bigdo26

I'd thought about doing this several times, finally went to Lowes today and bought some flexible aluminum dryer piping. I've had the stock airbox resonator removed for a while now, with the opening out the bottom just open to the engine bay. So today I cut out the extra little "flap" of plastic in the small inlet below the driver side fog lamp and connected the dryer pipe from this opening up to the airbox.

My main thought on doing this is when at highway speeds, a surplus of air is being fed to the airbox (at least at lower RPMs, might be not surplus at WOT). This would be helpful both because its nice cool air, and there is less of a vacuum, maybe even a light pressure buildup in the airbox. I'll try to do some numbers for airflow into the tube at say 75 MPH (the opening is ~1.5"x6") compared to the airflow thru the engine. If anyone feels like doing these calculations before me, feel free!

Anyways, I'm sure others have done this before, didn't see any threads in my brief search though. I'll try to snap a couple pics tomorrow during lunch as well.

LeeDan00

this sounds very interesting to me... i want to see some pics for visuals...

any gains on this btw? i can't even picture how this looks...

orgnlprankster7

sounds cool, but what about rocks, leaves and other debree cloging the tube?

ThreePointTwoTeeEl

iTrader: (1)

could put some Screen stuff like on windows.

Unkn0VV17

I actually thought about doing that but never had a chance to cause of the accident. I am still debating whether i should do it cause I don't really want to do anything to the car anymore cause of the accident. I guess let me know if theres any improvements and i'll think about it...lol

bigdo26

I'll snap some shots today or tomorrow for ya.

bigdo26

I had a similar setup on my Maxima for a couple years and never did I have something clog up the tube. Larger debree doesn't make it up the tube into the airbox either, just smaller things like leaf pieces, and maybe a little sand. But thats what the air filter is for!

bigdo26

I thought about this as well. Might still do it to sort of pre-filter the incoming air.

As for any performance gains, probably going to be hard to say. I'll be driving to New Jersey this weekend (bout 500 miles round trip) so I'll have to report back any differences I feel (or think I feel )

bigdo26

OK so I just did the approximate numbers for the airflow through my setup.

At 75 mph, or 3,353 cm/sec, there is 194,688 cm^3/sec of air entering the tube intake (assuming its 100% free flowing). At 6000 RPM WOT, there is about 321,000 cm^3/sec of air moving through the engine. So at 6000 RPM there is not a surplus of air entering the engine, however there is air flowing into the airbox at a pretty high mass flow rate, so there would certainly be less of a vacuum.

It turns out that for RPMS below ~3600, there is a surplus of air being delivered to the airbox, which could create a slight positive pressure.

Additionally, if the tube opening could be round (4" diameter tube) instead of 'squished' as it currently is, 271,800 cm^3/sec of air could flow into the airbox, which would allow for potentially positive air pressure in the airbox at RPMs below 5080.

Feel free to check my numbers too, I did the calculations assuming in one revolution, each cylinder pulls in its maximum volume of air, which is 535 cm^2, or a engine total of 3210 cm^2 per revolution.

Comments??

Razzi

there's a guy at my school who did the same with his intake, he routed it to about where the foglights would be. you'd see this enormous 5 inch diamater tube in his front bumper

dnd2984

iTrader: (6)

hmmmm Home made Icebox.....I am gonna try it to.

bigdo26

I was careful to limit the visual exposure. Really can't see it at all the way I have it set up. Will try and post pics tomorrow!

t0ast

good calculations. the only things I can think of is that the engine recirculates some exhaust gas through the EGR system and of course, the fuel that's in the chamber so the volume of air required should be less - by how much, who knows?

bigdo26

Yeah, I purposely did not factor in the fuel as I didn't feel like figuring out the volume that atomized fuel takes up. At a A/F ratio of 12.6:1, you could roughly estimate the fuel takes up 8% of the volume, however since fuel is far more dense than the air, it's probably quite a bit less than that. Hence why I left out that aspect of the calculation.

The recirculated exhaust gas is a good point, but like you said, who knows how much??

Razzi

hey, numbers dont mean a thing until you run that bad boy

bigdo26

I'm an engineer, numbers are my thing

More numbers for those interested:

I ran a Fluent (computational fluid dynamics program) scenerio a while back for a simplified 2D sketch of my car. The simulation was run at an airspeed of 65 MPH, relatively close to 75 MPH that I did my earlier calculations for.

Anyways, I plotted relative pressure for the simulation once it converged, and got the below plot (pressure is in Pascals).



