AEM vs. Cobb intake system questions - Page 2
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This is a discussion on AEM vs. Cobb intake system questions within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Originally Posted by KronosPerformance People don't realize that while your car is in movement, there is a lot of air ...

  1. #16
    Registered User jd92677's Avatar
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    Quote Originally Posted by KronosPerformance View Post
    People don't realize that while your car is in movement, there is a lot of air circulation which would change the under hood temperature. I have also yet to see any proof that the Intake Temperatures were lower in one setup than the other...mainly because its insignificant and they probably aren't. Just because you're getting air from one source at one temperature, doesn't mean by time it travels through your intake system that it will be that same termpature...it would only be different if there was a drastic change it ambient temperature (like going from 50 degrees outside to 80 degrees outside). Changing the source of your air location isn't going to make a big different either way.
    Any temp difference would be better IMO.

    Quote Originally Posted by KronosPerformance View Post
    Also, the only thing CAI do is make the path of air flow longer, making intake velocity slower....even for a turbocharged vehicle, especially because most CAI setups are 3" in diameter making the volume larger and path longer since its extending to the fender area. Thats something to consider.
    The velocity of the intake air shouldn't matter, it's the volume of air that the turbo can access in order to compress and build boost that matters. A larger intake would allow more air to be accessed by the turbo and therefore would allow for higher boost levels.
    Last edited by jd92677; 06-15-2011 at 05:16 AM.
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  3. #17
    dmk
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    Quote Originally Posted by KronosPerformance View Post
    Everyone overplays it. You would literally have to have your filter submerged in water for a long period of time in order for that to happen from that type of setup. I've been around the car scene for years, never once heard of it happening.
    I agree. I had a CAI on my last car for more than 10 years and never had a problem (never had any problems with that car actually). The CAI on that car went down into the fender well just over and behind the foglight. The car was also lowered 1.5". I drove through some horrible rain storms and some road flooding.

    Avoid water that is deeper than your wheel hubs. Which you want to do on any car anyway. (Learned that on a 4x4 I used to own when I was young and ignorant. Ended up having to replace all the bearings and races in the wheels due to deep water)
    Last edited by dmk; 06-15-2011 at 05:24 AM.

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    Gold Member lokey's Avatar
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    Quote Originally Posted by KronosPerformance View Post
    People don't realize that while your car is in movement, there is a lot of air circulation which would change the under hood temperature. I have also yet to see any proof that the Intake Temperatures were lower in one setup than the other...mainly because its insignificant and they probably aren't. Just because you're getting air from one source at one temperature, doesn't mean by time it travels through your intake system that it will be that same termpature...it would only be different if there was a drastic change it ambient temperature (like going from 50 degrees outside to 80 degrees outside). Changing the source of your air location isn't going to make a big different either way.

    Also, the only thing CAI do is make the path of air flow longer, making intake velocity slower....even for a turbocharged vehicle, especially because most CAI setups are 3" in diameter making the volume larger and path longer since its extending to the fender area. Thats something to consider.
    ^ this!! + this > The gains are the same. Why even risk it? Just for the sake of argument, let's say there's a 1% chance of running through a puddle a foot deep and hydrolocking your car. That's 1% more than 0. Also, I'd like to squash the stance that changing/cleaning the filter on the AEM is easier or quicker just because its dry flow. Just the location and mounting alone of the AEM makes it much more of a PITA to take out and clean. Be honest fellas. Changing/cleaning my Cobb SFI entails removing 3 screws from the top of the box and loosening a hose clamp to pull the filter off. re: nighthawk's "dry flow filter was much easier to clean than a oiled filter" - Are you referring to the whole 10 seconds it takes to spray the filter after it dries?

    ps - Buy the accessport from Perrin (same price - $595), just so you don't have to buy their map. Cobb's maps are free, regardless of whether you buy the AP from them or not. Try both.
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    ClubWRX.net Vendor adam@kronosperformance's Avatar
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    Quote Originally Posted by jd92677 View Post
    The velocity of the intake air shouldn't matter, it's the volume of air that the turbo can access in order to compress and build boost that matters. A larger intake would allow more air to be accessed by the turbo and therefore would allow for higher boost levels.
    It always matters, thats how fluid dynamics works. Look at an engine for example without a turbocharger, your engine draws air in as well...yet when you change many of the characteristics of the intake system, it makes a different. Its the same difference when you switch from Top Mount to Front Mount...when you make the path of air longer, it takes longer to build up velocity. When you make the path larger (more volume) you make the velocity build up longer as well. Doesn't matter of the turbo has "access to air", it still will take it longer to draw in air in a consistent manner. Air isn't just magically there, the compressor needs a certain amount of air to create whatever pressure you're aiming for.

    Now this is all of course circumstancial...this doesn't mean that you get a CAI and its going to be a huge world of a difference but it may be something you naturally experience.

    If you guys want, I can show you a write up I did on Velocity and Resonating effects as well.
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    Registered User jd92677's Avatar
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    Quote Originally Posted by KronosPerformance View Post
    It always matters, thats how fluid dynamics works. Look at an engine for example without a turbocharger, your engine draws air in as well...yet when you change many of the characteristics of the intake system, it makes a different. Its the same difference when you switch from Top Mount to Front Mount...when you make the path of air longer, it takes longer to build up velocity. When you make the path larger (more volume) you make the velocity build up longer as well. Doesn't matter of the turbo has "access to air", it still will take it longer to draw in air in a consistent manner. Air isn't just magically there, the compressor needs a certain amount of air to create whatever pressure you're aiming for.

