FL5 / DE5 Downpipe Guide — Catted vs Sports Cat vs De-Cat, CEL Risk, and the Best Options Right Now
Sound, smell, heat, and check engine lights — a downpipe changes all of it. Here's what actually matters for daily drivers, tuned cars, and track builds.
The Honda Civic Type R FL5 and Acura Integra Type S DE5 both respond well to better exhaust flow, but a downpipe is one of the fastest ways to change sound, smell, heat, and your odds of seeing a check engine light. This guide focuses on the options FL5 and DE5 owners actually cross-shop, with special attention to daily drivability, catalyst quality, and fitment reality.
DE5 buyer note: Not every listing that fits the FL5 is explicitly sold for the DE5. Where a product is clearly listed for FL5/DE5, I say that. If a brand only lists FL5 or FK8/FL5, treat it as an FL5-reference option until the seller confirms exact DE5 fitment.
Emissions laws vary by state and country. "Race cat," "sports cat," "de-cat," and "cat-delete" parts may be sold for off-road or motorsport use only. Always confirm local legality before modifying emissions equipment.
Legal disclaimer: SBX Performance provides product information for educational purposes only. Laws and emissions requirements vary by jurisdiction and may change over time. It is the purchaser's responsibility to confirm legality and emissions compliance for their vehicle and location prior to purchase or installation. SBX Performance does not assume liability for inspection failure, fines, penalties, or non-compliance related to product use.
- FL5 focused
- DE5 buyer notes included
- Catted vs De-Cat
- Best-by-goal picks
- CEL reality
- Best daily-driver direction: a quality high-flow catted downpipe with good heat management and realistic CEL expectations.
- Best current DE5-friendly buying strategy: prioritize listings that explicitly mention DE5 or are already known to be sold as FL5/DE5 parts.
- Most aggressive sound and smell: de-cat / catless setups.
- Lowest headache on a street car: larger, higher-quality catalyst designs usually beat tiny "race cat" solutions.
- Biggest mistake buyers make: assuming every FL5 downpipe is automatically a perfect DE5 fit without checking the listing.
On paper, the FL5 and DE5 are very close. In the real world, buyers should still care about listed fitment, turbo outlet design, front-pipe connection style, sensor placement, and whether a brand has actually validated the part on the chassis they are selling it for.
If a product is marketed as FL5/DE5, that is the safest path for DE5 owners. If it is only listed as FL5 or FK8/FL5, it may still be relevant, but it should be treated as a comparison point until the seller confirms it for the DE5.
If you want the lowest-friction path today, start by looking hardest at the options that are already sold as FL5/DE5 or FK8/FL5/DE5, then work outward from there.
Daily Catted
Sound: Stronger than stock, easier to live with long-term.
Smell: Usually much lower than catless once warm.
CEL risk: Lower when catalyst quality and placement are good.
Best for: street cars, commuting, long-term ownership.
Sports Cat / Race Cat
Sound: Typically louder and sharper than daily catted setups.
Flow: Generally better than a denser OEM-style catalyst.
CEL risk: Middle ground — very dependent on catalyst quality and ECU behavior.
Best for: tuned cars that still want some catalyst in place.
De-Cat / Catless
Sound: The loudest and most raw option.
Smell: Highest odor, especially cold start and stop-and-go.
CEL risk: Highest.
Best for: track-first, off-road, or dedicated aggressive builds.
Heat Still Matters
The FL5/DE5 engine bay is not where you want to get lazy with thermal control. Whether catted or de-cat, plan for ceramic coating, blankets, hard lagging, or OEM heat shield retention if the design supports it.
These are not "absolute rankings." They are the most practical way I'd separate the current options if the goal is to help a real FL5 or DE5 owner buy the right part the first time.
Best Daily-Driver Direction
- SBX Performance 3.5" GESI Catted — 3.5" primary, 4.5" GESI GEN2 UHO #85200 catalyst (rated 850 HP), 3" outlet, titanium hardware option, true FL5/DE5 fitment. This is our part — we designed it around daily drivability, heat management, and real FL5/DE5 install reality.
- MST 300-Cell Catted — very daily-oriented positioning, CEL-free focus.
- TSP High Efficiency — large 5" OD / 400 CPSI GESI catalyst, daily-minded, no-CEL approach. Continuation of the discontinued PRL design. Some heat shield fitment issues reported, and TSP does not publish the specific GESI part number — worth noting if transparency matters to you. Long lead times.
- 27WON Catted Downpipe — 200-cell metallic foil cat, retains OEM heat shields, CEL-free, strong community reviews for fitment and build quality.
