Do Underdrive Pulleys Save Horsepower?
Underdrive pulleys save horsepower by reducing parasitic losses created by the water pump, alternator and power steering pump. By spinning these accessories more slowly, you have 10 - 20 more horsepower available to the wheels.
Will Underdrive Pulleys Cause Overheating?
Your water pump is designed to provide ample cooling on hot days during extended idle. OEM engineers also provide a safety factor to account for pump wear, radiator scale build-up and debris in the radiator. Generally, if your cooling system is in good working condition our underdrive pulleys will provide plenty of cooling flow. If you have a marginal cooling system and sit at idle for extended periods in the summer heat, you may want to consider upgrading your cooling system when you add a set of underdrive pulleys to your engine.
Will Underdrive Pulleys Cause Alternator Charging Problems?
Just like with your water pump, the alternator is designed for the worst-case scenario which is at idle, so naturally you won't have issues at higher RPM's. As with your cooling system, Engineers have built in quite a bit of safety factor to account for cold weather, wear, long period of idle, etc. Your battery will continue to charge as long as you are spinning fast enough for the voltage regulator to work.
Will Underdrive Pulleys Cause Power Steering Problems?
Just like with your water pump and alternator, the power steering pump is designed for the worst-case scenario which is at idle. Generally, we do not see issues with power steering pumps running out of flow. If they were to have problems, the worst that will happen is that your steering power steering will slow down slightly at idle. The only time that would cause a problem is during high speed parallel parking maneuvers.