The TOWMA High-Performance Downpipe for the Porsche 718 Cayman GT4 transforms the naturally aspirated 4.0L flat-six from sharp to brutal. This isn't a subtle upgrade—it's pure rebellion in stainless steel. Available as a catless or with a high-flow sports catalytic converter.
Advantages
- Maximum flow — free diameter for minimum restriction
- More power — 10-15 extra hp
- Better throttle response — more direct throttle response
- Brutal flat-six sound — unmistakable, raw sound
- OEM+ fit — direct mounting without modifications
- T304 Stainless Steel — High-performance stainless steel for extreme temperatures
- TIG welded — perfect welds for optimal strength and flow
Material & Construction
The TOWMA downpipe is manufactured from high-quality T304 stainless steel and fully TIG-welded for a perfect finish and maximum flow.
The free diameter pipe without internal restrictions ensures maximum exhaust flow, resulting in:
- Better throttle response — more direct throttle response
- More power — especially in the mid-range rev range
- Higher top speed — less exhaust restriction
- Enhanced sound — pure flat-six tone
Available in two variants:
1. Catless (without catalytic converter):
- Maximum flow and performance
- Loudest, most aggressive flat-six sound
- Maximum power gain (12-15 hp)
- Not MOT-proof in the Netherlands
- For track/export use only
2. High-Flow Sports Catalyst (200-cell):
- Balance between performance and emissions
- Sporty flat-six sound, slightly less loud than catless
- Good power gain (10-12 hp)
- Possibly MOT proof (depending on inspection)
- Suitable for daily use
Performance & Sound
Capital gain:
- Catless: +12-15 hp
- High-flow cat: +10-12 hp
- Total power: 425+ hp possible (standard 420 hp)
Sound character:
The TOWMA downpipe allows the naturally aspirated 4.0L flat-six to fully utilise its potential:
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Idle: Deep, menacing flat-six hum
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Acceleration: Screaming, metallic flat-six scream
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High revs: Deafening, racing-level sound (8000+ rpm)
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Deceleration: Pops and crackling
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Downshifts: Aggressive backfire
Note: The GT4 has a naturally aspirated engine (not a turbo), so the sound is different from turbo engines—more metallic, high-revving, and raw. Catalytic converters are VERY loud!
Installation & Assembly
The downpipe is designed for plug-and-play installation on the original Porsche mounting points.
Installation steps:
- Lift the GT4 and place it on a lifting bridge
- Remove original downpipe (3 bolts top, 2 bolts bottom)
- Install new TOWMA downpipe with supplied gaskets
- Tighten all bolts to specifications (45-50 Nm)
- Check for leaks upon initial start-up
- Reset error codes (if present)
Installation time: 2-3 hours for an experienced Porsche specialist
Recommendation: Professional installation by a certified Porsche specialist or performance shop is recommended.
ECU Tuning: For optimal performance, ECU tuning is recommended, but not mandatory. Naturally aspirated engines benefit less from tuning than turbocharged engines.
Compatibility
Suitable for:
- Porsche 718 Cayman GT4 (2020+) — 4.0L flat-six NA
- Porsche 718 Spyder (2020+) — 4.0L flat-six NA
- Porsche 718 Cayman GTS 4.0 (2020+) — 4.0L flat-six NA
- Porsche 718 Boxster GTS 4.0 (2020+) — 4.0L flat-six NA
Not suitable for:
- Porsche 718 Cayman/Boxster (2.0L/2.5L turbo) — different engine
- Porsche 718 Cayman GT4 RS — different exhaust layout
Note: This is only for 4.0L naturally aspirated flat-six models. Check your engine code before ordering.
Technical Specifications
| Characteristic |
Specification |
| Brand |
TOWMA Carbon & Performance Parts |
| Product |
High-Performance Downpipe |
| Material |
T304 Stainless Steel |
| Welding method |
TIG welded |
| Diameter |
76mm (3 inch) |
| Variants |
Catless or High-Flow Cat (200-cell) |
| Fit |
OEM+ direct fit |
| Suitable for |
718 GT4/Spyder/GTS 4.0 (2020+) |
| Capital gains |
10-15 hp |
| Installation |
Plug and play, no welding |
| Warranty |
3 years on construction and fit |
| Price |
€1,499 |
Maintenance & Warranty
Maintenance:
- Check flanges for leaks regularly
- Inspect gaskets annually
- Clean the outside with stainless steel cleaner for a shine
- Check mounting bolts for tightness
Warranty:
TOWMA offers a 3-year warranty on construction, fit, and finish. The warranty covers manufacturing defects, leaks, and fit issues. Damage due to improper installation, accidents, or misuse is not covered by the warranty.
Frequently Asked Questions
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Do I need ECU tuning? Not required. Naturally aspirated engines benefit less from tuning than turbocharged engines. The downpipe alone provides 10-15 hp.
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Is this MOT-proof? Catless is NOT. High-flow cat is possible, depending on inspection.
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How loud is this? Catless is VERY loud. The 4.0L flat-six is metallic and high-revving—extremely so at 8,000 rpm. High-flow cat is sporty but more tolerable.
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Will I get a check engine light? Possibly. This can be resolved with ECU tuning or O2 sensor spacers.
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Will this fit my 718 Cayman S? No, only for 4.0L naturally aspirated models (GT4/Spyder/GTS 4.0).
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What's the difference with turbo downpipes? Naturally aspirated engines don't have a turbo, so no turbo whoosh. Instead, they deliver a pure, metallic flat-six sound.
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Does this fit the GT4 RS? No, the GT4 RS has a different exhaust layout.
