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Discussion Starter #1 (Edited)
[Perhaps I should have titled this: Real Cold Air OEM Intake ;)]

Just started this mini project today. One side down, one side to go.

Planning to meet up with Vacman sometime soon for some more dyno runs. Will post dyno results at that time, and will post driving impressions and "butt-dyno" results later this week

The important thing with this setup is getting direct ambient/cold air from the front of the car, and directing 100% of air into the stock intakes instead of the stock design, where it pulls air from behind the bumper next to the radiator, indirectly.

Enjoy :)


Parts required:
(1) 4" x 8" ducting of choice ($9 for kind I purchased)
(4) 4" duct clamps
10mm socket
Flat-head screwdriver
Dremel w/ cutting disks

1. Remove bumper.
2. Remove stock CAI tubes. Requires 10mm socket. 2 bolts on each side.
3. Cut section off stock CAI tubes right after the bend
4. Reinstall shortened CAI tubes.
5. Clamp one end of 4" ducting onto the CAI tubes.
6. If you don't have the duct w/ rings, probably a good time to install now.
7. Clamp opposite end of 4" ducting onto the grill rings. Repeat on opposite side.
8. Ensure no 4" ducting is in the way of bumper being reinstalled. You don't want to crush the ducting when you reinstall the bumper.
9. Reinstall bumper.
 

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Very cool idea.
But what happens in heavy rain? Is there the possibility of soaking the bottom end of the filters using this method?
 
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He drives his Honda when there's a chance of rain. :D
 
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Great idea but... I wouldnt use that type of ducting for this. The suction from the engine can cause them to pull closed. And IMO it will look kind of silly being so shiny and will potentially sound pretty bad! You may be hearing the flapping of the ducting moving around.

At any rate there wont be a ram air effect. And ram air effect will spend its energy pushing and moving the ducting, the energy in the air will not make it to the engine.

True ram air can be achieved, I want to duct right from the kidney grills. I want to find a lower profile radiator to make this happen.
 

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Great idea but... I wouldnt use that type of ducting for this. The suction from the engine can cause them to pull closed. And IMO it will look kind of silly being so shiny and will potentially sound pretty bad! You may be hearing the flapping of the ducting moving around.

At any rate there wont be a ram air effect. And ram air effect will spend its energy pushing and moving the ducting, the energy in the air will not make it to the engine.

True ram air can be achieved, I want to duct right from the kidney grills. I want to find a lower profile radiator to make this happen.
you want something like this:
 

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Great idea but... I wouldnt use that type of ducting for this. The suction from the engine can cause them to pull closed. And IMO it will look kind of silly being so shiny and will potentially sound pretty bad! You may be hearing the flapping of the ducting moving .
I personally never heard any flapping and I just spray painted mine, it did look kind of silly chrome, but again my "sink drains" are black.
 

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Discussion Starter #13
He drives his Honda when there's a chance of rain. :D
Very cool idea.
But what happens in heavy rain? Is there the possibility of soaking the bottom end of the filters using this method?
Correct! When it rains, drive the Honda ;)

In all seriousness, the stock black tubes have "drainage" holes in them, so any condensation that makes it though won't have the chance to wet the filters or anything of that nature. Non-concern.

Great idea but... I wouldnt use that type of ducting for this. The suction from the engine can cause them to pull closed. And IMO it will look kind of silly being so shiny and will potentially sound pretty bad! You may be hearing the flapping of the ducting moving around.

At any rate there wont be a ram air effect. And ram air effect will spend its energy pushing and moving the ducting, the energy in the air will not make it to the engine.

True ram air can be achieved, I want to duct right from the kidney grills. I want to find a lower profile radiator to make this happen.
I'd love to have a set up similar to the RPI scoops on the E60 M5 and the M6s.

I would not be too concerned about the suction from the engine. The ducts are not collapsible and there are no concerns about the duct closing due to engine suction.

Also, although the kidney grills would be most ideal, changing out to a lower profile radiator for my car is unnecessary for any gains to be had with this mod.

Given that the stock "CAI" looks like this:


These provide direct air to the intakes instead of maintaining the stock design where the air circulates behind the bumper, some of which goes into those stock tubes. With the direct tubes, flexible or not, air gets directed through them at high speeds especially as you increase in speed. So the little flexibility isn't a concern in terms of air getting to the intakes.

I really do wish there was an inexpensive RAM air type RPI kit for our car. But, as you mentioned, isn't attainable without forking money for a slim radiator.

is the piping and way your doing this similar to this member's project? http://www.m5board.com/vbulletin/e3...145724-diy-aa-style-intake-brake-project.html
Yes, exactly like that. His ducts are dual purpose, both cooling the brakes and ALSO has an inlet for the CAI. Mine are single purpose, only for the CAI, so 100% of the air entering the tube gets to the intakes.
 

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Discussion Starter #14
you want something like this:
YES!!! I want!!! :)

I personally never heard any flapping and I just spray painted mine, it did look kind of silly chrome, but again my "sink drains" are black.
Agreed, no flapping either. You can tell by the configuration of the pipes that there won't be flapping. And behind the bumper, you cannot see the "shiny" tubing so non-concern for me again :)
 

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Discussion Starter #16
Just like my previous setup, I use them for my brakes now and the fogs for my intake.
I'd love to see your new setup with the fog deletes.
 

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I bought my E39 with this mod already done. The biggest thing i noticed was that the the tubing gets squashed when the bumper is put back on. I would also never use this tubing. I would use the neoprene stuff from a race shop. Much more sturdy than home HVAC ducting. Eventually I will pull my bumper and redo the setup.
 

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Discussion Starter #18 (Edited)
I bought my E39 with this mod already done. The biggest thing i noticed was that the the tubing gets squashed when the bumper is put back on. I would also never use this tubing. I would use the neoprene stuff from a race shop. Much more sturdy than home HVAC ducting. Eventually I will pull my bumper and redo the setup.
I actually just rechecked mine and everything looks good. I may try the black race ducting if I can get my hands on some. But not too worried at this point. With the price tag of the black race ducting, I'm not convinced of any additional benefit to justify the cost. But time will tell.
 

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you want something like this:



that setup would NOT be good for a street car. that car is always at some serious speed with some serious engine bay ducting that allows under-hood temps to stay cooler - notice it's going past the radiator to get to the intake.
 
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you want something like this:
I do, thats exactly what I want! Im gonna research slim radiators so I can see if I cant make this a reality.

Matt, I do not believe that is a radiator. I am quite certain it is an air filter. Easy mistake though :wroom:

Edit: to OP, glad to hear everythings under control, I just wanted to point out a few issues that you may have run into. One could also use home and garden tubing, I have some pretty thick stuff I was going to use to make something like yours, but I havent had time the past couple months.

I believe its marketed as drainage piping for pond systems or stuff of that nature.
 
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