Unlock 20 HP: Installing a Greddy Exhaust on Your Hyundai Genesis Coupe

If you own a Hyundai Genesis Coupe and crave more power and a more aggressive exhaust note, upgrading to a Greddy exhaust system is one of the most effective and rewarding modifications you can make. Greddy has long been a respected name in performance exhaust engineering, offering systems specifically designed to reduce backpressure while improving exhaust flow. For the Genesis Coupe, a properly installed Greddy exhaust can deliver a genuine increase of up to 20 horsepower at the wheels, along with a weight reduction and a deeper, more refined sound.

This guide provides a comprehensive, step-by-step walkthrough for installing a Greddy exhaust system on your Genesis Coupe. Whether you’re a seasoned DIY enthusiast or a first-time installer, following these detailed instructions will help you achieve a professional-quality installation. We’ll cover everything from the necessary tools and safety precautions to post-installation checks and expected performance gains. Let’s get started.

What Makes the Greddy Exhaust Special?

Greddy offers several exhaust variants for the Genesis Coupe, including the popular Greddy RS Race and Greddy SP Supreme cat-back systems. These systems are constructed from mandrel-bent stainless steel or titanium, depending on the model, and feature smooth transitions that minimize turbulence. The result is a measurable drop in exhaust restriction, which allows the engine to breathe more freely. Combined with a tune or other bolt-on modifications, the horsepower gains become even more pronounced.

Key design elements include:

  • Mandrel-bent piping — maintains consistent diameter through bends, preventing flow restrictions that crush-bent pipes create.
  • Large-diameter tubing — typically 2.75 to 3 inches, matching or exceeding the flow capacity of the stock exhaust.
  • High-flow mufflers and resonators — tuned to reduce drone while still producing an aggressive tone.
  • Lightweight construction — saves up to 15–20 pounds compared to the factory exhaust.

These features combine to produce not just extra horsepower but also improved throttle response and a more engaging driving experience. For those considering a full exhaust upgrade, start with a Greddy cat-back and later add a downpipe or test pipe for even larger gains.

Tools and Materials You’ll Need

Before heading under the car, gather all the required tools and supplies. Having everything ready ensures a smooth, uninterrupted installation.

  • Greddy exhaust system (cat-back or turbo-back, depending on your model year)
  • Socket set with extensions (metric sizes: 10mm, 12mm, 14mm, 17mm)
  • Combination wrenches (10mm, 12mm, 14mm)
  • Torque wrench (capable of 30–50 ft-lb)
  • Floor jack and two jack stands (minimum 2-ton capacity)
  • Penetrating oil (e.g., WD-40 or PB Blaster)
  • Anti-seize compound for exhaust bolts
  • Safety glasses and mechanic’s gloves
  • Rubber mallet (for stubborn hangers)
  • Flathead screwdriver or trim tool (to release exhaust hangers)
  • Rags and a catch pan for any drips

Optional but helpful: an exhaust gasket set (if reusing OEM gaskets), a breaker bar for rusted bolts, and a reciprocating saw if you plan to cut the stock exhaust.

Safety and Preparation

Working under a vehicle carries inherent risks. Park the Genesis Coupe on a level, solid surface. Engage the parking brake and chock the rear wheels. Lift the car using the factory jack points, then place jack stands securely under the pinch welds or subframe. Never work under a car supported only by a jack.

Allow the exhaust system to cool completely — the pipes, catalytic converter, and mufflers can remain hot for hours after driving. Wear safety glasses to protect your eyes from falling debris and gloves to prevent cuts from sharp edges or rust.

If your car has been driven in winter conditions or has significant mileage, the exhaust bolts and hangers may be corroded. Apply penetrating oil to all nuts and bolts 15–20 minutes before you begin to ease removal.

Step-by-Step Installation Guide

1. Remove the Stock Exhaust System

Start by locating the flange bolts connecting the exhaust to the downpipe or catalytic converter. On the 2.0T and 3.8L Genesis Coupe, there are typically four bolts (12mm or 14mm) at this junction. Spray them with penetrating oil, then carefully loosen and remove them with a socket and ratchet. If bolts are seized, use a breaker bar or impact wrench — but be cautious not to snap them.

Next, disconnect the rubber hangers that support the exhaust. The best technique is to spray the hanger holes with lubricant, then use a flathead screwdriver or a hanger removal tool to pry the metal rods out of the rubber mounts. A rubber mallet can help free stuck hangers. You may need to remove the hangers from the body brackets or slide the rubber isolators off the exhaust hooks. Work from the rear of the car forward.

Once all hangers are free, slide the stock exhaust out from under the car. If the system is long, you may need to maneuver it out from the rear axle. On some models, the factory exhaust is one piece; in that case, lowering the rear axle slightly (by unbolting the lower shock bolts) can provide clearance. If you prefer, you can cut the stock exhaust with a sawzall for easier removal — but be careful not to damage any nearby lines or sensors.

2. Prepare the Greddy Exhaust

Unpack the Greddy system and verify all components are present: main piping sections, muffler assembly, hangers, bolts, gaskets, and instructions. Look for any damage from shipping. Dry-fit the exhaust components together loosely before installing them under the car. This helps you identify the correct sequence and orientation.

Apply a thin layer of anti-seize compound to all bolt threads and to the inside of the rubber hangers where the metal hooks will slide in. This will make future removal much easier.

