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MG MGF Technical - VVC Units & Camshafts

I have dismantled the VVC unit from the camshaft.I have
been told they should have been locked together.
Any Tips.
Margaret Spiers

First tip, read all the information you can about something before wading in, ask the question before dismantling rather than after.

The reason you keep them together is because they are tricky to get back together requiring a high degree of synchronicity between the components. There is also a good chance that some debris may be introduced or one of the control blocks might be inserted the wrong way round resulting in later failure.

If you examine the mechs carefully you will see there are two mechanisms at different levels within the end assembly, each one drives a separate cam, each cam has a pin which engages into a sliding block within the mech which has a central hole, the sliding block must be in the correct position to allow the pin on the cam to engage, a certain amount of radial movement between the two cams will be required in order to facilitate this, be careful and dont force the situation. If the blocks have fallen out of the mech, then ensure that the flat sides bear up against the sides of the channel, rather thasn the curved sides. Keep evryhting scrupulously clean.

When aligning the two mechs together in the cam ladder, consult the manual to see how its done, its simple but you need to know how to do it.

Dave
Dave Andrews

You will know if you have assembled them correctly when you start up;-)As a matter of interest why have you dismantled them??
mike
mike

Dave many thanks for the info.I have worked on the K16 engine but not the VVC. You mentioned about a manual could you give me more details. Cheers Margaret.
Margaret

The manual in question is the official Rover workshop manual for the K series. There is no exploded view of the VVC mechs themselves, but there is data on how to align them in their initial unmodulated position.

I know a man, who knows a man (repeat ad Nas.) who has a copy of said manual on CD, he might be persuaded to make a copy.

Dave
Dave Andrews

There is some information, and a diagram on the following website:

http://members.tripod.com/~RoverSD_1/k-seriesvvc.html

Mick
M F Anderson

A bit OT, but I was wondering how this compares with the mechanism used in the Honda Prelude, and other Honda cars?

Cheers!
L Reid

The Rover VVC works by effectively offsetting the centre of rotation of the cam, this slows the cams rotation during the period that the valve is open which increases its duration and speeds it up when the valve is closed. This is done on an incremental basis so that the timing is infinitely variable between 220 and 290 degrees. Unfortunately this also slows the valve acceleration during the opening cycle and the lift is also fixed and quite low due to the limited loads the mechanisms can withstand.

The Honda system uses two distinct cam profiles which are used at different points in the rev range, the two valves in each cylinder are initially opened by a pair of conservatively timed cam lobes which utilise finger type followers to operate the valves. In between these two lobes is a third lobe with much more extreme timings and lift which runs on another finger follower which is initially not connected to anything, it simply idles when the VETEC is not actuated. When the VETEC actuates (at a particular RPM) a pin is forced out of the active finger followers into the central more agressive follower effectively locking all three followers together. From then on the more aggressive cam lobe controls the opening and closing of the valves giving a large increase in torque and allowing better VE at higher RPM. This is not a continuously variable system but more of a switch from conservative timing to aggressive. Both cam duration and lift are altered.

Dave
Dave Andrews

Thanks for the info Dave!

Leigh
Leigh

I saw this available on ebay ... nothing to do with me but might be useful.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=18429&item=2409581758&rd=1

Mahatma
A Richards

This thread was discussed between 02/04/2003 and 06/04/2003

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