I’ve been reading all the threads that I can about performance filters and I’ve not got to grips with the pro’s and con’s of each type.

As I understand it there are two main types, foam filters and boxes such as K&N with wire like filters.

I get the impression that the box filters are the best and then foam and finally the carb sock.

Is this so?

And why?

The problem I have is space. I have 65mm from the face of the carb to the chassis rail which sits right across the centre of the carb mouth. I have some K&N filters which came with the engine but they are 75mm deep and so won’t fit. If I get thinner ones then the air flow will be reduced (less area) and therefore less horse power.

I have used carb socks, but one was blown apart in a carb back fire and luckily none was ingested by the engine.

The piper cross box for the pinto with 45’s is £200 and I believe it will not fit properly with out fouling the chassis. A lot of money to risk!

David J is making a filter for his bike carbs and that has got me thinking (I know a dangerous past time).

I had thought about making a box filter like the diagramme below with a cone filter on the end (80mm seems to be the diam that allows for up to 170 bhp).

The other alternative would be like the other diagramme, made of angle and mesh and covered in the foam type of material as David J.

What are your opinions..

Ditch

Rescued attachment box option 1.JPG

here is the foam option
Rescued attachment box option 1.JPG

ooops two the same, here is the box

ditch
Rescued attachment box option 2.JPG

I've gone for the box job in your bottom picture.

The outlet then goes to a BMC style air filter with a scoop in the nosecone to take cold air directly into the intake.

get an old dyson, chuck the motor and stick a hose from your engine into the dustcollector outlet

^^^^ is that an upright dyson or the smaller type? just happen to have a small dyson in the garage which won't suck.

my first plan was the air box with a remote filter.

why are the "air boxes" better than the foam sox?

ditch

quote:

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Originally posted by ditchlewis
why are the "air boxes" better than the foam sox?

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I have option no 2. Seems a better choice to me....

I've had a go at similar - have a look in my archive

Sorry, I can 't post fotos for some reason????

What ever system you go for, how much cold air you can get in will make a huge difference, i am currently running a domed pipercross 600 series, i will cut side vents in the bonnet post SVA and when funds become available i will go for the pipercross airbox as it fits straight on the backplate and has a built in cone filter then duct cool air from the front, this should be worth 5 to 8%.
Its worth remembering that you will not gain bhp persay its just that you are not loosing the full potential of your level of tune by sucking in hot air.

many thanks for the explanations lads.

i will go with my box option. i liked the idea of getting a clod air supply into the engine.

it's also easier to build.

should i use aluminium sheet folded or should i use fibre glass?

ditch

I would think of how stiff you need the walls. Engines pull quite a vacuum, so as long as the aluminium is stiff enough to withstand the vac you will be fine!

if it pulls that much vacuum then your air filter is MUCH too restrictive!!

There should be virtually NO pressure drop across the filter at full engine power.