3. Install the Greddy Exhaust System

Start by installing the section that connects to the downpipe or catalytic converter. Slide a new gasket (or reuse the OEM one if it’s in good condition) onto the studs or bolts, then align the Greddy front pipe with the flange. Tighten the nuts or bolts hand-tight, but do not fully torque until all sections are aligned.

Work your way toward the rear of the car, connecting each section using the supplied clamps or flanges. For clamps, leave them loose enough to allow rotation and adjustment. Insert the exhaust hangers into the factory rubber isolators. You may need to use a little soapy water or lubricant to make the hooks slide in. Ensure the hangers are fully seated so the exhaust doesn’t sag.

Once all sections are connected and hangers are in place, align the exhaust tips so they sit centered in the bumper cutouts and are at the same height. Adjust the angle and position of the muffler and tips by sliding the sections in the hangers or by tweaking the hanger hooks. Tighten all bolts, nuts, and clamps to the manufacturer’s torque specifications (usually around 30–40 ft-lb for flange bolts and 40–50 ft-lb for band clamps).

Double-check that the exhaust does not contact any frame, suspension, or drivetrain components. If it does, reposition the system or add a slight bend to the hangers for clearance. Start the engine and listen for rattles or leaks. With the engine idling, feel around all joints for any escaping exhaust gas. If you detect a leak, tighten the affected connection further or replace the gasket.

Post-Installation Checks and Break-In

After the initial startup, let the engine run for a few minutes and check the exhaust for unusual noises. A slight ticking as metal expands is normal, but persistent hissing indicates a leak. Tighten all connections again once the system has cooled.

Take the car for a short test drive. Listen for interior drone, particularly at highway cruising speeds. Greddy exhausts are known for being relatively drone-free, but if you notice excessive resonance, check that the exhaust is not touching the chassis or that the hangers are properly isolated. Drive at varying RPM ranges to ensure the system performs well under load.

After the first 100 miles, re-check and re-torque all bolts and clamps. The thermal cycling can slightly loosen connections. At this point, the system is fully broken in, and you will begin to notice the full power and sound benefits.

Expected Performance Gains and Dyno Results

On a bone-stock Genesis Coupe (both 2.0T and 3.8L), a cat-back exhaust like the Greddy RS Race typically produces 10–15 wheel horsepower gains. When paired with a cold air intake and a custom ECU tune, total gains often reach the 20–25 wheel horsepower mark. The 3.8L V6, in particular, responds well to exhaust upgrades because its stock exhaust is notably restrictive past 5,500 RPM.

Independent dyno testing from forums such as GenCoupe.com and Reddit r/genesiscoupe shows that the Greddy RS Race adds roughly 12–15 hp and 12–15 lb-ft of torque at the wheels without a tune. With a flash tune, those numbers can climb to 20 hp. The torque curve also becomes fatter in the mid-range, improving daily drivability.

For the 2.0T, spool time often improves slightly due to reduced backpressure, though too large an exhaust can cause lag on a stock turbo. Greddy’s 2.75-inch piping is well matched for the 2.0T’s factory turbo, providing gains without sacrificing low-end response. For both engines, the weight savings further enhance the power-to-weight ratio, making the car feel noticeably quicker.

For detailed dyno charts and owner reviews, check resources like Greddy’s official website or the GenRacer community.

Sound and Driving Experience

The Greddy exhaust transforms the Genesis Coupe’s character. The stock system is quiet and muted; the Greddy adds a deep, refined growl at idle that builds into a purposeful roar under full throttle. The SP Supreme is more civil, with less drone and a tone that remains composed during highway cruising, while the RS Race is louder and more track-oriented. Both options eliminate the “fart can” stereotype and deliver a European-style note.

Drivetrain feel improves significantly. Throttle response sharpens, and the engine revs more freely toward redline. Many owners report that the car feels “unlocked” above 4,000 RPM, where the stock exhaust previously choked power. Combined with a short shifter or a tune, the Greddy exhaust makes the Genesis Coupe a genuinely engaging sports coupe.

Maintenance Tips for Longevity

To keep your Greddy exhaust performing and sounding great for years:

  • Periodically inspect all clamps and bolts for tightness, especially after the first month.
  • Clean the exhaust tips with a non-abrasive metal polish to prevent corrosion.
  • If you drive in winter climates, spray the exhaust with a corrosion inhibitor or apply a light coating of oil to the visible hardware.
  • Check the rubber hangers for cracks and replace them if they become brittle. Stiff or broken hangers can cause rattling and misalignment.
  • After any track day or hard driving, let the exhaust cool before parking. Quick temperature shock (like driving through deep water) can warp thin-walled piping.

With minimal care, a Greddy exhaust will outlast many other bolt-on modifications and continue to deliver its advertised horsepower gains.

Conclusion

Installing a Greddy exhaust system on your Hyundai Genesis Coupe is a rewarding project that yields real, measurable performance improvements. By following the steps outlined in this guide, you can achieve the full 20 HP boost while ensuring the system is installed safely and correctly. The combination of added power, weight savings, and an exhilarating exhaust note makes this one of the best modifications for the platform. Whether you’re building a street car, a weekend track toy, or just want more excitement from your daily driver, a Greddy exhaust is a smart upgrade. Get your tools ready, take your time, and enjoy the transformation.