Description

STM Water Pump Bypass with -16ORB for Evo 8/9 Part #EVO89-WPB

Firstly, Buy STM Water Pump Bypass for Evo 8/9 (EVO89-WPB) with -16ORB outlet. The STM Water Pump Bypass with -16ORB for Evo 8/9 (EVO89-WPB) is a billet aluminum water pump bypass plate designed specifically for the Mitsubishi Lancer Evolution VIII and IX. Developed by the STM team for performance applications, this bypass plate is designed to be used with an electric water pump, allowing the factory mechanical water pump to be removed from the cooling-system setup.

The STM EVO89-WPB features an integrated -16AN ORB outlet, providing a convenient connection point for a custom electric water-pump cooling system. It is manufactured from 6061 billet aluminum, includes stainless mounting hardware, and is made in the USA. STM states that the design has been used on its race cars over the years for electric water-pump installations.

STM EVO89-WPB Water Pump Bypass

The STM Water Pump Bypass for Evo 8/9 provides a clean way to convert the 4G63 cooling system for an electric water pump. Instead of retaining the factory mechanical water pump, the bypass plate closes the original water-pump location while providing a dedicated coolant outlet for the new electric-pump system.

This type of setup can be useful for dedicated performance, drag racing, track, and competition vehicles where the cooling system is being redesigned around an electric water pump.

STM explains that high-revving Evo applications can place additional demands on the factory mechanical water pump. Using the bypass plate with an electric pump removes the mechanical pump from the system and allows the builder to select the desired coolant-flow direction and control coolant speed.

Designed for Mitsubishi Evo 8 and Evo 9

The STM EVO89-WPB is specifically designed for 2003–2006 Mitsubishi Lancer Evolution VIII and Evolution IX applications. It is intended for the 4G63-powered Evo 8/9 platform and should not be confused with STM’s separate Evo 4-7 water-pump block-off plate.

Vehicle application:

• Mitsubishi Lancer Evolution VIII
• Mitsubishi Lancer Evolution IX
• 2003–2006 model years
• 4G63 turbocharged engine
• Custom electric water-pump cooling systems
• Motorsport and performance applications

Always verify your vehicle generation before ordering, particularly with JDM and modified vehicles.

Integrated -16AN ORB Outlet

One of the main features of the EVO89-WPB is its integrated -16AN ORB port. This provides a large coolant outlet for building a custom electric water-pump system and gives the installer flexibility when selecting the appropriate hose and AN fittings.

STM recommends several Vibrant ORB-to-AN fittings for the -16ORB outlet:

• -16ORB to -10AN – Vibrant 16838
• -16ORB to -12AN – Vibrant 16842
• -16ORB to -16AN – Vibrant 16845
• -16ORB to -20AN – Vibrant 16847

These fitting options make it possible to adapt the bypass outlet to different coolant-line sizes depending on the electric water pump and overall cooling-system configuration.

6061 Billet Aluminum Construction

The STM water pump bypass is manufactured from 6061 billet aluminum. This provides a strong, lightweight component suitable for demanding motorsport and performance applications.

STM redesigned the EVO89-WPB in November 2024 and now manufactures the component in-house from billet aluminum. The current design incorporates the -16ORB outlet directly into the bypass plate for a clean and compact installation.

The billet construction also gives the component a clean appearance that works well with custom engine bays and professionally fabricated cooling systems.

Designed for Electric Water Pump Conversion

The STM EVO89-WPB is not a conventional replacement mechanical water pump. Instead, it is a water pump bypass plate intended for use with an electric water pump.

This distinction is important when ordering.

The bypass plate is designed to work as part of a complete electric water-pump conversion. The electric pump becomes responsible for circulating coolant through the engine and cooling system, while the STM plate provides the necessary bypass connection at the original water-pump location.

This allows the builder to design the cooling system around the electric pump, coolant-line size, desired flow direction, and overall vehicle requirements.

Potential Benefits of an Electric Water Pump Setup

An electric water pump can offer greater flexibility for custom cooling-system designs. Because the pump is electrically driven rather than mechanically driven by the engine, the cooling system can be configured independently of engine speed.

For a competition Evo, this can allow the builder to control coolant circulation according to the requirements of the application. It can also eliminate the mechanical water pump as another rotating component in the engine’s accessory system.

The actual cooling performance of an electric water-pump system depends on the pump selected, plumbing design, radiator capacity, electrical system, coolant flow, and overall engine setup. Proper system design is therefore important.

Stainless Mounting Hardware Included

The STM EVO89-WPB includes the mounting hardware required for installation of the bypass plate.

Package contents include:

• 1 × STM Water Pump Bypass – EVO89-WPB
• 5 × M8x1.25×12 stainless bolts
• 5mm-head mounting hardware

STM specifies that the included bolts are stainless steel and designed for the bypass installation.

The required AN fitting and electric water pump are separate components and are not included with the bypass plate unless specifically stated in the product package.

