We can build filters to pretty much any size and shape you need: we can build flat panel, cylindrical, and domed filters as well as large, one-piece sock filters. It's also possible for us to build many of our standard range of filters using different foams or sizes to better suit your needs.
This will make a difference to the specification of foam we use. We have many different grades and laminates of foam that are all suited to different conditions. Circuit racing applications where there is minimal dust may only require a thin, free-flowing foam, whereas off road or rally filters will need a thicker foam with higher filtering efficiency, but lower flow rates.
The choice of foam will dictate the size of the filter needed. Better filtering efficiency requires finer foams that have lower flow rates, so the filter needs to be larger to avoid becoming more restrictive compared to a free flowing filter with low filtering efficiency. For example, on a 200bhp car using free flowing Touring Car foam for circuit use, we would need 250cm² of area compared to 400cm² if using fine G60 foam for a dusty rally stage.
Depending on your setup, you may need to make room for a properly sized filter. It's vital to increase your engine power and make sure the filter has sufficient room to breathe. For example, if the filter is pushed up against the bulkhead, firewall or the underside of the bonnet/hood, then air won't be able to flow into the filter. A minimum gap of 20mm / 3/4
This is a particular concern for race engines with carburettors or multiple throttle bodies. Some engines experience fuel stand-off where a fine mist of fuel hovers over the rampipes at certain points in the rev range and can be ignited if the engine misfires or spits back a flame. A stainless steel flame trap layer can be added to the inside of domed filters and the underside of panel filters to prevent this happening. This is also recommended for high value classic cars running carburettors or throttle bodies where the risk of an under bonnet fire far outweighs the extra cost involved.