Thanks for the heads up on the metal cap. I'll have to pull it and inspect, don't remember if it has one. I know the Amsoil filter uses rubber molded into the filter there.

"Its amazing what you can get away with. "

Dann -2015

The things you only read on miataturbo...


Off to buy a bigger filter.

Thisthreadisuselesswithoutdyno.

For sure, because seeing the pressure drop at the air filter change, the boost level change, and the AFR change isn't enough to detect a change in air flow.

:bowrofl:

Oh yeah, it's faster with the air filter that has less restriction. Makes more power. :)

remember how you thought your car was making 350 for a very long time, and then made 250 on a road dyno?

that's why everyone keeps bugging you for a dyno

(but I agree with you that it's not really needed for this specific little experiment at least)

A dyno isn't needed to measure pressure drop of an air filter, in fact dyno's don't measure pressure drop. So we agree on that.

Still haven't dyno'd it, but it ran a 7.58 @ 95mph in the 1/8 a week ago. With the new stereo system installed. :dealwithit: :rofl:

Did you happen to get a chance to look at the AEM Dryflow filter?

No, but the Amsoil is a dry flow filter. Mail me one and I'll test it.

Just for curiosity's sake, have you measured the pressure *outside* the air filter under the same conditions? Pressure drop may be caused by airflow inside your bumper cover.

ooh that's quite a lot better than the last one.
congrats

what was the '60?
got the slip?

Electric fan+
cardboard +
duct tape +
length of transparent hose=
actual repeatable testing rig

You know, science and stuff...

There's a clear trade off of filtration efficiency and filter restriction. Any filter with a lower pressure drop will let more dust through.

K&N filters can be bought in anywhere from 4 to 8 plys. I don't remember the exact numbers but the 4 ply has the lowest pressure drop but maybe 92% filtration efficiency. The 6 play had a slightly higher pressure drop and a 96% efficiency. The 8 ply had a much high pressure drop and a 98% efficiency. We went with the 6 ply because of the trade off of filtration efficiency to filter pressure drop.

If you don't care much about filtration and performance is your only concern I'd see if K&N or any other company makes a 2 ply filter.

I have not. Good point. Easy enough to do, I'll test that. I doubt that's the problem, but man would that be awesome if that actually was affecting it!

I made several pulls on each filter, the results were very repeatable. I could build a test rig, and then people would say " that's not the same as an actual engine". :) But I do approve of cardboard and duct tape.

It was a 1.80 60', spun through first big time. Actually it spun first on every pass, this one I just stayed in it. I got to work on my launch RPM whenever the track opens back up, there's better times to be had with a better launch. And my flat shift needs work too, not sure why but the car lurches forward between gearchanges.

Yeah the thing is I do care about filtration though, cause I daily this car and I want it to last. I think I'm going to end up installing a pair of big filters Y-fitting together to 1/2 the flow through each filter to reduce the pressure loss. I have read about people getting high silicone in their oil analysis after going to a high flow filter such as a K&N and then the oil analysis improving with a air filter that has better filtration. Good info on the ply's, I didn't know they made different ones, not sure what the one I bought was.

I honestly think you're over thinking this filter testing. On Truck air intake systems that I'm familiar with at 500 CFM the intake system has about 20-25 in H20 (tested on a flowbench) mostly due to the throttle body for NA or turbo Inducer inlet for FI (usually about 3-3.5" inlet). Of that, 20 in H20 pressure drop the filter accounts for less than 2" H20 at 500 CFM. It's a tiny piece of the puzzle. Switching from high flowing 4 ply oiled filter to a highly restrictive 8 ply dry filter changed the filter pressure drop from maybe 2" to 2.5" H20 and the pressure drop of the system increased by 2%.

Basically, the filter is a very small piece of the puzzle in an intake system. I'd focus on keeping the filter inlet diameter larger than turbo inducer inlet (an inch larger diameter is good rule of thumb). An the path from the filter to the turbo or TB optimized.

By the way, we've found that filter size (filter media surface area) affects only mass of dirt accumulation possible before an increase in pressure drop occurred. Larger filters, with the same outlet diameter, typically only give you an increase in mileage intervals between cleanings, not a lower pressure drop when clean.

Yeah, this is the filter on my 250whp example above. Check the hose clamp on it for scale.

http://www.assassindirtbikes.com.au/images/R-1080L.jpg
https://www.miataturbo.net/attachmen...ine=1451442495

Its 3.5" wide at its widest part. Made 250whp at the same boost as the regular large filters have.

I think it makes little difference. Im surprised by this, but its my conclusion so far.

Dann

that tiny little guy is definitely choking down the setup, maybe not drastically, but it's not insignificant. I'll see if I can find results I've seen on a subaru forum. I really like it, and ran one before, and was saddened to find out it's insufficient.

But what Pat is playing with is not tiny. It's not even big. It's downright giant. So I doubt it matters.

I mean look at this plot


https://www.miataturbo.net/attachmen...ine=1451445093

and the filter it was made with
https://www.miataturbo.net/attachmen...ine=1451445093

Pat's is like twice that size. And he's not even coming close to making that kind of power

I guess someone made math for this stuff.
 

Kinda surprised this hasn't been referenced yet:

Air Filter | Turbobygarrett

A few air filter company's web sites also have calculators:

K&N Air Filter Facts You Should Know

Doing the math for my car I'm going with this K&N filter K&N RR-3003.

https://www.miataturbo.net/attachmen...ine=1451493649

At my goal of 250 crank hp, the math said 402 in^2 of filter material was needed and this one I estimated at ~417.

I'm curious what Pats calculations will be and how the filters measure up.

~ Chris

Power is the only change anyone cares about. Anyone can measure differences in random variables, but it doesn't mean it's significant to real world applications.

Get it on the dyno. Do 3 base pulls, swap filters, then do 3 more. That'll give you actual data.

I'm not going to lie, your numbers are not insignificant differences, but as others have said above, plenty of people have ran much smaller filters with much more dynoed power, so something's up with your setup, or your measuring methods.

Give it a try, you'll stop wasting everyone's time on these conspiracy theories.

My work bought this as a mistake for a customers car and all laughed at it's size. We'll be dyno'ing the changes between this tiny thing and a slightly bigger one on a NA8 with a GT2554 soon. I'm theorizing little to no difference.