How much to fix KV6 inlet?

[Mgaz]

Well.. I've had the vis motor off, the one at the highest point that sits flat . And the arm inside the manifold is totality loose. Doesn't feel like its attached to anything at all.

Its completely loose and floating around inside the manifold .

[kaiser]

As in so many other cases, you ask a question and get many varied responses!

As a good piece of advice, I suggest you pay attention to the people who have been there and done that, rather than armchair warriors giving advice from the comfort of their living rooms.
You know the expression, "expert"? that is the person that have made all the errors and learned from them.

But enough talk, here is some visual stuff, which normally is easier to digest. Should you be interested in some of the "science" behind it, look up my posts on the subject.

https://www.youtube.com/watch?v=hPyT...eature=youtube

if the manifold rattles, there is not much you can do about it, if the individual flaps, well- err flap!. Repair is possible, if you are skilled, but if I am going in there, make it simple, is always my motto. So out my flaps went, and simply put, the car went much better thereafter.

But draw your own conclusions.

[SD1too]

Originally Posted by Mgaz

... the arm inside the manifold is totality loose. Doesn't feel like its attached to anything at all.
Its completely loose and floating around inside the manifold.

The linkage does feel very light because it only operates plastic flaps. However, from what you have said it sounds as if it has broken. The solution is a replacement manifold chamber assembly. They come up for sale now and again.

Simon

[SD1too]

Originally Posted by kaiser

https://www.youtube.com/watch?v=hPyT...eature=youtube
But draw your own conclusions.

This video appears to show full throttle acceleration to the rev. limit. Does that prove that the VIS power valves are unnecessary? No it doesn't.

The VIS system is designed to smooth the torque curve over the entire range of engine revs. This makes the car more relaxing and responsive to drive without having to use excessive engine speeds. This video does not address this fundamental principle.

Also note that at the rev. limit the car is travelling at 103 mph. The published top speed of the 2.5 V6 automatic is 134 mph.

Simon

[Arctic]

Hi Daz.
Stick one of those two manifolds you have in the boot on, after as I suggested give them a good clean out with carb cleaner, then get them blew out with an air line to dry them that's quicker than letting them dry over a few days.

As you know I checked the ones it the boot and they both felt nice and firm so not an hard job to change over, but remember both your Vis motors are not working.

https://youtu.be/sa5jiUdAfxU

Trim the flap if it is sticking
https://youtu.be/gssAdwMMH0Y

[Mgaz]

Originally Posted by SD1too

The linkage does feel very light because it only operates plastic flaps. However, from what you have said it sounds as if it has broken. The solution is a replacement manifold chamber assembly. They come up for sale now and again.

Simon

OKAY.. so today I finally took the spare inlet manifolds out of the box they came in. In anticipation of my vis motors returning from stocktake.

I've pulled the linkage arm back and forth on both manifolds and one feels 'free-er' but seems to not move 100% totally smoothly, the other manifold feels a bit smoother but a little heavier to shift.

which one should I pick?

Because how strong are the VIS motors at pulling on the arms? Do the motors have plenty of guts to them? so a little resistance wouldn't be an issue?

Can I take off the bottom panel off the manifold and put some greese on the linkage? or will I encounter any problems taking it apart?

ALSO.. I Think I've detached everything I need to on the old manifold, but How the *beep* do I unbolt the rear part of the manifold?

[kaiser]

If you don't want to listen, you must make your own discoveries.
That's life.
https://www.the75andztclub.co.uk/for...ad.php?t=89142

[Mgaz]

Originally Posted by kaiser

If you don't want to listen, you must make your own discoveries.
That's life.
https://www.the75andztclub.co.uk/for...ad.php?t=89142

looking at your pictures, it looks as if some of the valves were attached/working and some weren't .

Did the arm still pull in and out and still feel un broken?

Im worried that there might be no way of knowing if ALL the butterfly are connected to the mechanism correctly on the replacement manifold.

?

[SD1too]

Originally Posted by Mgaz

which one should I pick?

I'm afraid that you'll have to make that decision Gareth. We cannot possibly advise without testing the two linkages for ourselves.

Can I take off the bottom panel off the manifold and put some greese on the linkage?

Not without cutting it open. It was probably high frequency welded when manufactured. You'd then have the problem of gluing it back together again. Besides, the whole point of using plastic was to avoid the need for lubrication but it gets it anyway due to engine oil being drawn into the intake system.

... but How the *beep* do I unbolt the rear part of the manifold?

There are two screws securing it to the RH cylinder head in the sparking plug region. You need to lift off the plenum chamber covers and remove the access panel in the bulkhead. Even then, they are very difficult to see. I'm pretty sure that this is covered in Haynes.

Simon

[egremont]

Originally Posted by Mgaz

If your KV6 has a rattle in the inlet manifold, how much is it to be fixed?

A guy on youtube has said

Is this an okay solution? Has anybody tried this?

Just trying to get an idea of how much trouble a VIS problem is going to be to put right.

I like the idea of removing the offending parts from inside the manifold. If that can be done?

If only the masters had allowed an aluminium inlet manifold. The 800 had one.

From what I have read, Rover designed the KV6 on the then present F1 engine technology.
The variable intake system is about getting the maximum volume of air into the cylinders at the critical time – when the inlet valves open to get the maximum power.

The engineers have to seek the best torque performance over a wide rev band – especially important for road cars that operate over a wide rpm range and this is why we have a variable intake system.

Cars without a variable intake manifold only have one power peak in its torque curve.

Through its variable intake manifold, the KV6 has expanded its torque peaks to four – thus increasing its power torque over a good part of its rev range. A second plenum is imbedded within the inlet manifold to assist in this objective. Granted not quite a flat “power curve” but on the graph that I have seen, all four peaks are above the “single torque curve” of a non- VIS engine – naturally aspirated engines. I read that power and torque gains of up to 30% have been achieved in some engines (as much as low-boost turbocharging achieves).

I guess that without a VIS system, engine designers have to make concessions that, to a point affect performance across the rev range.

The engines cycle is constantly affecting the engines airflow intake as the inlet valves shut off. This pressure wave (in the intake port) then rebounds back towards the plenum, lowering the pressure in the intake port. As the piston descends, and low pressure develops in the combustion chamber, a negative wave (being below atmospheric pressure) rushes towards the inlet valves. This wave when tuned properly has the potential to ram more air into the engine and improve the power. That is if this rushing pressure wave (of air) reaches the engine at the critical time - when the inlet valves open. That is the theory of varying the intake length to match the engines requirements and pressure waves.

If the incoming pressure wave “arrives” whilst the inlet valves are closed, this powerful pressure wave rebounds back up the inlet manifold towards the plenum, and the engine will only receive a portion of its potential intake. This will have a detrimental effect on the engines next cycle and those following.

Development work on VIS systems showed that engines could gain more than 100% volumetric efficiencies.