The Toyota GR Corolla, with its potent G16E-GTS three-cylinder turbocharged engine, has quickly become a modern icon in the hot hatch world. Enthusiasts have embraced its all-wheel-drive grip, rally-bred DNA, and surprising power output from a 1.6-liter engine. Yet, like any performance car, there is always room for improvement. One of the most impactful and rewarding modifications is an aftermarket exhaust system. Among the top choices for discerning owners is the HKS Super Turbo Back Exhaust. This guide provides a comprehensive look at the installation costs, the engineering behind the system, and the real-world performance gains you can expect after fitting this exhaust to your GR Corolla.

Understanding the HKS Super Turbo Back Exhaust

HKS has been a dominant force in Japanese performance tuning since the 1970s. Their Super Turbo Back exhaust for the GR Corolla is a full replacement system, meaning it replaces every factory exhaust component from the turbocharger outlet to the tailpipe. This contrasts with a cat-back or axle-back system, which only replaces sections after the catalytic converter. By replacing the restrictive factory downpipe, front pipe, and mid-pipe along with the rear muffler section, the HKS system dramatically reduces back pressure and improves exhaust gas flow. The result is a significant power increase and a more aggressive exhaust note.

Key Components and Design Features

  • Downpipe (Turbo Back Section): The system begins with a high-flow downpipe that replaces the restrictive factory unit. It is designed to reduce spool time and improve turbocharger efficiency. The downpipe includes a bung for the factory oxygen sensor, and it retains the catalytic converter in some configurations (required for street legality in many regions), though a decatted version is available for off-road use only.
  • Front and Mid-Pipes: These sections are crafted from high-quality stainless steel (T304) with smooth mandrel bends to maximize flow. The front pipe connects the downpipe to the mid-pipe, and the mid-pipe leads to the rear section. HKS uses precision welding and robust flanges to ensure a leak-free seal.
  • Muffler and Tailpipe: The rear muffler uses HKS’s unique perforated core design to dampen excessive noise while still producing a deep, authoritative tone. Available with a choice of polished stainless steel or carbon fiber heat-shielded tips, the tailpipe provides a clean, OEM-plus aesthetic.

The exhaust is engineered to be a direct bolt-on replacement. All mounting points and hanger positions match the factory locations, making installation straightforward for a competent DIY mechanic or professional shop. The system is also lighter than the stock exhaust, contributing to a modest weight reduction—typically 10–15 pounds (4.5–6.8 kg).

Cost Breakdown

Budgeting for an HKS Super Turbo Back Exhaust involves more than just the price of the exhaust itself. Below is a detailed cost analysis based on current market prices and typical installation fees. Note that prices can vary based on supplier, location, and any ongoing sales or promotions.

Exhaust System Cost

The HKS Super Turbo Back Exhaust for the GR Corolla G16E-GTS typically retails between $1,400 and $1,800. This price includes the downpipe, front pipe, mid-pipe, and rear muffler section with a tip. The exact price depends on whether you choose the street-legal version (with a high-flow catalytic converter) or the competition version (without a cat). The street-legal variant is more expensive due to the catalyst, but it is required for road use in many states and countries.

Installation Labor

Professional installation can cost between $350 and $600 depending on the shop’s hourly rate (typically $100–$150 per hour) and the time required (around 3–4 hours). DIY installation is possible with basic tools and a lift or jack stands, but if you lack experience, professional installation ensures a perfect fit and avoids potential issues like exhaust leaks or stripped bolts.

Additional Parts and Consumables

  • Gaskets and Hardware: While HKS includes new gaskets and bolts, some installers prefer to use high-temperature copper gaskets for extra sealing. Expect to spend $20–$40 on additional gaskets if you choose aftermarket upgrades.
  • Exhaust Hangers: Factory hangers can be reused, but if they are worn, new polyurethane hangers cost about $20–$30 per set.
  • O2 Sensor Spacer or Extension: If you install a decatted downpipe, you may need an oxygen sensor spacer to prevent a check engine light. This can cost $15–$30.
  • Engine Oil (optional): Sometimes it's convenient to change oil while you have access underneath. Add $40–$60.

