Honda S2000 Supercharger Kits: KraftWerks vs HKS GT2

There are exactly two supercharger kits still worth buying for the Honda S2000, and the honest comparison between them is not the one most forums make. The KraftWerks 30mm Belt Supercharger Kit and the HKS GT2 S/C System Pro are both centrifugal, traction-drive superchargers — not a centrifugal-versus-twin-screw matchup. They differ in blower sizing, boost, what comes in the box, and roughly $400 of sticker price. The KraftWerks kit runs a Rotrex C38-81 and owner dynos land between 407 and 431 whp; the HKS GT2 runs an HKS GTS7040 and measures 310 whp. On a car that leaves the factory with 237–240 crank horsepower, that gap decides the entire build.

KraftWerks vs HKS GT2: S2000 Supercharger Kits Compared

The KraftWerks kit makes roughly 100 more wheel horsepower than the HKS GT2 and costs $422.48 less. That is the comparison in one sentence. Both are centrifugal traction-drive blowers, both include an air-to-air front-mount intercooler and a dedicated traction-fluid cooler, and both require a standalone tune you buy separately. The difference is boost level and completeness: KraftWerks delivers roughly 11–12.5 psi as configured and ships the injectors and pump needed to feed it, while the HKS GT2 runs about 10 psi and expects you to add 750cc injectors and a 255 lph pump on top of the $5,500 kit price.

How we compared them: every figure above comes from manufacturer documentation (KraftWerks part-number listings, HKS product data, the Rotrex C38 technical datasheet) or from published dyno results and owner build threads — not from marketing copy. Where sources conflict, we say so rather than picking the flattering number. Our team in Tampa, FL fields the fitment and tuning-path questions on these kits daily, and the single most common mistake we correct is buyers ordering a kit whose tuning solution their model year cannot run.

One caveat on the HKS before you buy: US retailers list part number 12001-AH010 as fitting 2000–2009 S2000s, but HKS Japan’s own product database lists the kit for the AP2 F22C only and states it cannot be installed on the AP2-110 (October 2007 onward) due to part interference. Confirm your car’s exact build date with HKS before ordering. The KraftWerks kits carry no such ambiguity: three part numbers, three clean fitment windows.

Why Both S2000 Kits Are Centrifugal (And Why That Suits the F20C)

A centrifugal supercharger is a belt-driven compressor wheel whose output rises with the square of impeller speed, so boost builds non-linearly with engine rpm — little down low, hardest at redline. A positive-displacement blower (Roots or twin-screw) pumps a fixed volume per revolution instead, so it makes near-flat boost from just off idle. Every serious S2000 kit on the market — KraftWerks/Rotrex, HKS GT2, and the discontinued Comptech and Vortech systems — is centrifugal. There is no mainstream twin-screw kit for this car, so any "centrifugal vs twin-screw" debate about the S2000 is academic.

That is arguably the right architecture for this engine anyway. The F20C revs to a 9,000 rpm redline (9,150 rpm fuel cut) and the F22C1 to 8,200 rpm (8,350 rpm cut), and both make their power at the top of the tach after the VTEC crossover. A centrifugal’s rising boost curve stacks on top of that character instead of replacing it — which is exactly what the dyno sheets show, with supercharged KraftWerks cars pulling steadily all the way to 8,500 rpm and one AP2 measuring 15 psi at redline. A Roots blower would fill the F20C’s famous low-end torque hole, but it would also blunt the thing that makes an S2000 an S2000.

KraftWerks 30mm Belt Supercharger Kit Review (Rotrex C38-81)

The KraftWerks 30mm Belt Kit is the highest-output bolt-on supercharger system for the S2000, with owner dynos landing between 407 and 431 whp at 12.2–12.5 psi on 93 octane. It is built around a Rotrex C38-81, a planetary traction-drive centrifugal with a 7.5:1 internal drive ratio, a 90,000 rpm maximum impeller speed and 0.63 kg/s of airflow — enough compressor to support 600+ hp, meaning the blower is nowhere near its limit on a stock-internals F22C1.

What separates this kit from every other S2000 blower on the market is what is already in the box. KraftWerks includes four Grams Performance 1,000cc injectors with plug-and-play connectors, a Grams high-flow fuel pump (265 lph on 2006–2009 cars, 320 lph on 2000–2005), the 24in x 12in x 3in air-to-air front-mount intercooler and piping, a dedicated supercharger oil cooler for the Rotrex traction fluid, a recirculating bypass valve, and CNC-machined brackets. Factory A/C and all OEM accessories are retained. Add a tune and a clutch and the car is done.

The "30mm" in the name refers to the width of the cogged supercharger drive belt, and it is a genuine engineering upgrade rather than marketing. The previous generation used a 20mm belt; KraftWerks rates the 30mm version as 57% stronger. Note what the cogged drive actually solves: cogged belts do not slip, so the wider belt is about resisting breakage under load, not curing boost loss. If anyone tells you to fix belt problems with the serpentine retrofit, ignore them — S2KI owners describe that conversion as a bandaid that loses boost because it has too little belt wrap to stay tight.

