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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Cobb's take on DCI vs. stock air box (article)



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      09-04-2011, 10:43 AM   #1
riceygts
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Cobb's take on DCI vs. stock air box (article)

I hope this is not a re-post. Take it as another data point for the dci vs. stock air box debate.

I wonder if the superiority of the stock air box will still hold for a stage 2 car.

http://blogs.cobbtuning.com/2011/06/...ir-box-vs-dci/

Last edited by riceygts; 09-04-2011 at 10:48 AM.
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      09-04-2011, 10:51 AM   #2
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looks like im putting my stock airbox on?
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      09-04-2011, 10:54 AM   #3
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First and foremost a dyno does NOT replicate the air flow of real world roads and highways so the debate is negligible.

What is important is removing the restriction of the stock air box and anyone can easily agree on that.

However you do that is up to you. Naturally, an intake breathing better and colder air would be ideal.
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      09-04-2011, 10:57 AM   #4
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group m replica hows that thing?
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      09-04-2011, 11:22 AM   #5
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This one has been beaten to death, DCI's are not optimized when sitting on a dyno with no where near real world air flow. DCI's prevail over the stocker when driven under load and experiencing proper air flow.
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      09-04-2011, 11:32 AM   #6
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Quote:
Originally Posted by Irishace View Post
This one has been beaten to death, DCI's are not optimized when sitting on a dyno with no where near real world air flow. DCI's prevail over the stocker when driven under load and experiencing proper air flow.
Actually, the dcis win at dyno only. Irish tested them until the numbers stabilized. single passes typically show the dci winning on the 1st couple of passes, especially with hood closed. Once things get hot and the temps stabilize to the conditions, the oem box wins as it draws colder air.
I showed that at the track on stg1 the dci performed worse.
http://www.e90post.com/forums/showthread.php?t=491005

The best intake for this car is the mr. 5 intake. My logs of it vs the stock box are here:
http://www.e90post.com/forums/showthread.php?p=10352970#post10352970
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      09-04-2011, 11:58 AM   #7
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In their testing they made the most power with the airbox lid removed which is functionally equivalent to a DCI. They are also using load targeting tuning that will just arise the boost should air intake temperatures increase. Their testing was internally inconsistent and flawed.

Mike
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      09-04-2011, 12:29 PM   #8
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Quote:
Originally Posted by boom View Post
Actually, the dcis win at dyno only. Irish tested them until the numbers stabilized. single passes typically show the dci winning on the 1st couple of passes, especially with hood closed. Once things get hot and the temps stabilize to the conditions, the oem box wins as it draws colder air.
I showed that at the track on stg1 the dci performed worse.
http://www.e90post.com/forums/showthread.php?t=491005

The best intake for this car is the mr. 5 intake. My logs of it vs the stock box are here:
http://www.e90post.com/forums/showth...0#post10352970

Then how come mr used the dci when he was at the track?? The stock airbox is garbage !!!The stock box is for stock cars .
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      09-04-2011, 01:49 PM   #9
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Quote:
Originally Posted by Mike@N54Tuning.com View Post
In their testing they made the most power with the airbox lid removed which is functionally equivalent to a DCI. They are also using load targeting tuning that will just arise the boost should air intake temperatures increase. Their testing was internally inconsistent and flawed.

Mike
Except that it's not functionally equivalent to a DCI because the DCI made less power than both the stock airbox and the the stock airbox w/o lid. Read the post.

Quote:
Originally Posted by thebigragu99 View Post
Then how come mr used the dci when he was at the track?? The stock airbox is garbage !!!The stock box is for stock cars .
Do yourself a favor and actually read the posts before commenting...
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      09-04-2011, 01:55 PM   #10
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Okay boom keep using the stock box ..Your telling me a stock airbox can feed more air then a two cone filter inserted into the turbos?????I have read all the posts.
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      09-04-2011, 02:15 PM   #11
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Quote:
Originally Posted by thebigragu99 View Post
Okay boom keep using the stock box ..Your telling me a stock airbox can feed more air then a two cone filter inserted into the turbos?????I have read all the posts.
The turbos will only pull so much air at boost levels it's trying to hit, and the stock box flows just as well as the DCI's up to 13-14 PSI, anything beyond that it becomes restrictive.

By your logic I could slap in even bigger DCI's than BMS sells and make even more horsepower. Which we all know is false. What you are forgetting is that the runners that connect from the intake to the turbo's is flat and pancaked in the engine bay. So you can only flow so much more air before those runners become restrictive.

Also boom is running the Mr5 intake not the stock box read the post.

Quoted from Mr Terry himself seller of the BMS DCI

Quote:
Originally Posted by Terry @ BMS View Post
That design looks much better than your first one! Looking at the wastegate duty cycles clearly shows the compressors are working less with the Mr.5 intake and DCI compared to the stock airbox. I know you went with single 3rd gear pull to avoid shifting variance, but a 60-130 run might show a more realistic spread. With only 4-5 seconds its hard to see the real performance difference between the three. But at 9-10 seconds we'd see more of a spread.