Total Estimated Cost Range

  • DIY Route: $1,400 (exhaust) + $50 (additional gaskets) + $30 (spacer/hangers) = approximately $1,480–$1,550.
  • Professional Installation: $1,600 (exhaust average) + $500 (labor) + $80 (misc) = approximately $2,180–$2,250.

Compare these figures against other premium exhaust systems from brands like GReddy, Tomei, or AWE Tuning. The HKS typically sits in the mid-to-upper price tier, justified by its brand heritage, quality of materials, and R&D backing.

Installation Process (Step-by-Step)

Installing the HKS Super Turbo Back Exhaust requires mechanical aptitude and the right tools. The process is considered moderate difficulty. Here is a detailed guide to help you through it.

Required Tools and Safety Equipment

  • Socket set (metric: 10mm, 12mm, 14mm, 17mm, 19mm)
  • Wrenches and ratchets with extensions
  • Breaker bar or impact wrench for stubborn bolts
  • Jack and jack stands (or vehicle lift)
  • Penetrating oil (e.g., WD-40 or PB Blaster)
  • Safety glasses and gloves
  • Exhaust pipe spreader or pry bar (for separating stuck joints)
  • Torque wrench (for final tightening)

Procedure

  1. Prepare the vehicle: Park on a level surface, allow the engine to cool completely, and disconnect the negative battery terminal (to prevent electrical issues when removing sensors).
  2. Raise the vehicle: Use a jack to lift the car and secure it on jack stands placed at the factory lift points. Ensure the car is stable before working underneath.
  3. Remove the factory exhaust: Start at the rear. Unbolt the rear muffler hangers (2–3 rubber hangers) and the bolts connecting the mid-pipe to the rear section. Lower the rear muffler. Then remove the mid-pipe, front pipe, and downpipe. Note that the downpipe bolts to the turbocharger housing—these are high-temperature bolts and may require penetrating oil and a careful hand to avoid shearing. Also, unplug the O2 sensor from the downpipe before removing it.
  4. Transfer the O2 sensor: Carefully unscrew the oxygen sensor from the factory downpipe and install it into the provided bung on the HKS downpipe. Use anti-seize compound on the threads to ease future removal.
  5. Install the HKS system: Begin with the downpipe, loosely bolting it to the turbo. Use the supplied gasket. Hand-tighten the bolts initially. Then install the front pipe, mid-pipe, and finally the rear muffler section. Only tighten the clamps and bolts once all sections are aligned. Pay attention to clearances: ensure the exhaust does not contact the underbody, heat shields, or sway bars.
  6. Tighten everything: Using a torque wrench, tighten all bolts to the manufacturer’s specifications. For M8 bolts, typically 15–20 ft-lbs; for M10 bolts, 30–35 ft-lbs. Snug downpipe bolts to 25–30 ft-lbs to avoid leaks.
  7. Check alignment and leaks: Visually inspect the entire system. Start the engine and listen for any exhaust hissing or ticking. If detected, tighten connections or apply exhaust sealant to flanges.
  8. Lower the vehicle and test drive: Reconnect the battery, lower the car, and take a short test drive. Rev to 3,000–4,000 RPM and listen for drone between 2,000–3,500 RPM (most common range). The HKS system is designed to minimize drone, but some highway resonance is expected.

If you encounter rusted bolts, consider using a torch to heat them or cutting them off—a professional shop may be safer. The entire process typically takes 2.5–4 hours for an experienced mechanic.

Real-World Gains: Horses, Torque, and Experience

Enthusiasts who have installed the HKS Super Turbo Back Exhaust report notable improvements across the rev range. Below is a data-driven summary based on dyno charts and owner testimonials.

Dyno-Proven Power Increases

Independent dyno testing on a stock-tuned GR Corolla with the HKS system (with high-flow cat) shows gains of 15–20 horsepower at the wheels and 15–18 lb-ft of torque at the peak. The mid-range gains are particularly impressive: an extra 20–25 lb-ft around 3,500–4,500 RPM, improving throttle response and real-world drivability. When combined with an ECU tune (e.g., from Cobb or ECUtek), those numbers can climb to 35–45 whp, but that adds cost and warranty risk.