- RV6 High Temp Catted — 300-cell high-temp metallic cat, OEM heat shield provisions, strong all-around option. Needs tune for best results.
Best DE5-Minded Shopping Path
- SBX Performance 3.5" GESI Catted — designed from the start as a true FL5/DE5 solution.
- RV6 High Temp Catted — already sold as FK8/FL5/DE5.
- PLM Power Driven Catted — budget option sold as FL5/DE5.
Best Premium Catted Options
- HKS High Flow Sports-Cat — dual 150-cell metal catalyst, premium engineering, includes heat shield.
- Milltek with HJS High Flow Sports Cat — 3" with HJS 200-cell, premium UK option.
- Milltek with Twin 200 Cell HJS Cat — high-end HJS-based solution, availability can depend on HJS supply.
Best Aggressive / Track-First Direction
- Dream Automotive De-Cat — 3.5" tapering to 3", tangential outlet, hard lagging and Zircotec coating options.
- Milltek Large-Bore De-Cat — simple, recognized catless option.
- Scorpion DE-CAT — FL5-specific, 3.5" pipe, budget-friendly aggressive path.
- Cobra Sport De-Cat — 4" reducing to 3", handmade UK, removes PPF.
Best "Both Worlds" Option
- Axion Industries 2N1 Downpipe — the center section swaps between catted and catless. Sounds clever on paper, but the V-band clamp design introduces long-term concerns: V-bands in high-heat exhaust applications can seize and become extremely difficult to separate after heat cycling, and every additional clamp joint is another potential leak point. Not our first recommendation for a daily driver.
This is our part, so I'm going to be transparent about exactly what it is and why we built it this way.
- Primary section: 3.5" directly off the turbo — this is where the most heat and restriction lives, and where diameter matters most for spool and turbo efficiency.
- Catalyst: 4.5" GESI GEN2 Advanced G-Sport UHO #85200 — rated up to 850 HP. Not an entry-level core, not vague "GESI style" language. We tell you exactly what catalyst is in the pipe.
- Outlet: 3" to match the factory front pipe location cleanly. The larger section is kept where it delivers the greatest benefit, then reduced appropriately downstream.
- Hardware: Complete Install Kit includes JD Customs titanium studs (turbo flange, burnt finish) and titanium bolts (front pipe flange, burnt finish). No mixed stainless. No zinc bolts. No chasing old corroded hardware during install.
- Fitment: Honda Civic Type R FL5 (2023+) and Acura Integra Type S DE5 (2024+). This was designed for these cars from the start — not adapted from something else.
- Includes: O2 sensor extension harness, lower gasket (3" three-bolt, high temp), heat shield hardware/spacer kit.
Pricing: Downpipe Only — $1,349 (MAP $1,499). Complete Install Kit — $1,399 (MAP $1,599, includes full titanium hardware at both flanges). Optional OEM Honda turbocharger gasket add-on — +$89.99.
The turbo flange and front pipe flange are the two highest-heat connection points in the system. Zinc hardware rusts. Stainless can gall or seize. Titanium resists corrosion, handles heat cycling better, and comes apart cleaner later when the car needs service. Most customers should choose the Complete Kit.
RV6 High Temp Catted Downpipe
Fitment: FK8 / FL5 / DE5
- 300-cell high-temp metallic cat, 304 stainless, cast transitions, OEM heat shield mounting points retained.
- 24-month warranty on castings and welding (no warranty on catalytic converters).
- Ceramic coating option available (+7–14 business days processing).
- Who it fits best: Buyers who want one premium answer instead of gambling. One of the few options already sold across FK8/FL5/DE5.
- Note: Tune recommended for best results. Community reports CEL P1039 on some cars without a tune.
27WON Catted Downpipe
Fitment: FK8 / FL5 / DE5 / Accord 2.0T
- 200-cell metallic foil catalytic converter, T304 stainless steel construction, TIG welded.
- Designed to retain all OEM heat shield pick-up points.
- Dyno-proven: +10 WHP and +28 lb-ft average over stock (best run: +33 lb-ft) on Dynapack.
- No CEL reported by owners. Strong community reviews for build quality and fitment.
- Available as standalone or with $49.99 discount when purchased with 27WON catback as a full turboback system.
- Who it fits best: Owners who want a proven, CEL-free catted option with excellent build quality and the option to pair it with a complete 27WON exhaust system.
TSP High Efficiency Downpipe
Fitment: FK8 / FL5 / DE5 / Accord 2.0T / RDX / TLX
- 304 stainless investment-cast ends, CNC pocketed for smooth transitions.
