Is cotton gauze better? Better than what? Oiled or dry? What are the filter options?
There are few different air filter options commonly available, from the factory style, which tend to be a “paper” element, to performance style, which are typically foam or a cotton gauze type, which can either be ran dry, or oiled, for maximum dust filtration.
Stock paper filter elements, according to most of the articles you’ll read, actually flow quite well when new, but as they clog up with dust, naturally their flow reduces. You can blow the dust out with an air compressor, and it’s satisfying to see all that dust shoot out from the filter element, and you think you’ve got a fresh filter again. The felling I get is that dust is better out than in, so to speak, better to have a clean filter, than a clogged up dust sponge. But apparently the potential air flow isn’t restored to a paper filter after cleaning in such a way, and they filtering ability is compromised for futre use. They’re actually considered a disposable item, and can’t be cleaned.
Foam and cotton gauze filters on the other hand, can be cleaned, they’re marketed as being able to be washed, and can be re-used, costing you less money in the long term. And they flow really well, Possibly better than a brand new paper filter element. They can also be oiled, so they become “sticky” and dust particles flowing through the filter element have more chance of being extracted from the air moving through. Or you can run them dry, and get the improved flow and re-usability benefits.
So which is better, foam or cotton gauze?
We did a back to back test on the dyno with a Datsun A14 engine running a 32/36DGV carb, making about 65hp@wheels. Customer brought car in with a black foam element filter, and a simple check was a power run with the filter, then removing it, and then putting it back on. We constantly saw a 2-3hp loss with the foam filter, and it seemed pretty new, with no dust clogging it up. This is typical for air filters, as they naturally restrict air flow and engine power as they try to filter out the incoming airflow.
We put one of our rectangular DGV cotton gauze filters on, from another car in the car park, the filter was near new, and didn’t look dirty, but was used. So similar back to back comparative style test. And we got zero power loss with the cotton gauze filter. They do look like a higher flowing option, when looking through the cotton gauze when held up to the light, so not a big surprise, and if you want more effective filtration, you can oil it, but for the best flowing option, giving maximum power output, cotton gauze is the go!