If you notice right up front at the verticle surface of the bumper, the pressure is at a maximum (indicated by the red coloring). If we assume that the engine is working at next to no load at highway speed, then there is approximately a 600 Pa air pressure at the front bumper, and therefore in the airbox. 600 Pa is about 0.09 psi. If the pressure increases with the same relationship as force (velocity doubled, force increased by 4x), then at 90 mph you'd see ~1200 Pa, which is 0.17 psi.

Of course as soon as you open the throttle this pressure will shrink to zero or negative relative pressure (as I showed earler), but I'd have to imagine that having a slight positive pressure when first going WOT could help increase the throttle response.

haha i'm having way too much fun with this

Fender Bender

You're an engineer? I wouldn't have guessed
This is getting way to scientific! Give us what we want:
1. Does it work or not?
2. Does it look like garbage under your hood / from your front bumper?
I'm assuming by all the scientific calculations that the structural design would be equally as meticulous

bigdo26

hahaha sorry, maybe I got carried away a bit. I'm sure there are a couple people on here who would like to see the calculations though...

To bring things back down a notch,
1. Will give you my input after driving to and from Jersey this weekend.
2. Visually can't tell its there at all. Can't see it outside, can't see it when you open the hood either.
3. Calculations just keep me entertained

Fender Bender

Nice! Can't wait for pix and the detailed report!

Unkn0VV17

You know he loves his job when he go technical on our asses...

GQstyle

I swear bigdo26...you're doing everything I want to do to my car! Sways, XS headers, resonator removal, and now this piping (which i've been thinking of for a while). Oh and those calculations make my head spin...you're just like my buddy who's a civil engineer...

Sounds like a neat setup, although I'm having a bit of trouble visualizing how you "hung" it down near the foglight. Actually, how did you attach it to the airbox for that matter? One think I've seen on other boards is the ribbing in the dryer pipe disturbs the air flow, but that was in comparison to an CAI, straight up. I guess it's better than no piping at all and just having the airbox exposed to that little hole in the frame (I've removed the intake resonator too).

I'm anxious to see the pics and hear about the results of the butt dyno!

bigdo26

OK here are a couple of pictures I snapped this morning:



Right now the end you're looking at is just secured down with duct tape. Duct tape fixes everything!! If I decide I want to keep the setup, I'll do something more permenant, like put a couple screws in.

Here's a closer view:




The piping is only about 1 foot long, and from where you see it in the above photos it just curves up and slides into the opening in the bottom of the airbox. It takes a little time to open up the airbox, so I didn't take any pictures of that this morning. I think it's pretty self explainatory though.

bigdo26

Followup:

Car drove quite well on my trip to Jersey this past weekend. Didn't notice much of a difference on the drive down (~275 miles), but coming back it felt more responsive at highway speeds. Also, even with hitting about 1 hour of stop and go traffic, it looks like I hit about 30 mpg (estimate based on the fact I got to ~230 miles at the half tank mark which is roughly 7.5 gallons). I also had a bunch of 0-80 WOT sprints from tolls and rest-stops, and was cruising (when I could) at 80+.

Also, when I suddenly gave it more gas while traveling at say 75 or 80, the car seemed to respond more quickly and would pull a tad better in 5th gear.

I'm not going to say it felt faster, as an increase of a couple HP cannot be felt, but I liked the way the car drove and plan to keep this tubing in place. Hope some of you guys find this thread helpful!

01tl4tl

Any efforts at directing outside air to the airbox is a good thing
Dont worry about ribs and dynamic flows and vortex generation

Your dryer works using this stuff!!!

S1CK TypeS

how well do u think this works in comparison to a CAI? if this is somehow better i might just get get rid of my aem. in reality it looks the same as a CAI since it sits exactly where my filter sits

dnd2984

iTrader: (6)

I think this looks like a better alternative to a CAI

01tl4tl

CAI is totally different because of the airflow design in the tube, moving the pressure waves of air into the engine- yadayada

For the easy super budget way to make a ~general improvement~
- remove lower resonator and direct some extra air at it

CarbonGray Earl

I have done this before with my previous cars (civic and integra). Its a great idea, but I would NOT use aluminum dryer hose. The aluminum is on the inside of the hose, and it WILL flake off into tiny pieces. Its a bitch to clean out of your reusable filters.

