lets discuss air filters
 

Maybe its time to discuss this issue?
1st I dont think there is any need to panic about anything but there is more to an air filter than some may think? So in breaking it down (and please add anything I may have left out!)

1- right size is needed---how do you determine the size of a/f you need in reference to the modifications you have done? Is it obvious that a FI engine would need a larger a/f than a na engine? Is the oem size in reference to sq inch filtering ok for a fi engine or does the oem size restrict the air flow that is really needed? How is this determined?
I had a little discussion on this in the Pettit thread some time ago--but i have since lost it and fogotton some formulas we were using. If i recall correctly the oem size was not big enough for 300+ hp engines?

2- true cold air intake--- not as simple as it sounds. Placement is key. IMHO this cannot be done with the af inside the engine bay. Even racing beats setup with the airscoop does not cool the incoming air like an air filter placed out side the engine bay. It is also very susceptable to heat soak. It is better than oem
10f of increased air temp=1 hp is the standard rule I believe
Heat shields inside the engine bay do not work nearly as well--- period.
So the oem/mazdaspeed style is better or the long straight homemade "rams" that run outside the ngine bay or ok---right? Well MAYBE. because of the following #3

3- filtering ability------ something that hasnt been talked about much. But this is raising its ugly head lately. Race teams have lost engines due to sand being sucked in through the AF when the AF is placed outside the engine bay. The AF used by the teams was the K&N, which was properly oiled etc. Two engines lost iby one team in one w/e and sand was actually found in the oil pan. This info caused me to take another look at mine. When I did I could actually see little holes visable through the filter medium with the naked bifocaled eye. As I held it up to the sun and looked inside out many little holes were clearly shining! THAT AINT GOOD. Yes it was oiled.
Further research ,I discovered many sources saying do not use just the k& n by itself--- it is wise to also use a wet foam wrap around it to catch the small stuff (this includes exhaust soot etc) or use a paper type throw-a-way.
used engine oil analysis recently being done also reveals findings that can indicate poor air filtration. IMHO this is not an issue to ignore if you want your engine to last a long time.
I guess the day of just slapping a performance air filter on the engine is over.


So whats the best? Again imho the aem/mazdaspeed (both have paper type filters) units or a k& n outside the engine bay with a wet foam wrap seems to be the best way to go if you want a good true cai that filters well. Just dont forget to use the appropiate size----and what would that be?
thoughts and opinions?
OD

Subscribed. I don't know that I can add anything of value, but sure am interested.

A true CAI is probably the best solution, performance wise. I was researching your same formulae lately but didn't find much.

With the Revi intake from racing beat intake temps tend to be higher than ambient temp and i'm afraid that its insulation doesn't match the oem airbox one. In fact, i just received a mail from an italian guy that reported a pretty constant intake temp of 14°C with an ambient temp of 4°C. This is not a big issue but i told him to buy some house radiator's insulation foils and he replied after a couple of days stating that his intake temps with the same ambient temperatures as before were 4-6°C lower.

Now i wonder if anybody else tried something similar, in that case we could consider that kind of airbox again as an alternative to a CAI.

subscribed as well with the same reasons as RIWWP

Great topic OD, I have some info here in my thread as well. After reading and researching a bit I got rid of my K&N and went with a WIX filter. I believe Eric Meyer also posted up some info about sand in the oil pan on some dustier tracks when using the K&N and confirmed that a lot of teams use the OEM paper filter. I believe this combined with poor OCI and not getting all of the oil out has a huge effect on the engine. It seems logical to me but what do I know.

https://www.rx8club.com/showthread.p...ght=air+filter


Here is a test that I read.

http://www.bobistheoilguy.com/airfilter/airtest3.htm

That same experience turned me off of K&N some years back. Maybe a filtration expert can tell me I'm wrong, but it just doesn't seem good when you can see daylight through the filter! Not worth it for such a small power increase (if any).

You have to worry about an air filter company that claims their filter efficiency actually improves when it starts to clog up with dust.

I prefer a filter that doesn't use oily dirt as the filtering medium.....

Unfortunately, that test doesn't tell us much, other than all filters allow some dirt to pass. What's really needed to form an opinion is the particle size distribution. There will always be some minimum particulate size that will be passed. For an engine, this should be small enough to not compromise the oil film. Likely, the bulk of the visible dirt in each test was made up of these very fine particles.

