Space permitting, there's no reason you can't run two air filters.

In for complexity. :D

Where do I get some more space? :party:

Air filter is in the drivers side bumper cover right now. I'd try installing another if there was space... Maybe I'll pull the bumper cover and look, but I don't think that's possible, without a large order of complexity.

https://www.miataturbo.net/attachmen...ine=1450824565

Awesome! You really should do one no filter to get a baseline. I'm curious how much vacuum an open pipe has. Because velocity stacks exist for a reason. Whatever it may be.

All of these filters have a bellmouth/velocity stack shape on the inlet of the air filter. Due to the location of my air intake (in the bumper, immediately in front of the drivers side tire) I'm not driving this thing without an airfilter. One tiny piece of debris can trash this SC, and it cost more than an EFR.

In for results. I'd love to see a no filter run too. I see tons of crazy builds running with no filter and it seems like half the daily driven honda's around here have their no filter intake plumbed right through the bumper or headlight. It can't be that risky to make one quick pull, but I guess I can't blame you for not wanting to try it.

Well, that K&N is an oiled filter so i suspect that will be the worst of all. But it will also catch the most gunk.

Speaking of, i should pull mine off my car and clean it.

Ditch the filter and use some (new) women's pantyhose instead.

$10 says pantyhose (maybe even a screen) is more of a restriction than the original filter. The surface area on the filters pictured is huge.

^ He kids . . . he kids.

Seriously Pat, hit the dyno and give us some real A/B data?

I will be datalogging the pressure drop across the filter, and the boost level at the intake manifold. That will tell me if the air filter flow changes, which is what I'm measuring. Don't need a dyno to see the airflow change. A less restrictive filter will result in less pressure drop at the filter, and more boost at the intake manifold. I'll have that data soon. :) I don't need a dyno to tell me that more airflow will make more power.

Test done, data is in.

Observation: K&N filter material visually has larger holes in it than the Spectre. However, the Spectre has more fins, and has a filter that is recessed into the end of the filter for added filter area. Amsoil filter has the recessed filter too, though it is a lot larger on the Amsoil.

Air/Fuel ratios changes as expected, the filter that flowed the most air resulted in the leanest AFR, filter that flowed the least was the richest.

Conclusion: Spectre air filter shows the least restriction of the three air filters tested.

While the Spectre filter does flow well, it still falls to 85kPa at 7,000 RPMs. So... I might do a dual air filter setup one day, but not now. Have to buy the sawzall Joe linked before I can think of doing that.

Data (Amsoil data in first post, Spectre and K&N below)

https://www.miataturbo.net/attachmen...ine=1451072084

https://www.miataturbo.net/attachmen...ine=1451072084

https://www.miataturbo.net/attachmen...ine=1451072084

Also I now have a fitting installed in the supercharger inlet manifold (between the SC inlet and the throttle body) so next I'm going to measure the pressure drop at the actual SC inlet itself. That will show me to total pressure loss upstream of the SC, including the throttle, bends, pipe, filter.

You're welcome again :)

I just finished a car with a K&N filter, cone shaped dimensions:

2.25" outlet
3.5" Base diameter
2" cone tip diameter
4" total length

Its frikking tiny, but it made 250whp just fine.

Just saying.

I did this with the Spectre filter. At the same 7,000 RPM the pre-sc inlet pressure is 83.3kPa while the pressure at the air filter is 85.3kPa. So 2 kPa loss for all bends, pipe, and throttle body. Not too bad. At 5,000 RPM is shows the same 2kPa difference too. Air filter is clearly the major loss in the system. So one day, I'll try a dual air filter intake but I'm not up to fabbing that anytime soon.

Thanks Eric for your help. :)

Dan, what are you just saying? I bet I could put that same filter on my setup and make 250whp too, so what? I've proven my car both benefits from more air, and needs a better air filter to increase the top end power.

If the Spectre has the metal cap on the End of the filter Keep an eye on it, they have had problems comming apart.

The shiny cap in the middle.
http://www.pepboys.com/product/details/9291232/

Yanks shop had a car lose an engine to a cheap filter cap getting sucked in. Company ended up paying for the rebuild.

I never thought I'd see the day Spectre filters being taken seriously :likecat:

Interesting results. :bigtu: