I changed my air filter today and had a good look at the intake system on my car.

And frankly it seems crazy, the air flow is forced in a loop and make 2 180 degree hairpin turns. Jsut wondering what those who know a bit more think - I've no idea if this is normal.

How it works is air is channelled into the front left hand corner and there is a plastic pipe (missing in the picture but shown by yellow lines) that that feed the air to the right hand side. It is now below the air filter and the air flow is forced to turn right and up through the filter, and forced back toward the left. This loops round and goes back round into where the throttle is and presumable into the engine.

Why?

replying to my own thread :shakehead

The filter I put in yesterday was a KN panel filter and I'm genuinely, pleasantly surprised by the difference.

I'm not sure if its a) placebo effect due to a clean filter after 22k miles or c) due to the actual filter itself

but...

It 'feels' like its made a big difference. Even on the trip to work this morning, (16 miles) the economy seems better and the difference in response/pick-up is very noticable. Less getting bogged down at low revs and the 60-70mph pick-up on the motorway was much better. Not more powerful, just more eager.

Maybe I don't need a straight through intake yet

What's the yellow box, then? There obviously is normally something there, but why it's not the air filter is a little beyond me. My copy of Perry's tells me that a 180deg bend is responsible for a loss of 1.5 velocity heads, which can be combined with various factors and dimensions to tell you the actual pressure drop. I don't have those things, but (taking into account I'm not properly awake yet!) it works out as something like 6 times what it would be for a straight piece of pipe of the equivalent diameter. So assuming the nominal diameter is 4 inches, you're looking at an extra couple of feet of intake pipe!

What's the yellow box, then? There obviously is normally something there, but why it's not the air filter is a little beyond me.

The picture is sourced from google and part of the intake is removed so that a CAI can be installed instead claims to add an extra 12whp between 4k and 5k rpm :eek: Not bad for a 100hp NA engine.

In that front left corner there's a plastic arrangement to guard an empty space and the end of the intake is in there - the intake must be less than 2" in diameter and the 'pipe' flattens to an oval as it enter the main air box with the filter. You can just see the oval shape at the end of the parallel lines

At bumper level there's some fences to guide air up into that free space for the intake.

The CAI filter is mounted low down in that front left space and the pipe comes up turns 90 degrees and feed straight into the throttle mech.

Seems a bit crazy to me :crazy: - is the engine shared with something smaller like the 2, because the air filter would be much better in that gap, right next to the throttle body...

Seems a bit crazy to me :crazy:

Me too, that's why I asked the question

It is shared with the prev. gen Mazda2 but I doubt it was a common engine - would have been mostly the 1.25 and 1.4 from the fiesta. Maz2 1.6 panel filters are much smaller than the Maz3 version though.

But this 1.6 engine is also the current 1.6 100hp DURATEC engine in the mk2 Focus and AFAIK the Focus shares a similar route.