PS. The testing seems to indicate what we saw in our testing. Specifically that there was a slightly potential advantage with the stock filter + 2nd filter compared to the DCI. But our testing was 40-120 and we saw less than .1th gain and only on some runs. After a few tests back and forth we concluded the open element was about as good, easier to install, and less expensive. It is possible your new design out flows our development design though. Maybe I'll hack up another airbox and make a Mr5 replica for testing.
Quote:
Originally Posted by Terry @ BMS View Post
I like the Mr.5 option also but it's just not practical to mass produce.
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      09-04-2011, 02:21 PM   #12
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Quote:
Originally Posted by thebigragu99 View Post
Okay boom keep using the stock box ..Your telling me a stock airbox can feed more air then a two cone filter inserted into the turbos?????I have read all the posts.
That's right, because you believe it to be so, it must be despite the actual data indicating otherwise.

Quote:
Originally Posted by ErvGotti View Post
The turbos will only pull so much air at boost levels it's trying to hit, and the stock box flows just as well as the DCI's up to 13-14 PSI, anything beyond that it becomes restrictive.

By your logic I could slap in even bigger DCI's than BMS sells and make even more horsepower. Which we all know is false. What you are forgetting is that the runners that connect from the intake to the turbo's is flat and pancaked in the engine bay. So you can only flow so much more air before those runners become restrictive.

Also boom is running the Mr5 intake not the stock box read the post.

Quoted from Mr Terry himself seller of the BMS DCI
THIS!
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      09-04-2011, 02:26 PM   #13
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All of this reminds me of the CAI vs Stock Airbox discussions in the VW/AUDI world from about 10 years ago when they introduced the 1.8T (Nevah' Loose) engine.

I've been saying this for a while now, but I'll repeat it again: the best flowing intake would be gutted and smoothed out stock air box with drop-in performance filter.

Dinan intake and Mr.5's intake mod are also excellent solutions as well!
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      09-04-2011, 02:28 PM   #14
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Quote:
Originally Posted by MikeyComputers View Post
group m replica hows that thing?
The Simota..I run it..its actually very good..I log my air intakes temps..and as soon as the car is on the move the temps drop rapidly..I have ran it wit both the lid on and off. and the temp differences are significant

Simota and the new AFE sealed box are prolly the best intakes for alleviating heat soak issues..and still removes the stock box restriction

The Mr 5..Dinan style is prolly the best option..but out of the question for me due to rain and flooding in NY..these cold air intakes are safe to run in dry climates..but not in wet climates
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      09-04-2011, 02:35 PM   #15
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Quote:
Originally Posted by thebigragu99 View Post
Okay boom keep using the stock box ..Your telling me a stock airbox can feed more air then a two cone filter inserted into the turbos?????I have read all the posts.
These are Forced induction cars..if on an NA platform then air filter sizes would matter greatly..not as important on an FI..
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      09-04-2011, 02:50 PM   #16
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Quote:
Originally Posted by tibra1 View Post

The Mr 5..Dinan style is prolly the best option..but out of the question for me due to rain and flooding in NY..these cold air intakes are safe to run in dry climates..but not in wet climates
These styles are NOT a problem in wet climates.If the lower pipe where to become restricted the engine would get all the air it needs from the upper stock intake - especially at the low speeds you should be going if there was that much water present.
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      09-04-2011, 02:57 PM   #17
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Quote:
Originally Posted by tibra1 View Post
The Simota..I run it..its actually very good..I log my air intakes temps..and as soon as the car is on the move the temps drop rapidly..I have ran it wit both the lid on and off. and the temp differences are significant

Simota and the new AFE sealed box are prolly the best intakes for alleviating heat soak issues..and still removes the stock box restriction

The Mr 5..Dinan style is prolly the best option..but out of the question for me due to rain and flooding in NY..these cold air intakes are safe to run in dry climates..but not in wet climates
i wonder if you put a valve in like my old nismo intake on my Z...... hmmm

http://www.nissanraceshop.com/image/...6576-rnz36.jpg

check that out... why has nobody put a valve in on a MR.5 intake im in ny too flooding is a issue around here
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      09-04-2011, 03:01 PM   #18
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pardon the thread hijack, but what is the option on Stett V2 CAI?
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      09-04-2011, 03:04 PM   #19
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Quote:
Originally Posted by NoQuarter View Post
These styles are NOT a problem in wet climates.If the lower pipe where to become restricted the engine would get all the air it needs from the upper stock intake - especially at the low speeds you should be going if there was that much water present.
Tell that to my buddy who had a CAI that got completely water logged..and hydrolocked the engine on his G35...no way am I running a CAI here..if I lived in a desert climate or place where it rains a few times a yr then maybe
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      09-04-2011, 03:06 PM   #20
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Bottom line the more air feed to
The turbos the more power will be made .The turbos need to breath.
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      09-04-2011, 03:15 PM   #21
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tibra1,

It seems that you don't understand the simple principles of fluid dynamics. Your buddy got his engine hydro locked with the CAI because the air has only one path to the engine: through the CAI.

Both Mr.5 intake mod and the Dinan intake add an additional air source. If water completely submerges the intake filter in the fender area, the engine will still be fine because air will be sucked in though the stock intake tract above the kidney grilles.
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      09-04-2011, 03:20 PM   #22
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Quote:
Originally Posted by vasillalov View Post
tibra1,

It seems that you don't understand the simple principles of fluid dynamics. Your buddy got his engine hydro locked with the CAI because the air has only one path to the engine: through the CAI.

Both Mr.5 intake mod and the Dinan intake add an additional air source. If water completely submerges the intake filter in the fender area, the engine will still be fine because air will be sucked in though the stock intake tract above the kidney grilles.
I never pretended to know fluid dynamics..Im not a physicist..I wont take the chance no matter how remote it is..not if the net difference is +/- 3-5HP
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