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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > People Still Do This These Days?!



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      04-23-2014, 03:31 AM   #1
alexchen86
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People Still Do This These Days?!

So looking around Amazon I came across this electronically controlled butterfly valve which basically bypasses the rest of your exhaust system as you would want to install it towards the headers area.

http://www.amazon.com/Godspeed-Perfo.../dp/B00892WGOO

Besides creating an obnoxious ruckus won't the loss in exhaust back pressure actually decrease performance at the benefit of sound?

And with a 335i F30 I would need two.....might as well get a DP does the rumble I want and the power I need!
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      04-23-2014, 08:07 AM   #2
RaceTruk
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Quote:
Originally Posted by alexchen86 View Post
So looking around Amazon I came across this electronically controlled butterfly valve which basically bypasses the rest of your exhaust system as you would want to install it towards the headers area.

http://www.amazon.com/Godspeed-Perfo.../dp/B00892WGOO

Besides creating an obnoxious ruckus won't the loss in exhaust back pressure actually decrease performance at the benefit of sound?

And with a 335i F30 I would need two.....might as well get a DP does the rumble I want and the power I need!
With an f30 it's a single midpipe before the muffler. You can relocate the factory valve that's at the exhaust tip to a Y pipe on the midpipe. I did this on my x5. It's controller by the dme so it only opens above 3000k or a little lower on wot.
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      04-23-2014, 09:06 AM   #3
JETmn
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You have a turbo on the car, no need for more back pressure. You will gain performance, but not tons on a stock turbo car (you will gain back all the losses from the exhaust).
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      04-23-2014, 09:15 AM   #4
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People do electronic cut outs all the time. Cheaper than a full catback and will give the same performance. Exhaust back pressure is a very misused term; basically if you use too large of an exhaust pipe, you lose velocity and scavenging. That's why you'd lose power running a 4" exhaust on a stock Honda or something. But if you put the cutout behind your headers or downpipes, it's fine. There is no scavenging happening after the collectors or where the exhaust merges. After the collectors, the exhaust system is pretty much a restriction so if you can minimize that restriction, you will pick up some power.

Downside of cut outs is that they fail a lot because it's an electric motor next to a very high temperature area. But lots of guys run them to maintain stock exhaust sound while cruising, but can open them up if running hard. On our cars, very little benefit since the exhaust is pretty decent. But on some cars with restrictive exhausts and forced induction, it can be a significant power gain.
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      04-23-2014, 09:35 AM   #5
Sidewinderpb
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lol

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