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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > 2012-2019 BMW 3 and 4-Series Forums > General F30 Sedan / F32 Coupe / F36 Gran Coupe Forum > 1100 to 2500 rpm lag
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      09-24-2017, 03:43 PM   #23
BMWtight2me
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      09-24-2017, 03:52 PM   #24
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Originally Posted by jnecr View Post
Yes, this is the exact reason why a larger IC causes increased boost delay. However, I doubt you could really fit an IC that is significantly bigger to produce noticeable increased lag.

The stock IC is well designed, so finding an IC of the same size that is more efficient at cooling the charge is unlikely.
Here is an example with some data to show how a much larger aftermarket FMIC improves conditions.

Article: http://f30.bimmerpost.com/forums/sho...d.php?t=955430

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      10-06-2017, 01:27 AM   #25
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Originally Posted by jnecr View Post
Yes, this is the exact reason why a larger IC causes increased boost delay. However, I doubt you could really fit an IC that is significantly bigger to produce noticeable increased lag.

The stock IC is well designed, so finding an IC of the same size that is more efficient at cooling the charge is unlikely.
The problem is the volumetric efficiency of the turbo. With these small turbos, you quickly reach the point at which the boost falls off as you increase RPM. Often for a lower and higher peak, you sacrifice a lot more on the top end, so when you get a higher peak HP and torque, instead of a flatter curve to say 6000rpm, you get a much more significant fall-off after 5000 all the way to 6500. It literally feels like the car runs out of breath. The RPMs keep going up, but you don't really go any faster.

Clearing out the DP and exhaust is usually one of the best ways to get a little more performance from the existing setup. Going to a bigger intercooler is usually reserved for going with a bigger turbo, UNLESS the car came with a relatively large turbo and small intercooler, but that's rare, a manufacturer would almost never do that because it costs more and doesn't do anything. Some of the Evos came with turbos big enough to get some serious performance boosts out of, but the 4cyl BMWs use pretty tiny TD04 based turbos, which I know pretty well So if you put things like a bigger intake on without increasing the amount of air that the turbo can actually move, you are increasing lag. There can still be benefits as far as lowering the intake temp, but it's increasing the traditional turbo behavior in terms of having to get the RPM up high enough. Clearing out the exhaust headers, DP, cats, etc., can bring some of this back, but you run into the volumetric problem and run out of power earlier. So then you put a bigger turbo in, which requires a better fuel pump, lines/rails, bigger injectors, possibly bigger intake, and so on. Nothing is free if you are going to set this up correctly.
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      10-06-2017, 10:11 AM   #26
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Originally Posted by BMWtight2me View Post
Here is an example with some data to show how a much larger aftermarket FMIC improves conditions.

Article: http://f30.bimmerpost.com/forums/sho...d.php?t=955430

As you'll see in my comment I said finding an intercooler of the same size that is more efficient is unlikely. Of course a larger intercooler will cool the charge better. But OP is talking about reducing lag, which a larger IC will not help.
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      10-07-2017, 07:33 PM   #27
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nobody has recommended an intake yet?

and if you want to improve cooling without an aftermarket intercooler, you need a water/meth kit.
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