Specifically what is restrictive? I have to keep the stock airbox for emissions/insurance inspection purposes.

Thanks
-Ross

 

Stock airbox?

I think you could construct your own and it would still be legitimate wouldn't it?

 

Like most stock airboxes, it's the shape of the inlet and outlet. Anytime you dramatically change direction or cross-sectional area you create turbulence. Good airboxes have bellmouths to minimise this and you can add these to some airboxes with a little work, but the shape of the FC airbox makes this almost impossible to do

Don't bother with aftermarket panel filters unless you're looking for long-term dollar savings. Replacing the element with a K&N or whatever will give you no measureable performance gains, because the stock filter is not a restriction.

 

For what it's worth, I installed a K&N filter and cut the top out of my box. Left the edges to hold the filter. It seemed to increase performance and sounds good too.

 

The ribs inside and guide duct is the biggest restriction to the stock box.

If you are going to keep the stock box, make these mods for increased HP and Torque:




Ideally you would want to remove all the ribs and the duct, but making those cuts will provide you with a good proven compromise (based on RB air box work in the late 80's).

BTW, cutting the lid off/open is a bad idea and lets too much hot air in. Minimal extra holes on the cold air side are what is needed.

 

Awesome pics mark. I'm going to keep my stock airbox too, but only because I like the stock look of the engine bay. I was planning on cutting out part of the bottom to make room for a cone filter. This airbox cutting idea looks interesting too though! I might try it. I wanted to clarify though, which side in the cold air side? The side that already has holes drilled in the picture? Thanks!

Steve

 

Yeah I call the cold side of the box, where I (and RB used too also) drill the holes that are close to the head light and fender- rather than the hot side which is closer to the rad and engine.

Its pretty surprising the difference of flow with just those minor holes drilled. instead of the cold side building up all the dirt (as in the stock design), it is much more evenly distributed through the filter panel.

 

Hey Icemark. Looks like your idea is better than mine. I kept my original box. Think I'll convert the same way.

 

Hey IceMark, have you had any experience with removing the airbox in favor of a cone filter, but leaving the fresh air intake duct, with an extention to direct cooler air to the filter?

 

I use a K&N cone filter with factory fresh air duct and cool air box right now.

The drilled air box above I use at emissions testing time.

 

Icemark... if I did this to my airbox, would that increase the fuel consumption? Does letting more and colder air increase fuel consumption?

I'd do this... but not if it increases fuel costs...

 

id like to know that also...my mileage is bad enough as it is

 

I have seen no increase in fuel consumption.

other than putting your foot into it a little more from a minor seat of the pants HP increase, and a slight audible increase.

 

yah i did that mod way back in the day, its amazing you can actually feel the difference

mike

 

Why holes on the interior portion of the inlet duct, as opposed to removing it completely?

JDP

 

If you take the lid off, or the whole box off, you'll be sucking in hot air from the engine bay. The best bet is to cut holes in the front of the box and remove the rubber trim right behind the headlight.

 

Probably would be better to remove the duct for reduced turbulence, but leaving part of it does force the air to flow over the entire filter, rather than straight in and down.

 

Correct me if i'm wrong, but isnt turbulence before the air filter better? It will dissipate the airflow over the entire filter area, instead of a single concentrated spot.

 

There are two unproven thoughts on that.

One, is that the smoothest air flow in, no matter what is better.

The other is mixed stream turbulence is better before the AFM, but smooth stream after.

The holes drilled work on the 2nd idea.

 

Cool... I am gonna do it! But... how did you cut those oval holes?!

 

Would you really need to keep the tunnel thing? into the air box or just cut it completely off?

 

with a 1"x2" oval hole saw.








Just kidding there is no such thing as a oval hole saw.

anyway, I just cut two holes, one on each side of the rib, and then filed it down between them.

 

This will have little if any effect. The stock snorkel needs to be connected to a sealed airbox to draw any air in. Air won't be pushed through it to a pod filter.

 

That's great! I already HAVE an oval saw. Thanks!

 

Well I'll be damned. Is there anything you don't know?
You know, I didn't really think about it like that, I just have a cone filter, but i still have the fresh air snorkel in place. I guess it can't really hurt anything, so I'm just gonna leave it there.