removal of air filter

[DropKickMurphy]

Hi all,

now this is an entirely hypothetical question, and i am more than aware fo the dangers of entirely removing the air filter from my car, but please indulge me here.

my brother and I were discussing this after reading an aritcle about a ferrari 250 california spyder which had velocity stacks instead of an air filter as this was supposed to improve performance.

would removing the air box/filter entirely give an accurate indication of what power gains are likely to be had from changing the stock air filter to some kind of induction kit/performace filter? or would it run like a tractor and suck up leaves until it explodes?

i suggested that it probably would, as there would be slightly worse air flow down the barrel of the throttle body with an air filter of any kind due to the impedace of the air flow, but this is likely to be countered by the relative density of cool air being sucked down the TB compared with having the induction kit removed entirely.

my brother said it would likely make the air intake volume worse as it would be gulping down hot air from the engine bay.

I am NOT advocating doing this - and before anyone asks it will not make your 1.4 into a ferrari baiting monster - but just as a hypothetical question.

comments welcome.

DKM

[SammoVWT]

Your brother is right.

If you remove the air filter you will be sucking in lots of heatsoaked air. Not to mention the fact that you will be sucking up all the dirt off the road and stuffing it straight into the cylinders - not good.

It will run better if youre at a high enough speed to stop sucking in the hot air by forcing enough cold air via the radiator into your bay. But you have to be going some to do that! So if anything removing it completely will make it sluggish and eventually damage something if you leave it off for too long.

Removing a stock paper filter/box is always better if you replace it with an after marker air filter - the results are improved by using airboxes and cold air feeds speaking from experience.

Hope that answers your question.

[DropKickMurphy]

I wondered if that might be the answer! oh well, i owe him a quid then...

I assumed that it would pick up loads of grot even on a hot dry day, and it looks like we have had our quota of those for 2009.

on a related note are velocity stacks just bad news all around then? the ones in the magazine article had a mesh filter on them, but would allow anything smaller than a bee in without any trouble. sounds like an expensive risk to take on a 250 swb!

DKM

[SammoVWT]

I guess theres a reason why these supercars have expensive services

Im not sure about a super/sports car, I'd imagine the same principles apply, but on a road car, dirty air is bad for sure.

As for race cars, they get stripped and rebuilt for every race, I guess thats the downside of having no filter.

I guess the only way to really test the potential of an engine without a filter on is a rolling road in a nice clean garage!

Edit: also remember that youre going to be encountering a lot more resistance with hot turbulent air with a restrictive airbox, your pressure losses will be huge. An aftermarker filter massively reduces the pressure loss, granted there still is a pressure loss - but it filters and flows a lot better than most stock boxes.

I know a lot of BMW's use foam filters as standard, so these are probably ok stock.

[DropKickMurphy]

I guess a service for a 1961 250 GT California SWB is probably hideously expensive!

it was an article on the road car, rather than a race-prep'd one which sparked the discussion, which was what surprised me. i assumed that dust and bugs and grot would be present everywhere and therefore the velocity stacks would have been a bad idea even way back in the sixties?

obviously the ferrari engineers were far more intelligent that I ever will be, but the question of why they were fitted in preference to a normal filter was never answered so i thought i would ask the assembled multitude for some other opinions.

thanks for the input though!

DKM