DIY: Extra air to stock airbox

Mandingo · 12-13-2011, 12:06 AM

Idea:
I thought up this simple mod in an effort to make the most of my K&N drop-ins and post-maf tubes. After looking over the stock air inlets to the airboxes, I decided the draw location was ok (temp wise) but I wanted a little more capacity. I am using the holes where the resonators connect to the airboxes to bring more cool air to the filters.

Disclaimer:
This mod will not appeal to everyone as it requires cutting of the stock airbox. My 2010 Z doesn't have airbox resonators, just the plugs where they used to be. I'm not sure which models actually have them but you may have to use a different approach for earlier Zs.

Tools:
10mm socket and ratchet
flathead screwdriver
hobby knife or box cutter
dremel with grinding bit for plastic

Materials:
5 feet of 1.5 inch ID corrugated tubing
I used heavy duty vacuum hose from Lowes with deep convolutions

Step 1:
Remove front bumper and airboxes
I used DIGItonium's DIY for bumper removal.
The airboxes are pretty simple to remove. Depress the clip for the maf sensor wire and pull it out. Loosen the hose clamp on the airbox tube with your flathead and shimmy the tube off. Remove the 10mm bolt holding the airbox to its bracket in the engine bay. Pull up on the airbox firmly while wiggling side to side (the airbox, not yourself) to disengage it from the grommets on the bottom.

Make sure there's an is250 nearby that is trying its best to be as cool as your Z. Then, remove your two air filters and set aside in a clean area.

Step 2:
Find and remove the plugs for the airbox resonators. They twist off counter clockwise.

Step 3:
The point of no return.
Grind away the tabs in the above picture to make as perfect a circle as you can. The hole should be just over 1.5 inches in diameter. Be careful you don't accidentally make the hole too large (test fit then enlarge if needed). It needs to be a relatively tight fit.

My original plan was to add a flange to the airbox to secure the tube. But the convolutions on the hose are so deep that I decided to just screw the tube into the hole in the airbox for simplicity. You can see a notch on the left side of the hole with a little ramp carved into the side (theres another ramp on the underside). This allows the tube to connect nearly seamlessly to the airbox.

Instead of my ghetto rigged idea, you might opt for a flange and hose clamp or even industrial strength flexible adhesive such as 'E6000' to secure the tube better. Mine have been on for 350 miles and haven't unscrewed a bit. They're in there very tight.

Step 4:
After cutting holes and notches in each airbox, connect 2 feet of tube to the driver's side airbox and 3 feet of tube to the passenger side (to snake around the washer fluid reservoir). You may want to use more tube than I did. It just depends on where you want to draw air from.

Clean up the end of your tube better than this!

Step 5:
Test fit the assembled driver's side airbox.
Snake the end of the tube down the highlighted area. Then fit the airbox back into the two little grommets on the bottom. Feel around and make sure the tube won't be rubbing on anything sharp or rough. I used a small telescoping mirror like this from a local hardware store to check for binding and rubbing.

Step 6:
If everything looks good, go ahead and cut a hole in the panel for the tube to pass through. It cuts very easily so be careful you don't slip.

You might want to bring the tube down to the fang area like Modshack did. I decided the air at this location would be just as cold as outside air once the car was moving with any speed.

Step 7:
Test fit the assembled passenger side airbox.
This one is a little trickier because of the tight quarters. Again, snake the tube down this path before you try to fit the airbox in place.

Check for rubbing at the first bend at the top. You may have to do some dremel work on an excess plastic piece near the red circle.

Its not as tight a fit as it looks in the pic above. There should be no binding or compressing of the tube when it is properly in position.

Step 8:
Route the tube all the way to the right of the reservoir. Cut a hole in the thin plastic wall. I secured the the tube with wire wrapped in r/c hobby fuel line for extra security but its not required. Of course making a little scoop out of the end of the tube doesn't help anything either, but I was going all out!

Get the bumper back on. Bolt the airboxes down. Reconnect the maf sensors. Secure the intake hose clamps. And Bob's your uncle.

I later marked the tubes here with sharpie to watch and see if they were slowly coming unscrewed from the airboxes. So far they haven't budged. I think all the bends and the two tight connections keep them from moving at all.

Gains:
I am extremely skeptical when it comes to feeling small gains. I'll update after I get a touchup on my tune. This may end up not having any impact on power at all. I'm tempted to say that what I do feel in throttle response and higher revs is just because of the cooler temperatures we've had in my area lately.

