Capristo Alfa 4C High Flow Cat (HJS Catalyst)

Alfa9 Supply was the first Alfa Romeo specialist to offer the Capristo high-flow cat for the 4C, and we remain committed to the best available pricing on it for our 4C customers. The Capristo high-flow cat is purpose-built to improve flow and lower exhaust gas temperatures on the Alfa 4C coupe and spider — a proven, trusted upgrade for any 4C.

Better Mid-Range Response and Turbo Spool

Both the 100 cel and 200 cel versions noticeably improve mid-range response and turbo spool-up. The unique sound is a clear step up from the stock 4C exhaust, with a more refined tone than an open downpipe delivers.

Lower EGTs, More Power

Lower exhaust gas temperatures let the turbo boost more freely without ECU intervention — especially useful in hard-use situations like track days. Paired with our ECU tuning, expect roughly an 8 hp gain from the high-flow cat alone.

Built by HJS — the Motorsport Catalyst Standard

Capristo's proprietary castings are engineered for the smoothest possible exhaust flow, outperforming typical welded-tube designs. Both 100 cel and 200 cel material flow nearly like an open downpipe while staying emissions-compliant, with no CEL codes triggered. Some 4Cs running OEM factory cats have had the catalyst brick break loose and cause a blockage — this eliminates that risk.

The catalyst media itself is made in Germany by HJS-Motorsport, widely regarded as the world leader in motorsport catalyst development. HJS material is FIA-approved and used in BTCC, WTCC, WRC, WEC, and Le Mans programs. Don't trust your 4C's exhaust calibration to an unproven import catalyst — use Capristo HJS for maximum reliability and longevity.

Reliable, Bolt-In Fitment

This is a 100% bolt-in factory replacement, compatible with any aftermarket or factory exhaust using OEM Alfa 4C mounting points. Flow is matched to the factory turbo's operating range — unlike oversized aftermarket downpipes that can upset turbo/ECU behavior. Built from T309 stainless for heat resiliency, so there's no need to wrap or ceramic-coat it. The housing is a robust proprietary casting, far less prone to cracking than the thin-wall aftermarket downpipes other brands sell.

100 cel vs. 200 cel vs. Cat-Delete

• 100 cel — maximum flow while remaining emissions-compliant in many states

• 200 cel — marginally more restrictive, slightly quieter

• Cat-Delete — open cat option, for race track use only

Legal Notice

Sold for off-road and track use only — not for sale or use in California or other CARB-regulated states. Replacing your OEM catalytic converter may trigger a Check Engine Light; ECU tuning or O2 sensor extensions can resolve this.

Full System Layout

The schematic photo shows the high-flow cat as part of the complete Capristo catback valved exhaust system. We also sell the full system — [link here] — if you're looking to upgrade the whole exhaust at once rather than just the cat.