As particle size increases past the ability of the oil film to carry them the likelihood of engine wear and damage increases. Even a small amount of these particles are much more important than the amount of "allowable" particulate size.

Yeah, I don't think the damn near unnoticeable HP gain is worth it. And honestly going back to the WIX I saw no difference in my Butt dyno and the WIX appears to test well from what I have read.

Good point.

unfortunitly auto air fliters are not classified to the particulant size filtering ability. unbelieveable and polictical.
I am buying the aem today. I just figured out that my 40lbs/min of needed air flow will be covered by the "standard" rx8 aem filter. It flows over the 526cfm of flow i need. I am going to do a straight "ram" type with the filter outside the bay.
I bet a lot of people dont realize the importance of the air filter.
OD

Cone filter?

it is --almost like the one that comes with the rx8 aem intake.
I almost dont want to change it as i would like my next uoa to have all the same controls as my 1st.
OD

This is the filter I'll be using, note that the 3.5" inlet size is rated @ 450 BHP, it weighs maybe 3 or 4 ounces

http://www.itgairfilters.com/airfilt...ection=maxogen

you'll have to wait for pics later on the rest of it

Mine is about as Cold air as you can get :evil_laug

Are you sure that one side isn't sucking hot air from the intercooler :dunno:

Only when I"m driving backwards. Its not up against it.

where are yall finding the 90% pipe that goes behind the front bumper support? I have a silicone elbow but it has to compress to get through that space and I dont want that. Are yall using 3.5 "?

I couldnt install the aem filter outside the bay. Not enough room for the size of filter I need.
So I just placed it up agaisnt the "opening" as much as i could. its actually touching it.
measured temps between the bottom of the filter and the airbox tray on the way to work this morning and it was only 3degrees greater than ambient. It does heat soak some when you are not moving but it cools off fairly quickly once you start to move again. Not as good as the hang down type of mazda speed etc but ok for now.
dadgum a/f's now have a smoother transistion than I had with the k&N. I will never use those again.
Team --that is a interesting filter you have there--in just looking/reading its the best foam type I have seen. Do you DD the car with it?
OD

by the way how many lbs of air/min are some of the turbo guys requiring, and what are they running?

My filter is a 3" inlet. The silicon elbow that turns down there is a 3.5" to 3" reducing elbow :)

I did 3" filter > 3" tube> 3" to 3.5" 90 elbow > 8" of 3.5" tube > screen > MAF > 6" of 3.5" tube > 3.5" to 3" 90 degree elbow > 3" pipe with vacuum and BOV recirc > Turbo inlet

3" filter and piping? http://www.uuddlrlrba.co.uk/forum/im...s/facepalm.gif

OD, this filter is new for me, but the car won't be a DD. It is large and not easy to package in some situations. This will be a V2revision of my previous home depot NA intake, with a little more thought and polish but unfortunately slightly heavier than the original V1 concept which used a smaller K&N cone. The OD of the outer bell inlet base is approx. 7.125". The interior is interest, neither solid nor completely open, but more like a large honeycomb support pattern. The outer foam surface does all the filtering. It starts out course and progressively tightens up to very fine. I still can't believe how light it is, it weighs almost nothing.



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pics when you are done olddragger.

i think i might be doing what you are trying to do!

sounds sweet Team--i know you are keeping the inside of the intake tubing smooth and clean.
Are you funneling the piping?

Mawee-- i dont like pinching that 90% silicone elbow----i am actually thinking of whittling some off the front bumper support so i can get a better path. Whats that thing for anyway--low speed damage?

OR--maybe a lavaris air intake directly in front of where i have it now. decisions, decisions.

Has anyone thought about having a "trumphet style" pipe to the maf pipe?

the foam thing does nothing. the bumper is a 5mph impact bumper.

IIRC.

i've seen a few people do this (carbonrx8 i've seen personally). they knock the middle area out (with a sledgehammer) or you can cut yours out whatever. and then some people just leave the two towers. or some people weld a bar of good strength steel between the 2 towers. so its much smaller and just as strong, if not stronger, then the original.

The inlet on my turbo is 3".......I only expanded to 3.5" for the sake of the MAF.

Greddy kit guys go down to 2" piping.....

I ran a 3.5" filter for my 650rwhp vette, how much RWHP are you running with your Rx8 to make you think a 3.5" is so crucial?