Why Upgrade Your Exhaust System?

Upgrading the exhaust system on your Honda Prelude H22 is one of the most effective modifications you can make. The factory exhaust is designed to meet noise and emissions regulations while keeping costs low, which often means restrictive bends, small-diameter piping, and heavy mufflers. By replacing it with a performance system like HKS or Greddy, you free up the engine’s ability to breathe, leading to measurable gains in horsepower and torque, particularly in the mid-to-high RPM range where the H22 naturally shines.

Beyond raw performance, an upgraded exhaust can improve throttle response, reduce overall vehicle weight (especially when switching from a heavy stock cast-iron manifold to a lightweight stainless steel header-back system), and deliver a more satisfying exhaust note. Many owners also report slight fuel economy improvements when driving conservatively, thanks to reduced backpressure. Each of these benefits contributes to a more engaging driving experience.

For a deeper dive into the theory behind exhaust tuning, check out Engine Basics’ exhaust system guide.

HKS Exhaust Systems: Engineering and Owner Feedback

HKS has been a pillar in the Japanese performance aftermarket for decades. Their exhaust systems for the H22 Prelude are typically cat-back or turbo-back designs, using mandrel-bent 304 stainless steel tubing and high-flow mufflers with straight-through internals. Models like the HKS Hi-Power and the HKS Silent Hi-Power have different sound and flow characteristics, but both share a reputation for consistent quality and power gains.

What Owners Say About HKS

Online communities such as PreludeOnline and Honda-Tech are filled with firsthand accounts from H22 owners who have installed HKS exhausts. Here are the most commonly cited experiences:

  • Mid-Range Torque Gains: Several users report a noticeable “pull” from 3,500 to 5,500 RPM after swapping to an HKS system. Dyno sheets from owners show gains of 8–12 whp when paired with a cold-air intake and a tune. The stock exhaust tends to choke the H22’s VTEC crossover, but the HKS smooths that transition.
  • Aggressive, Deep Tone: The Hi-Power muffler is known for its low, bassy rumble at idle that opens into a controlled roar under WOT. Some owners note that it can be loud inside the cabin during highway cruising, so those prioritizing daily comfort may prefer the Silent Hi-Power variant, which uses an additional resonator to tame volume without sacrificing flow.
  • Build Quality and Fitment: HKS systems are precision-welded and include all necessary hardware. Most owners report a direct bolt-on experience, though a few with older chassis (pre-1997) noted needing to slightly adjust hanger positions. The stainless steel finish resists corrosion well, even in rust-prone areas.

A detailed owner review on CivicX forums sums up the sentiment: “The HKS Hi-Power woke my H22 up. It sounds like it should have from the factory – purposeful, not obnoxious. Paired with a P28 ECU tune, I saw 10 whp and the car revs more freely to 7,500.”

Technical Notes on HKS Systems

The HKS Hi-Power uses a 2.75-inch (70mm) main pipe diameter, which is optimal for naturally aspirated H22 builds up to about 220 whp. For forced-induction setups, HKS offers a 3-inch option that supports higher flow. The muffler features HKS’s patented “Super Mega Flow” outlet with a straight-through perforated core, minimizing turbulence. Additionally, the inclusion of a flexible coupling reduces stress on the exhaust manifold and prevents cracking over time.

Greddy Exhaust Systems: Design Philosophy and Real-World Results

Greddy (also known as Trust in Japan) is another heavyweight in the import performance scene. Their exhaust offerings for the H22 Prelude include the popular Greddy EVO2 and the Greddy SP2 (Supreme SP2). The EVO2 is a cat-back system with a unique angled exit tip, while the SP2 is quieter and more refined, featuring a dual-chamber muffler design. Both use T304 stainless steel and mandrel bends.

Owner Experiences with Greddy

Feedback from Greddy-equipped Prelude owners highlights several key points:

  • Linear Power Delivery: Many users note that the Greddy exhaust provides a broad, smooth power curve rather than a sharp peak. This makes the car easier to drive aggressively on the street or track. Dyno results posted on forums show 7–10 whp gains, with torque improving across the entire RPM band, especially after 4,000 RPM.
  • Unique Sound Character: The Greddy SP2 is often described as having a “grunty” note – deeper than stock but not as loud as HKS Hi-Power. The EVO2 is slightly louder and has a more metallic echo at high RPM, which some love and others find tinny. Sound clips on YouTube help owners decide before purchase.
  • Ease of Installation: Greddy systems are engineered for direct fitment on the Prelude. Owners frequently mention that everything lines up perfectly with the factory hangers and that no cutting or welding is needed. The included gaskets are high-quality, with only minor complaints about the spring bolts sometimes being too short for some headers.
  • Long-Term Durability: A multi-year owner on Honda-Tech reported: “After four years and 40,000 miles, my Greddy SP2 still looks and sounds great. No rust, no leaks. The angled tip gives the rear a subtle JDM appearance.”

Greddy’s Engineering Choices

The Greddy EVO2 uses a 2.8-inch (71mm) pipe diameter – slightly larger than HKS’s 2.75-inch, which can favor top-end power at the expense of a bit of low-end torque on a stock internal H22. However, the SP2’s muffler design incorporates a Helmholtz resonator that cancels out drone frequencies around 2,000–3,000 RPM, making it more livable for daily driving. Both systems include a polished stainless steel tip engraved with the Greddy logo, adding visual appeal.

HKS vs. Greddy: Head-to-Head Comparison

Choosing between these two proven brands depends on your priorities. Let’s break down the critical factors side by side.

