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Topic: Variable valve timing

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	Variable valve timing - Wikipedia, the free encyclopedia
		VVT allows the lift or duration or timing (some or all) of the intake or exhaust valves (or both) to be changed while the engine is in operation.
		Valve timing gears on a Ford Taunus V4 engine — the small gear is on the crankshaft, the larger gear is on the camshaft.
		Variable valve timing was the sole domain of overhead cam engines until 2005, when General Motors began offering the LZE and LZ4, pushrod V6 engines with VVT.
	en.wikipedia.org /wiki/Variable_valve_timing (954 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		Valve actuating mechanism as in claim 2 wherein a slot is formed in the control member and a slide includes a pin on the control lever and operatively engaging the slot, the slot being angled from a radial direction to provide the higher angular ratio in the low valve lift range.
		Valve actuating mechanism as in claim 6 wherein the biasing means is a spiral spring acting between an oscillating cam and the control member to draw the roller follower against the rotary cam.
		Valve actuating mechanism as in claim 10 wherein a slot is formed in the control member and a slide includes a pin on the control lever and operatively engaging the slot, the slot being angled from a radial direction to provide the higher angular ratio in the low valve lift range.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/08309.000217&ELEMENT_SET=DECL (3205 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		Valve timing is generally expressed as the location of the inlet open, inlet close, exhaust open and exhaust close points relative to the crankshaft position.
		Timing variation of the inlet or exhaust events is achieved by a combination of rotation of the sleeves and variation of the rotary valves'angular velocity during the cycle.
		A variable valve timing mechanism as claimed in claims 1 or 2 or 3 or 4, wherein said drive mechanism is operably connected to an electronic control unit which controls the angular velocity of said drive mechanism and hence the angular velocity of said rotary valve.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/92705.011206&ELEMENT_SET=DECL (9607 words)

	Technical Mysteries Unraveled
		Combining cam-changing VVT and cam-phasing VVT could satisfy the requirement of both top-end power and flexibility throughout the whole rev range, but it is inevitably more complex.
		Like VVT-i, the variable valve timing is implemented by shifting the phase angle of the whole camshaft forward or reverse by means of a hydraulic actuator attached to the end of the camshaft.
		Moreover, the variation is continuous across a wide range of up to 60°, therefore the variable timing alone is perhaps the best design up to now.
	www.ukcar.com /features/tech/Engine/vv/vvt_31.htm (722 words)

	Untitled
		Valve diameters are 32.0 mm (1.26 in) for intake and 27.5 mm (1.08 in) for exhaust, and their lifts are 9.3 and 8.4 mm (0.37 and 0.33 in), respectively.
		Valves are inclined at a wider angle of 43° for freer breathing through the upright intake ports.
		At 6000rpm, the ECU sends a signal to an oil control valve at the end of the camshaft that puts oil pressure behind a lock pin in the rocker arm, sliding the pin under the spring-loaded slipper follower, locking it to the rocker arm and forcing the arm to follow the high-rpm cam profile.
	www.lotusofscottsdale.com /elise_engine.html (1000 words)

	Reference.com/Encyclopedia/Variable valve timing
		VVT allows the lift or duration and timing (or all) of the intake or exhaust valves (or both) to be changed while the engine is in operation.
		The next big step was taken by Honda in the 1980s and 90s, where Honda began by experimenting with variable valve lift.
		BMW VANOS - Varies intake and exhaust timing by moving the fulcrum of the camshaft
	www.reference.com /browse/wiki/Variable_valve_timing (553 words)

	Halfbakery: Simple Variable Valve Timing (Site not responding. Last check: 2007-11-06)
		Variable valve timing is so baked, its burnt, but I have a slightly different way.
		Still, the idea of adjusting the timing by rotating the differential case might have advantages in that it would be easier to lubricate the gears inside a fixed (except for adjustment) differential case vs trying to get oil to those gears in a rapidly rotating case.
		I would think it would also be possible to vary valve timing by adding two idler pulleys to the timing belt, one on each side of the crankshaft pulley.
	www.halfbakery.com /lr/idea/Simple_20Variable_20Valve_20Timing (968 words)

	The Alliance of Automobile Manufacturers
		For example, because of torque demands for trucks (towing, load carrying, etc), technologies such as turbochargers, variable valve timing, and continuously variable transmissions do not yield the fuel economy gains possible in cars—and may not be applicable at all.
		For example, variable valve timing and cylinder deactivation both target the energy “pumping loss” that occurs as the engine “breathes” (that is, operates at a lower intensity).
		Variable valve timing alters the valve timing between high and low engine speeds and improves efficiency throughout the entire engine range.
	www.autoalliance.org /fuel/fuel_efficiency.php (1385 words)

