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Topic: 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 (960 words)

	Valve timing control device for gas exchange valves on an internal combustion engine - Patent 5829398
		A valve timing device of claim 1 wherein the spring means (13) is a compression spring.
		A valve timing device of claim 2 wherein the spring means (13) is a compression spring.
		A valve timing device of claim 1 wherein the spring means (13) extends concentrically with a longitudinal axis of the camshaft (2) and annularly surrounds the gear sections (7, 10) of the adjusting piston (4).
	www.freepatentsonline.com /5829398.html (1850 words)

	B234F (16 valve) Timing Belt Replacement
		This means new timing and balance belts and a new oil pump bolt every 50k miles, and replacement timing belt covers, new tensioner, and shaft seals on a regular schedule.
		The timing belt used with the auto-tensioner is longer than the belt used with the manual tensioner.
		Based on observation, it would appear that the timing belt should be somewhere around 14 N (30 lbs-force) with the manual tensioner and closer to 18 N (40 lbs-force) with the auto-tensioner.
	www.vcoa.org /700-900-faq/B234Ftimingbelts.htm (5536 words)

	Replacing the Valve Seals in your 3.0 Liter Chrysler Minivan
		Because some of the valves and rockers are open and thus under compression, the rocker shaft assemblybolts must be removed a quarter turn at a time.
		Every time I connected the compressor air supply to the spark plug adapter (without concerning myself with the current cylinder's position,) the engine would spin a partial turn until that piston was at BDC.
		If you've lost distributor timing because the engine was moved when the distributor was out of the engine, and you're confident that you have maintained cam-to-crank timing, then you could do the crank and cam marks only and put the distributor in so that its rotor points at the "inside" #1contact.
	members.aol.com /ellsworthc/vs/ValveSeals.html (6189 words)

	Valve adjust and cam timing (Site not responding. Last check: 2007-10-11)
		Basically and in valve timing you must have the correct opening period at the right engine speed or the effect will be reduced Brake Mean Effective Pressure at the appropriate RPM ie peak.
		If they all are tight you have done all the valve clearances and you can reassemble it unless you want to check the cam timing too in which case skip the shim adjustments explained next and move on to timing.
		Or if they are small valve stem shims dig up a small piece of the cardboard in that spot with a screwdriver and stick the shim on it this holds all the shims in place whilst you shuffle.
	www.users.bigpond.com /jack_stands/motorcycle_advice/bike_servicing/adjust_valves.html (3224 words)

	phorum - 1 Steam Cars - Re: Valve timing (Site not responding. Last check: 2007-10-11)
		I speak of timing not lead because lead is the amount the valve is open at TDC and with poppet valves they are assumed to be fully open or closed.
		Flow resistance is higher with tandem poppet valves, and the valves still have to operate over twice as fast as valves in a 4-stroke IC engine at a given rpm.
		My valve system was worked out for the correct valve opening for early cut-off and the proper procedure followed for the design:- Valves designed, [single beat type] estimates for weights worked out for the valve trains, for accelerations on valve opening, inertia forces checked for acceptable design stresses.
	www.stanleysteamers.com /phorum-3.3/read.php4?f=1&i=1704&t=1691&v=f (5798 words)

	[No title] (Site not responding. Last check: 2007-10-11)
		Checking valve timing is too inaccurate at the standard tappet clearance, therefore timing values are given for an assumed tappet clearance of 0.4mm.
		The other valves may be checked in the same manner, comparing them against each other and the opening values given in the "Specifications." It must be remembered that turning the crankshaft contrary to the normal direction of rotation results in inaccurate readings and damage to the engine.
		If valve timing is not to specification, the easiest way of bringing it in line is to install an offset Woodruff key in the camshaft sprocket.
	www.autozone.com /servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/21/4d/1f/0900823d80214d1f.jsp (854 words)

	Timing Tutorial
		As slow as the valve opens and closes at the very beginning and end of its cycle, it would be impossible to find exactly where it begins to move.
		This is the lift at the valve as we said earlier.
		This means the lift at the lobe or the valve lift divided by the rocker arm ratio.
	www.compcams.com /Technical/TimingTutorial (2094 words)

	New Tech - Variable valve timing
		Concepts for both hydraulic and electromagnetic valve control may have broken out like a rash lately, but Honda’s VTEC (variable valve timing and lift electronic control) made its production debut in 1989 billed as the first system controlling both valve lift and 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.
	www.indiacar.com /infobank/ntech_valvetiming.htm (466 words)

