Code No. 33005-AT012
Achieves both purification performance that meets emission standards and improved exhaust efficiency
■Features
- Compared to the genuine fine-cell ceramic catalyzer, this product utilizes a low-density metal catalyst. Both the primary and secondary catalyzer adopt a 150-cell design, significantly reducing exhaust resistance.
- The primary catalyzer features a compact cell structure with an optimized ratio of precious metals, achieving both effective emission purification and reduced exhaust back pressure. This design meets regulatory standards and has obtained an official emissions certification.
- To protect against heat damage, the primary catalyzer is designed to allow installation of the genuine heat shield. ※
- While the stock pipe diameter is 70mm, this product increases it to 75mm to further enhance exhaust flow.
- The surface is buff-polished, and all welds are TIG-welded for a premium finish.
- Includes dedicated brackets for both MT and AT models.
Catalyzer Cell Comparison
■Structure
| Main Materials | SUS304 |
| Catalyst Specifications | 150 Cells |
| Main Pipe Diameter | 74.7mm |
| Exhaust noise (stock) | When equipped with stock muffler: 81dB (At idle:63dB) When equipped with STM:91dB (Idle: 70dB) |
| Exhaust noise (HKS) | When equipped with stock muffler:81dB (Idle:63dB) When equipped with STM:93dB（Idle：70dB) |
| Minimum Ground Clearance | 120mm (Front frame member) |
| Catalyzer Weight | 9.2kg (Stock 7.4kg) |
■Performance Comparison
| Max Power (kW/(PS)rpm) | Max Torque (Nm(kgf・ｍ)/rpm) | |
| HKS Cat + STM | 214.9(292.2)/6380 | 437.8(44.6)/3500 |
| HKS Cat + Stock Muffler | 209.5(284.8)/6620 | 427.7(43.6)/3720 |
| Stock Cat + Stock Muffler | 204.1(277.5)/6600 | 422.9(43.1)/3940 |
By replacing only the catalyzer,
A power increase of 5.4[kW](7.3[PS]) and a torque increase of 4.8[Nm](0.5[kgf・m]) is achieved
When combined with the Super Turbo Muffler (31029-AT017), the power increase reaches
10.8[kW](14.7[PS]), and torque increases 14.9[Nm](1.5[kgf・m])
Test Vehicle: GR Yaris Gen2 (4BA-GXPA16)
Vehicle Specs:
STM：31029-AT017 Super Turbo Muffler
HKS Catalyzer：Indicates this product
※ Graphs and figures are based on in-house measurements. Results may vary depending on the vehicle and measurement equipment.
■Layout Comparison
Compared to the genuine catalyzer, the number of catalyst cells has been reduced, and the pipe diameter and layout is optimized to achieve maximum reduction in exhaust back pressure
HKS Metal Catalyzer
Stock Catalyzer
| Proximity Exhaust Noise[dB] | At idling[dB] | |
| HKS Cat + STM | 93 | 69 |
| HKS Cat + Stock Muffler | 81 | 63 |
| Stock Cat + Stock Muffler | 81 | 63 |
Notes on the graph and table notations:
STM: 31029-AT017 Super Turbo Muffler
HKS Catalyzer: Indicates this product.
Graphs and figures are based on in-house measurements.
Results may vary depending on the vehicle and measurement equipment.
- Regarding changes in volume, replacing only the catalyst does not result in a numerical difference compared to the genuine part, but the sound quality shifts toward a higher tone. Frequency comparison during near-field exhaust noise measurement shows an increase around 300Hz and also between 500–700Hz compared to the genuine catalyst, resulting in a slightly higher-pitched exhaust sound.
- When combined with the Super Turbo Muffler (31029-AT017), the near-field exhaust noise level is 93dB, which is below the safety regulation limit of 96dB, so you can use it with confidence. The sound quality emphasizes the 500Hz range more strongly, and the low-frequency range below 200Hz is also enhanced, allowing you to enjoy a more powerful
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