How to Improve the Towing Performance of Gas Engines

by Richard Rowe
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Engine power may be crucial to towing performance, but focusing on peak horsepower alone is an oversimplification that could well ruin your hauler's towing capabilities. Two factors affect gas engine towing performance more than any other: torque across the RPM band and drive-train efficiency. An efficient transmission, drive shaft, axle and wheels can all reduce the amount of torque your engine must expend to move the vehicle, allowing it to commit more to moving the load.

Step 1

Install a cold-air induction kit with high-flow air filter and an aftermarket catalytic-converter-back (cat-back) exhaust system. These are two of the simplest and most common engine enhancements, and will allow your engine to produce higher horsepower and more torque at all RPM ranges. For turbocharged engines, a new down-pipe (which connects the turbo to the catalytic converter) will help your turbo to spool up quicker, maintain higher boost and run cooler for safe long-distance towing.

Step 2

Install a set of underdrive pulleys. An underdrive pulley set typically consists of a smaller crankshaft pulley and larger alternator, water pump and power steering pulleys to reduce accessory drive speed. This reduces the amount of torque required to drive the accessories, freeing up a bit more power to haul your load.

Step 3

Change your oil out for a race-grade full synthetic type. This seemingly minor modification will reduce the amount of power required just to spin the engine. Like the underdrive pulley set, synthetic oil reduces "parasitic drag" to increase engine efficiency and free up more torque for towing. Slippery synthetic oil will also reduce friction-induced heat buildup to increase engine longevity, and should last two to four times longer than conventional oil under towing conditions.

Step 4

Reprogram your stock engine control computer to enhance low-RPM torque and increase drive-train efficiency. Purchase an aftermarket "power tuner" that will allow you to play with variables like injection and ignition timing, air/fuel ratio, turbo boost and secondary cam engagement (for VTEC or equivalent systems). Slightly advance ignition timing, reduce air/fuel ratio (numerically higher), increase turbo boost and delay secondary cam engagement to widen your engine's torque band and increase towing power. Make your adjustments in small increments, and enlist the help of an experienced friend.

Step 5

Reprogram your transmission-control computer (using the power programmer) to delay shifting to a higher RPM and increase shift firmness. All automatic transmissions slip a little while shifting, which creates heat, reduces clutch life and decreases power transfer to the wheels. A firm, snappy shift at about 1,000 RPM higher than normal will allow you to fully exploit the engine's power output for increased towing power. As a side benefit, the transmission itself should last much longer between rebuilds -- especially if you do a lot of towing.

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