- January 26, 2004
- Reaction score
- City, State
- Mechanicsville, Virginia
- Year, Model & Trim Level
- 2004 Acura TL
Note: This doesn't have to deal with Explorers, but is just a good way to understand how evolved the automotive world is becoming with computers.
Valvetronic is currently only available on the V-12 and the V-8 (7 series). It is a great concept in engine "breathing." It varies valve lift to such a great degree, that the intake valves efectively assume the function of the traditional engine throttle (it replaces the butterfly). Since intake air does not have to snake around the throttle - the engine delivers quicker, more spontaneous response to the accelerator pedal, along with high power output, more refined operation, excellend cold starting, and low engine friction.
The Valvetronic system has a conventional intake cam, but it also uses a secondary eccentric shaft with a series of levers and roller followers, activated by a stepper motor. Based on signals formerly taken mechanically from the accelerator pedal, the stepper motor changes the phase of the eccentric cam, modifying the action of the intake valves. Most accelerator pedals are no longer attached with a cable; they are now just sensors that will send the information to the computer (seen now on some Chevrolets).
The Valvetronic engine does not require a timing belt or chain. Valvetronic has its own computer housed in a separate unit away from the engine management system, networked with the digital engine management system incorporating a 40-megahertz, 32-bit computer.
-Valve lift is variable between 0 and 9.7 mm.
-Adjustment of the worm gear from one extreme to the other takes 300 milliseconds.
-Combined with double-Vanos valve timing technology, the camshaft angle relative to the crankshaft can be adjusted by up to 60°.
-The intermediate arm is finished to a tolerance of 0.008 mm.
-The cams controlling the eccentric shaft are machined to tolerances of a few hundredths of a millimeter.
-In Valvetronic engines coolant flows across the head, resulting in a temperature reduction of 60%.
-The water pump size is cut in half, reducing power consumption by 60%.
-The power steering fluid is warmed quickly, reducing the power used by the hydraulic pump.
-Mounting the water and power pump on the same shaft and a heat exchanger between coolant and engine oil reduces oil temperature by 30%.
The downside is that at above 6,000 RPM valvetronics effeciency drops quickly since stronger valve springs are required. The stronger springs create higher friction losses. Don't except to see the Valvetronic system on any M series vehicles produced by BMW.