EVO 7 8 9 O2 Housing Atmosphere Dump

High-Flow Turbo O2 Housing Upgrade for Mitsubishi EVO 7, EVO 8 and EVO 9

The Mitsubishi Lancer Evolution 4G63 turbocharged engine is known for its tremendous tuning potential. However, exhaust restrictions immediately downstream of the turbocharger can influence turbine discharge flow, turbo response, and overall exhaust system efficiency.

The XS-POWER atmospheric dump O2 housing replaces the original cast-style turbine outlet with a fabricated 304 stainless steel tubular assembly. The divorced design routes turbine exhaust through the primary 2.5-inch outlet while directing internal wastegate discharge through a separate 1.75-inch atmospheric dump tube.

This layout is popular among EVO enthusiasts building track-focused, competition, and custom turbo exhaust systems where exhaust flow, turbine outlet configuration, and wastegate discharge routing are important considerations.

Technical Specifications

Mitsubishi Lancer Evolution Vehicle Fitment

Designed for compatible Mitsubishi Lancer Evolution 7, 8 and 9 models equipped with the 4G63 2.0L turbocharged engine and appropriate turbocharger outlet configuration.

Fitment advisory: EVO VII model-year availability varies by country. The EVO 7 was not originally sold as a regular US-market model. Verify turbocharger outlet flange, oxygen sensor configuration, downpipe connection, and vehicle clearance before purchase.

How a Divorced Atmospheric Dump O2 Housing Works

On a conventional internal-wastegate turbocharger system, turbine exhaust and wastegate bypass gases are typically combined into a common exhaust outlet before entering the downpipe.

A divorced atmospheric dump O2 housing separates these two exhaust streams:

1. Main turbine exhaust: Flows through the primary 2.5-inch outlet toward the downpipe.
2. Wastegate bypass exhaust: Travels through the separate 1.75-inch dump tube when the turbocharger's internal wastegate opens.
3. Atmospheric discharge: Wastegate exhaust exits through the open dump instead of rejoining the primary exhaust system.

This design can reduce interaction between the turbine discharge and bypass gases at the outlet. Actual effects on boost response, backpressure, and turbocharger performance depend on the complete turbo system.

Installation and Boost Control Considerations

Installation requires access to the turbocharger outlet and surrounding exhaust components. Confirm that the housing matches your turbocharger flange and downstream exhaust connection before installation.

• Verify turbocharger flange pattern and wastegate passage alignment.
• Confirm the internal wastegate flapper can move freely without interference.
• Check oxygen sensor provisions and wiring clearance.
• Confirm downpipe compatibility and sealing surfaces.
• Ensure the atmospheric dump exits safely away from wiring, hoses, fuel lines, body panels, and other heat-sensitive components.
• Use suitable high-temperature gaskets, fasteners, and exhaust hardware.
• Inspect for exhaust leaks and verify boost behavior after installation.
• Professional installation and boost-control inspection are recommended.

Package Includes

Frequently Asked Questions - EVO 7/8/9 O2 Housing

What is an atmospheric dump O2 housing?

An atmospheric dump O2 housing is a turbocharger outlet component that separates the internal wastegate bypass flow from the main turbine exhaust and vents the wastegate gases directly to the atmosphere.

Will this fit a 2003-2006 Mitsubishi EVO 8 or EVO 9?

It is designed for compatible EVO VIII and IX 4G63 turbocharger applications. Verify the turbo outlet, oxygen sensor arrangement, and downpipe configuration before ordering.

Does this O2 housing fit the EVO 7?

It is also intended for compatible EVO VII 4G63 turbo systems. Market-specific differences and aftermarket modifications must be checked.

What is the difference between an atmospheric dump and recirculated O2 housing?

A recirculated design returns wastegate gases to the main exhaust stream. An atmospheric dump design routes wastegate discharge through a separate open tube.

Will this make my EVO louder?

Yes, an atmospheric wastegate discharge can produce a noticeably louder exhaust sound when the internal wastegate opens. Actual sound levels depend on operating conditions and the vehicle's turbo and exhaust configuration.

What size is the main exhaust outlet?

The main exhaust outlet measures 2.5 inches, while the separate wastegate dump outlet measures 1.75 inches.

Is this O2 housing made from stainless steel?

Yes. The housing is fabricated from 304 stainless steel and uses CNC-machined 1/2-inch flanges surfaced after welding.

Does an atmospheric dump O2 housing require tuning?

Not every installation requires recalibration, but changes in exhaust flow can affect boost-control behavior. Boost pressure, wastegate operation, and engine tuning should be evaluated after installation.

Is this the same as installing an external wastegate?

No. This housing is designed to route discharge from a compatible internal wastegate through a separate atmospheric tube. It does not replace the turbocharger's wastegate mechanism.

Is this suitable for public-road use?

An open atmospheric wastegate dump may violate emissions and noise regulations. This product is intended for permitted off-road or closed-course competition applications only and is not represented as street-legal.