Repost from 2012:
So for this round of testing we used our 135i which happens to be 100% stock at the moment aside from the JB4 using 91 octane + NOS octane booster (~93 octane). I've been testing map 2 with a default CPS offset lately so kept that all the same between both tests.
The two sets of tests were performed within 20 minutes of each other under identical conditions. First I did a 40-110mph sprint (on a private track) to evaluate the intake temperature increases throughout the run. Secondly an 8 minute (limit of JB4 logs) idle test simply logging the car with the hood down and AC on to monitor intake temperatures at rest.
According to "hot air" conspiracy theorists the dual cone intake should result in higher intake temperatures during the wide open throttle run, no power gains, and heat up dramatically sitting at idle soaking up all that engine heat.
First up: Stock intake system
Next up: BMS Dual Cone Intake
I hate to say it again but the results were exactly as expected. The DCI did not produce higher air intake temperatures at wide open throttle, did not heat soak more sitting at a standstill for 8 minutes, and all around felt faster. I should also add it's certainly possible modifying your OEM airbox with an extra filter might offer minimal gains over a dual cone intake assuming you don't mind up cutting up your factory airbox but don't expect much. We've tested this as well with no significant performance gain over a DCI in 40-120mph VBOX times. You have a lot of options for intakes but three+ years later the tried and true DCI is still the intake of choice for those of us who are serious about performance...