I just completed a new version of the Ghetto Air Box mod and I am experiencing excellent results, so I thought I would take a moment to share it with everyone.

First, I had some very specific design goals:
1. Improve mid and high rpm band engine performance.
2. Maintain a relatively quiet intake.
3. Maintain low RPM torque.
4. Maintain stock air box.
5. Maintain stock air filter.
6. Minimize/remove risk of sucking water into the intake.

My first attempt did not work very well. Here's what I did on the first try:

Setup:
1. Cut open a 3" hole in the bottom of the existing tube on the bottom of the cold air "scoop".
2. Wrap 3" tube with 1/2" thick foam weather strip.
3. Use ideal clamps to attach a 4" dryer duct to 3" tube on bottom of scoop.
4. Route dryer duct straight up and then over (next to upper radiator hose) to the space in front of the battery and behind driver's side headlight.
5. Absolutely NO changes to air filter box.
6. Nissan paper air filter.

Results:

1. Increase in engine noise.
2. Big decrease in low end torque - engine bogs easily at 1500-2000 rpm. Stock intake does not do that.
3. Increase in mid and high rpm band performance.
4. Did not suck in any water, even during rain.
5. Ran this way for over a month.
6. Conclude that the 4" tube is too big and results in decrease in intake pressure and a resulting decrease in low end torque.

My second try I was much more successful. Here's what I did:

1. Purchased a 3" to 2" rubber pipe adapter from the plumbing section at Home Depot (thick black rubber and comes with 2 ideal clamps on it).
2. Purchased a single PVC 2" diameter elbow to fit inside the 2" end of the rubber pipe adapter.
3. Installed elbow into the 2" end of the rubber pipe adapter and installed the 3" end of the adapter onto cut open bottom of stock intake scoop.
4. Absolutely no changes to air filter box.
5. Nissan paper air filter.

Results:

1. Low end torque is still very strong. Might have a very slight decrease, but virtually unnoticable. I really can't tell a difference at all. Engine does not easily bog any more (like what happened with the 4" dryer duct). Low RPM performs very similar to stock.
2. But dyno says good increase in mid and high rpm power. Tires break loose in 1st and 2nd gears all through the mid-band without much trouble. Pulls harder over 5500 rpm and all the way to redline.
3. Intake is very quiet. Sounds very much like stock - might be very slightly louder but I am hard pressed to tell a difference.
3. Conclude that 2" diameter pipe sufficiently resists air flow to provide decent low RPM vacuum but also allows more flow at high RPM's when the engine needs to breathe better.
4. Running this way for 1 week.

Next steps (will try this weekend):

1. Buy two more PVC elbows and some 2" pipe to route the new intake pipe up and around to behind driver's side headlight. Current elbow sits down by alternator.
2. Wrap new 2" pipe with adhesive aluminum heat shielding wrap (from home depot) to keep intake air cooler. Plan to tie adhesive aluminum sheilding to the pipe with nylon zip ties to ensure a long lasting fit.
3. Drill 1/4" hole in bottom of elbow connected to 2" end of rubber pipe adapter to allow condensation to drain out - just like in original OEM setup prior to cutting hole in "scoop".

For anyone looking to get a performance increase without spending a lot of money (total cost is probably 30-40 dollars), not having to worry about water getting into the intake and without modifying their air filter box, I think this setup is a really good solution!

Please post your results to this thread if you choose to try this yourself. I will try to post pictures of the mod this weekend . . .

 

post pics of it if you can...

 

Try relocating the battery and building a true cold air box drawing from somewhere on the front fascia...

I've got that plan for mine...

 

That's a great idea, just it seems like lots of work . . . I like easy mods best!

 

pics please!!!!!

 

Pics, pics and more pics.

Pedro

 

I see this a lot posted by different people, i find it hard to believe that the intake is to be thanked for that. I have a completely stock intake and i can easily break loose in 1st and 2nd if i really want to. Plus the Max does pull hard all the way up.

Am i missing something here?

 

obviously not a maxima, but something similar to this would be neat

 

i cant see that changing the tubing size would really make a difference in power. If anything its easier to get air into the engine with a bigger pipe, but still the air has to travel through the stock piping into the manifold.

