Air filters. Confused.com

[Astonmazda]

Ive been looking at air filter kits on eBay and the prices range from £40-£599????? Wtf???

Which is the best filter to put on my 5???

Mike

[Mazda Mender]

I guess we are talking about cone filters here? as in getting rid of the OE air box?
M-m

[Shadgrind]

Just my thoughts, I remember some motorbikes that I have had and being told that air boxes are there for a reason. They allow for a forced air induction at higher speeds, and baffling inside keeps that air still at high pressure. Best to get a high flow filter in your air box, in my humble opinion.

Cutting holes in your air box is possibly the silliest thing I have heard, great sound, sure but performance, nope!
Won't a cone filter just flow more air but at the expense of losing the 'ram air' effect, so less air flow at higher speeds?

[Mazda Mender]

I 100% agree.
We laugh our heads off with the ..." i have drilled the bottom of my air box and it sounds great"... for what they cost just fit an aftermarket cone filter and have done.
Co*k ups will always come back and bite you in the ar*e.
M-m

[blackyb]

IMHO.

Mr n Mrs Mazda designed the car to have an air box as standard, so unless your going down the line of forced induction leave it be, if you must buy a K&N panel filter and look after it, that's what we did as well as fitting a nice sounding stainless system.

Right footies on so time for a brew!!!

[Skuzzle]

Better get an educated answer here.
Induction is important to get right although pretty much anything you do will have very little effect in either direction.
An open filter will draw in more hot air but if you are running forced induction it will also allow a greater mass of air flow.
The most important things with an intake are air temperature, restrictions, volume, flow turbulance, intake length and air speed.
The simple in theory, difficult in reality part is improving these past the standard system but it can be done.
The stock airbox/filter will flow enough volume for well past 200hp if the engine demands it but without fi it wont so there really is no restriction there. But it will restrict the speed of the air or the ease of the engine to breath that air, which is where high flow filters can help. The air will pass through them with more ease.
So we move on to turbulance. The standard airbox is not great for this but things are smoothed a little in the crossover pipe. The airbox does give a good volume of air available for quick throttle transition however as it is a large chamber of air sat ready for a rapidly opening throttle.
The turbulance can be improved by using a tubular system with a velocity stack at the opening to promote laminar flow. Smooth bends etc. The air this way will flow straight a smooth which will increase velocity. Air velocity is important as there is a moment on the intake steoke where the engine has done its job sucking in air. At this point air velocity takes over and gives an extra push to the air charge in the cylinder (a kind of boost if you like creating a small amount of compression and a larger mass of in cylindrr air than natural sucked in).
Even the stock setup does this to some extent but it can be improved and the improvement is more noticable at higher rpm where air velocity is increased.
On to length... i wont go into huge detail but this is the most critical part of intake design yet also the least. The length (due to reasons not worth explaining rigjt now) will have an effect on the shape of the power curve. Shorter intake pipes will give peaky top ends and longer pipes peaker mid to bottem ends. Agaim the stock system can be improved here but only if you have a clear mind of where you want the improvement and the skills to do the maths on the length you desire to make a gain at the rpm you want while sacrificing other rpms.
From there you can look at other ways to improve air velocity. Take a little look on the world wide web at the term venturi effect. This will give you an idea of what im talking about.. but essentially if you start at a large diameter pipe and then shrink the diameter the air will speed up as the pipe shrinks (already happens in your inlet ports.. but other venturis can help).
After you have all of this science and theory in your head and you fully understand it you can make educated decisions about what works and what doesnt.... but ultimately intake air temperature will have as much effect as anything else above and being 1 of the easier things to improve (wheel arch or mouth mounted air duct) is probably the first place i would start improving.
A fantastic improvement design is what has been well documented as the randall cowl intake (designed by a guy named randall) which uses a hole cut in the bulkhead as the air feed. The area where the window wiper mech sits is high pressure when at speeds and in my test lab (or something similar) with data logging positive pressure has been recorded in the inlet manifold with this setup when above 95mph.
Essentially what im saying is the easiest way to see a good improvement is a free flow panel filter.. remove the little pioe from the airbox that goes into the wing and replace with a 3" duct through a hole to the but the wiper mech sits in.

Thank you and goodnight ;)

[Shadgrind]

Essentially what im saying is the easiest way to see a good improvement is a free flow panel filter.. remove the little pioe from the airbox that goes into the wing and replace with a 3" duct through a hole to the but the wiper mech sits in.

Didn't quite get this last bit? But thanks very enlightening![WHITE SMILING FACE]️

[Skuzzle]

Sorry. Keep the air box but put a free flowing filter inside it. The small pipe that routes to tje airbox from the inner wing can be rwmoved and replaced with a big fat hose to take air from under the windscreen basically. Best setup you will get without having a dyno and a racetrack and a car with datalogging.

[Shadgrind]

Sorry. Keep the air box but put a free flowing filter inside it. The small pipe that routes to tje airbox from the inner wing can be rwmoved and replaced with a big fat hose to take air from under the windscreen basically. Best setup you will get without having a dyno and a racetrack and a car with datalogging.

Nice![FACE WITH STUCK-OUT TONGUE AND WINKING EYE]

[Shadgrind]

Where to get the 'big fat hose'?

[Mazda Mender]

The bay of E have them.
M-m

[Shadgrind]

Great, what sort of dimensions? Or do I just look for 'big fat hose'?

[Mazda Mender]

In different coloured ends in this search, all from china , but someone in the UK will sell them if you go throught the full search .
M-m

[Mazda Mender]

But i am sure these guys will have something, i hate looking on there web page because i end up with a massive list.....

http://www.carbuildersolutions.com/uk/
M-m

[Shadgrind]

Had a look but still unsure what I am looking for what sort of hose, went to the ducting part of the site :confused: