Don Terrill’s Speed-Talk

I’ve used AEM dry flows. They were 3.5” inlet i think and maybe 7-8” long? On my turbo inlets. Dyno and track with the on and off made same power same times at up to 800 whp range. Didnt try any higher

FWIW, I have 2 k&n filters attached to the 3.5" hoses that connect to my airboxes. The intake MAP didn't increase running with them vs without them. IMO it's a good indication that they at least do not restrict airflow.

As far as filtering is concerned : I don't really know, but you have to clean them and re-oil them regularly.
Recently I checked the compression pressure on my engine and it's still the same as when I measured it after breakin, which was 5000 miles ago. So I think it does its work. I would expect the compression pressure to fall off when it would wear out due dirt getting in the engine which would happen really quick.

I agree that it's a definate no-go to have them suck in hot air. Mine are under the car behind the front spoiler. Not ideal but I couldn't get any suitable pipe over the radiator support and still have the hood close. At least they don't suck hot underhood air.

A big panel paper element filter seems ideal to me, but you need to be able to fit it somewhere.

As for foam ; I'm reluctant to use them as these were the first I tried over my stacks. One of them started seriously smoking after the engine spit back once. I never had to rush so fast to get the damn thing off.

How many times have you seen an engine with way to small an air filter on it.just got in a big inch Pontiac with twin 4 bbl carbs and tiny little air filters.i don't know who built it but you would think they would tell car owner about air filters.engine seems well built.

A frequently overlooked source of delta p is those 'sparrow-strainer' mesh screens on many IR systems.

Some foam socks can be a big power loss on IR especially if they get oiled with the stuff they use on dirt bikes. Last time I made the mistake of doing that lost 30% power. Getting rid of the oil meant it was down only about 8%

I can imagine that, however it's mostly the oil that does the filtering in those. So getting rid of it impairs filtering ability imo.

Being compressed into <40% of the available time, IR filters (and carbs!) are often badly undersized. Their pulsating instantaneous airflow peaks much higher than the near constant rate for plenum system ones.
It doesn't look nearly as cool with the stacks all covered up, but a throw pillow-sized single filter is usually more efficient.

This is what a few NMRA Coyote Stock guys do with those "cone" style filters.

Mind you, there is no gauze in them, strictly a screen.

We call this the "bucket scoop".