Alternator

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.

Air Filters

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.

Engine Oil

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).

Summation

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!

Stolen Numbers
Accessory Peak Torque Peak Horsepower
Power Steering Pump 8.3 7.6
Water Pump 6.4 4.0
Alternator 1.9 4.5
Paper Element air filter 10.4 14.4
High-Flow air filter 5.5 5.9
5W20 oil vs. 20W50 oil 12.0 16.4