N54 Catless vs Catted DownpipesPin

BMW N54 Downpipes: Catless vs. Catted High-Flow Downpipes

About Zach Mayock - DieselIQ

Meet Zach

Zach is a BMW enthusiast with a passion for performance. With over 10 years of experience modifying and performing DIY work on BMWs, he’s developed a deep understanding of virtually every BMW engine. He’s also the proud owner of a 600whp N54 with upgraded twin turbos and an E30 325i drift car and has a particular affinity for the S58 engine. Zach is highly knowledgeable about all things BMW, but his expertise in tuning and performance mods sets him apart. His experience as an enthusiast, combined with his technical knowledge, makes him an essential resource for anyone looking to improve the performance of their BMW.

Why Upgrade my N54 Downpipes?

One of the biggest restrictions on the BMW N54 powered 135i, 335i and 535i is the factory catted downpipes. Downpipes bolt directly to the turbochargers and the factory catalytic converters create significant back-pressure which results in slower turbo spool. Modifying your N54 with catless or high-flow catted downpipes results in faster spool, tremendous power gains, and an aggressive exhaust note. Upgraded downpipes are a great modification especially for N54’s that have dual cone intakes. Dual cone intakes bring more air into the engine, and the more that flows in, the more that has to flow out.

N54 Catless Downpipes

As with any turbocharged car, exhaust backpressure post-turbine, leads to a significant loss in turbo spool and power. I don’t want to delve too deep into the boring details of backpressure pre/post turbo, but it is an important relationship that affects turbo spool. The drop of pressure from the exhaust gas pre-turbo to post-turbo plays a key role in why a turbo is able to spool. A larger pressure drop causes the exhaust gas to accelerate quicker leading to an increase in turbo spool. In a perfect world, the best post-turbo exhaust would be no exhaust at all. Of course, for those of us daily driving our n54’s on public roads, having no exhaust is likely not a viable option.

N54 Catless Downpipes Performance Benefits

Catless downpipes help mitigate the downside of having an exhaust system post-turbo; they lead to a considerable decrease in backpressure and allow the turbocharger to spool faster. Additionally, as air is accelerated faster towards the turbine, boost pressure increases thereby causing an increase in power. OK fine, I will move on to why I believe catless downpipes are one of the best mods for the n54 powered 135i 335i and 535i:

  • +15-25 Horsepower and Torque
  • Incredible turbo spool
  • Intoxicating Sound

I run VRSF catless downpipes on my 335i, of which I am very impressed with; the quality and welds looked excellent. Combine that with a lifetime warranty for fitment and defects and a price of only $305 it’s hard to pass up on them. I bought the downpipes with the goals of spool, power, and torque in mind and boy did these deliver. The turbo spool is immediate and the instant low-end torque is unbelievable. A loud car is never something I have been interested in – I love that the 335i appears to be a sleeper on the surface. Once again, the VRSF catless downpipes delivered. While idling or cruising at any speed it is hard to notice a significant difference between stock downpipes and catless. However, at WOT or on a cold start the catless downpipes are intoxicating; the exhaust note is very aggressive without being overly intrusive.

Best N54 Downpipes: VRSF

VRSF is our favorite downpipe manufacturer. We run their catless downpipes on both our 335i and 135i. Their product provides the best bang-for-the-buck and the fitment is awesome. At the end of the day a catless downpipe is a hollow piece of steel so opting for $500+ downpipes just isn’t worth it.

At $270 you can’t beat them. Additionally, they do offer a high-flow catted version for those concerned about passing emissions. The high-flow option runs $529 and again is one of the best values on the market.

Check out our sound clip below of Zach’s 335i with catless downpipes.

Price: $269

Buy Here: N54 VRSF Catless/High-Flow Downpipes

Listen to Zach’s 2007 BMW 335i with BMS Dual Cones, JB4, and VRSF Downpipes

Similar to cattless downpipes, high-flow catted downpipes will allow your turbos to spool faster and deliver more power. However, as you likely assumed, these downpipes have catalytic converters and are more restrictive than catless downpipes. They still provide relatively solid gains for turbo spool, power, and sound. Although, the biggest benefit of opting for high-flow catted downpipes is that your car will still pass emissions testing.

Overall, if you are looking for the best power and spool catless downpipes are the way to go. High flow catted downpipes are typically more expensive than their catless counterparts and do not offer as much of a benefit. However, if you are worried about having an exhaust system that won’t pass inspection then high flow catted downpipes are the right choice for you.

Similar Posts


  1. Jeff – Yes, so long as the JB4 is “turned on” you will not get a CEL. Do note that even though there is no CEL, you will still fail inspection unless you get a special add-on wire for the JB4 which I think is like $100 new.

    1. Thank you for your great information around N54! I can’t have such information in Japan.

      Are there any MHD Custom Flash Maps which can pass inspection with catless DP? It is OK that the flash map produce lower power. I use the map while inspection only.

Leave a Reply

Your email address will not be published. Required fields are marked *