Toyota Supra MK4 2jz-gte JZA80 HKS Silent Hipower exhaust system

HKS Silent Hi-Power exhaust (Part No. 31019-AT005) is widely considered the premier “mature” choice for the Toyota Supra MK4 (JZA80). It is specifically designed to provide the high-flow benefits of a straight-through racing exhaust while using HKS’s patented “Silent Chamber” technology to eliminate the intrusive low-frequency drone common in the 2JZ-GTE.

Technical Specifications

• Main Material: High-grade SUS304 Stainless Steel for the entire construction (piping, muffler, and tip).

   

• Center Pipe Diameter: 95 mm (approx. 3.74 inches) at its largest point. This is significantly larger than the standard 3-inch (76 mm) aftermarket average, making it suitable for high-horsepower builds.

• Tip Diameter: 120 mm (approx. 4.7 inches) with a polished finish and an engraved HKS logo.

• Sound Levels: * Idle: ~73 dB

   

  • Close Noise (under load): ~98 dB (vs. 87 dB OEM)

     

• JASMA Approved: It meets strict Japanese noise regulations, ensuring it remains civil during highway cruising.

   

The “Silent Chamber” Technology

The defining feature of this system is the external Silent Chamber—a closed-end resonator welded to the main pipe.

• Function: It acts as a frequency trap. Exhaust pulses enter the chamber, bounce back, and cancel out specific low-frequency sound waves (drone) without creating a physical restriction in the main exhaust path.

• Performance Benefit: Because it uses a straight-through muffler design rather than internal baffles, it maintains a very low backpressure profile, supporting significant power gains on both twin-turbo and single-turbo setups.

Fitment and Compatibility Notes

1. VVTi vs. Non-VVTi: Official HKS documentation states this part number is for Non-VVTi (1993–1997) models. While it physically fits the JZA80 chassis, minor adjustments to the hanger positions or the mid-pipe connection may be required for 1998+ VVTi models to meet perfect OEM-standard alignment.

    

2. Road Clearance: The system is designed with a minimum road clearance of approximately 130 mm (at stock height). If your Supra is heavily lowered on coilovers, the 95 mm center pipe is the lowest point and should be monitored when crossing speed bumps.

    

3. Hanger Orientation: It uses the factory mounting points but includes heavy-duty reinforced hangers to account for the larger 95 mm piping and the weight of the SUS304 steel.

Maintenance Tip

Since you deal with “like new” luxury parts, note that while SUS304 is highly rust-resistant, the heat-affected zones (welds) can develop a golden/straw-colored patina over time. Using a high-quality stainless steel polish can maintain the “mirror finish” of the 120 mm tip indefinitely.