Here is a representative dyno pull description:

Before installation: 240 whp / 265 lb-ft (stock). After HKS turbo-back: 258 whp / 280 lb-ft. The power curve is noticeably flatter, with the torque peak arriving about 300 RPM sooner, enhancing responsiveness out of corners.

Sound and Driving Experience

The factory exhaust is subdued for daily driving. The HKS system adds a deep, aggressive note without being obtrusive at idle. Upon full throttle, the G16E-GTS emits a crisp, metallic roar reminiscent of a rally car. At highway speeds, cruising is relatively quiet with minimal drone (slightly more than stock but tolerable for most owners). Many users note that the exhaust “wakes up” the character of the car, making every acceleration event more satisfying.

Weight Reduction

The factory exhaust weighs approximately 38–40 pounds (17–18 kg). The HKS unit weighs about 28 pounds (12.7 kg), saving roughly 10–12 pounds. While not transformative, every pound of rotating and unsprung mass reduction helps handling and acceleration.

Spool and Response

Lower back pressure allows the turbocharger to spin up faster. Owners report improved pedal response and earlier boost onset. The small G16E-GTS turbo feels more alert, reducing lag when exiting corners or merging onto highways.

Considerations Before Installation

Before purchasing and installing the HKS Super Turbo Back Exhaust, carefully evaluate the following factors to avoid unintended consequences.

Warranty Voidance

Replacing the downpipe (which houses the first catalyst) can be viewed by Toyota as a powertrain modification. If a related failure (e.g., turbo failure, O2 sensor code) occurs, the dealer may deny warranty coverage. The Magnuson-Moss Warranty Act in the U.S. protects consumers to some extent, but you should document the installation and keep your original parts. Consider using a tuner that offers a flashback feature to revert to stock software.

The HKS exhaust is available in EPA-compliant (with high-flow cat) and off-road only (no cat) versions. If you live in California or other states with strict emissions testing, ensure you purchase the catted version. Even then, visual inspection stations may reject the aftermarket downpipe if it lacks an EO (Executive Order) number. HKS does have some CARB-approved parts for other vehicles, but as of this writing, the GR Corolla system is not CARB-certified. Check local laws carefully. The U.S. EPA website offers guidance on aftermarket parts legality (EPA Aftermarket Exhaust Parts).

Noise Concerns

The HKS system is loud under load. At full throttle, noise levels can reach 92–95 dB at close range. If you live in a noise-restricted area or track day venues have sound limits (often 90 dB drive-by), you may need to add a resonator or use the factory exhaust for events. Many owners who daily drive the car find the noise acceptable, but those sensitive to drone may prefer the quieter “Legamax” cat-back from HKS instead.

Insurance Implications

Modifications can affect your insurance premium. Some insurers require disclosure of performance modifications, and failure to do so could invalidate claims. Contact your provider and ask about adding the exhaust to your policy. Some specialty insurers (e.g., Hagerty for classic cars) have tailored policies for modified vehicles, but for a daily driver, expect a slight increase in premium.

Future Performance Upgrades

Consider whether you plan to add a larger intercooler, cold air intake, or ECU tune. If so, the HKS Super Turbo Back Exhaust will be a foundational upgrade that pairs well with these mods. A tune will extract the most power from the exhaust, but also increase the likelihood of requiring a new clutch or fuel system components. Plan your build roadmap in advance.

Conclusion

Fitting the HKS Super Turbo Back Exhaust to the GR Corolla G16E-GTS is a rewarding modification that delivers tangible performance gains, enhanced sound, and improved throttle response. With a total investment ranging from roughly $1,500–$2,250 depending on installation choice, the cost-per-horsepower is competitive among bolt-on upgrades. The quality construction and engineering from HKS ensure a durable product that will last the life of the car. However, careful consideration of warranty, emissions laws, and noise tolerance is essential before committing. For the enthusiast seeking to unlock more of the G16E-GTS’s potential while enjoying a more engaging driving experience, the HKS Super Turbo Back Exhaust stands out as a top-tier choice. For further reading, visit the official HKS product page (HKS GR Corolla Exhaust Systems) or consult the GR Corolla Forum (GR Corolla Forum) for owner experiences and dyno results.