    Now this is all of course circumstancial...this doesn't mean that you get a CAI and its going to be a huge world of a difference but it may be something you naturally experience.

    If you guys want, I can show you a write up I did on Velocity and Resonating effects as well.
    You're talking 2 different instances, pre-turbo and post-turbo. Post turbo, when it comes to interoolers, more tubing will absolutely make a difference, you need to create pressure in a larger space. Pre turbo, the turbo will injest as much air as it can to compress, so a larger volume of air pre-turbo is better. The velocity of the air from the filter to the turbo is dictated by the turbo. Volume and velocity are inversly related, the more volume, the lower the velocity, for example, if the intake was the size of a straw, the air would be moving at a high velocity, but there wouldnt be enough to feed the turbo, whereas if you had an intake the size of a 55 gallon bucket, you would have a huge amount of air for the turbo to pull in, yet it would not be moving very fast. As long as the MAF is correctly accounting for the amount of air being fed to the turbo, larger is always better, regardless of velocity.
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    Gold Member lokey's Avatar
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    Okay, sounds like we need a Cobb vs. AEM MAF compaarison to get to the bottom of this.

    ....But does it really matter? Here's the thing, man - Neither will do any better than the other on any setup stage 2+ and below. The reason - They only provide as much air as what is demanded by your modifications/setup. Hell, the stock air box still isn't the "choke point" on 350+ HP setups. So......pick either one. Cobb's is louder. AEM's comes in pretty colors. The End.
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    ClubWRX.net Vendor adam@kronosperformance's Avatar
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    Quote Originally Posted by jd92677 View Post
    You're talking 2 different instances, pre-turbo and post-turbo. Post turbo, when it comes to interoolers, more tubing will absolutely make a difference, you need to create pressure in a larger space. Pre turbo, the turbo will injest as much air as it can to compress, so a larger volume of air pre-turbo is better. The velocity of the air from the filter to the turbo is dictated by the turbo. Volume and velocity are inversly related, the more volume, the lower the velocity, for example, if the intake was the size of a straw, the air would be moving at a high velocity, but there wouldnt be enough to feed the turbo, whereas if you had an intake the size of a 55 gallon bucket, you would have a huge amount of air for the turbo to pull in, yet it would not be moving very fast. As long as the MAF is correctly accounting for the amount of air being fed to the turbo, larger is always better, regardless of velocity.
    Pre-Turbo is dictated by the Turbo, true...but also the size of the tube, the length of the tube and even down the restriction of the air filter. Everything plays an effect on it. You keep using the word compress when its ingesting air in order to compress it. It has to pull air...same as an engine would have to pull air...its the same difference. Fluid dynamics always plays an effect, science doesn't just turn itself off because there is a turbo involved.

    The only reason I brought up Top Mount and Switching to Front Mount was to point out the slow down in velocity due to the additional length.
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  9. #23
    Registered User mudferret's Avatar
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    IMO the best intake set up (if you must go aftermarket) would be an SRI with a box (like the Cobb unit) + a silencer delete. My only concern with SRI's would be intake temps off the line or in stop and go traffic (hence the box), otherwise temps even out when in motion, as mentioned above.
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    He simply abides. SD_GR's Avatar
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    The best intake setup is the one that filters air better.

    The rest is marketing.

    Which intake filters air better? Where are the data to prove it?
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    Registered User mudferret's Avatar
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    Quote Originally Posted by SD_GR View Post
    The best intake setup is the one that filters air better.

    The rest is marketing.

    Which intake filters air better? Where are the data to prove it?
    Don't get me wrong, I thoroughly dig my OEM set up and paper filter.
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    Registered User skudda33's Avatar
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    Whould there be a huge difference if the airbox is not Purchased with the Cobb sf?

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    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by mudferret View Post
    Don't get me wrong, I thoroughly dig my OEM set up and paper filter.
    I don't blame you. I've had analyses done and the data showed it's an excellent setup. It's the best priced setup, the most effective from any/all data I've seen, and the best at protecting not only from important things that people somehow routinely ignore when considering an intake but also from less likely things, like water etc.
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    Subaru Newb MainFrame's Avatar
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    I would still be on the stock intake if it worked with my FMIC, but that thing takes up a lot of room in the engine bay so something had to go. My Perrin SRI works fine.


    I'm getting ready to build a box for it.. maybe I should design an experiment to see if it really does make a difference. I bet it's negligible.

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    It would be interesting to see certainly.
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  16. #30
    Registered User mudferret's Avatar
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    Quote Originally Posted by MainFrame View Post
    I would still be on the stock intake if it worked with my FMIC, but that thing takes up a lot of room in the engine bay so something had to go. My Perrin SRI works fine.


    I'm getting ready to build a box for it.. maybe I should design an experiment to see if it really does make a difference. I bet it's negligible.
    It could get "ugly" but reflective tape on the outside and some insulation on the inside might help. Not sure I'll ever reach the limits of the stock intake so I'm not sure I'll ever change it out. I know people with some more aggressive set ups (e.g. HTA68+meth) and they're still on the stock intake with no intention of changing it out. With dyno testing however they did find that a velocity stack had real gains above 4k rpm with that particular set up (~10 whp 20 wtq IIRC), likely much less with a simple TBE + tune set up.
    ...Rob.
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