Diesel Tech: Variable Valve Timing

Mahle’s variable valve timing product aims to be a simple, robust, low friction design capable of functioning reliably over the life of the engine.

Variable valve timing (VVT) has yet to make a real impact on industrial diesels.  True, it finds limited use to achieve internal exhaust gas recirculation in the emissions reduction technology of one leading heavyduty diesel builder and another market leading diesel builder is rumored to have a camless engine running. But the technology has been common on passenger cars for some years now, where it improves both engine performance and engine emissions.

Recently, German engine component specialist Mahle GmbH presented its contending technology. In contrast to the hydraulic or hydromechanical valve timing adjusters on the market, including the improved two-stage valve stroke adjustment systems or the continuous adjustment system used by a number of up-market car builders, Mahle reports that it has aimed for mechanical systems that offer low production costs while matching the performance of competitive systems.

To this end the company is working simultaneously on several approaches, ranging from two-point stroke adjustment and continuous stroke adjustment to continuous variation of stroke and valve opening time. Functional testing of these systems has already been carried out and the first test in a complete engine took place in 2003, according to Mahle.

In addition to the adjusting function per se, Mahle reports that its product objectives also address aspects like simple, robust design, low frictional losses, reliable functioning over the entire service life of the engine and applicability in existing cylinder head designs. The system should also be suited to use on both diesel and gasoline engines on either the inlet or exhaust side, or both.

Following successful functional testing, one of Mahle’s new VVT systems is to be tested in cooperation with a leading engine manufacturer. At the time of this writing, market launch and series production would be possible in two to three years, the company states.

The Mahle all-plastic oil filter is part of a multifunctional module comprising the oil cooler, the oil feed to the turbocharger, major components of the crankcase ventilation system, a pressure control valve and temperature sensors for lube oil and cooling water.

Also at Mahle, the Automotive Filter Systems division has launched what it claims to be the world’s first oil filter made entirely of plastic. The first applications for Mahle’s new all-plastic oil filter are the Audi V-8 4.0L and V-6 3.0L common rail diesel engines and the company cites as product objectives reduced weight and lower cost of filter elements combined with significantly improved performance.

For example, the new filter is instrumental in a doubling of oil change intervals to 18,600 miles, and its materials are chosen to withstand temperatures of up to 302 degrees F and pressures up to 290 psi. In the applications cited, the all-plastic filter forms part of a multifunctional oil module that also contains the oil cooler, the oil feed for the turbocharger, major components of the crankcase ventilation system including a three-cyclone oil mist separator, a pressure control valve and several temperature sensors for lube oil and cooling water.

A further major development goal, the company states, was to position the filter to facilitate easy maintenance. On the Audi vee configuration engines, it is located upright between the cylinder banks where it also serves as a crankcase cover and can be readily accessed from above. An emptying system prevents oil fouling during maintenance work, Mahle states.