Instead, try and find the vinyl/plastic dryer hose, or better yet, I've seen more rigid lawn drainage tubing used thats more durable.

bigdo26

However, those beneficial pressure waves are in the intake runner, not so much the CAI tube, correct? Seeing as each valve opens at a different time, there would be multiple pressure waves traveling down the CAI tube, and I can only imagine that these would interfere with one another. Within the intake runner, however, the only pressure wave present would be the one applicable to that particular cylinder, which will benefit performance at certain RPMs, say 1500, 3000, 4500, and 6000. The range around each of those exact RPMs is small, maybe 100 RPM? Those numbers are just an estimate of course.

I don't believe the CAI tubing contributes to the pressure waves, rather it is made just long enough to access the outside air entering the engine bay through the small opening in the bumper that I showed in an earlier post. I could be wrong on this, but it makes more sense to me that there isn't much tuning done for the CAI, rather it just provides a nice smooth passage for cool air to move through before entering the intake manifold.

The CAI still operates under full vacuum, that is the air entering the tube is being 100% pulled at all times. With the setup I am trying out, the air is still pulled into the engine, but at speed the air already has some velocity when entering the tubing, so it only makes sense to me that the engine has to work "less hard" to get the air into the cylinder.

Again, on a large scale, this probably only makes a small difference, but that's what we all go for anyways right? A bunch of parts that each make a small difference...

And of course I could be wrong on the CAI tube affecting pressure waves, but in general I think most or all CAI's are not tuned.

bigdo26

Hmm, didn't think of that. I'll keep an eye out, if (when) it starts to happen, I'll have to get an alternative hose. Shop vacuum hose would probably work well too, if I could find a large enough diameter that is.

Thanks for the tip!

01tl4tl

Do some internet research and each CAI maker has a way they designed the airflow- some use different diameters along the path- or bends a certain angle or 2 pipes inside each other....
A cheapie is just a piece of tube- a good one is planned and built by computers

Its not that you are throwing higher speed air at the engine (speeds below 60)
- its the total volume you provide- via the removal of resonator, adding low restriction
hi flow air filter, and the free access to outside air of lower temp than engine compartment air or inner fender air
Colder air is denser- you want that!

LIPPSTUH

iTrader: (2)

this has been done on the CL board. go search "ghetto box"

bigdo26

Agreed that the good ones are designed in computer modeling systems, hopefully with some CFD analysis performed as well! If they tune them to take advantage of the pressure waves, even better, I just was not sure what kind of benefits (if any) could be attained by tuning the intake to take advantage of pressure waves. I'm sure they are tuned in terms of diameters, materials, curvature, smoothness, etc to optimize flow rate, turbulence, and such. Who am I to say though I suppose, I dont design them!! I just make my own in hopes I have the basic concepts right!! haha

As for the supply of air, when driving there is a certain volume of air being delivered (at a velocity given velocity) which I imagine helps "replenish the vacuum" that is created by the engine pulling in air. I agree that the volumetric flow of air is what is important. In the case of a CAI, it is subjected to the vacuum created by the engine, and it allows air in freely. However, there is always a vacuum within the tube, which causes the air to flow. If a scoop is created (such as the one I made), then at lower RPMs and higher speeds (say 75 mph), there would not be a vacuum in the tube, but rather a slight (very slight) pressure or less of a negative relative pressure, which I imagine would actually be better than the free flowing CAI, even though it is not tuned by any means.

It's all speculation really, I'm not going to dyno in a wind tunnel, or create CFD models, but really I'm just looking to talk out my theories and such. I guess I could disconnect the tubing and do a couple 50-90 runs in various gears, video taping each and maybe get some acceleration times for with and without the airscoop. Maybe I'll give that a shot sometime this week, see if I can come up with any repeatable results.

6MTUA5

iTrader: (2)

Hmm I've seen a thread on this on the local car club's website. They actually used some hard piping, I'll try and find the thread and post a link. I just don't like how you can see the dryer piping behind the hole under the fogs.


FOUND IT.. see if this link works -- http://www.tallyimports.com/showthread.php?t=10164

bigdo26

Need to be a member for the forum for the link to work. It's a good thread? Maybe I'll sign up for the forum later today...

6MTUA5

iTrader: (2)

I'll just copy paste it here give me a few minutes...

01tl4tl

How do you think air actually moves anyway?
Basic physics and pressure waves rule air intake

We ran similar ducting to the airbox on the racecar and to its brakes,
because a little extra airflow a good thing

6MTUA5

iTrader: (2)

sorry it's so long but you get the idea...

fsttyms1

doing a mod like this with a CAI would be more beneficial. I wouldnt get rid of the CAI to add this to a stock airbox.

6MTUA5

iTrader: (2)