SPDZ1 B58 True 4.5" Catless Downpipe 

🔧 Product Overview

Unlock the full potential of your B58-powered Supra or BMW with the SPDZ1 True 4.5" Catless Downpipe—now delivered with a premium exhaust gasket included. Unlike many “4.5” downpipes on the market that neck down immediately after the turbo, ours maintains the full 4.5" internal diameter right to the transition point, eliminating restriction and allowing your turbo to breathe freely. 

This is a high-performance, race-intended upgrade designed to drastically reduce backpressure, improve spool characteristics, and sharpen throttle response.

🌟 Key Features & Benefits

• True 4.5" full-length flow — no early step-downs or chokes, for maximum gas throughput

• Bolt-on fitment — mates directly to your OEM or aftermarket exhaust (no major modifications required)

• 304 stainless steel construction — corrosion-resistant and built for durability

• TIG welded mandrel bends & smooth transitions — minimizing turbulence and preserving exhaust velocity

• O2 sensor bungs retained — plug-and-play compatibility with factory sensors

• Aggressive, raw exhaust note — delivers the roar your B58 is capable of

🚗 Fitment & Compatibility

Designed for Gen 1 and Gen 2 B58 engines, this downpipe is compatible with a wide range of BMW and Toyota Supra models:

• Toyota: A90 / A91 Supra 3.0L (2020+)

• BMW (Gen 1 & Gen 2 B58): M240i, 340i, 440i, 540i, 740i, X3 M40i, X4 M40i, etc.

• Works for both Left-Hand Drive and Right-Hand Drive variants

• Fits OEM and most aftermarket Cat-Back systems

Note: This is an off-road / track use component. Use may be restricted or illegal in some jurisdictions — always verify local emissions laws before installation.

💥 Performance Gains & Driving Feel

When paired with a proper tune, users typically see 30+ wheel horsepower increases on stock turbos. Expect:

• Sharper turbo spool & reduced lag

• Lower backpressure under load

• Stronger midrange torque

• More aggressive, raw exhaust sound

Because your SPDZ1 retains full 4.5" ID through its length (before transitioning to the stock or aftermarket midpipe), you avoid the common pitfall of early diameter reduction seen in many “4.5” downpipes. Many competitors taper down almost immediately after the turbo outlet—ours does not. 

Fitment:

• 2015+ BMW M240i & Xdrive
• 2016-2019 BMW 340i & Xdrive
• 2020+ BMW M340i & Xdrive
• 2016+ BMW 440i & Xdrive
• 2016+ BMW 540i & Xdrive
• 2016+ BMW 740i & Xdrive
• 2017-2020 X3 M40
• 2017-2020 X4 M40
• 2019+ Toyota Supra 3.0L