 

The point is, according to my butt dyno, it is pulling harder than stock, especially in the mid rpm band and the over 5000-5500 rpm to redline band.

 

Something like that is exactly what I'm thinking of. It wouldn't be too hard to fab something up...and once the battery is out of the way, it'd give plenty of space. It could almost be a ram air setup that way. Just have the air draw higher up so that you don't accidentally injest any water...

 

Ok, I finally took some pics of how I setup just the 2" elbow and now I have some pics of my newest intake setup which I installed over the weekend and which I like the best of all so far!

http://www.cardomain.com/memberpage/460442

The pics on page 1 are of the just the elbow and the pics on page two are of the elbow plus a 2" PVC riser set between the two radiator fans and then turning 90 degrees and ending up behind the passenger headlight. When you see it you'll understand . In my earlier post, I'd mentioned that I wanted to wrap the PVC in this heat duct insulating adhesive foil I'd bought at Home Depot. Unfortunately there was not enough room on the vertical rise pipe to realistically expect to fit the material, so I skipped it. I doubt it would help much anyhow. The OEM intake has no insulation and the plastic is thin, whereas the PVC I used is at least 1/4" thick - it should be more resistant to heat soak.

My impressions of the new intake design so far are as follows:

1. Slightly worse low end than with the elbow alone noticable in the idle-1300 rpm band.
2. Slightly increase in engine noise, mostly in the 2000-3000 rpm band - sounds like a deep vibrating/sucking sound. I'm guessing from the various lengths of tube in the intake section may be resonating or causing some type of standing waves at certain engine speeds.
3. The best mid and high end performace yet! This intake really pulls hard at every RPM and especially as it gets into the over 5K range which is where the OEM intake really starts to fail us. On my butt dyno, it also feels like I'm pulling harder at every RPM over about 1500.
4. Throttle tip in or throttle feel was a little better with just the single elbow at low rpm and light throttle. Just give it a little gas and it felt like a surge of power from the engine. This new version of the intake is more linear in terms of throttle tip in - it does not feel as punchy when the throttle is lightly touched.

The OEM air box remains unchanged.

Feedback is welcome!

 

Y not make it grab air from the bottom of the car?

 

I think that you have a pretty good idea but how successfull is it really?. I would think that running the tube under the car would bring the best results. If you run the tube where the headlight or the battery is you will still get a lot of hot air since the temp under the hood is very high. Buts thats just my .02

 

that is the rustiest 2k2/2k3 Max I have ever seen

 

Yes, I've seen the other intake designs where the plastic is cut below the radiator and a duct is run down to it. I see this as a big risk in terms of pulling up water into the intake. I know the "fix" for that problem is to cut holes in the air box above the air filter, but by doing that, I see a big risk of sucking in hot air from that slot/opening instead of from the CAI under the car or from the OEM intake opening below the hood. Also, and I'm guessing here, cutting open the air box like that would probably change the air pressure conditions inside the air box and inside the intake such that low end torque is reduced (below 1500 rpm).

My solution avoids risk of water being sucked in, keeps the OEM box, but provides another feed into the stock intake. It is relatively quiet, and improves the power where I wanted it to (mid and high rpm) with only very minimal impact to low rpm performance.

I could have run the pipe below the radiator and then back up to the spot behind the passenger headlight, but I chose not to since this would have added more lengths of pipe and at least two additional elbows . . .

As a side note, I really did like just having the single elbow in place and, for anyone with similar design goals to my own, that solution is extremely easy and very inexpensive to impliment. I can almost guarantee that anyone who does that mod will be pleased with it. The only caveat is that I did not test that mod during high temp (summertime) conditions. I can not be certain what the impact might be of pulling in very hot air from that part of the intake during the summer months. In early November, in NY, I did not experience any "heat soak" issues with this setup.

 

I don't know what you're talking about, I don't have any rust nor can I see any. Admittedly, there is some oxidation on the battery tied down strap and the hood pin switch bracket, but I think that's normal for a car purchased in late 2001 and that has almost 45K on it!