HKS GT2 S/C System Pro Review (GTS7040)

The HKS GT2 S/C System Pro is the milder, mid-range-focused option, measuring 310.33 whp and 212.77 wtq at roughly 10 psi out of the box. Despite the persistent forum claim that it is a screw-type blower, HKS states plainly that the GT Supercharger uses a centrifugal charger driven by a Torque Response Traction Drive System — the same basic architecture as the Rotrex, just a different unit (the GTS7040) at lower boost. HKS Japan claims "more than 300 PS and 30 kgf-m" (about 217 lb-ft), but that figure is quoted with the HKS Fuel Upgrade Kit, which is sold separately.

The HKS kit is comprehensive on the hardware side: the GTS7040 unit, traction fluid with filter, tank and cooler, crank and supercharger pulleys, a 120mm S/C pulley, two idlers, the belt, intercooler and piping, relief valve assembly, air filter and suction pipe. What it does not include is fuel. HKS itself states the stock injectors are insufficient for full performance and recommends 750cc injectors and a 255 lph fuel pump, plus Super Fire Racing M45i or colder plugs, a higher-torque-capacity clutch, 40-weight or heavier engine oil, and a compact battery to clear the install. Budget those on top of the $5,500.

Which S2000 Supercharger Kit Fits Your Car?

KraftWerks sells three S2000 part numbers and the right one depends entirely on your model year, because the tuning path changes at 2006. The 2006–2009 S2000 is drive-by-wire, so a Hondata FlashPro can flash the factory ECU — that is why the AP2 kit is listed "w/o FlashPro." The 2000–2005 cars use a cable throttle, which FlashPro does not support, so those kits are listed "w/o AEM" and need an AEM EMS Series 2 or a Hondata K-Pro with ECU and harness instead. Get this wrong and you will own a supercharger you cannot legally or safely run.

Supporting Mods You Cannot Skip on a Supercharged S2000

The S2000’s hard limit is not the bottom end — it is compression. The F20C runs 11.0:1 and the F22C1 runs 11.1:1 static compression, which is extraordinarily high for a boosted engine. Evans Tuning’s guidance for supercharged S2000s on stock internals is about 12 psi on 91 octane and 14–15 psi on 93 octane. Push past that on pump gas and the tune pulls so much timing to fight knock that power actually goes down. Roughly 400 whp is the sensible stock-internals ceiling; above 400–500 whp, you are into built-motor or turbo territory.

Clutch: the first thing that will let go

Both KraftWerks and HKS explicitly recommend an upgraded clutch, and at a claimed 280 lb-ft the KraftWerks car sits right at the edge of the 350–400 lb-ft capacity that popular S2000 clutch packages are rated for. The stock unit is not in that conversation. An ACT Prolite flywheel paired with a performance street sprung disc is the common starting point.

Fuel: mandatory on the HKS, included on the KraftWerks

Stock S2000 injectors are roughly 310–320 cc/min and run out of fuel at about 6–7 psi — well below what either kit makes. The KraftWerks kit solves this in the box with 1,000cc Grams injectors and a high-flow pump. HKS GT2 buyers must add fuel themselves: 750cc-plus injectors and a 255 lph pump. For a supercharged AP2 we stock DeatschWerks 1,000cc Bosch EV14 injectors at $420.60 and a DeatschWerks 255 lph in-tank pump with the 06-09 S2000 install kit at $83.08. Owners running smaller boost sometimes prefer Grams 550cc injectors ($341.95).

The belt, the traction fluid, and the failure mode nobody mentions

A Rotrex is a traction-drive unit and must run exclusively on Rotrex traction fluid — which is why KraftWerks includes a dedicated supercharger oil cooler and HKS includes a traction-fluid tank, filter and cooler. Treat it as a real maintenance item, not a sealed box. The cogged drive belt is a consumable too; a KraftWerks replacement belt is $216.78 and is cheap insurance to keep on the shelf. Worth knowing for track cars: the cogged belt is strong enough that a seized blower can stop the engine rather than snapping the belt, which is why some hard-use owners deliberately fit a weaker ribbed-belt conversion as a fuse.

Suspension: 400 whp changes what the chassis needs

Doubling wheel horsepower on a 2,800 lb roadster exposes the stock damping quickly, especially on corner exit. A KW Coilover Kit V3 for the S2000 ($3,494.00) is the usual answer for owners who plan to use the power on track, with independently adjustable compression and rebound.

S2000 Supercharger Install: What the Instructions Do Not Tell You

KraftWerks markets the kit as a simple bolt-on with "no cutting, drilling, or welding," but real installs disagree in two specific places. First, the front center skid plate must be trimmed at the edges to clear the lower intercooler pipes. Second, the A/C condenser bracket has to be modified — owners unbolt the condenser, flip the mounting portion and flatten it so the condenser sits closer to the radiator. Skip that step and the condenser fouls the intercooler. The front bumper comes off, the cooling system gets drained, and the crank pulley drive adapter goes on.

There is no official labor-hour figure. Owner reports span 5 hours for an experienced crew to a shop quoting roughly 20 hours for its first one, so budget accordingly. Two more field notes from S2KI owners: buy spare T-bolt clamps and silicone reducers, since not everything you want is in the box, and on 2000–2003 AP1 cars inspect the banjo-bolt oil squirters and valve spring retainers before you add boost — cracked retainers are a known way to drop a valve on early cars.