Where this could be improved:
-Possibly extend the tube to the fang area like Modshack did
-Do mine and Modshack's modification
-Buy Stillen G3 intakes

I enjoy doing things like this and had a blast modifying (maiming/mutilating) my airbox and making this diy. I just hope is spurs someone else on to experiment with their intake set up!

haitech · 12-13-2011, 01:19 AM

Nice cheap DIY

wstar · 12-13-2011, 01:36 AM

I think it would be hard to tell whether that was helping or hurting. It probably depends on the effective pressure differential between the main openings and the tube openings. They're both going to get a little pressure bump from being in nose cavity. If the tubes get more pressure than the main openings (or even the same really), I could easily see the sideways airflow from the tubes disrupting the flow of the main inlet and leading to overall loss. Could be that in the end it actually helps flow though. It's just sort of impossible to know unless you can replicate real conditions (XX mph airflow onto the whole face of the car) and actually measure the difference in airflow (MAF sensor maybe?).

TreeSemdyZee · 12-13-2011, 10:29 AM

Be VERY careful driving in the rain. I had the bumper tube on my 350z and sucked water into the engine and killed it. Mind you, there was massive amounts of rain at the time (6" in a few hours), but it's always something to be leery of.

Mandingo · 12-13-2011, 12:14 PM

Quote:

Originally Posted by TreeSemdyZee

Be VERY careful driving in the rain. I had the bumper tube on my 350z and sucked water into the engine and killed it. Mind you, there was massive amounts of rain at the time (6" in a few hours), but it's always something to be leery of.

Thanks for the heads up. I feel like airflow would be %100 coming through the large main inlet once the small tube saw any kind of restriction from water. The path of least resistance would become the large stock inlet up top instead of sucking water up the little hose like a straw.

Mandingo · 12-13-2011, 01:21 PM

Quote:

Originally Posted by wstar

I think it would be hard to tell whether that was helping or hurting. It probably depends on the effective pressure differential between the main openings and the tube openings. They're both going to get a little pressure bump from being in nose cavity. If the tubes get more pressure than the main openings (or even the same really), I could easily see the sideways airflow from the tubes disrupting the flow of the main inlet and leading to overall loss. Could be that in the end it actually helps flow though. It's just sort of impossible to know unless you can replicate real conditions (XX mph airflow onto the whole face of the car) and actually measure the difference in airflow (MAF sensor maybe?).

Thats true. The whole time I was working on this I was thinking about how both inlets would have the same pressure being inside the nose. There could, however, be a difference in pressures at each inlet as you said. I know very little about fluid dynamics so I'm not sure how the sideways flow could affect the flow in the airbox at speed. I need a wind tunnel with a dyno inside

Like I said, I'm pretty skeptical when it comes to using the ole butt dyno. I must say though, it really doesn't feel like I've lost power anywhere. If anything, it seems a little stronger on the highway when trying to pass.

Vbp6US · 02-24-2013, 03:00 PM

What a great thread. Thanks OP. I can't believe this isn't getting that much attention. Great pics!

Z370Z011 · 02-25-2013, 12:11 PM

Lets see some dyno results!!!

Z370Z011 · 03-11-2013, 09:23 PM

Any updates on this mod??

Kingbaby · 03-12-2013, 01:17 AM

driver side is nice, the passenger side can be more refine both on the routing and the finish to the outlet...

for rain just poke a couple small small holes in it...it would take a huge downpour for you to start picking up water...

MR.nismo · 03-15-2013, 05:24 AM

How about re-routing the hoses to the cabin, as in inside. So on a hot summer day, as you drive with the AC on, it will breathe cold air from the inside. Hint Hint "cold air intake"

Really, I don't know.

SouthArk370Z · 03-15-2013, 08:51 AM

Quote:

Originally Posted by MR.nismo

How about re-routing the hoses to the cabin, as in inside. So on a hot summer day, as you drive with the AC on, it will breathe cold air from the inside. Hint Hint "cold air intake"

Really, I don't know.

The A/C is cooling the cabin air. The engine is powering the A/C. In a universe with 100% efficiency, you would, at best, break even. Figure in all the inefficiencies of the Real World and you have a net loss.

CDepp · 03-15-2013, 12:07 PM

Quote:

Originally Posted by TreeSemdyZee

Be VERY careful driving in the rain. I had the bumper tube on my 350z and sucked water into the engine and killed it. Mind you, there was massive amounts of rain at the time (6" in a few hours), but it's always something to be leery of.

Negative, Ghostrider.

You can never suck that much water up the hose to kill the car unless you have deleted a bypass. Water is denser than air and you'll always avoid pulling water up if air is allowed to get in through the bypass. To accomplish this, you'd have to submerge parts listed: 5, 6, 11, 21.

And, as some of the older generation turbo-nuts here know, you periodically want a spray of water in an engine to 'steam-knock' carbon buildup off valves. I've even seen technicians take a spray bottle of water directly to the throttlebody inlet. Old turbo-prop planes would blow water into the intake to do this.

