Newer cars minimal - and really not worth the rediculous prices of some of them.

I did however put a K&N panel filter in my old Saab 900 turbo..... just cos it was gong cheap. no real gains felt though!!! But that said, its believed the standard filter was good upto 300bhp on that model anyway!!!

[Dudey Head]

This one is such a common question on all car forums i've been on!
My two pence, older cars with very restrictive breathing systems can see actual gains.
Newer cars minimal - and really not worth the rediculous prices of some of them.

I did however put a K&N panel filter in my old Saab 900 turbo..... just cos it was gong cheap. no real gains felt though!!! But that said, its believed the standard filter was good upto 300bhp on that model anyway!!!

They're such a common mod.
I've been tempted by it in the past but always thought that there really isn't going to be any noticable difference. I can see how some of the proper induction kits that actually channel cold air in can make a difference, just about. If you click on the link below, the last 3 items (ignoring the last which is filter cleaner!) are induction kits that actually have a bit science to explain how they can make a difference.

http://www.jetex.co.uk/website/jetexfilters.php

Likewise here:

http://www.pipercross.net/fastroad/products_viper.asp


But consider they're in the 100's price-wise, are they worth it? I'd need convincing with a before and after demonstration to be convinced before shelling out three figures on one.