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    Thread: Debunking the Cold Air Intake myth

    1. Member Moljinar's Avatar
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      03-22-2006 06:36 PM #1
      While cleaning the garage I found my trusty indoor outdoor electronic thermometer so I figured what a good day for a test of my intake temperature.
      I placed the probe up in the intake of the CIS airbox. No hose is attached to the inlet so it is currently sucking ONLY engine bay air just like those fancy "cone" filter setups everyone wants to buy.
      So I get ready to drive to work. Outside air is 40*F . I start the engine and without warming it up drive thru the neighborhood to the interstate (about a mile away.)
      By the time I get to interstate the intake temp is up to 50*F
      5 miles of 70mph driving later temp is up to 70*F
      5 more miles and we're up to 80*F
      It levels out at 110*F for the rest of the trip.
      Here's a shocker. After all that driving when I pull off the interstate onto city roads it goes down for a second and then soars upward over 120*F and my thermoster goes overrange and starts flashing HHH
      I repeated this test on the way home today and got identical readings.
      So as you can see engine air is usually 80*F higher in temp than the ouitside air. Now let's pretend is a sunny summer day and it's 80*F outside. Wanna guess what your "cold" air intake is doing? Cooking your friggin engine that's what! You should have at least 160*F or worse due to the added rays of the sun baking the car itself.
      Now let's add in that turbo you always wanted. Any idea what your intake temp might reach?
      Now if I get time I'll hook the usual front bumper intake back up and see what's "normal" for a 1.8 CIS setup.

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    3. Member G60 CAB's Avatar
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      03-22-2006 08:39 PM #2
      That's a good test. A true cold air sits low, near the ground and is sheltered from the heat in the engine bay.
      I have an open element filter on the G60 surrounded by a home-made heat shield (that does a damn good job too) and have done air intake temp tests multiple times. Because I have an air-to-water intercooler, the intake temps are basically the same no matter if I am at full boost or at idle (within a certain time period). What I do is start it up, check the temp at the boost dump after the intercooler at the throttle body. I then go HOG WILD for atleast 20 minutes, checking the IATs everyonce in a while, and then finally coming back home after a super hard boost run.
      The hottest I have ever seen the IATs go was 108F with my 15 psi setup with that open filter. I would imagine with the stock airbox it could be less then 100, but barely.
      So, if you are running an open element filter, shield it as best as you can from the engine bay heat or just leave in the stock airbox. [IMG]http://*****************.com/smile/emthup.gif[/IMG]
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    4. 03-22-2006 08:52 PM #3
      hey!
      cool!
      i didnt know that.

    5. 03-23-2006 12:57 AM #4
      uh oh

    6. 03-23-2006 01:05 AM #5
      It would be interesting if you could run a hose to your airbox to suck in cold air and measure the temps for comparison. I always thought those cone filters were a big gimmick. IMO the best way is to have hose ran behind the grill to "ram" the cold air into the airbox.

    7. Member VeeDubDriver1990's Avatar
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      03-23-2006 02:40 AM #6
      Quote, originally posted by Moljinar »
      While cleaning the garage I found my trusty indoor outdoor electronic thermometer so I figured what a good day for a test of my intake temperature.
      I placed the probe up in the intake of the CIS airbox. No hose is attached to the inlet so it is currently sucking ONLY engine bay air just like those fancy "cone" filter setups everyone wants to buy.
      So I get ready to drive to work. Outside air is 40*F . I start the engine and without warming it up drive thru the neighborhood to the interstate (about a mile away.)
      By the time I get to interstate the intake temp is up to 50*F
      5 miles of 70mph driving later temp is up to 70*F
      5 more miles and we're up to 80*F
      It levels out at 110*F for the rest of the trip.
      Here's a shocker. After all that driving when I pull off the interstate onto city roads it goes down for a second and then soars upward over 120*F and my thermoster goes overrange and starts flashing HHH
      I repeated this test on the way home today and got identical readings.
      So as you can see engine air is usually 80*F higher in temp than the ouitside air. Now let's pretend is a sunny summer day and it's 80*F outside. Wanna guess what your "cold" air intake is doing? Cooking your friggin engine that's what! You should have at least 160*F or worse due to the added rays of the sun baking the car itself.
      Now let's add in that turbo you always wanted. Any idea what your intake temp might reach?
      Now if I get time I'll hook the usual front bumper intake back up and see what's "normal" for a 1.8 CIS setup.

      I'm glad someone finally posted the truth
      If you want to spend $120 on your Cabs to make them faster, people-
      get a cam or put it towards a bigger motor

    8. 03-23-2006 08:35 AM #7
      bump for alllll to see.
      I tried telling this to ssooo many people and they all look at me sideways like "Wha?! - you dont know what you're talking about"

    9. Member Black_cabbie's Avatar
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      03-23-2006 08:45 AM #8
      I always said that its useless unless you drill your airbox and put a big flexible hose somewhere up front where it can get cold air only.
      I believe Ron did the mod in his cab as well and he documented everything that needs to be done.
      Chip Tuning for a living @ www.microchips-tuning.com

    10. 03-23-2006 08:50 AM #9
      Quote, originally posted by Moljinar »
      So as you can see engine air is usually 80*F higher in temp than the ouitside air. Now let's pretend is a sunny summer day and it's 80*F outside. Wanna guess what your "cold" air intake is doing? Cooking your friggin engine that's what! You should have at least 160*F or worse due to the added rays of the sun baking the car itself.

