Has anyone fitted a K&N air filter to the 12TSi engine? I see they offer a straight replacement filter claiming a much greater airflow than the standard filter or a replacement air box with claims of up to 10 bhp improvement. I could see that the airbox might well invalidate the warranty but a straight replacement filter I think should be OK.

I have fitted a K&N filter to SWMBO's Jazz and we saw a 10% improvement in fuel economy but thought I would ask if any one had experience with a SM.

I fail to understand how a different air filter could make any significant change in a turbocharged and intercooled engine?

The pressure loss differential in the filter has to be minimal compared to the pressure losses in the air flow piping and intercooler.

Edited 8 December, 201015 yr by Agerbundsen

ive always had good results from junking the whole airbox and fitting an open filter...might be doing same to the yeti, as i love the rasp of a k&n'...and it defo improves throttle response

ive always had good results from junking the whole airbox and fitting an open filter...might be doing same to the yeti, as i love the rasp of a k&n'...and it defo improves throttle response

Rasp on a turbo enigine??? More likely a whine.

You only get lower pressure drop in a filter by either making it much bigger - or less effective for the intended purpose. I don't s'pose there is room for bigger? Hence poorer filtration

I fitted one to my 2lt capri years ago, definately faster but I had to put different jets in the carb to get more fuel through to get the power.

Ended up 4mpg worse all the time, and came with an unpleasant induction roar.

And then the engine had to be rebuilt due to bore wear at 60k miles, more foreign particle getting through?

I would tend to avoid any oiled type of filter, they can play havoc with mass air flow sensors. Don't get me wrong, I'm not anti modding, but tend to stay clear of the oiled ones.

Unless, of course they've changed the spec of the K&N.