- 5.00" OD 400 CPSI GESI G-Sport catalytic converter — TSP markets it as 48-state EPA approved.
- This is the continuation of the discontinued PRL downpipe design. TSP picked up production after PRL ceased downpipe manufacturing due to California emissions concerns.
- No tune required, no CEL on most installs.
- Heat shield fitment: Some owners have reported heat shield fitment issues on certain units — bolt holes not lining up cleanly, requiring drilling or modification. Not universal, but it's come up enough to be worth mentioning.
- Catalyst transparency: TSP does not publicly list the specific GESI part number of the catalyst used in the downpipe. For comparison, we list our exact catalyst (GESI GEN2 UHO #85200) because we think you should know exactly what's in the pipe you're buying. When a company doesn't tell you the part number, you can't independently verify the catalyst spec, HP rating, or cell count. That's a transparency issue.
- Lead times: Can be very long — multiple weeks to months. Plan accordingly.
MST 300-Cell Catted Downpipe
Fitment: FL5
- Very daily-friendly positioning, CEL-free focus, large catalyst design.
- 304 stainless, hand TIG welded, high-flow cat rated for 500 HP.
- Includes install hardware + O2 sensor extension.
- Note: Some community reports of heat shield bolt hole alignment issues — minor but worth knowing.
PLM Power Driven Catted
Fitment: FL5 / DE5
- Budget catted option with FL5/DE5 listing support.
- Attractive pricing, but budget parts always deserve careful inspection before install.
- Who it fits best: Cost-conscious buyers who still want catted + DE5 listing support.
Axion Industries 2N1 Downpipe
Fitment: FK8 / FL5 / DE5
- Swappable center section — catted AND catless in one downpipe.
- The concept is appealing: one pipe, two configurations for emissions compliance vs. track use.
- The reality: V-band clamps in high-heat exhaust applications are a long-term headache. After repeated heat cycles, V-bands seize — and getting them apart without damaging the flanges becomes a real fight. Every additional clamp joint is also another potential exhaust leak point that a single-piece downpipe simply doesn't have.
- My honest take: If you're the kind of person who actually swaps between catted and catless regularly (inspection season vs. track season), I get the appeal. But for most people, you're better off just buying the right downpipe for your use-case and leaving it alone. A single-piece design with proper flanges will seal better, last longer, and give you fewer problems over the life of the car.
Cobra Sport HN29 Sports Cat / De-Cat
Fitment: FL5
- 4" / 101.6mm reducing to 3" / 76.2mm pipework.
- Sports cat version: 4.5" 200-cell high-flow catalyst.
- Removes the PPF — tuning required to cancel EML on PPF-equipped vehicles.
- Handmade to order in the UK, typically 7–10 working days.
Scorpion Sports CAT / DE-CAT Downpipe
Fitment: FL5
- 89.9mm / 3.5" pipe diameter. Available in sports cat or de-cat configurations.
- Fits OEM or Scorpion exhaust systems.
- Stage 2 ECU remap recommended. EML may be activated.
- Good FL5-specific option without ultra-premium pricing.
HKS High Flow Sports-Cat Downpipe
Fitment: FK8 / FL5
- Dual 150-cell metal catalyst design with premium engineering.
- Includes specially designed heat shield.
- Serious premium catted solution — not a budget compromise.
Milltek HJS High Flow Sports Cat
Fitment: FK8 / FL5
- 3.00" / 76.2mm downpipe with HJS 200-cell high-flow cat.
- Milltek recommends pairing with Milltek exhaust components rather than mixing systems.
- Often 1–3 day dispatch when in stock.
Milltek Twin 200 Cell HJS Cat
Fitment: FK8 / FL5
- Higher-end HJS-based catted solution. Often listed at 5–15 day dispatch.
- Availability can depend on HJS catalyst supply chain.
Dream Automotive De-Cat
Fitment: FK8 / FL5
- Lightweight T304 stainless. Tangential turbo outlet, 3.5" bend tapered to 3" outlet.
- Available without coating, with hard lagging, or with black Zircotec ceramic coating.
- One of the better de-cat choices for buyers who actually care about heat control.
- Motorsport use only.
Milltek Large-Bore De-Cat
Fitment: FK8 / FL5
- Large-bore de-cat design. Track/motorsport use only, Stage 2 remap required.
