K&Ns seem to cost quite a bit. Some of my pals have fitted them to Self Build Motorhomes and have claimed good results.
My view is that you could change a lot of air filters for that sort of money.
Mattb and jagman are quite right in what they say. You would better of looking at having a proper fuel pump set up and injector service before you ever spend out on filters. When I did a Smiley Transit I was getting around 37 to 38mpg: Before that, I was lucky to get 31mpg
Another good one is to have the engine re-mapped or re-chipped. It has made a heck of a difference to my Fiat 2.8L Turbo diesel
It won't make a blind bit of difference on a turbo engine. A turbo will quite happily suck it's way through a dirty or clean filter. A "performance" filter will be a waste of money. If you want more power out of your lump then a superchip is your answer for a decent gain without too much effort.
Wont transform your car into a beastie, but IMO not a bad move. From £28 delivered ebay you get a relative fit-and-forget filter that helps rather than hinders. With the price of fuel most minor improvements tend to pay for themselves that bit quicker these days.
Something to avoid are the bogus chips for a few quid if applicable to Diesels?. Theyre NOT chips, theyre just a ten-a-penny resistor (usually K3300 I think) that essentially enriches the mix till most cars EMC compensates.
Diesels are very good cars to remap, you can get quite a difference out of the performance with them. Air filters aren't going to add 50hp to the car, 2-3 at most if at all, but they won't harm the car.
Thanks for the info fellas.
Plan B,chipped/remapped again I no not a jot what they are/do.Anyone out there use/had these done to there car? Prices and any decent companys around London/Reading area would be appreciated.
There are a couple of option for you but the main ones are Superchips and TDI-Tuning, basically you buy the ECU plug in box (circa £100) then get it mapped on a rolling road.
standard ECU's are mapped at factory with for economy, loise levels and emisions so they run the engine slightly lean or rich in different parts of the rev range to get through the test, once the box is remapped it will run closer to ideal air/fuel mixture throughout the rev range and give you an increase in performance.
It's a deisal so don't expect massive changes in your BHP figures because your engine has a small rev range but you will get a healthy increase in torque so your car will pull better.
Mapping time on a rolling road will depend on how long it takes to get the fueling right but a couple of hours @ about £40/£50 an hour should do the job.
So all in a couple of hundred quid and a morning at the rolling road and you should be cooking with hexy, oh and you should get a small increase in fuel economy as an added bonus
superchips sites and tdi-tuning should have local rolling road addresses, you should be able to buy the chip from them as well.
A K&N filter is a good investment if you intend keeping the car for a long time and will also allow for higher performance set-ups to achieve their full potential if you have other work done later. On its own it will make no noticeable difference.