EXPERT REVIEWS

 

from Heavy Duty Trucking, May 1990, p. 142

PRELUBE SYSTEM CUTS ENGINE WEAR

To help extend engine life of truck diesels, make sure all moving parts have oil before starting the engine. Pre-Luber system developed by Lubrication Research Inc. eliminates dry starts which are said to be the cause of over 50% of engine wear.

The pre-lube idea has been used for years on race cars, large stationary engines and low-rpm marine diesels. Lubrication Research has adapted the technology to truck engines using a small, high-capacity 12-volt external pump to circulate oil throughout the engine before it starts.

The pump is mounted on or near the engine and connected by an oil line to the crankcase oil pan where it picks up oil and pumps it into the main oil gallery. From there it's distributed to all lubrication points-- rods, mains, camshaft, rocker arms, turbocharger, etc.

The pump is wired to the "accessory" side of the ignition switch. The driver activates the system and waits for pressure to register on the oil pressure gauge before starting the engine. Depending on the temperature, this can be as long as 20 seconds, according to Keith Johnson, the company's national marketing manager. An automatic timer is offered optionally to automate the pre-lubrication cycle.

An optional feature permits drivers to activate the pump for up to five minutes when the engine is shut down, providing oil to critical turbo bearings during turbocharger spin-down, Coked or scored turbocharger bearings are said to be one of the principal causes of turbocharger failures.

Turbochargers also fail prematurely from marginal lubrication at startup which is why drivers are cautioned never to race a cold engine. Turbos can spin at 50,000 rpm or higher before thick, cold oil reaches the bearings. The company also offers a "Turbo PreLuber" kit which prelubes only the turbo bearings rather than the entire engine.

According to Johnson, a secondary benefit of pre-lubrication is to fill newly changed oil filters before starting the engine.

 

Joe Craft, equipment superintendent for Great Valley Materials, a ready-mix concrete fleet in Devault, PA, disconnected the turbocharger oil line to show how much oil is reaching the turbocharger bearings when the "Pre-Luber" is turned on. Pump is rated at 1½ gallons per minute. System cuts engine wear by lubricating all moving parts before engine starts.

The prelubrication system can also be used in the shop to prime the entire engine following an overhaul.

As part of its ongoing product development program, Lubrication Research hired RC Engineering & Management Services Inc., Grand Blanc, MI, to compare bearing wear on two identical Chevrolet 5.7-liter gasoline V-8 engines, one with the pre-lubrication system, the other without.

All bearings were removed and measured before tests started. Engines were cold soaked to 0° F before starting, then run through a prescribed start/stop sequence.

Tests were run over a 10-day period until each engine had completed 650 coldstart cycles.

At completion, both engines were disassembled and engine bearings compared against initial measurements. The test report shows that connecting rod bearing wear on the prelubed engine averaged 37% less, main bearing wear averaged 11% less, and cylinder bore showed less scuffing on the pre-lubed engine.

 

 

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