Performance Output

Both HKS and Greddy deliver similar peak horsepower gains (8–12 whp) on a basically stock H22 with a good tune. The differences lie in the shape of the power curve. HKS owners often report a more pronounced surge at VTEC engagement, while Greddy owners feel a flatter, more progressive torque curve. If you’re building a naturally aspirated engine with mild upgrades (header, intake, cam gear), either system works. For a turbo or supercharged setup, the larger diameter of the Greddy EVO2 or the HKS 3-inch option may better support high-flow demands.

Sound and Noise Level

Sound is subjective, but here are general observations:

  • HKS Hi-Power: Deep, loud, and bassy. Noticeable drone between 2,500–3,000 RPM. Best for those who want an aggressive, track-inspired note.
  • HKS Silent Hi-Power: Tamed down with a secondary resonator. Much of the deep tone remains but volume is reduced by 20–30%. Suitable for daily drivers.
  • Greddy EVO2: Sharp and metallic at high RPM, quieter than HKS Hi-Power in daily driving. Some find the tip whistle unique.
  • Greddy SP2: Deep, mellow, minimal drone. Often considered the best option for a car that gets driven daily and occasionally sees the track.

To hear real clips, search for “H22 Prelude HKS Hi-Power dyno” or “Greddy SP2 Prelude cold start” on YouTube – the audio quality of owner videos is more reliable than manufacturer samples.

Price and Value

As of 2025, retail prices for cat-back systems range from roughly $600 to $900 USD:

  • HKS Hi-Power: ~$650–$750
  • HKS Silent Hi-Power: ~$750–$850
  • Greddy EVO2: ~$600–$700
  • Greddy SP2: ~$700–$800

Prices vary by retailer and sales events. Both brands offer lifetime warranties against manufacturing defects, but always verify with the specific seller. Note that header-back systems (including downpipe/test pipe) will cost more but yield greater gains if you’re willing to go full exhaust.

Installation and Fitment

Both HKS and Greddy provide bolt-on kits for the Prelude H22. Owners frequently note that Greddy systems often fit with slightly less hanging adjustment due to the use of multiple support brackets. HKS systems sometimes require minor repositioning of rubber hangers or the addition of a spacer on the test pipe flange. Neither is difficult for a DIY mechanic with basic hand tools and a jack.

Complementary Mods: Get the Most From Your Exhaust

An exhaust alone is a great start, but pairing it with other modifications maximizes your returns. Here are the most common combinations owners recommend:

Cold Air Intake

A quality cold-air intake like the AEM V2 or the Injen CAF helps the engine suck in cooler air, complementing the exhaust’s improved outflow. Many owners report an extra 5–8 whp when adding an intake to an exhaust upgrade.

Header Upgrade

The H22’s factory exhaust manifold is restrictive. Swapping to a 4-2-1 header (e.g., from DC Sports, PLM, or the DC 4-1 ceramic) can drop exhaust gas temperatures and add another 5–10 whp. Combined with a cat-back system, you’re looking at 15–20 whp over stock before a tune.

P28 ECU or Hondata Tune

To unlock the full potential of any exhaust system, a proper tune is essential. The stock ECU has conservative fuel and ignition maps. Switching to a chipped P28 ECU with a basemap, followed by a dyno tune, can increase power by 10–15% over a bolt-on-only setup. Many owners use Hondata S300 for easy tuning and datalogging.

Test Pipe vs. Catalytic Converter

Removing the catalytic converter with a test pipe reduces backpressure further, but be aware of legality in your area. Test pipes are common on track-only Preludes, but for street use, a high-flow catalytic converter (like a Random Technology unit) keeps emissions in check while still flowing better than the stock cat.

Long-Term Ownership Considerations

An aftermarket exhaust is a durable upgrade, but here are a few things to keep in mind for sustained enjoyment:

  • Inspect gaskets annually: The flanges at the cat and muffler connections can develop leaks over time. Replacing gaskets with OEM or copper-impregnated types prevents noise rattles.
  • Check hanger condition: Rubber hangers sag and crack after years of heat cycles. If the exhaust starts to shift, replace all four hangers (OEM or aftermarket polyurethane).
  • Watch for bumper melting: Some exhaust tips on the Prelude can get close to the rear bumper plastic. Heat shielding or repositioning the tip may be necessary to avoid warping.
  • Consider sound compliance: If you drive in areas with strict noise limits (like California’s 95 dB limit), the Greddy SP2 or HKS Silent Hi-Power are safer choices.

Community Resources and Further Reading

The Prelude community is active and generous with data. Here are a few resources to help you decide:

Final Thoughts: Which Exhaust Should You Choose?

There is no universal “best” – the choice between HKS and Greddy comes down to your personal driving preferences. If you crave an aggressive soundtrack and don’t mind a bit of cabin drone, the HKS Hi-Power delivers an exhilarating experience and proven mid-range punch. If you daily your Prelude and want a refined tone that still performs, the Greddy SP2 offers a balanced package with minimal compromise. For the best of both worlds, the HKS Silent Hi-Power gives the HKS brand’s performance benefits in a more street-friendly envelope.

Whichever system you pick, invest in a proper tune and complementary intake or header to unlock the H22’s true potential. The owner reviews are clear: both brands transform the Prelude from a tame commuter into a responsive, exciting machine that rewards every throttle input. Take your time, listen to clips, and read the experiences of others – your upgrade will be all the more satisfying for it.