 

Yes, the air might be a little warmer than a true CAI. On the other hand, I think that, when the car is moving, air will blow into the engine bay around the headlights and that particular area will be cooler. Especially since it is not in the direct path of the hot air from the radiator . . . That is probably the biggest difference between my current setup and using just the elbow. The intake will get cooler air - I just don't know how much cooler. Also don't forget that the OEM intake is still in effect and cool air will still get pushed/sucked in through the OEM opening . . .

 

good job...

 

I like the set up and think it's very creative. I'm pretty sure that where you connected the 3" section if rubber to is supposed to trap water coming in from the front part of the intake. If you connect an intake tube to that what happens whe you are driving on a rainy day? Water is coming in from the front of the car, won't the air coming in from the adapted piece bring the water in the air box??? Just curious because my Injen is causing my max to knock & ping like a big POS.

 

I was just waiting for someone to ask me this question! If you look carefully at your OEM intake, and you look at the bottom of the stock 3" pipe, you shoud see a small 1/4 hole drilled into it. It is my understanding that this is a "drain" hole for just the purpose you mention - to trap and then drain any water that might enter the intake.

In my current setup, I used my dremmel to drill a 1/4" hole at the lowest part of the intake - namely at the joint between the first elbow (the one connected to the rubber 3" to 2" pipe adapter) and the first pipe (which exits the elbow and points toward the passenger wheel well). This hole I drilled will allow any water to drain out of the intake regardless of where it comes from - the OEM scoop or my additional PVC intake!

By the way, if you were to just use a single elbow connected to the 3" to 2" rubber adapter and nothing else, it would inherently act as a drain point since it points sideways and is wide open. Any water would literally drain out.

I have not yet noticed any knocking or pinging. Also, I did get the MAF and ECM TSB applied to my car (it was an early 2K2 purchased in 11/01).

I hope this helps!

 

although creative, I dont see how that set up can create a beneficial stream/flow of air to the intake manifold (too many bends/ too far away)

 

the radiator bracket is rusted and so are the bolts for the battery and the hood sensor, and the bolts for the plastic cover...its all good i guess

sorry for the hihjacking back on topic now

 

Trust me, it does. The difference is very noticable. Try it out and let me know what you think then . . .

A few points:

1. How much water, under some pressure, do you think could flow through a 2" diameter pipe? Probably quite a bit (just think how much water pours out of a 1/2" pipe that brings water to your kitchen faucet). The way gases move through pipes is very similar to the way liquids move through pipes . . . I don't have all the formula's handy, but it is possible to look them up. Regardless, the pipe allows more air to flow into the intake than the OEM intake would and the rate of flow increases as the pressure differential increases between the inside of the pipe and the outside of the pipe . . . The bends are more or less irrelevent since the elbows are a larger diameter than the pipe and, in turn, there is never a decrease in pipe diameter which is really the critical factor anyhow. Don't forget that my airbox is completely stock, so a low pressure area develops in the OEM intake ahead of the air filter . . .

2. I took some rough measurements of the square hole feeding into the stock air box. I think it measured about 3"x4" or 12" square. The OEM intake has less than 12" square surface area . . . I think I estimated it at around 8-9" square . . . The surface area of the pipe opening is PI*R^2 which in this case is approximately 3.14" square. Guess what? The tube almost exactly makes up for the restriction at the OEM intake!

 

Just in case anyone is interested in trying this out, here are the pipe sizes I used:

Bottom horizontal 2" PVC pipe = 5"
Middle vertical 2" PVC pipe = 6"
Top horizontal 2" PVC pipe = 19"

Be sure to check your fittings before assembly and final assembly must be done on the car to get everything lined up just right . . .

One zip tie at end of the 19" pipe near headlight.

Have fun!

 

Rust and oxidation are basically the same thing. I suppose it would be normal for a car up north that is/was not garaged most of the time.

 

Florida must be nice . . .

 

Other than an occasional Hurricane, it is very nice.

