There are numerous ways to gauge an engine’s power, from using the manufacturer’s specifications, extrapolating numbers by estimating the benefit of aftermarket parts, using computer dyno software, or actually measuring an engine’s output on an engine or chassis dynamometer. One thing is certain though, when it comes to horsepower and torque, we all want more of it, and there are a variety of ways to achieve higher power numbers from our Mopar engines. Of course bolting on aftermarket parts is a proven (and expensive) way to achieve higher torque and horsepower, but did you ever consider improving your engine’s performance by simply eliminating one or more of the power-robbing accessories from the engine?
01] We know that engine accessories, the air filter, and thick oil take power away from th
The only real way to know if engine modifications equate to additional power is to either measure the engine’s output on a dyno, or to take the car to the track and see if it runs quicker elapsed times. And while the track is a fun place to test, there are certainly fewer variables involved with an engine dyno, so we prefer to use the dyno cell to measure gains or losses of power and torque whenever possible. We recently had a couple of big-blocks on the dyno at Auto Performance Engines to perform some tuning and testing of various parts, and since we had a little extra dyno time to spend with each engine, we decided to see exactly how much power it took to run the accessories like the alternator, power steering pump, and water pump, and we even tested a couple of different air filter styles.
Of course we all know that turning an alternator, power steering pump, water pump, or air-conditioning compressor robs an engine of power that could be transferred to the rear wheels, and restricting the air coming into the engine with a filter reduces power as well. Engine oils with high viscosity ratings will also require more power to pump through the engine. But without measuring the power it takes to spin these items, it’s anyone’s guess as to how much horsepower and torque each actually requires. We thought it would be interesting to measure the power and torque of an engine with, and without each of these accessories so we could put an actual number to each item.
02] The power steering pump we tested is a 1969 unit from a 383hp Road Runner engine. This
Most Mopars produced during the ’50s, ’60s, and ’70s were equipped with power-assisted steering, which consisted of an engine driven hydraulic pump, combined with a special steering box and valve. Of course, savvy car buyers who wanted the most power to get to the wheels, would opt for manual steering, but this option wasn’t generally a good one unless you wanted a real workout when parallel parking. Power steering adds weight to a car because of the engine-driven pump, and heavier, more complex steering box, and it also takes engine power to drive the pump. We bolted a power steering pump to a big-block we had on the engine dyno, just to see how much power it robbed. With the pressure hose bypassed to the return line (just as if the car were going straight with no assist), our engine lost 8.3 lb-ft of peak torque and 7.6 peak horsepower when turning the power steering pump. Average loss of torque was 6.8 lb-ft throughout the rpm range and average horsepower loss was 6.6. Remember that no matter how much power your engine makes, these numbers will be the same across the board. So if you want your Mopar to be easy to steer, you’ll either need to make this sacrifice or build a more powerful engine.
03] An engine-driven water pump takes power to turn. We ran our engine with the water pump
No matter how efficient your engine’s cooling system is, it relies on a water pump to push the coolant through the heads and block, and then to the radiator to be cooled. So while it would be impossible to run your Mopar without a water pump, there is the option of running an electric pump that doesn’t create parasitic drag on the engine’s crankshaft. There are plenty of electric water pumps on the market, and most pump plenty of coolant. An additional benefit of an electric water pump, especially for racers, is the ability to run the pump while the engine is shut down, for additional cooling between rounds at the drag strip. On the dyno, we ran our big-block with the engine driven water pump at a 1:1 ratio (same size crankshaft and water pump pulley), and then removed the belt and ran the pump with an electric motor. Our test determined that the engine driven water pump took 6.4 lb-ft of torque to turn at peak, and 4 peak horsepower. On average, the water pump cost 6.2 lb-ft and 3.9 horsepower throughout the engines effective rpm range. Remember that most Mopar engines actually overdrive the water pump (spin if faster than the crank), which would consume even more of the engine’s power.