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      08-07-2009, 06:59 PM   #1
Mr. 5
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2007 e90 335i  [4.00]
Dyno Runs--DCI vs OEM air box (Hood Closed)

So I went to MD Automotive today because it was bugging me about the intake vs OEM air box discussion that we had recently.
It occurred to me that nobody dynos with the hood closed when testing an intake. It was bugging the crap out of me because I keep hearing things like, "Wow, all I did was put on the dual cones and I gained 15 hp" or "What are you doing using the stock air box still? You should be using dual cones."

First off, here are my mods:

-JB3 Map 3
-Active Autowerke Intercooler
-Autobahn Exotics Exhaust with HFCs
-Ultimate Racing catless DPs

So this is what I did today:

-I compared a dual cone setup with the OEM airbox with the AFE filter. Both setups were using AFE scoops.
-I did 3 runs with each setup.
-Each dyno run was done with the hood closed using the huge fan. I don't know exactly but I was told that it was a 100mph fan, but realisticaly, once the air actually enters the car and the air ducts, it's most likely hitting the car at 60 mph.

Between each run, I opened the hood and let the fan cool off the engine bay for 5 minutes. This was done with both setups.
The DCI setup was done first because I didn't want there to be any comments like "the reason why the DCI didn't do well was because the DCI was used after the OEM air box" bla bla.

I was actually surprised with how well the DCI setup did for the first run, but thinking about it after the fact, I honestly feel that the AITs of the DCI were lower in the first run due to the engine not being up to normal operating temperature. This is why I believe that the AITs of the OEM air box were higher than the DCI with the first run.

The first graph is the 3 runs with the DCI.
The next graph is the IATs of 3 runs of the DCI.
The 3rd graph is the 3 runs with the OEM air box.
And then the IATs of the 3 runs.

I graphed the best run of each on the 5th graph and then the worst run of each on the 6th graph.

Here's my summary...
I know that it's hard to duplicate real world conditions on a dyno, but I honestly think that it's more realistic with the hood closed.

Use A DCI if...

-You want to get a good 1/4 mile time at the strip.
-You want to impress your friends with dyno numbers.
-You like the sound of the whooshing noise.

Use the OEM air box if...

-You want something that is consistent.
-You drive on road courses/autocrosses.
-You like the OEM look.
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