What's an underdrive pulley?

An underdrive pulley is a replacement pulley that bolts up the same as stock, but has a different size (ratio) and material specifications intended to free up lost horsepower. By increasing the diameter of each accessory pulley and decreasing the size of the crank pulley, the speed at which the accessories are turning relative to engine RPM decreases.

Under drive pulleys do not add power to the engine, they free up the power that is normally wasted on overdriven accessories. The theory is that a larger pulley will drive the accessories slower thus reducing their parasitic horsepower loss. No more power total, but more power sent to the wheels. As an additional benefit, the reduction in wear (less usage) on the accessories due to the lower duty cycles can extend the life of these parts.

For example, the alternator, power steering, water pump and air compressor rob horsepower from the engine. By replacing factory-sized crank balancer/pulley and water pump drive pulley with a resized pulleys, the accessories are slowed, resulting in more horsepower available to the drive wheels.

MOTOBLUE™ H.O. Series pulleys will increase horsepower up to 14 RWHP, and increase mileage by 2 to 3 MPG. MOTOBLUE H.O Pulleys are manufactured from billet steel, exceeding factory quality and are the only Pulley system available on the market today that use a new replacment balancer.

Installation: The kit includes all required components and hardware for a complete installation.
Tech Notes: Use of Harmonic Balancer Puller tool required for factory Harmonic Balancer removal.

Above images in order from left to right;


1. 99-04 3.8L V6 stock dampner verification.
   
   
2. 99-04 factory harmonic balancer image.
   
   
3. MOTOBLUE™ H.O. 42% reduction crank pulley, harmonic balancer.
   
   
4. MOTOBLUE H.O. Pulley Kit will not effect charging system

Proof Positive the MOTOBLUE H.O. Pulley Kit will not effect your charging system.

INDEPENDENT TEST RESULTS:


• MOTOBLUE H.O. Pulley Kit Installed
  1. Engine running everything else off: 13.8 V @ idle (750 RPM) ... 14.06 V @ 2500 RPM
  2. Add A/C (low blower speed): 12.55 V @ idle ... 13.94 @ 2000 RPM
  3. Add Rear Defrost: 12.11V @ idle
  4. Add Stereo w/amp (low vol): 12.05 V
  5. Add Headlights (low beams): 11.83 V
  6. All above @ 2000 RPM: 13.65 V
  
  
  Note: idle voltage requirment ... 12.00 V

MOTOBLUE™ H.O. PULLEY KIT
• MOTOBLUE™ H.O. Water Pump Pulley
• MOTOBLUE™ H.O. Power Balancer Pulley Kit
• Correct GOODYEAR Gatorback Belt
• Adds up to 14+ RWHP(up to 4% fuel economy)

MOTOBLUE™ H.O. PULLEY KIT
• SFI Approved Power Pulley Kit
• 25% Reduction Replacement Balancer Pulley
• 5% underDrive Water Pump Pulley
• 8% Alternator Pulley
• Correct Replacement GoodYear Belt

* When ordering crank pulley on 2000 mustang v6, check stock blancer design.

5% Billet underDrive Water Pump Pulley
Adds up to 2.6+ HP

Replacement GOODYEAR Gatorback Belt
• For use with ALL MOTOBLUE™ Pulley Kits
• View image on left of this page for validation
• Click-On image at left of this page for larger image