Hey peoples,

I've been thinking of picking one up to adapt to the 7....if possible.

If you don't know what it is, picture a K&N filter that completely replaces the blue airbox. The entire top, and sides are K&N, and the bottom is just a chrome base.

I'm sure it will flow alot better than my blue snorkel box does with just the K&N ring filter in there.

I know I will have to run an adapter since the ring of the carb is not the standard (I think 5 1/8") size.

I believe it will fit......but that brings up the question of the stock exhaust manifold. This new box won't have the little flexible tube from the manifold to the airbox (preheater hose?). Is it bad to run with that not connected?

Any feedback from anyone who has done this?

 

to keep all the houses that go into the airbox, you can use the Bonez intake system. Alternatively if you are able to, you can make it yourself. Here's what it looks like:

http://www.rx7.com/pics/sa-bonez-intake5.jpg

 

Im making my own intake, by taking the filter box off of a junkyard 7, cutting the sidewall and snorkel off of the bottom half of the box, and sandwiching a K&N between the lid and the bottom tray. Only thing is, the donor car is a diffrent trim level than my GSL, so it doesnt have all the vaccum/PCV nipples that mine has, and i dont know what ones i need to be hooked up, what ones i can plug, or whatever. Any suggestions?


***(EDIT)***
Oh ya, but i was thinking of using the X-TREME. but i have trouble dropping $100+ on an air cleaner.

 

I know you don't need the hose for the shutter valve. Mine is plugged off with a wheel lug.

 

Right. and which one is the shutter valve?

 

I dunno, itll be in pretty bad shape after that. (get $50 ready). Seriously though, opening the top ala Bonez is good for flow, but the base of the blue airbox still sux airflow wise. And adapting something for a Holley will have the same shape/transitional problem. Basically itll suck. Youd be better off with a K&N and a metal plate like the bonez. If you want a real improvement (proof on teh flowbench) I got what you need.

 

The shutter valve is located at the base of the carb, toward the back passenger side I think. It has two hoses coming out of it; one about 3/4" running in an L-shape to the base of the carb, and another longer, smaller hose that runs behind the carb to the rats nest I think

Also it has a small plunger that operated a butterfly in the base of the manifold. If I remember the shutter valve is sort of cylinder shaped

 

Well, i got it cut with a plasma cutter, so the cuts are smooth. And it only cost me 10 bucks all in all(havent bought the element yet), so its really cheap, and im sure its gonna flow a helluva lot better than the snorkel.

 

Yes, the snorkel is a big flow restriction, actually the black plastic flapper is the culprit (tested all this for you guys), thats why the bonez or cutting holes is effective. But the base of the blue box is still ill shaped for good airflow into the carb throat.

 

Ya, i figured that the little flapper was the problem. Anyways, my intake is better than the snorkel, and next to free. Ill eventually get something better, but probably not until i get exhaust and do some work on my carb/intake maniflod setup.

 

I think these things are a good comprimise to all of that.

http://www.knfilters.com/universal/X-stream.htm


Just the top filter, cut a hole in the top of your airbox and your done, takes about 10 minutes and requires no other mods...


But they are too expensive, somethin like 60 bux for one...

 

Ugh, nobody listens.

 

Some traditional Pontiac racers found a whopping 2 HP gain from 440+ HP mills with the filter lid addition and deemed it a "don't bother" buy....we need rx7carl to do a flow test and see if some unknown turbulence is being caused by the air coming in on different vectors to the carb throats...ps., these are sharp racers who regularly trash stuff and then tell all...Gach had to start his own website after being kicked out by one of the big sites who relied heavily on some of those manufacturers..

 

Im listening. And in understand what your saying. I just dont got the cash for the Bonez.

 

I`am listening Carl! (I did your airbox mod :to cut open the sides)

Nice difference!

Sent you a PM

Karis

 

mar3 I did the flow tests. The biggest restriction is the flapper in the snorkel. The bonez style lid helps by allowing air to bypass the snorkel, and works good for emissions/stock cars as it allows all the hoses to remain intact. The second problem with the box is the sharp 90* turn into the carb throat and the big bridge used to hold down the box itself. There is a big shearing of air as it tries to make the turn, effectively choking the inlet. I have solved that with the airbox mod.

 

I was thinking of you testing one of those K&N filter lids, no other mods....there has to be some reason why no significant gains were being seen on hot street and all-out race mills....or maybe it was because they were Pontiacs....naaahhh, that can't be it!

 

You know, good flow isn't as helpfull if you're still sucking hot air off the engine to get it. We tried an extra tall filter in our 84 and it did little to nothing to improve things. (for those that don't know, if you get an air filter the same diameter and an inch taller the clips will barely snap on, but leave you a 1" gap around the stock air box).

Point is, we ended up taking it off, and are going to build a custom airbox that draws cold air from where the front of the car (currently there's a coolant resivior where we're going, but that will change).

Point is, you want more fuel (air and gas) and cold air is denser and better for your engine.

BTW, that preheater hose is generally useless apart from extremely cold areas (I'm in florida, it's 80 outside, winter is in full swing). You won't miss it.

 

Look for the insulated cold air intake Spiv. BTDT. But thats half the story. The other half is getting the air into the airbox, and then onto the carb inlet in an effecient manner to maximize airflow. Think of it as a system.

 

 

Show a pic of the base of that setup.

 

hehehe...i need to paint the blue part.

 

Thats nice, but i think what carls trying to say is that the 90 degree bend into the carb is killing airflow. A nice curvy cone shape would be much better. (he has one, do a search)

 

you can read the thread here. The stock box with a K&N flows 259 CFM and the modded box (sides cut and cone thing) flows 315 CFM

 

Exactly. If I could make a 5 sec movie it would be obvious. The sharp 90* turn causes the air to try to conform to the shape. But since it has mass (remember science class?) it continues in a straight line. Eventually it turns down into the carb, but since it cant turn fast enough, the carb is effectively sucking through about a 2" hole. The rest of the area in the blue stack (an outer ring if you can picture it) is filled with stagnant, turbulent air that is going nowhere. This is called a boundary layer. Its a layer of air that has seperated/sheared off and is just sorta hanging out. Its a volume of air that is "lazy". It has very little to no velocity and just sits there and tumbles around. Now if you have a gentle sloping change to the shape, then the air can follow the contour much more easily (this is most important at high velocity or hi demand or RPMs). This means that the effective area in sq/in that the carb can draw from is much greater, which leads to much improved airflow capability. Thats why "velocity stacks" work, and also why they are named as such. I could go on about sub sonic aerodynamics all day, but thats the meat and potatoes of the subject.

FWIW, I did a test on the flowbench with this using dryice and water to create dry smoke to see this for myself so I could be sure that this is whats really happening in this situation. I wish I could make a vid of it. veddy interesting.