Competition Clutch Stage 3 Kit, 17-23 Civic Si

Competition Clutch Stage 3 Kit, 17-23 Civic Si

If the stock clutch in your 2017-2023 Civic Si is slipping every time the 1.5T builds boost in third, the Competition Clutch Stage 3 kit (8091-ST-2600 or 8091-STU-2600) is the complete clutch-and-flywheel fix. Both options use the same Stage 3 segmented ceramic clutch for the Civic Si 1.5L turbo only. The choice is the flywheel: ST lightweight steel or STU ultra lightweight steel. It doesn't fit a non-Si 1.5T Civic, and it doesn't fit a Type R.

What It Is and Why It Works

This is Competition Clutch's 2600 Series street/strip kit with the flywheel in the box. Competition Clutch rates Stage 3 at up to a 150 percent increase in torque capacity over stock. Segmented ceramic holds more heat than the organic Stage 2 disc on the 8091-ST-2100 / 8091-STU-2100 kits already in the catalog, so it won't glaze the way a stock Si disc does when you keep it in boost. Engagement is quicker and less polite in traffic. That's the trade-off. Generic Stage 3 copy that mentions a 250 mm plate is template language, not a measured 8091 spec.

ST (8091-ST-2600) includes the Lightweight Steel flywheel. Competition Clutch makes ST flywheels from 4140 one-piece steel and recommends ST for naturally aspirated and/or street use because it preserves low-end torque and driveability. That same flywheel page also says ST is well-suited for Gravity, Stage 1, and Stage 2. This SKU is a Stage 3 kit on a turbo car, so that pairing note doesn't match this application. ST is still the milder, street-oriented steel wheel of the two. STU (8091-STU-2600) includes the Ultra Lightweight Steel flywheel. Competition Clutch recommends STU for forced induction and/or track and rally, machines it with less material for quicker revving, and lists it as well-suited for Stage 3 and up. That pairing matches this SKU.

Competition Clutch only publishes flywheel weight as 8 to 18 lbs by application, so no per-SKU mass is claimed here. Each kit includes the pressure plate, the segmented ceramic disc, an alignment tool, a pilot bushing, a throwout bearing, and the chosen steel flywheel. This is a complete kit, not an RK.

Specs

Available Options

Fitment

This kit is for the 2017-2023 Civic Si 1.5L turbo only. It doesn't fit a non-Si 1.5T Civic, a Civic Type R, or an earlier K20 Civic Si (those are the 8090 and 8037 families). Competition Clutch's page doesn't split 10th-gen vs 11th-gen and doesn't name hatch vs sedan. If your Civic isn't an Si, this isn't your clutch.

What to Know Before You Buy

Be honest about the flywheel before you order. ST is the street-oriented wheel that Competition Clutch says preserves low-end. STU is the quicker-revving wheel they recommend for boost and track. The clutch disc is the same Stage 3 ceramic either way, so you're not buying more holding power when you step to STU. You're buying less rotating mass and more chatter risk at idle. If you daily the Si in traffic, ST is the one we'd put in our own car. If you track it or you want it to rev like a lighter wheel, take STU.

Ceramic engagement is grabby. There's a narrow slip zone, the pedal is heavier than stock, and you'll get some low-speed chatter, especially if you pair it with the STU wheel. Take the 500-mile break-in seriously: normal street driving, no launches, no clutch-slipping heroics until the disc beds into the new flywheel. Skip it and you'll chase engagement problems and blame the kit.

While the transmission is out, inspect the rear main seal, the slave cylinder, and the clutch master. A tired hydraulic system behind a stiffer plate feels worse than the clutch itself. If the car is still on a stock tune and you hate traffic, look at the Stage 2 8091 kits we already sell before you commit to ceramic.