Something else was going on with your setup.

MR.nismo · 03-16-2013, 03:56 AM

Quote:

Originally Posted by SouthArk370Z

The A/C is cooling the cabin air. The engine is powering the A/C. In a universe with 100% efficiency, you would, at best, break even. Figure in all the inefficiencies of the Real World and you have a net loss.

I knew that my friend. I was just being a......... refer to first word of my signature.

Mandingo · 03-17-2013, 01:35 PM

I actually did go to the dyno again after this just for *****. I saw a meager peak improvement of 2 wtq and 1 whp which is within error of the machine. The dyno's were done on the same Mustang Dyno (at JKS Performance), but obviously on different days. I'm sure I could find the charts somewhere if interested.

After I wrote this up I scored an Injen washer-fluid bottle to replace my large stock one. This allowed for a much cleaner path for the blue tube on that side and saved some weight. I'm still happy with it and won't be purchasing an aftermarket CAI for a while.

12-13-2011, 12:06 AM	#1 (permalink)
Mandingo Track Member Join Date: Nov 2010 Location: Dallas Posts: 624 Drives: '10 370z 6spd Rep Power: 3370	DIY: Extra air to stock airbox Idea: I thought up this simple mod in an effort to make the most of my K&N drop-ins and post-maf tubes. After looking over the stock air inlets to the airboxes, I decided the draw location was ok (temp wise) but I wanted a little more capacity. I am using the holes where the resonators connect to the airboxes to bring more cool air to the filters. Disclaimer: This mod will not appeal to everyone as it requires cutting of the stock airbox. My 2010 Z doesn't have airbox resonators, just the plugs where they used to be. I'm not sure which models actually have them but you may have to use a different approach for earlier Zs. Tools: 10mm socket and ratchet flathead screwdriver hobby knife or box cutter dremel with grinding bit for plastic Materials: 5 feet of 1.5 inch ID corrugated tubing I used heavy duty vacuum hose from Lowes with deep convolutions Step 1: Remove front bumper and airboxes I used DIGItonium's DIY for bumper removal. The airboxes are pretty simple to remove. Depress the clip for the maf sensor wire and pull it out. Loosen the hose clamp on the airbox tube with your flathead and shimmy the tube off. Remove the 10mm bolt holding the airbox to its bracket in the engine bay. Pull up on the airbox firmly while wiggling side to side (the airbox, not yourself) to disengage it from the grommets on the bottom. Make sure there's an is250 nearby that is trying its best to be as cool as your Z. Then, remove your two air filters and set aside in a clean area. Step 2: Find and remove the plugs for the airbox resonators. They twist off counter clockwise. Step 3: The point of no return. Grind away the tabs in the above picture to make as perfect a circle as you can. The hole should be just over 1.5 inches in diameter. Be careful you don't accidentally make the hole too large (test fit then enlarge if needed). It needs to be a relatively tight fit. My original plan was to add a flange to the airbox to secure the tube. But the convolutions on the hose are so deep that I decided to just screw the tube into the hole in the airbox for simplicity. You can see a notch on the left side of the hole with a little ramp carved into the side (theres another ramp on the underside). This allows the tube to connect nearly seamlessly to the airbox. Instead of my ghetto rigged idea, you might opt for a flange and hose clamp or even industrial strength flexible adhesive such as 'E6000' to secure the tube better. Mine have been on for 350 miles and haven't unscrewed a bit. They're in there very tight. Step 4: After cutting holes and notches in each airbox, connect 2 feet of tube to the driver's side airbox and 3 feet of tube to the passenger side (to snake around the washer fluid reservoir). You may want to use more tube than I did. It just depends on where you want to draw air from. Clean up the end of your tube better than this! Step 5: Test fit the assembled driver's side airbox. Snake the end of the tube down the highlighted area. Then fit the airbox back into the two little grommets on the bottom. Feel around and make sure the tube won't be rubbing on anything sharp or rough. I used a small telescoping mirror like this from a local hardware store to check for binding and rubbing. Step 6: If everything looks good, go ahead and cut a hole in the panel for the tube to pass through. It cuts very easily so be careful you don't slip. You might want to bring the tube down to the fang area like Modshack did. I decided the air at this location would be just as cold as outside air once the car was moving with any speed. Step 7: Test fit the assembled passenger side airbox. This one is a little trickier because of the tight quarters. Again, snake the tube down this path before you try to fit the airbox in place. Check for rubbing at the first bend at the top. You may have to do some dremel work on an excess plastic piece near the red circle. Its not as tight a fit as it looks in the pic above. There should be no binding or compressing of the tube when it is properly in position. Step 8: Route the tube all the way to the right of the reservoir. Cut a hole in the thin plastic wall. I secured the the tube with wire wrapped in r/c hobby fuel line for extra security but its not required. Of course making a little scoop out of the end of the tube doesn't help anything either, but I was going all out! Get the bumper back on. Bolt the airboxes down. Reconnect the maf sensors. Secure the intake hose clamps. And Bob's your uncle. I later marked the tubes here with sharpie to watch and see if they were slowly coming unscrewed from the airboxes. So far they haven't budged. I think all the bends and the two tight connections keep them from moving at all. Gains: I am extremely skeptical when it comes to feeling small gains. I'll update after I get a touchup on my tune. This may end up not having any impact on power at all. I'm tempted to say that what I do feel in throttle response and higher revs is just because of the cooler temperatures we've had in my area lately. Where this could be improved: -Possibly extend the tube to the fang area like Modshack did -Do mine and Modshack's modification -Buy Stillen G3 intakes I enjoy doing things like this and had a blast modifying (maiming/mutilating) my airbox and making this diy. I just hope is spurs someone else on to experiment with their intake set up! conquistador likes this. __________________ some mods