- Often shown as 1–3 day dispatch. Simple and straightforward catless option.
| Option | Fitment | Type | Bias | Key Detail |
|---|---|---|---|---|
| SBX Performance 3.5" GESI | FL5 / DE5 | 3.5"→4.5" GESI GEN2 UHO→3" | OEM+ street / performance | 850 HP rated cat, titanium hardware, designed for FL5/DE5 from the start |
| RV6 High Temp Catted | FK8 / FL5 / DE5 | 300-cell high-temp metallic cat | Best all-around | Premium construction, OEM heat shields retained, tune recommended |
| 27WON Catted | FK8 / FL5 / DE5 / Accord | 200-cell metallic foil cat | CEL-free daily | OEM heat shields, +10 WHP / +28 WTQ avg, no CEL |
| TSP High Efficiency | FK8 / FL5 / DE5 / Accord | 5" OD 400 CPSI GESI (part # not published) | Daily-minded | PRL design continuation; heat shield fitment issues reported; long lead times |
| MST 300-Cell Catted | FL5 | 300-cell catted | Daily-driver bias | CEL-free focus, daily-oriented positioning |
| PLM Power Driven Catted | FL5 / DE5 | High-flow catted | Budget street | Price and DE5 listing are the draw |
| Axion Industries 2N1 | FK8 / FL5 / DE5 | Catted + catless (V-band swap) | Concept car | V-band clamps seize after heat cycling; more leak points than single-piece |
| Cobra Sport HN29 | FL5 | Sports cat or de-cat | Motorsport-leaning | 4"→3", handmade UK, removes PPF, tuning required |
| Scorpion Sports CAT / DE-CAT | FL5 | 3.5" sports cat or de-cat | Street / aggressive | FL5-specific, affordable, Stage 2 remap recommended |
| HKS High Flow Sports-Cat | FK8 / FL5 | Dual 150-cell metal catalyst | Premium catted | High-end catalyst engineering, includes heat shield |
| Milltek HJS Sports Cat | FK8 / FL5 | 3" with HJS 200-cell cat | Premium street | Best matched with Milltek exhaust components |
| Milltek Twin 200 Cell HJS | FK8 / FL5 | Twin 200-cell HJS | High-end catted | Premium HJS, availability varies with supply |
| Dream Automotive De-Cat | FK8 / FL5 | 3.5"→3" de-cat | Track / heat-managed | Tangential outlet, hard lagging + Zircotec options |
| Milltek Large-Bore De-Cat | FK8 / FL5 | Large-bore de-cat | Track-first | Simple motorsport-style catless option |
- Turbo hardware matters: Heat-cycled turbo fasteners can turn a "quick install" into a time sink. Plan for penetrant, patience, and replacement hardware — or just get a kit with titanium hardware from the start.
- Heat management is not optional on harder-driven cars: Blankets, coatings, and OEM shield retention matter more than most people think.
- Do not assume DE5 fitment from an FL5-only title: Confirm it first.
- Sports-cat and de-cat setups frequently want a tune: Especially if you remove major restrictions or emissions equipment.
- Think about the whole exhaust path: Downpipe, front pipe, cat-back, and tune all change the final result together.
- Stock-tune reality: Most dyno charts online are on tuned cars. On a stock ECU, peak gains can be smaller than expected. Once calibration is optimized, a downpipe becomes a stronger "multiplier."
If your car is a daily-driven FL5 or DE5, stay focused on a quality catted setup with good heat control and realistic fitment support. The SBX 3.5" GESI, RV6 High Temp, 27WON, and TSP High Efficiency are all strong daily-driver paths depending on your budget and priorities.
If your goal is a more aggressive car, the sports-cat options from Cobra, Scorpion, and HKS are the middle ground. If you know you want the loudest, rawest, highest-flow result and accept the tradeoffs, Dream Automotive and Milltek de-cat options are where that conversation starts.
For DE5 owners specifically, the safest shopping path today is still to prioritize products already listed for DE5 — SBX Performance, RV6, PLM, and Axion Industries all have you covered.
- SBX Performance FL5/DE5 3.5" GESI Catted Downpipe — $1,349 / $1,399 Complete
- RV6 High Temp Catted Downpipe (FK8 / FL5 / DE5)
- MST 300-Cell Catted Downpipe (FL5)
- MAPerformance Downpipe (FL5)
- PLM Power Driven Catted Downpipe (FL5 / DE5)
- Milltek Cast Downpipe with HJS Hi-Flow Sports Cat
- Milltek Cast Downpipe with Race Cat
- Milltek Large-Bore Downpipe + De-Cat
Need Help Choosing?
We've installed, heard, and tuned around most of these downpipes. Hit us up and we'll help you pick the right one for your goals, fuel setup, and daily-driving reality.