Balance VIS problem

[Clickernick]

There is a graph around on here that shows all. Have a search under 'VIS' and it may surface!!
Basicaly, both closed under light pedal use right up to the 'top',,,, unless you gas the throttle to over 30 or so degrees from closed and/or take the revs over approx 3100 rpm, the power vis is also activated similarly but there is a differential of operation at the upper end dependant on rev range and throttle position under load.

To sum up, 'Floor' the pedal from rest, and both will activate so long as you have the foot to the floor!! (over 30 deg)

[rrobson]

Originally Posted by Clickernick

There is a graph around on here that shows all. Have a search under 'VIS' and it may surface!!
Basicaly, both closed under light pedal use right up to the 'top',,,, unless you gas the throttle to over 30 or so degrees from closed and/or take the revs over approx 3100 rpm, the power vis is also activated similarly but there is a differential of operation at the upper end dependant on rev range and throttle position under load.

To sum up, 'Floor' the pedal from rest, and both will activate so long as you have the foot to the floor!! (over 30 deg)

i understand the basic functions of the vis, but was curious to know the operation of the two motors. after cracking the back off my old manifold, i could clearly see how everything was linked regarding how all the valves work, what happen when each set is open/close etc, but simply wanted to know when each one did so. so thanks again for the explanation

[stocktake]

Just a note gents.

A VIS motor not connected to its flap can over run and jam, this is one of the reasons the testers are 9v. At full 12v chat they are known not to stop in time. The balance one is particularly prone to continuing round and round and round and round. quite confusing 1st time it happens . Where as the power one just jams and needs to be disassembled and either wound back by hand or take drive wheel out and reposition

[stocktake]

Originally Posted by rrobson

after cracking the back off my old manifold, i could clearly see how everything was linked regarding how all the valves work, what happen when each set is open/close etc,

[SD1too]

Originally Posted by Clickernick

Fraid not, wrong end of stick!! ...
Closes at higher rpm to shorten tract length to increase torque (runs as 2 x 3 cyl engines as regards air intake)

MG Rover's RAVE says exactly the opposite! I quote:

"At low speed the balance valve and the power valves are closed. This allows the engine to breathe as two, three cylinder engines each having a separate plenum and long primary tract. The primary and secondary tracts, and the plenum volume, are tuned to resonate at 2,700 rpm giving a torque peak at this speed.

For increased mid-range torque performance the plenums are connected together by opening the balance valve, while the power valves remain closed. This allows the engine to use the long primary tract length, which is carefully tuned with the balance valve, to produce maximum torque at 3,750 rpm (2.5 litre) and 4,000 rpm (2.0 litre).

At high engine speeds the balance valve remains open and the six power valves are opened. This allows the engine to breathe from the third plenum via the short primary tract lengths. These lengths and diameters are tuned to produce a spread of torque from 4,000 rpm upwards, with maximum power at 6,250 rpm (2.5 litre) and 6,500 rpm (2.0 litre)."



Simon.

[rrobson]

Originally Posted by SD1too

MG Rover's RAVE says exactly the opposite!



Simon.

so i could be right yet on the first generation v6 in the 800, it has a different manifold design, but that is how that works. iirc, the connect valve (balace on 75) opens first, then the balance (power on the 75) so both are open, then they both shut at high rpm. theres a vid on youtube but i cant think what its called.

Originally Posted by stocktake

as requested Mr D


for anyone who has not had the misfortune of trying to split open the 'inspection' pannel, this is what a duff manifold looks like inside (if you have split one, you will understand why inspection is in inverted commas)


under the manifold, brown linkage connects each buterfly by a ball joint


as you can see, it is not connected to any butterfly, which is why it was ratteling


when the power valve activated, it opens every one simutaniously when working properly


this is connected to the throttle body and splits into two chambers to feed each bank of cylinders


this is where the balance butterfly is located, and is either open or closed under normal operating (i have no boubt a debate will form now simon has made that contribution)

-the manifold has been left outside, which is why it is full of emulsified oil. when it was first removed, it was dark and not civered in bits of foliage

[stocktake]

It does comfirm that any up and down movement in the bar is wear of the joints.

[Clickernick]

This correct for the rover 800 kv6 but not ours on the 75. I have proved this by allowing the vis to operate externally so I could see the vis action for myself ( see post above)

the video on YouTube with the bod in a wine coloured jacket is referingbto the earlier kv6 design. You will notice he refers to MEMS engine management, the 75 uses Siemens, and we do not have connect valve either.

Originally Posted by SD1too

MG Rover's RAVE says exactly the opposite! I quote:

"At low speed the balance valve and the power valves are closed. This allows the engine to breathe as two, three cylinder engines each having a separate plenum and long primary tract. The primary and secondary tracts, and the plenum volume, are tuned to resonate at 2,700 rpm giving a torque peak at this speed.

For increased mid-range torque performance the plenums are connected together by opening the balance valve, while the power valves remain closed. This allows the engine to use the long primary tract length, which is carefully tuned with the balance valve, to produce maximum torque at 3,750 rpm (2.5 litre) and 4,000 rpm (2.0 litre).

At high engine speeds the balance valve remains open and the six power valves are opened. This allows the engine to breathe from the third plenum via the short primary tract lengths. These lengths and diameters are tuned to produce a spread of torque from 4,000 rpm upwards, with maximum power at 6,250 rpm (2.5 litre) and 6,500 rpm (2.0 litre)."



Simon.

[rrobson]

Originally Posted by stocktake

It does comfirm that any up and down movement in the bar is wear of the joints.

yes, that is a fact.

on mine, there was easily more than half an inch up and down movement, and as proven by the pics, it was well and truly dead. i think there were one or two still connected when most of the pannel broke free, but a closer look at the balls and cups, the balls are now far too small for the cups, and look more square than round, and the sides of the cups were ready to break off. if rover hadnt been so cheap, and made these components out of metal, or even put guides for the arm to run on, there would be very little manifold trouble.

[rrobson]

Originally Posted by Clickernick

This correct for the rover 800 kv6 but not ours on the 75. I have proved this by allowing the vis to operate externally so I could see the vis action for myself ( see post above)

the video on YouTube with the bod in a wine coloured jacket is referingbto the earlier kv6 design. You will notice he refers to MEMS engine management, the 75 uses Siemens, and we do not have connect valve either.

yes, was refering to the first gen v6. only problem is RAVE quotes both 2L and 2.5L v6's and there wasnt a 2L v6 in the 800 range was there? and even though the two manifolds are different, they work in a similar way. im not saying you are wrong, as you have clearly proven, but the theory would still be the same for both engines wouldnt it i mean if the engine produces more torque running as one engine rather than 2 three cylinder engines, then by closing the valve at 3000rpm, wouldnt it just follow the normal torque curve, rather than give the car a healthy boot up the back?