View Full Version : Air Filters - to run one or not

18th March 2004, 13:22
The logic behind running an air filter seems obvious.. but I know of an old sportscar which was built in 1934 runs twin carbs and no air filters..
It has done 117,000miles and is still running original engine and left the factory with no filters..

The carb intakes sit about 1inch from the side lifting bonnet so the chance of anything large getting sucked in are fairly slim..

Obviously the engine is not as complicated as the scoob engine..

What would be the problem doing the same on the scoob?

Simon smile.gif

18th March 2004, 13:58
Simon, ye olde cast iron blocks are somewhat more robust than choccy box ally, plus a turbine wouldn't like a spec of crap hitting it when its doing 20,000rpm, just look at what a bird strike does to a jet engine.


18th March 2004, 14:01
if you want your engine to wear itself out very rapidly, take the filter off. You will make marginally more power for small while until the crap going in increases the blow by to such an extent that you will have lost more power than you gained by removing the filter in the first place.

18th March 2004, 14:03
lol.. but it would be so nice to refit the resonator in the wing and connect straight to it.. lol

Oh well stick with running a boring filter then smile.gif


18th March 2004, 17:48
A friend of mine was awaiting the filter end of thier HKS induction kit (same as I had fitted to the wagon) and had a stocking over it instead :D make for an interesting 'filter' :D

Richard Askew
18th March 2004, 18:42
Never ran one on my old Golf

..nor in the rallycar.. just used to ram a duffle coat over the top of the carbs to get through noise scrutineering ;) :D

..would never risk no filter on the subaru (is that double negation in that sentence poor grammar?) smile.gif

19th March 2004, 07:22

But why was it okay to run without on the other cars but not on the Scoob?

My five minutes of madness have gone and I'll stick with the filter.. just curious..


Richard Askew
19th March 2004, 19:26
Cos the total cost of both engines on the Golf and the Escort come to about 8.34 :D

19th March 2004, 21:04

19th March 2004, 21:17
plus I am guessing neither car had a turbo, and as said, nasty things hitting a spinning turbo would be a bad thing equivelent to asking me if I have a nice selection of shirts :D

20th March 2004, 07:10
I am sure the turbo is okay to cope with a bit of dust.. the amount of oil the standard breathers through at it etc..

You must get dust from pipe wear anyway.. just in a lesser volume.


20th March 2004, 08:22
Simon, a water droplet can destroy the compressor wheel when it hit's those thin aluminium fins at 20,000rpm :eek: I would certainly not run without a filter for any length of time...

I guess it wouldn't be quite as bad using the original airbox...but I still wouldn't do it ;)

Lateral Performance Ltd
20th March 2004, 08:54
Small turbo's will be doing more like 140,000rpm on boost. A large grain of dust hitting a compressor wheel at this speed, could, if you're lucky, just take a lump out of a blade, more likely to take a blade off.


20th March 2004, 09:09
I am not planning to do it just thinking all this talk of must run with filter etc..

appears there is logic and reason behind that but I am noticing other things which appear to be myth so wanted to question this one..

It is good to readdress things I feel.


20th March 2004, 13:05
I can see no logic in running without an air filter.
A properly sized air filter will cause little or no restriction to power. Even an air filter that is marginally too small would cause such a small drop, it wouldnt be worth risking no air filter..
And a stocking would do nothing either for performance, or for preventing dirt entering the engine.
What logic can possibly outweigh the risks of damage for virtually no increase in power ?
There is always a way to fit an adequate air filter, even if it means remotely mounting it.