Click to zoom in
SKU: KB-050-EJ-S
Kartboy Aluminum Crank Pulley EJ Engines - Alternator Belt with A/C Pump Delete
The Kartboy KB-050-EJ-S Aluminum Crank Pulley is the best lightweight underdrive pulley upgrade for Subaru EJ engines (EJ20/EJ25) with alternator belt drive and A/C pump delete setups. CNC-machined from high-grade billet aluminum, this pulley reduces rotational mass for quicker throttle response, faster revs, and small horsepower/torque gains while eliminating the A/C compressor load – ideal for track-focused WRX/STI, Legacy GT, Forester XT, or any EJ-series build where maximum performance and reduced parasitic drag matter, without retaining air conditioning.
Key Features
- Lightweight Billet Aluminum: Significantly reduces rotational inertia over stock pulley – quicker engine response
- A/C Pump Delete Design: Eliminates A/C compressor belt load for freed-up horsepower and cleaner engine bay
- Alternator Belt Compatible: Maintains alternator function with dedicated belt path – no electrical issues
- Precision CNC Machining: Perfect balance and fitment anodized finish for corrosion resistance and style
- Direct Bolt-On Fit: Uses factory crank bolt and timing marks no modifications required
- Kartboy Quality: Trusted Subaru performance brand reliable for street and track EJ builds
Specifications
| Specification | Detail |
|---|---|
| Part Number | KB-050-EJ-S |
| Material | Billet Aluminum |
| Finish | Anodized (Silver / Black Options) |
| Compatibility | Subaru EJ Engines (EJ20/EJ25) with Alternator Belt & A/C Delete |
| Installation | Direct Bolt-On (Uses Factory Crank Bolt) |
| Country of Origin | United States |
| Warranty | Limited (Kartboy) |
| Shipping Weight | Approx. 2-3 lbs |
Product Notes
- A/C delete pulley – removes compressor load for performance gains (A/C no longer functional)
- Underdrive design frees up horsepower noticeable throttle response improvement
- Recommended for track, autocross, or high-performance street builds not for daily A/C use
Installation Notes
- Estimated time: 1-2 hours, moderate difficulty, basic hand tools required
- Remove stock pulley, install Kartboy pulley with factory bolt, torque to spec, reroute alternator belt
- Professional installation recommended check timing marks and belt tension
This Part Fits
| Year | Make | Model | Notes |
|---|---|---|---|
| 1992-2021 | Subaru | Impreza WRX / WRX STI | EJ20 / EJ25 Engines (A/C Delete Setup) |
| 2004-2009 | Subaru | Legacy GT / Outback XT | EJ255 / EJ257 Engines (A/C Delete) |
| 2003-2014 | Subaru | Forester XT | EJ25 Turbo Engines (A/C Delete) |
| Various | Subaru | EJ Series Swaps | Custom Turbo & Performance Builds |
Why Choose Kartboy Aluminum Crank Pulley?
- Lightweight billet design reduces rotational mass quicker revs and throttle response
- A/C delete frees up horsepower ideal for track or performance EJ builds
- Limited warranty trusted Subaru-specific upgrade from Kartboy
Frequently Asked Questions
-
Q: Will this pulley fit my 2015 Subaru WRX STI EJ257?
A: Yes, Kartboy KB-050-EJ-S fits all Subaru EJ20/EJ25 engines with alternator belt and A/C delete setup. -
Q: Does it eliminate A/C completely?
A: Yes, designed for A/C pump delete; air conditioning will no longer function. -
Q: How much power gain?
A: Small gains (5-10 whp typical) from reduced parasitic drag most noticeable in throttle response. -
Q: What is the warranty?
A: Covered by Kartboy limited warranty built for performance.
Shipping & Handling
- Method: UPS/FedEx Ground
- Availability: In stock - ships same or next business day
- Packaging: Secure protective packaging
- Weight: Approx. 2-3 lbs
Engine
This engine parts collection covers oil catch cans, thermostats, thermostat housings, radiator components, coolant accessories, engine covers, fuse box covers, cap covers, throttle bodies, supercharger pulleys, idler pulleys, tensioner pulleys, and engine bay dress-up parts for trucks, SUVs, muscle cars, boosted builds, high-horsepower street cars, and performance vehicles that need better reliability, cooling, airflow, oil control, and under-hood styling. The collection is particularly strong for Dodge Challenger, Charger, Durango, Jeep Grand Cherokee Trackhawk, and Ram TRX platforms running 6.2L Hellcat, 6.4L HEMI, and 5.7L HEMI engines, where oil catch can and cooling upgrades address known OEM weaknesses in the PCV and thermal management systems. Import performance platforms including GM LS-based builds, Chevrolet Camaro, and Corvette applications are also represented through Mishimoto, CSF, and ZPE GripTec product lines. Builders who invest in engine bay organization and reliab...
