Does the Type RS 1.5-Way LSD for FK8 also fit the FL5?

Yes. Cusco USA lists part number LSD 3A9 C15 for both the FK8 Civic Type R and the FL5 that followed it. The two share the 2.0L K20C1 turbo engine and a six-speed manual gearbox, so one Type RS 1.5-Way LSD for FK8 and FL5 cars fits either generation.

What does 1.5-way mean on a front-drive car?

A 1.5-way differential locks fully under acceleration and partly under deceleration. Cusco specifies 45/15 degree cams for this unit, so it adds a smaller locking force when the driver lifts or brakes, which ties the front wheels together on corner entry and steadies the car under trail braking.

Should I choose the 1-way or the 1.5-way?

The 1-way leaves the diff open off the throttle, so turn-in feels close to stock and the car rotates more freely on lift. The 1.5-way trades some of that rotation for stability on the brakes, which suits hard trail braking and time attack. A mostly road-driven car suits the 1-way.

How is it different from the factory helical differential?

The factory helical diff can only bias torque while both front tires carry load. The Cusco unit is a clutch-type LSD with spring-set initial torque, so it keeps driving both wheels when the inside tire goes light, and it also locks partly on deceleration. Clutch plates wear over time, so it is a serviceable part.

Can the initial torque be changed after it is installed?

Yes. Cusco states that the initial torque of the Type RS is set by the number of RS springs inside the pressure rings and quotes 3 to 5 kgf-m for this unit. Changing the spring count means taking the differential out and opening it, so the work is best done alongside a gearbox service.

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Description

Cusco Type RS 1.5-Way LSD for FK8 / FL5 Honda Civic Type R

Cusco’s Type RS 1.5-Way LSD for FK8 / FL5 Honda Civic Type R swaps the factory helical front differential for a clutch-type unit that locks fully on acceleration and partly on deceleration. Where a helical diff lets the light inside wheel spin out of a slow corner, the Type RS keeps both wheels driving. On the brakes, the coast side of the cam adds a measured amount of lock, which makes the car calmer on trail braking. Initial torque comes from coil springs rather than heavy preload, so engagement is smoother than Cusco’s MZ series. Choose it for a Type R that spends real time on track; a mostly road-driven car suits the 1-way.

Design and Performance

RS springs inside the pressure rings pre-load the clutch plates, pushing in the same direction as the initial torque so the plates pick up quickly and progressively. The pressure rings carry cam faces on both the drive and the coast side, which Cusco specifies as 45/15 degrees, so the Type RS 1.5-Way LSD for FK8 and FL5 cars adds locking force under power and a smaller amount when the engine is braking the car.

Features

45/15 degree cams for 1.5-way action: full locking on drive, partial locking on coast
Coil-spring initial torque system with RS springs inside the pressure rings
Smoother, quicker engagement than the Cusco MZ series
Initial torque adjustable by changing the number of RS springs
Clutch-type multi-plate design in place of the factory helical gears

Specifications

Cusco part number: LSD 3A9 C15
Type: Type RS
Action: 1.5-way, 45/15 degree cams
Optional setting: 1-way, 45 degree cam, per Cusco
Initial torque: 3-5 kgf-m (approx. 22-36 lb-ft)
Position: Front differential
Drivetrain: Front-wheel drive
JAN code: 4996338102461

Applications

Honda Civic Type R: FK8 | 2017-2021 | 2.0L K20C1 turbo
Honda Civic Type R: FL5 | 2023-present | 2.0L K20C1 turbo

Notes

Fitting the Type RS 1.5-Way LSD for FK8 and FL5 cars means removing and splitting the transmission; installation labor is not included
The 1-way version, which stays open on deceleration, is sold as the Cusco Type RS 1-Way LSD for FK8 / FL5 Honda Civic Type R

Frequently Asked Questions

Does the Type RS 1.5-Way LSD for FK8 also fit the FL5? Yes. Cusco USA lists part number LSD 3A9 C15 for both the FK8 Civic Type R and the FL5 that followed it. The two share the 2.0L K20C1 turbo engine and a six-speed manual gearbox, so one Type RS 1.5-Way LSD for FK8 and FL5 cars fits either generation.
What does 1.5-way mean on a front-drive car? A 1.5-way differential locks fully under acceleration and partly under deceleration. Cusco specifies 45/15 degree cams for this unit, so it adds a smaller locking force when the driver lifts or brakes, which ties the front wheels together on corner entry and steadies the car under trail braking.
Should I choose the 1-way or the 1.5-way? The 1-way leaves the diff open off the throttle, so turn-in feels close to stock and the car rotates more freely on lift. The 1.5-way trades some of that rotation for stability on the brakes, which suits hard trail braking and time attack. A mostly road-driven car suits the 1-way.
How is it different from the factory helical differential? The factory helical diff can only bias torque while both front tires carry load. The Cusco unit is a clutch-type LSD with spring-set initial torque, so it keeps driving both wheels when the inside tire goes light, and it also locks partly on deceleration. Clutch plates wear over time, so it is a serviceable part.
Can the initial torque be changed after it is installed? Yes. Cusco states that the initial torque of the Type RS is set by the number of RS springs inside the pressure rings and quotes 3 to 5 kgf-m for this unit. Changing the spring count means taking the differential out and opening it, so the work is best done alongside a gearbox service.

About CUSCO

CUSCO is the brand of Carrosser Co., Ltd., founded in December 1977 and based in Takasaki, Gunma Prefecture, Japan. Carrosser designs and builds coilovers, limited-slip differentials, clutches, roll cages and chassis parts, sells its steel cages under the Safety 21 name, and competes in every All Japan Championship category from circuit racing to rally and gymkhana. CUSCO USA, a division of Carrosser, is based in Huntington Beach, California.

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