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Bmw variable valve timing8/14/2023 ![]() BMW did not put a sensor on the cam sprocket itself and another on the camshaft. To verify that the requisite cam twist has actually taken place, the DME monitors sensor inputs. These are available through your local BMW dealer’s parts department. When installing the variable valve timing actuators on Double VANOS, you’ll need these special tools to properly set the gear depth position. Poor performance, MIL-on, and noise are typical symptoms of something gone awry in the system, and electronic troubleshooting will probably be the first thing you think of. ![]() Scope and scanĪll generations of VANOS are big contributors to the superior performance characteristics of BMW vehicles, but, just as with everything else automotive, stuff happens over time, which brings us to the art of diagnosis. ![]() Everything from a weak pump to loose engine bearings should be taken into consideration if psi is below specs. It adds complexity, but enhances power output and efficiency.Īs you can easily imagine, all VANOS systems require high and steady oil pressure for adjusting the camshafts quickly and accurately (any time lag may set a code). This system advances the intake cam and retards the exhaust cam through a range of up to 40 crankshaft degrees for the former, and 25 degrees for the latter. Doubleĭouble VANOS was the next evolutionary stage of BMW variable valve timing. As we said, this original system is either on or off. ![]() At 5,000 rpm and up, valve timing is again retarded for maximum cylinder fill. As rpm rises, the DME applies the hydraulic pressure that pushes the gear, twisting the camshaft and providing 12.5 degrees of advance for improved response and extra efficiency. In other words, the cam is twisted slightly from its static position with regard to the crankshaft.Ĭam timing is retarded with the engine off, at idle, and just above, which contributes to smoothness and helps get the cat hot quickly. When engine oil pressure is applied to this mechanism (as controlled by the DME through a one-wire solenoid valve), it moves the gear axially against a spring, changing the positional relationship between the sprocket and the shaft. The basic mechanical principle at work here begins with a cam-drive sprocket that engages the camshaft itself through a helical or spiral gear. It only featured two phase changes, but allowed for a combination of smooth idle and improved mid-range and top-end power. The first VANOS unit, which debuted in ’92, has one helical-gear mechanism for advancing the intake cam. This is a separate system that we’ll cover in a future issue of the bimmer pub. In many models beginning in 2001, it’s used in conjunction with VANOS for the most efficiency and power imaginable. It uses a fast-acting (300 milliseconds for full range!) mechanism controlled by a dedicated module to dynamically alter valve lift profoundly enough to allow for the elimination of the traditional throttle and its attendant pumping losses. NOTE: Valvetronic is BMW’s variable valve lift system. This evolved into the much more sophisticated Double Vanos, which not only adjusts the timing of both the intake and exhaust cams, but does so in an infinitely variable manner. The original version, introduced in 1992 on the M50, operated on the intake camshaft only, and had just two phase-change points. This situation was the impetus for the introduction of VANOS (a somewhat implausible abbreviation of the German variable Nockenwellensteuerung), BMW’s name for its highly-accurate variable valve timing system. How about if you could make this dynamic with valve timing changes occurring when appropriate? Combined with separate adjustments for the intake and exhaust cams of a DOHC engine, the potential improvements in power output, efficiency, and idle smoothness become very dramatic indeed. ![]() But, obviously, you have to choose one or the other, and, with single-cam designs, intakes and exhausts are equally affected, which isn’t anything like optimal. Having the valves open and close earlier gives better low‑end and mid‑range output, while the opposite contributes to increased power as you near redline. A variation on this is the offset bushing used for pin-drive‑type sprockets. If you’ve ever built an old-fashioned pushrod V8 engine for high performance, you might be familiar with a little item called an “offset cam drive key.” This is basically just a Woodruff with a step in it that indexes the sprocket to one side or the other of its slot in the nose of the camshaft, allowing you to advance or retard valve timing as you see fit to shift the power curve up or down the rpm scale. ![]()
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