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.
04 There are two basic Mopar alternators: the 40-amp unit, which generally came with a sin
If your Mopar is a street car, we can’t think of any way to get around running an alternator on your vehicle. Since the alternator provides power for the electrical system while the car is running, and recharges the battery after starting, this item is pretty much mandatory unless your car is dedicated for drag racing. There are ways, however, to reduce the power it takes to spin your alternator such as an underdrive pulley, or by simply installing an alternator of lower amperage output. Most Mopars with a dual-groove alternator pulley are 60-amp units, and single-groove pulley alternators put out 40 amps. By installing the lower output alternator, less engine power is required to turn the unit, meaning more power to the rear wheels. We installed a 60-amp alternator on our big-block, and ran our engine on the dyno without putting any electrical load on the alternator. With the alternator free spinning (simulating a fully charged battery and no electrical equipment on), our alternator reduced peak torque by 1.9 lb-ft and peak power by 4.5 horsepower. Horsepower loss was greater because the cooling fins in the alternator require more power to spin as rpm increases. For this reason, average power loss was about 3 horsepower at 3,000 rpm, and increased to 4.5 horsepower at 6,000 rpm. With an electrical load applied (charging a battery, lights or other electrical equipment on) these numbers would certainly increase.
Most of us run an air filter on our engine, simply to keep the inlet air clean, and improve the life expectancy of our engine. Restricting the air coming into (or out of) an engine, can only reduce power, however, so the idea would be to have the least restrictive air filter possible for maximum power. With our big-block on the dyno, we ran the engine without any air filter, then with a three-inch paper element air filter, and then finally with an AirAid four-inch tapered high-flow air filter. Compared to running no filter at all, the three-inch paper element filter robbed our engine of 10.4 lb-ft of torque and 14.4 horsepower. With the AirAid high-flow filter the engine performed significantly better, only losing 5.5 lb-ft of peak torque and 5.9 horsepower at peak. And while you should certainly run your car’s engine with an air filter of some type installed, it won’t hurt most engines to remove the air filter assembly for an occasional blast down the quarter-mile.
05] We ran our big-block without an air filter, and then installed a standard open element
06] With an AirAid high-flow cotton element air filter assembly installed, torque was down
The engine oil is certainly the most important fluid in terms of protecting and lubricating your engine, and it can have a dramatic affect on performance as well. As a rule, you should always consider the manufacturer’s recommendations when picking engine oil, but a general rule of thumb is to use the thinnest oil possible that still gives adequate engine oil pressure. Pumping pressurized oil through an engine requires a significant amount of power, and to show this, we first ran our engine with 20W50 motor oil, and then changed the oil and filter using AMSOIL 5W20 engine oil. Using the thinner weight AMSOIL synthetic oil, our engine gained 12 lb-ft of torque and 16.4 peak horsepower. Torque and horsepower were up significantly throughout the rpm range of the engine and our oil pressure only dropped slightly from 80 psi to 75 psi during the dyno pulls. Be sure to consult your engine builder and take all of your engine’s parameters (such as bearing clearances), into consideration before choosing motor oil, but as our test shows, thinner oil definitely makes more power. And while 5W20 may not be right for your engine, you’re likely giving away significant power by running thick oil, such as the 20W50 we ran in our baseline dyno pull. (Editor’s Note: We do realize that there could be some confusion of using a non-synthetic to a synthetic comparison. This article was based solely on the end result of horsepower robbers. The discussion of comparing nonsynthetic and synthetic oils is something for another day).
07a] To test the difference that oil viscosity makes, we ran our engine with nonsynthetic
08] Of all our tests, the thinner engine oil made the biggest difference in power and torq
We hope this article helps put to rest some rumors, and gives you some hard numbers with regards to the amount of power robbed by engine accessories, air filters, and motor oil thicker than is necessary. What you decide is right for your Mopar is certainly your choice, but performance will be enhanced if you decide to run fewer engine-driven accessories, free-flowing (or no) air filter, and thinner engine oil. In total, our engine made 39 additional lb-ft of torque by eliminating the alternator, power steering pump, water pump, and air filter and using thinner engine oil. Horsepower was up an amazing 46.9 compared to the engine with the water pump, power steering pump, alternator, 20W50 oil, and three-inch paper element air cleaner. While an alternator and air filter are a must, changes such as using a lower amp alternator and a gauze-type, reusable air filter will definitely help. As far as changing your car from power steering to manual, that’s your call. And while you may not want to run your engine this way all of the time, it might be fun to pull the belts and air filter off, install thinner oil, and see what difference it makes in your quarter mile time. 46.9 additional horsepower is certainly enough to turn a low 13 second car into a high 12 second car, which earns the owner some bragging rights!
|Power Steering Pump
|Paper Element air filter
|High-Flow air filter
|5W20 oil vs. 20W50 oil