	Halfbakery: Valve-timing "throttle" (Site not responding. Last check: 2007-10-11)
		This valve reduces the amount of fuel/air mixture that is drawn into the engine on each stroke, and thus reduces the amount of power produced.
		If the computer valves were wide open until the piston was 2/3 of the way down and then closed, the amount of air admitted to the cylinder would be the same as if the valve was open for the whole stroke but a throttle restricted intake pressure to 2/3 atmosphere.
		The valve does indeed waste large amounts of energy, but the airflow past it is sufficient to keep it cool.
	www.halfbakery.com /idea/Valve-timing_20_22throttle_22 (1745 words)

	UpToDate Timing of valve replacement in aortic stenosis in adults
		Although there is some lack of agreement about the optimal timing of surgery, it is still possible to develop rational guidelines for the evaluation and management of most patients [1,2].
		Distinguishing between these disorders is important because surgical correction of the valve lesion in pseudostenosis is associated with a high mortality rate and is unlikely to be beneficial.
		The factors determining the optimal time for valve replacement in aortic stenosis and the settings in which aortic balloon valvotomy might be considered will be reviewed here.
	patients.uptodate.com /topic.asp?file=valve_hd/3020 (621 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)

	VTEC
		At high rpm, the secondary intake valve rocker arm is connected to the primary intake valve rocker arm to allow normal valve lift, A synchronizing piston connects/disconnects the two intake valve rocker arms.
		Hydraulic pressure against a timing piston moves the synchronizing piston one direction, while a stopper piston and return spring moves the synchronizing piston back when hydraulic pressure is reduced.
		VTEC factoid-of-the-week: Valve timing change conditions that must be met include 5 km/h (3 mph) or faster and 60 degrees C (140 deg F) or faster.
	www.nsxprime.com /FAQ/Technical/VTEC.htm (1608 words)

	AE: Variable valve timing and lift from Honda
		At this time, the center power cam is sitting idly, and so is its rocker arm which is pressed against the cam by a lost-motion spring.
		The variable timing and lift system is adopted on both intake and exhaust.
		The valve spring retainer is forged from sintered and extruded aluminum-ceramic alloy whose ceramic content is about three per cent.
	dwolsten.tripod.com /articles/jan89b.html (511 words)

	AutoZine Technical School - ENGINE
		For instance, if the engine management system signals the valve at the green chamber open, then hydraulic pressure acts on the thin piston and push the latter, accompany with the cap, towards the camshaft, thus shift the phase angle forward.
		Continuous variation in timing is easily implemented by positioning the cap at a suitable distance according to engine speed.
		Like VVT-i, the variable valve timing is implemented by shifting the phase angle of the whole camshaft forward or backward by means of a hydraulic actuator attached to the end of the camshaft.
	www.geocities.com /gkurka2001/CarTech/vvt_3.htm (956 words)

	M130 Valve Timing - ShopForum (Site not responding. Last check: 2007-10-11)
		While inspecting valve clearances, noticed that when the cam timing notch is aligned with mark on cam support tower, crank timing reads 5-6 degrees ATDC.
		Timing chain does not appear to be stretched (chain is taut over top of cam sprocket) nor is cam sprocket worn.
		The process for checking the valve timing is not complicated, but requires a good understanding and good measuring tools.
	www.mercedesshop.com /shopforum/showthread.php3?t=6982 (854 words)

	Ferrari-Talk.com Home: 400i valve timing
		Can Timing has to be set with a degree wheel indexed at O on the flywheel.
		The marks on the caps are reference marks that allow one to quickly set all the cams in close to home so there is no chance of bending valves while the real "timing is checked useing the degree wheel and dail indicators.
		Once the factory assembler verified timing he etched a mark on the cam to reference the cap reference mark.
	www.ferrari-talk.com /cgi-bin/forum/show.cgi?tpc=5&post=8619 (234 words)

	Halfbakery: Simple Variable Valve Timing (Site not responding. Last check: 2007-10-11)
		Variable valve timing is so baked, its burnt, but I have a slightly different way.
		When the timing is to be retarded or advanced, the motor just needs to spin the worm gear one way or the other.
		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.
	www.halfbakery.com /idea/Simple_20Variable_20Valve_20Timing (800 words)

