Does the Type RS 1-Way LSD for FK8 also fit the FL5?

Yes. Cusco USA lists part number LSD 3A9 C for both the FK8 Civic Type R and the FL5 that replaced it. Both use the 2.0L K20C1 turbo engine and a six-speed manual gearbox, so one Type RS 1-Way LSD for FK8 and FL5 cars covers both generations.

What is the difference between the 1-way and the 1.5-way Type RS?

The 1-way locks only under acceleration and stays open when the driver lifts or brakes, so turn-in feels close to stock. The 1.5-way adds a smaller amount of locking on deceleration, which steadies the car on corner entry at the cost of a little more push. Cusco sells both, as LSD 3A9 C and LSD 3A9 C15.

How is it different from the factory helical differential?

The factory helical diff can only bias torque while both front tires carry load, so it loses its effect when the inside wheel goes light. The Cusco unit is a clutch-type LSD with spring-set initial torque, so it keeps both wheels driving even then. The trade-off is that clutch plates wear and need servicing over time.

What does initial torque mean on this LSD?

It is the locking force the differential applies before the engine sends any power through it. Cusco sets it on the Type RS with coil springs inside the pressure rings and quotes 3 to 5 kgf-m for this unit. Lower values feel smoother on the road; higher values hold the inside wheel harder on corner exit.

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, so changing the spring count raises or lowers it. The job means taking the differential out of the gearbox and opening it, so it is best planned with a gearbox service.

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Description

Cusco Type RS 1-Way LSD for FK8 / FL5 Honda Civic Type R

Cusco’s Type RS 1-Way LSD for FK8 / FL5 Honda Civic Type R replaces the factory helical front differential with a clutch-type unit that locks under power and opens again when the driver lifts. Where a helical diff lets the light inside wheel spin out of a tight hairpin, the Type RS keeps both wheels driving. Initial torque comes from coil springs rather than heavy preload, so engagement is smoother than Cusco’s MZ series. In 1-way form it does nothing on the brakes, and corner entry feels much like stock. Choose it for a Type R that commutes and does regular track days; for more stability on trail braking, compare the 1.5-way.

Design and Performance

Small RS springs inside the pressure rings load the clutch plates before any drive torque arrives. They push in the same direction as the initial torque, so the plates pick up quickly and progressively instead of snapping on. Under power the cams add locking force in step with torque, so the harder the K20C1 pulls, the harder the Type RS 1-Way LSD for FK8 and FL5 cars holds both front wheels together.

Features

Coil-spring initial torque system with RS springs inside the pressure rings
1-way 45 degree cam that locks on acceleration only
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 C
Type: Type RS
Action: 1-way, 45 degree cam
Optional setting: 1.5-way, 45/15 degree cams, per Cusco
Initial torque: 3-5 kgf-m (approx. 22-36 lb-ft)
Position: Front differential
Drivetrain: Front-wheel drive
JAN code: 4996338102454

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

Frequently Asked Questions

Does the Type RS 1-Way LSD for FK8 also fit the FL5? Yes. Cusco USA lists part number LSD 3A9 C for both the FK8 Civic Type R and the FL5 that replaced it. Both use the 2.0L K20C1 turbo engine and a six-speed manual gearbox, so one Type RS 1-Way LSD for FK8 and FL5 cars covers both generations.
What is the difference between the 1-way and the 1.5-way Type RS? The 1-way locks only under acceleration and stays open when the driver lifts or brakes, so turn-in feels close to stock. The 1.5-way adds a smaller amount of locking on deceleration, which steadies the car on corner entry at the cost of a little more push. Cusco sells both, as LSD 3A9 C and LSD 3A9 C15.
How is it different from the factory helical differential? The factory helical diff can only bias torque while both front tires carry load, so it loses its effect when the inside wheel goes light. The Cusco unit is a clutch-type LSD with spring-set initial torque, so it keeps both wheels driving even then. The trade-off is that clutch plates wear and need servicing over time.
What does initial torque mean on this LSD? It is the locking force the differential applies before the engine sends any power through it. Cusco sets it on the Type RS with coil springs inside the pressure rings and quotes 3 to 5 kgf-m for this unit. Lower values feel smoother on the road; higher values hold the inside wheel harder on corner exit.
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, so changing the spring count raises or lowers it. The job means taking the differential out of the gearbox and opening it, so it is best planned with 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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