STM Water Pump Bypass Features

The STM Water Pump Bypass with -16ORB for Evo 8/9 offers several features for performance-oriented cooling-system builds:

• Designed specifically for Evo 8/9
• 2003–2006 Mitsubishi Lancer Evolution VIII/IX fitment
• 6061 billet aluminum construction
• Integrated -16AN ORB coolant outlet
• Designed for electric water-pump conversions
• Stainless mounting bolts included
• Manufactured in-house by STM
• Made in the USA
• Compatible with multiple ORB-to-AN fitting sizes
• Compact and clean installation

These features make the EVO89-WPB suitable for custom 4G63 cooling-system configurations where the factory mechanical water pump is being eliminated.

Evo 8/9 Cooling System Applications

The STM bypass plate can be used as part of a larger cooling-system build on an Evo 8 or Evo 9. It is particularly suited to vehicles that have already moved away from a factory-style cooling system and are using custom radiator plumbing, AN coolant lines, and an electric water pump.

Typical applications can include:

• Drag racing Evo 8/9 builds
• Track and race cars
• High-RPM 4G63 engines
• Custom electric water-pump conversions
• Motorsport cooling systems
• Engine swaps and custom builds
• Competition-focused cooling-system setups

For a street-driven Evo retaining the factory mechanical water pump, this product is generally not a simple replacement part. It is intended for a properly planned electric water-pump configuration.

Previous STM Part Numbers

STM notes that the current EVO89-WPB design replaced several earlier water-pump bypass configurations. Previous part numbers included STM-EVO89-WPBO-10AN, STM-EVO89-WPBO-12AN, and STM-EVO89-WPBO-16AN. The current design uses the integrated -16ORB outlet.

This makes EVO89-WPB the current reference to use when looking for STM’s Evo 8/9 water pump bypass with the -16ORB connection.

Water Pump Bypass vs. Block-Off Plate

STM also offers a separate Evo 8/9 water pump block-off plate. The EVO89-WPB is different because it includes a -16ORB coolant outlet for an electric water-pump system.

The bypass version is therefore the appropriate choice when the cooling-system design requires a coolant connection at the original water-pump location.

Buy STM Water Pump Bypass for Evo 8/9 (EVO89-WPB) with -16ORB outlet, 6061 billet aluminum bypass for electric water-pump conversions.

Before ordering, determine whether your build requires an outlet for an electric water pump or simply a block-off plate.

Product Specifications

• Brand: STM
• Product: Water Pump Bypass
• Part Number: EVO89-WPB
• Application: Mitsubishi Evo 8/9
• Vehicle Years: 2003–2006
• Engine: 4G63
• Material: 6061 billet aluminum
• Outlet: -16AN ORB
• Hardware: Stainless steel bolts
• Manufacturing: Made in-house by STM
• Country of Manufacture: USA
• Use: Electric water-pump conversion / custom cooling system
• Previous Part Numbers: STM-EVO89-WPBO-10AN, STM-EVO89-WPBO-12AN, STM-EVO89-WPBO-16AN

Frequently Asked Questions

What is the STM EVO89-WPB?

The STM EVO89-WPB is a billet aluminum water pump bypass plate for Mitsubishi Evo 8 and Evo 9. It features an integrated -16AN ORB outlet and is designed for use with an electric water pump.

What Evo models does EVO89-WPB fit?

It is designed for 2003–2006 Mitsubishi Lancer Evolution VIII and Evolution IX applications.

Does the STM bypass plate include an electric water pump?

No. The EVO89-WPB is the bypass plate only. The electric water pump, coolant lines, and ORB-to-AN fitting are separate components.

What size outlet does the STM EVO89-WPB use?

The bypass plate features an integrated -16AN ORB outlet. STM lists compatible -16ORB-to-AN fittings for -10AN, -12AN, -16AN, and -20AN coolant-line configurations.

What is the bypass plate made from?

The current EVO89-WPB is manufactured from 6061 billet aluminum and includes stainless mounting bolts. STM states that the current design was redesigned in November 2024 and is made in-house.

Is the EVO89-WPB suitable for a stock Evo 8/9 cooling system?

The EVO89-WPB is designed specifically for an electric water-pump conversion, rather than as a standard replacement for the factory mechanical water pump. A complete custom cooling-system setup is required.

Does STM make a version without the -16ORB outlet?

Yes. STM also offers a separate water pump block-off plate without the ORB outlet for applications that do not require the coolant outlet.

Conclusion

The STM Water Pump Bypass with -16ORB for Evo 8/9 (EVO89-WPB) is a purpose-built cooling-system component for Mitsubishi Evolution VIII and IX performance applications. Made from 6061 billet aluminum and featuring an integrated -16AN ORB outlet, it provides a clean connection point for an electric water-pump conversion while eliminating the need to retain the factory mechanical water pump. With stainless mounting hardware included and compatibility with several ORB-to-AN fitting sizes, the EVO89-WPB is well suited for custom 4G63 cooling systems, high-RPM builds, drag cars, track cars, and other performance-focused Evo 8/9 applications.

Buy STM Water Pump Bypass for Evo 8/9 (EVO89-WPB) with -16ORB outlet. 6061 billet aluminum bypass for electric water-pump conversions.