	AutoZine Technical School - ENGINE
		Moreover, the variation is continuous across a wide range of up to 60°, therefore the variable timing alone is perhaps the most perfect design up to now.
		It used timing chain to vary the phase angle of camshaft, thus provided 3-stage variable valve timing.
		One well-known Porsche expert described the variable valve timing as continuous, but it seems conflicting with the official statement made earlier, which revealed the system has 2-stage valve timing.
	www.autozine.org /technical_school/engine/vvt_31.htm (972 words)

	New Tech - Variable valve timing
		In broad terms, big valves and extreme high-lift camshafts with substantial overlap of inlet and exhaust valves, while essential for top-end power, are not particularly compatible with a dawdle to the supermarket.
		Each pair of valves is opened by the third lobe, which has higher lift and opens the valves for longer.
		Instead, overlap is adjusted on the inlet cam using a new device called VTC (variable timing control) which, thanks to data from the engine management system, responds to load as well as speed.
	www.indiacar.com /infobank/ntech_valvetiming.htm (466 words)

	AutoSpeed - Variable Valve Timing
		The time that the valves open and shut is really optimised for only one engine speed - away from those rpm, fixed camshaft timing is a downer.
		Opening the exhaust valve when there is still some residual pressure in the cylinder allows some of these exhaust gases to escape before the piston starts its upwards stroke.
		So the exhaust valve shuts a little after the inlet valve opens, which in turn stays open a little longer than you'd initially expect it to.....and then you go back to the beginning of the process again.
	www.autospeed.com /cms/A_1606/printArticle.html (1081 words)

	ZX2 Racing.com : Variable Valve Timing
		Variable Valve Timing allows the point at which an engine's valves open and close to change with operating conditions - such as engine speed and throttle position.
		In addition to changing the valve timing with respect to the crankshaft, some systems also change the duration the valve is open and the extent to which it opens.
		Varying these parameters allows the engine to operate more efficiently at all engine speeds while maintaining drivability.
	www.zx2racing.com /pages/articles/vvt.htm (184 words)

	AutoZine Technical School - ENGINE (Site not responding. Last check: 2007-11-06)
		The timing of breathing, that is, the timing of air-intake and exhaust, is controlled by the shape and phase angle of cams.
		With Variable Valve Timing, power and torque can be optimised across a wide rpm band.
		In some designs, valve lift can also be varied according to engine speed.
	www.geocities.com /gkurka2001/CarTech/vvt_1.htm (361 words)

	Variable Valve Timing (VTEC)
		Variable valve timing has been developed, tested and put into production.
		This results in better fuel economy, and quicker response time when sudden application of power is required.
		At the same time docile handling qualities are retained for starting and slow running.
	www.firewall.ca /VTEC.html (635 words)

	Technology Summary - WARF: P97166US - Variable Valve Timing Actuator
		The invention involves a variable valve timing actuator that allows the opening and closing of engine valves to be variably and individually controlled without using a camshaft.
		This is done by (1) moving the spring seats in relation to the valve, thereby "charging" the springs in relation to the valve, and/or by (2) moving the valve with respect to the spring seats to "charge" the springs with respect to the valve.
		To hold the valve stationary when desired, a latch (e.g., a one-way clutch) is used to releasably fix the valve in place.
	www.warf.ws /technologies.jsp?casecode=P97166US (249 words)

	AutoZine Technical School - ENGINE
		Note that their dimensions are also different - the middle cam (fast timing, high lift), as shown in the above diagram, is the largest ; the right hand side cam (slow timing, medium lift) is medium sized ; the left hand side cam (slow timing, low lift) is the smallest.
		Therefore the left rocker arm, which actuates the left inlet valve, is driven by the low-lift left cam.
		Both cams' timing is relatively slow compare with the middle cam, which actuates no valve now.
	www.geocities.com /gkurka2001/CarTech/vvt_2.htm (620 words)

	1ZZFE Engine Details (Site not responding. Last check: 2007-11-06)
		The 2ZZ-GE is a new-generation engine used in the Celica GT-S and is equipped with a two-stage variable valve lift/timing system called VVT-L on both the intake and exhaust sides, combined with the VVT-i continuously variable intake-valve timing.
		Valves are larger in diameter, at 34.0 mm (1.34 in) for intake and 29.0 mm (1.14 in) exhaust.
		Not only varies timing according to engine speed, it also consider other conditions such as acceleration, going up hill or down hill.
	www.spyderchat.com /enginedetail.htm (786 words)

