When BMW was producing the N54 Twin Turbo I-6 engine, for all its greatness, there are a few parts of the stock motor that are really the Achilles heel of the car – namely the N54’s chargepipes and diverter valve. Before we get started, let’s discuss what the chargepipe is, where it is and what it does. The chargepipe is the part of the intake system after the turbo and intercooler, before the throttle body. It’s the part of the system that’s filled with boost pressure and so, it makes sense that it would be under a lot of stress. Unfortunately, the OEM part is a rather brittle piece of plastic fitted with slow, leak prone diverter valves, as you can see in the photo below from E90post.

What’s happening? When tuned, the plastic stock chargepipe and plastic stock diverter valve cannot stand up to the added boost pressure, crack and fail, causing boost leaks and other poor running conditions, not to mention robbing you of bottom end power on the order of 29wtq LOSS at lower revs.

About that 29wtq LOSS in 1st and 2nd gear – why is that? The OEM diverter valves are plastic-  plastic is cheap, it sticks, leaks boost and actuates slowly. This slow actuation is about a second’s worth of boost when you’re in gear, creating a much laggier feeling car than it ought to be- the car will feel much faster with a Dual Port Blow-Off Valve or Plumb-Back Diverter Valve setup.

So, how can you prevent the chargepipe from cracking under pressure? Simple, replace that janky, cheapo piece of plastic with a hard N54 chargepipe from Evolution Racewerks paired with your choice of Blow-off Valve, or Cobb Tuning’s new N54 Chargepipe paired with a Turbosmart Plumb-Back Diverter Valve or Turbosmart Dual Port Blow-Off Valve to suit your style and taste.


E92 Jeff MRR GT7 Wheels 18x8.5 18x9.5 225-40-18 255-35-18 CKS Coilovers (14)

The graph above is a dyno chart of a BMW 1M, completely STOCK, ONLY the diverter valves were replaced with Turbosmart Dual Port Blow-Off Valves – you can see just by following the dyno chart where the stock diverter valves are leaking boost, sucking up your power like some sort of awful plastic horsepower vampire. The torque gains throughout the rev range are consistent and picks up more than 25wtq down low where it counts, and you’ll really feel that difference in 1st and 2nd gears.

The above graph charts manifold pressure on the same BMW 1M as the last chart, again, with ONLY the diverter valves changed – with leak-free diverter valves, peak boost is sustained and held for maximum power. Turbosmart‘s N54 diverter valve setup works for most intakes and the OEM chargepipe as well as some aftermarket chargepipes, like Cobb’s N54 Charge pipe, but Evolution Racewerks N54 Charge Pipe features an integrated BOV and optional meth bungs and the Titek N54 Chargepipe features an integrated HKS SSQV blow-off valve, so you have a number of options available to you.


If you have questions about the charge pipes of your BMW N54 or aren’t sure how to best upgrade, we invite you to call our friendly, knowledgeable and enthusiastic Modification Experts at 714-582-3330 or chat live at www.modbargains.com

Story by Nicholas Gregson

Want to know more about modding your N54? Check out these N54-related posts on the ModBargains blog.

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