how much of an improvrement does fitting a k&n type filter make ?????

It makes a nice noise, and saves you money on replacement filters in the long-run.

I have one (a JR, actually) on my C900 and I can't say I've noticed a tremendous improvement in performance, but there should in theory be a slight gain.

James

Deeks , James,

what youv'e got to understand is that any modification is relative to the overall engine spec.
Yes a free'er flowing air filter will help, but you have to ballance it with the exhaust output and fueling.
If you improve all of these aspect then you will get a more noticeable percentage of gain, you will also have to re-set the ecu - see Andy Bowles thread in the 9000 bbs

Damian

Damo9k: I quite agree. The JR filter came soon after I'd had a free-flow exhaust fitted. The car also has an Abbott chargecooler and dump valve, and runs (at the moment) on Super Unleaded. No ECU, though, because it was originally an LPT!

What's your opinion on rising rate fuel pressure regulators? Seems like that would be my next logical step.

Cheers

James

Hi James,

Rising rate fuel pressure regulators can / will help in almost all cases. But you will have to get them set up correctly on a rolling road.

All they do is increase the fuel pressure so that a)you get a punchier (is that a word?!) response when you put your foot down. And B, more importantly when your running at higher boost than the stock setup was designed for you dont run lean, which will lead to problems (see my response in 9000 bbs by Paul Ingeby - Hybrid turbos).

With most engine management systems the ECU will determin the duty length and cycle (frequency) of the injector fireing, so when you increase the fuel bar pressure the ecu will turn the length down a bit, This can actually give you better fuel consumption at normal driving conditions (what ever they are!) But at higher revs / boost the car has always got enough fuel.

Cya

Damian

I must admit considering the size of the normal turbo air filter (i.e. huge) i would'nt have thought you would get much improvement.

Having said this I would be interested in any positive responses as it's quit cheap to do.

Regards

Its not the size of the turbo or the air box housing that matters, If you look at the housing for the standard air filter it has a conicle neck with a diameter of about 2.5inches. That's where your restriction is.
Compared to an air filter that breathes from a 360 degrees.

Also if mounted correctly you actually get cooler air into the turbo which helps a lot, as I said earlier coupled with better exhaust flow this will help the tubo spin up better and the to breathe better.

D