 

Ok, I just wanted to post an update to this new intake setup I've been running since last Saturday. My general sense is that this setup, with the three pipes and the feed from behind the passenger headlight, does offer some benefits over stock. From about 3500-redline, the engine pulls really hard. Unfortunately, these new intake components are generating some type of resonance, which I can hear, between 2500 and 3000 rpm. I also think that it is not performing as well in the below 2500 rpm range as the elbow alone or the original OEM setup.

Since the performance of the latest setup is not meeting my design criteria, I will be pulling the pipes out this weekend and reverting back to the original elbow alone . . . The original elbow provided really good low rpm performance as well as increased mid and high rprm performance. I might try to run a short length of tube off that elbow to get a little further under the car and try to pull in more cold air. I'm also considering doing that with a 3" pipe and adapter. This means that intake will go from 3" to 2" then back to 3" . . . this might help improve the intake performance by creating some air speed when the pipe size drops from 3" to 2", but I'll have to test to see if it works.

 

ABS,
Thanks for sharing your progress. It easy to look at the stock box and snorkel setup and see it has to be limiting the performance of our cars.

I know it would require modifying the stock box, but have you considered creating another port above the current port, in that little square area at the upper corner of the box, just behind the positive battery terminal and then plumbing into that port? Your plumbing could run forward just beside the radiator and light housing. It would probably require some fenageling of the battery cable.

Would opening up the box with another port reduce low-end torque? probably. Oh well, hundreds of possibilities... I'll be reading your post to see what works best for you.... Thanks again.

 

If you want to keep the lowend punch/responsiveness, you can only have one intake path. Having multiple intake pathes causes a loss in intake resonance and pressure which in turn gives the motor a "soft" lowend feel at part-throttle. The stock intake system stores air and pressurizes itself slightly in lower rpms by keeping a column of air in the intake at all times. This is what makes the motor feels torquey in the lower rpms. At WOT and at any rpm, the pressurization is lost so it really doesn't matter what type of intake you have attached to the throttle body. The stock intake offers excellent driveability, but does choke the motor a bit after 5000rpms. If you don't race at the track, keep the intake stock. If you race against the clock, then an intake will help a little because you spend about 1 second of the race below 3800rpms which is where the stock intake really has an advantage.

Take it from a guy that has experimented at the track and dyno with countless intake setups, they perform about the same. A modified (hacked) verison of the stock intake teamed with a midpipe seems to work best on my car, then the hybrids, then POP, then CAI, then stock. The difference between the hacked/midpipe and stock intake in about .13 seconds and 1.2mph (yes, I'm a numbers freak).


Dave

 

Could you explain more about this... hacked/midpipe intake?

 

Dave:

It's obvious that you have already spent a LOT of time researching this topic . . . I don't know if you have tested the setup I described above, but I seem to be getting REALLY good results with the bottom of the OEM intake duct cut open and a 3" to 2" rubber adapter on it with a 2" elbow sticking out the bottom. Everything else is 100% stock.

When I run the intake this way, I've noticed that upper mid RPM and high RPM performance is really good. Plus, at low rpm, the engine feels a little more "punchy" under light throttle than stock!

I'd hoped that the more creative CAI setup to the passenger headlight would be better, but I'm certain that's not the case.

Have you ever tried the combo I described or one like it?

If you wouldn't mind sharing, what kind of hacking did you do to your stock air box that gave you the best times?

 

Dave:

One more question for you. The mods you described in your post, are they for a 4th gen or a 5th gen 3.5, and if they are indeed for a 4th gen, do you think the results would be the same for the 3.5VQ?

 

Ok folks, I just re-installed the 3" to 2" rubber adapter and the short elbow. I can tell you that this I was correct in thinking this setup is better than stock and is also better than my second try.

There is no question in my mind that for a very cheap $15, anyone running with a 2K2 or later 3.5VQ will get better performance with this mod! If you should decide to try it, please post your findings here . . .

 

Since search is down, I figured I'd bump this up for anyone who hasn't seen this thread yet . . .

 

What about the original hole? Isn't having 2 sources of air supposed to be a problem? Should you plug up one?

 

... Oh ya I'm not a mod

 

IBsomeonesaysatleastthisisn'tarepost

 

explain this IB thing...i came back to OT one day and your all using it like crazy...