	Back Room: What's variable valve timing?
		Variable valve timing, or VVT, is a generic term for an automobile technology that allows the lift, duration, and timing (or all three) of the intake or exhaust valves (or both) to be changed while the engine is in operation.
		I don't know the specific manufacturers' technologies, but the simplest method (well, the one I remember!), is where you have a cambelt/chain (say vertically) as usual, but with movable tensioners which slide (say horizontally) to give a longer or shorter run of belt/chain on one side, and vice-versa on the other.
		F1 engines do not have electronically actuated valves, but they are operated pneumatically (removing the need for fragile valve springs), allowing them to run reliably at very high revs (up to 19000 rpm).
	www.honestjohn.co.uk /forum/post?t=28028 (805 words)

	Which Variable Valve Timing is better ? ? - Honda-Acura.net (Site not responding. Last check: 2007-11-06)
		Of those 3 VVt-i is probably the best because the variation is done in the head, not in the cam as is the case with VTEC and MIVEC reducding paracidic loss to wight in the valve train.
		The way I remember I tell the difference between variable cam timing and varible valve timing, is that vvt changes the actual lift and duration of the valves (as can be seen by the fatter lobes on a vtec cam).
		Instead the valves are pneumatically (or maybe hydraulically) actuated and their lift, duration and timing is all computer controlled.
	www.honda-acura.net /forums/showthread.php?t=34779 (1653 words)

	VWvortex Forums: Does the new 2.5 I5 have variable valve timing system?
		W8 on Passat have variable valve timing on the intake camshaft.
		In the most simplest of terms, yes the engine does have variable intake valve timing, but it is simply for emissions purposes, not performance enhancement.
		VVT-i continuously varies intake valve timing throughout the rev range by hydraulically rotating the camshaft relative to its drive gear.
	forums.vwvortex.com /zerothread?id=1989699 (1472 words)

	GM - GMability Advanced Technology: POPULAR MECHANICS Awards GM 3.9 V-6 For Breakthrough Technology (Site not responding. Last check: 2007-11-06)
		The engine is designed new from the block up and in addition to variable valve timing, incorporates a host of advanced, premium features, including a variable intake manifold, piston-cooling oil squirters, and an advanced 32-bit engine controller.
		The variable valve timing system incorporates a vane-type camshaft phaser that changes the angular orientation of the camshaft, thereby adjusting the timing of the intake and exhaust valves to optimize performance and economy, and helping lower emissions.
		In other words, the intake valves and exhaust valves are varied at the same time and at the same rate.
	www.gm.com /company/gmability/adv_tech/100_news/pop_mechanics_award_093005.html (423 words)

	Variable Valve Timing \| Advance Auto Parts (Site not responding. Last check: 2007-11-06)
		That meant, for example, that in a given cylinder, the intake valve(s) always opened at exactly the same point in the piston stoke, regardless of how fast or slow the engine was running.
		The reason that valve timing needs to change to match the engine's operating condition from moment to moment is due to the physics of air.
		Basic variable cam timing systems advance the whole cam, which means that the valves affected open sooner at high revs (good) but also close sooner (often not necessarily desirable).
	www.advanceautoparts.com /english/youcan/html/dsm/dsm20040901vt.html (677 words)

	Re: Automotive: Please explain Variable Valve Timing in curent practice.
		Early in the development of automobile engines it was realized that the timing of the ignition had to be different for easily starting an engine and for the smooth running of an engine at speed.
		Initially a manual ignition timing adjustment lever was provided for the driver to start the engine and then to readjust the ignition timing when the engine came up to speed.
		At the same time, to meet stringent emissions standards in the 1990s and beyond, engineers began to study the control of intake and exhaust valve timing.
	www.madsci.org /posts/archives/jun2000/962210758.Eg.r.html (794 words)

	My Ford 500 Why no variable valve timing?
		Variable valve or cam timing can add some power by making the engine breathe better but it does add cost, and complexity, and can add weight, increased parasitic losses, and size to the engine.
		The Five Hundred gets many of the benefits of variable cam timing, though not all, by using tuned split intake runners, and by using either the 6 speed o the the CVT which maximize effifiency.
		A more powerful 3.5 l engine with variable valve timing is due in about a year and a half, it uses a different casting technique for the block which should bring costs down considearbly.
	www.myford500.com /forums/viewtopic.php?t=157 (363 words)

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