      Open element filters that sit inside of your engine bay are never refered to as cold air intakes unless you buy them on E-bay for $6. Reputable sites and or brands call them something like "short ram" or "ram air" intakes. As redvdubvert said
      Quote, originally posted by redvdubvert »
      A true cold air sits low, near the ground and is sheltered from the heat in the engine bay.
      My cold air intake puts the cone filter between the inner and out fender and only sees about a 10 to 15 degree temperature difference between intake air temp and ambient air temp.

    11. Member das-yeti's Avatar
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      03-23-2006 01:50 PM #10
      i have a hole cut on the inner wing with a hose that goes from the airbox out to in between the fender and innner wing.

    12. Member tolusina's Avatar
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      03-23-2006 02:47 PM #11
      Quote, originally posted by Black_cabbie »
      I always said that its useless unless you drill your airbox and put a big flexible hose somewhere up front where it can get cold air only.
      I believe Ron did the mod in his cab as well and he documented everything that needs to be done.

      Here's the link......
      http://reflectionsandshadows.com/digi-cold/
      I used 2" pipe and ducting, it's significantly larger than stock but fits easily.
      The flex hose does accordion when the engine is revved, that kind of indicates a more radical mod using larger that 2" components would probably be even more beneficial.
      There are lots of possible reasons my mod may not work for you, just use it as a concept, make your own version.
      It's not a big priority to me right now, but if I get near the neighborhood where my thermocouple is stored, I'll get some live temperature measurements. Thanks for this thread Oran, like I needed another task........ (jk) Seriously, this thread is great, Kudos to Oran for de-bunking this old myth. [IMG]http://*****************.com/smile/emthup.gif[/IMG] [IMG]http://*****************.com/smile/emthup.gif[/IMG]
      Quote Originally Posted by kamzcab86
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    13. Member Moljinar's Avatar
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      03-23-2006 02:59 PM #12
      It was 24*F out this morning and I still over-ranged the thermometer on the way into work!

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      06-19-2007 01:09 PM #13
      My car ran cooler, and idled smoother after doing this


      Cleaning, inspecting, ordering parts, looking for parts, collecting parts, modifying things...
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    15. Member Moljinar's Avatar
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      06-19-2007 01:54 PM #14
      Nice job on the airbox. I'm planning to do mine the same way.

    16. Member csampson311's Avatar
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      12-07-2010 02:12 AM #15
      Quote Originally Posted by VeeDubDriver1990 View Post
      If you want to spend $120 on your Cabs to make them faster, people-
      get a cam or put it towards a bigger motor
      Where do they sell cam shafts that will ad power for this price?
      Quote Originally Posted by oldschool eighty8 View Post
      It sounds like 4 unicorns gang banging a mermaid

    17. Member Moljinar's Avatar
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      12-07-2010 07:39 AM #16
      That was posted 4 years ago. Try the classifieds for a cheap cam.

    18. Member hessiandave's Avatar
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      12-07-2010 12:08 PM #17
      My fox has a swiss cheesed airbox, and there's a line that goes into it, its right behind the grill. Gets plenty of cool air.

      I once saw a kid who did a g60 swap intoa mk1.
      He had the cone filter and intercooler like in the engine bay, I told him he'd get way cooler intake temps if he re-routed some of the piping so the "CAI" was in a cooler spot, and intercooler was in the path of some air. He's like yeah well that's why I got the intercooler in there, it cools it down. Facepalm.
      Where the intercooler was, it was most likely a heatsink.

    19. Member CISinjected's Avatar
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      12-07-2010 02:39 PM #18
      Wow, I think we need a necro post emote.

      On a related note, its fun and easy to measure and experiment with intake setups on my '02 Passat. With the sensors and vag-com I can moniter the IAT really easily while driving around. I found that the difference between open face and factory is actually not very large at all while driving around, especially on the highway. I currently have an open face on the Passat right now because of the way I had to set up the CNG kit on it. I like the way it sounds and I have slight suspicions that it flows better than the factory one, but the Passat intake is fairly stifling and is just HUGE, takes up a third of the whole engine bay. The air velocity on the vag-com showed a slight improvement, as did throttle response. I still really don't like the setup as it is right now though, intake temps while stopped are very high. I think simple heat shield isolation would pretty much solve the problem.

      Totally different from a CIS though. The best way is as noted on the forum...K&N panel and then modify that valve and tubing on the bottom of the box and run a tube down and out to get cool air. Simple, cheap, effective. Its basically a Colorado Outlaw Airbox Mod - which is the actual slang term for cutting out pieces of any airbox (including cabrios) and attaching tubing routed to the front bumper area.

    20. Senior Member dubdaze68's Avatar
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      12-07-2010 05:07 PM #19
      The factory piece mounted behind the bumper does a fairly admirable job, it's the missing tubing (and the tin foil they were made out of) that were a problem.

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      12-07-2010 06:11 PM #20
      What you need to get any benefit from this is one of these........... or some setup like this ...... and then you'll need one of these ....... .... Lmao !!!!!!!!!!!!!!

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      12-08-2010 12:07 PM #21
      Quote Originally Posted by csampson311 View Post
      Where do they sell cam shafts that will ad power for this price?
      Techtonics tuning or Autotech.

    23. Member Moljinar's Avatar
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      12-08-2010 02:12 PM #22
      Most manufacturers set their airboxes to mix cool and hot air to provide about a 90*F intake temp. That way they can count on consistent air fuel mixtures and emissions results. I'm not saying that 's good for performance but that's what they do (which is why you almost never see a real cold air intake on a stock vehicle)

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