View Engine Products
Pulleys
Welcome to our Vehicle Engine Pulleys collection, where you will find an extensive range of premium products tailored for automotive enthusiasts and professionals alike. Whether you're repairing, upgrading, or maintaining your vehicle, our collection offers pulleys that ensure efficiency and reliability. Why Choose Our Vehicle Engine Pulleys? High Performance: Engineered for optimal functioning under various driving conditions. Quality Materials: Crafted from durable materials to withstand wear and tear. Compatibility: Designed to fit a wide range of vehicle makes and models. Value for Money: Affordable options that do not compromise on quality. Types of Vehicle Engine Pulleys Available Crankshaft Pulleys Water Pump Pulleys Alternator Pulleys Timing Belt Pulleys Applications of Vehicle Engine Pulleys Our vehicle engine pulleys are ideal for various applications, including: Car repairs and maintenance Engine rebuilds and modifications Performance upgrades Restoration pr...
View Pulleys Products
Pulleys - Crank, Underdrive
Welcome to our exclusive collection of Pulleys - Crank, Underdrive Vehicle Pulleys. Engineered for performance and efficiency, these pulleys are essential for any car enthusiast looking to enhance their vehicle's capabilities. Why Choose Underdrive Pulleys? Improved Performance: Underdrive pulleys reduce the rotational mass, allowing your engine to rev up faster. Increased Horsepower: Experience a noticeable boost in horsepower by minimizing accessory drag. Enhanced Fuel Efficiency: Optimize your vehicle's energy consumption with these lightweight, high-performance pulleys. Featured Products Our collection includes a variety of crank and underdrive pulleys suited for different vehicle makes and models: High-Performance Crank Pulleys: Manufactured with precision to ensure durability and performance. Lightweight Underdrive Pulleys: Crafted from high-quality materials to reduce weight without compromising strength. Universal Fit Options: Designed to fit a wide range o...
View Pulleys - Crank, Underdrive ProductsLet customers speak for us
Looks pretty nice
Looks pretty nice, pricing was good and the reinforcement is a big plus.
Randy H.
Black Ops Auto Works
I emailed customer service to inquire about when it would be shipped
I emailed customer service to inquire about when it would be shipped. They checked and emailed me with the answer. Customer service is A1
Ralph J.
Black Ops Auto Works
Installation was easy
Installation was easy. The price is good and it looks great on the truck.
Ralph J.
RHO Small Grille Badge
Looks as good as it fits
Looks as good as it fits,
zachary d.
Seibon 70-73 Datsun 240Z OE Carbon Fiber Hood
Nothing like it
I love it great sound and response
Luis P.
Legmaker Dodge Durango HEMI Short Ram CAI 2011-Present 5.7L
Car totally diferent with the whole kit
Car totally diferent with the whole kit. Ive stood next to wide bodies and my car gets more attention at times . Ive bought the kit twice already.
Ding D.
2015-2023 Dodge Charger Carbon Fiber Wind Splitters
Fantastic emblem! Exactly what I was looking for
Fantastic emblem! Exactly what I was looking for. Great quality emblem.
Jacobus S.
Direct Connection Black Metallic Fender Badge
Worked great for my aftermarket hood on my Chrysler 2023 300C
Worked great for my aftermarket hood on my Chrysler 2023 300C. Thanks
Robert G.
Windshield Washer Squirter Relocation Kit Universal
Easy to install and makes car sound even better
Easy to install and makes car sound even better love the winn
Tracy H.
Legmaker Challenger/Charger Hellcat Demon & Redeye Air Intake
Awesome customer support
Awesome customer support. Had multiple issues with fedex and these guys were excellent in helping me sort everything out. The drop springs are great too! I highly recommend
Anonymous
Swift Spec-R Lowering springs Jeep Grand Cherokee 2011-2021
100/100! perfect CF crafted cold air intake for 6
100/100! perfect CF crafted cold air intake for 6.4 jeep .. even makes my AWE exhaust sound even deeper and you cam here this thing sucking when accelerating even at normal speeds🥶
srt.boizzz
Legmaker 392 TH Short Ram Jeep Grand Cherokee SRT 2012-2021