	Honda Worldwide \| July 5, 2005 "Honda Develops New 1.8l i-VTEC Engine"
		The engine employs an intelligent VTEC system that switches the valve timing for maximum efficiency during startup and acceleration to achieve powerful, torquey performance, then delays intake valve closure timing during cruising and other low-load conditions for improved fuel economy.
		Use of the valve timing control system results in off-the-line acceleration performance equivalent to a 2.0-liter engine, fuel economy approximately 6% better than the current 1.7-liter Civic engine, making it one of the world’s most efficient 1.8-liter engine designs.
		During this time, pumping losses are incurred due to intake resistance, and this is one factor that leads to reduced engine efficiency.
	world.honda.com /news/2005/4050705_a.html (469 words)

	VVT - Variable Valve Timing Basics by Auto Media
		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.automedia.com /drivesmart/dsm20040901vt/dsm20040901vt.asp?affid= (692 words)

	Checking Valve Timing and Clearance
		Normally the valve clearance should be checked or adjusted when the engine is cold at an outside air temperature of approx.
		Intake valves 0.10 mm (0.004 in) Exhaust valves 0.15 mm (0.006 in)
		Proper valve adjustment results in a well running engine only when the valves are seating well, the valve guides are not worn, and the valve stem ends are not pounded in or otherwise worn.
	www.hillmanimages.com /912/manual16.html (233 words)

	AutoZine Technical School - ENGINE (Site not responding. Last check: 2007-10-11)
		The timing of breathing, that is, the timing of air-intake and exhaust, is controlled by the shape and phase angle of cams.
		Without Variable Valve Timing technology, engineers used to choose the best compromise timing to design their camshafts.
		An ordinary sedan will adopt valve timing optimise for mid-range engine speed so that both the low speed drivability and high speed output will not be significantly deteriorated.
	www.geocities.com /gkurka2001/CarTech/vvt_1.htm (361 words)

	Howstuffworks "How Camshafts Work"
		VTEC (Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to have multiple camshafts.
		Closing the valve 20 degrees later is good, but it would be better to be able to increase the duration that the intake valve is open.
		For example, imagine that each valve had a solenoid on it that could open and close the valve using computer control rather than relying on a camshaft.
	auto.howstuffworks.com /camshaft6.htm (474 words)

	AutoZine Technical School - ENGINE (Site not responding. Last check: 2007-10-11)
		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.
		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)

	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)

	InsightCentral.net - Encyclopedia - Honda Insight Engine (Site not responding. Last check: 2007-10-11)
		Its design includes comprehensive weight-reducing and friction-reducing features which ensure fuel-efficient, environmentally-friendly operation.
		The engine employs a VTEC mechanism which maximizes running performance by optimizing the valve timing and lift at all engine speeds.
		Very precise control over fuel injection, a strong air-fuel swirl created in the combustion chamber, a new linear air-fuel sensor and lean-burn NOx catalyst allows the use of stratified-charge lean burn combustion technology.
	www.insightcentral.net /encyclopedia/enengine.html (322 words)

	Variable Valve Timing (Site not responding. Last check: 2007-10-11)
		This is a problem because many engines, such as an engine in an automobile, operate in a large range of speeds.
		The purpose of our proect would be to eliminate this compromise by changing valve timing relative to the engine speed and intake manifold air pressure.
		Because variable timing improves volumetric efficiency, smaller, lighter engines could be employed for the tasks that larger engines are currently used.
	www.messiah.edu /departments/engineering/projects/senior_design/abstracts/VariableValveTiming2000.htm (190 words)

	VWvortex Forums: Variable Valve Timing on the VW
		However, the intake cam timing helps with higher rpm efficiency and cylinder scavenging also.
		The intake cam has 3 lobes because there are 3 valves, the exhaust has 2 because there are 2 valves.
		Vtec uses an entirely different "high speed" cam lobe, so that duration, lift, and phasing can all be optmized to the top end, the downside it is is not progressive (its either on the low speed lobe, or the high speed lobe-although many people don't consider that a downside).
	forums.vwvortex.com /zerothread?id=2014557 (763 words)

	NASIOC - valve timing
		Flat Tapped-Adjusted on the stem of the valve w/ a screw and a locknut
		Shim and Bucket-Adjusted by chaging the shim that resides between the cam and the valve stem
		I gently revved a little with the throttle body and the sound is faint, but it is coming from the front of the engine, on the right side of the timing belt housing (or very close to).
	forums.nasioc.com /forums/showthread.php?t=108810 (1334 words)

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