12-13-2011, 01:36 AM	#3 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3594	I think it would be hard to tell whether that was helping or hurting. It probably depends on the effective pressure differential between the main openings and the tube openings. They're both going to get a little pressure bump from being in nose cavity. If the tubes get more pressure than the main openings (or even the same really), I could easily see the sideways airflow from the tubes disrupting the flow of the main inlet and leading to overall loss. Could be that in the end it actually helps flow though. It's just sort of impossible to know unless you can replicate real conditions (XX mph airflow onto the whole face of the car) and actually measure the difference in airflow (MAF sensor maybe?). __________________ 7AT Track Car! Journal thread / Car setup details

03-15-2013, 05:24 AM	#11 (permalink)
MR.nismo Enthusiast Member Join Date: Nov 2011 Location: Hackensack, NJ Age: 50 Posts: 373 Drives: 2014 Nismo Gun Metal Rep Power: 13	How about re-routing the hoses to the cabin, as in inside. So on a hot summer day, as you drive with the AC on, it will breathe cold air from the inside. Hint Hint "cold air intake" Really, I don't know. __________________ Sarcasm and Orgasm are about the same thing. One is good....the other is better.

03-17-2013, 01:35 PM	#15 (permalink)
Mandingo Track Member Join Date: Nov 2010 Location: Dallas Posts: 624 Drives: '10 370z 6spd Rep Power: 3370	I actually did go to the dyno again after this just for *****. I saw a meager peak improvement of 2 wtq and 1 whp which is within error of the machine. The dyno's were done on the same Mustang Dyno (at JKS Performance), but obviously on different days. I'm sure I could find the charts somewhere if interested. After I wrote this up I scored an Injen washer-fluid bottle to replace my large stock one. This allowed for a much cleaner path for the blue tube on that side and saved some weight. I'm still happy with it and won't be purchasing an aftermarket CAI for a while. __________________ some mods

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12-13-2011, 01:19 AM	#2 (permalink)
haitech Track Member Join Date: Sep 2011 Location: Austin/Dallas Posts: 922 Drives: 11' 370z Magnetic M6 Rep Power: 14	Nice cheap DIY

12-13-2011, 10:29 AM	#4 (permalink)
TreeSemdyZee Premium Member Join Date: Dec 2009 Location: Kentuck-IANA Age: 59 Posts: 4,880 Drives: '09 370 & ‘14 Juke Rep Power: 27408	Be VERY careful driving in the rain. I had the bumper tube on my 350z and sucked water into the engine and killed it. Mind you, there was massive amounts of rain at the time (6" in a few hours), but it's always something to be leery of.

02-24-2013, 03:00 PM	#7 (permalink)
Vbp6US Enthusiast Member Join Date: Nov 2011 Location: SoCal Posts: 442 Drives: 2009 370z MB 6MT Rep Power: 13	What a great thread. Thanks OP. I can't believe this isn't getting that much attention. Great pics!

02-25-2013, 12:11 PM	#8 (permalink)
Z370Z011 A True Z Fanatic Join Date: Jul 2012 Location: Los Angeles CA Posts: 1,052 Drives: PearlWhite 370z 6MT Rep Power: 14	Lets see some dyno results!!!

03-11-2013, 09:23 PM	#9 (permalink)
Z370Z011 A True Z Fanatic Join Date: Jul 2012 Location: Los Angeles CA Posts: 1,052 Drives: PearlWhite 370z 6MT Rep Power: 14	Any updates on this mod??