How much to fix KV6 inlet?

[Mgaz]

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

A guy on youtube has said

"i stripped my manifold removed every thing inside sealed and refitted it no performance/fuel difference and all for nothing" .

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?

[rrobson]

You'll loose torque in certain areas of the rev range by removing all the internals. It will certainly stop the rattle but will definitely affect day to day driveability. Unless of course the needle is always near the red line...

[Mgaz]

Originally Posted by rrobson

You'll loose torque in certain areas of the rev range by removing all the internals. It will certainly stop the rattle but will definitely affect day to day driveability. Unless of course the needle is always near the red line...

Loss of torque is what I guessed.
But by how much?

Are we really talking anything noticeable here?
Can anybody actually speak from experience?

Call me old fashioned, but I've owned/driven plenty of cars that don't have fancy inlet manifolds, and they are all perfectly drivable.

Also, surely the car will drive much better without VIS compared to an inlet with a faulty VIS?

If I was to make a total guess here, surely the power will still be pretty much the same, with the only noticeable difference being that there will no longer be the 'kick' you feel when the inlet VIS motors opens fully?

Basically, you lose the kick, but only because the power now gains in a more traditional manner.

Or am I totally off base here?

[trikey]

Originally Posted by Mgaz

Loss of torque is what I guessed.
But by how much?

Are we really talking anything noticeable here?
Can anybody actually speak from experience?

Yep I can, bluebirds V6 came with an inlet manifold that had been gutted by a previous owner, below 3000rpm it was flatter than a flat thing.

Get a decent inlet with working vis motors, still wont be fast by todays terms, but at least it will be as the factory intended.

[Mgaz]

Originally Posted by trikey

Yep I can, bluebirds V6 came with an inlet manifold that had been gutted by a previous owner, below 3000rpm it was flatter than a flat thing.

Get a decent inlet with working vis motors, still wont be fast by todays terms, but at least it will be as the factory intended.

Thanks for the input

So.. If I roughly understand this, With the throttle open between 40% and 100% the VIS valves are restricting air flow until the engine revs reach about 3k and above, at which point the VIS Valves open up and allow more airflow?

So removing the VIS valves causes the engine to 'bog down' with too much air and not enough fuel below 3k rpm. Is that correct at all?

So.. Purely out of curiosity, What If the ECU was remapped to deliver more fuel below the 3k rpm mark? (or fit larger injectors,) would this improve the 'flatness' that you describe?

Or am I off base again? Lol

And before anyone says it, Obviously the simplest solution would be to fix the VIS issue.

[SD1too]

Originally Posted by Mgaz

So.. If I roughly understand this, With the throttle open between 40% and 100% the VIS valves are restricting air flow until the engine revs reach about 3k and above, at which point the VIS Valves open up and allow more airflow? It is not a case of restricting airlow.

No, it's much more complicated than that Gareth. The VIS system 'tunes' the inlet tracts and is triggered not only by throttle position but by the rate of change of the throttle opening.

Have you begun with checking that the power VIS actuator is correctly meshed with the power valves operating lever? Have you checked that both actuators are working and that the balance flap isn't sticking mid travel? These are all very common occurances.

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.

[trikey]

Originally Posted by charlie 22

If you fit a second hand unit and swap the units vi's motors for your original ones do you need to t4 It?
Many thanks in advance
Chris.

Nope, plug and play for the vis motors.