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Old 11th January 2018, 20:47   #1
Mgaz
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Default How much to fix KV6 inlet?

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

A guy on youtube has said
Quote:
"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?
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Old 11th January 2018, 21:23   #2
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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...
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Old 11th January 2018, 22:10   #3
Mgaz
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Originally Posted by rrobson View Post
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?
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Old 11th January 2018, 22:17   #4
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Quote:
Originally Posted by Mgaz View Post
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.
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Old 11th January 2018, 23:01   #5
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Quote:
Originally Posted by trikey View Post
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.
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Old 12th January 2018, 08:33   #6
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Quote:
Originally Posted by Mgaz View Post
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.

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Old 12th January 2018, 08:54   #7
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Originally Posted by SD1too View Post
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
well, the thing is, I am interested in buying a car with the rattle.

But its a few hours away, so i can't check any of those things.

Just trying to work out if Im going to be able to fix it. As it is £500 for a new inlet by the looks of it.
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Old 12th January 2018, 09:12   #8
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Hi Mgaz,

I posted a load of info on this a number of years ago, all from my personal experience on my 75 V6 auto. I tried duff rattley manifold, striped out manifold with nothing in it and a brand new manifold with new vis motors.

The stripped manifold did provide a boost in power at foot down high end of the rev range BUT for my daily commute in to London the lower end of the spectrum lost torque and driveability and it had a negative affect on fuel to. I think on issue is that people who strip out the internals tend to be comparing to an already duff manifold.

My preference was by far for the fully working manifold although at £480 it was painful!

I also did a full test of with and without oil catch tanks, on mine the manifold I fitted at new after testing is still going at 200K without catch tanks, the original was changed at at around 30k ish (10k after I got the car.) when I fitted full twin catch tanks, this manifold was dead in 40k miles ( this is when the testing and playing was done as I was reluctant to pay for another manifold after just 2.5 years.) eventualy I put the new manifold on and removed catch tanks and all has been well since.

Car Lives with my dad now.

Regards

Richard
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Old 12th January 2018, 23:45   #9
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Mg ZT kv6 inlet rattle: https://youtu.be/4KAfGcOL81M

This is the video I was sent of the rattle from the inlet manifold.

Any opinions welcomed as to how serious it sounds or not..

Apparently the car still drives nice and still pulls well above 3k rpm.. And performance is comparable to his other mk2 v6 zt.

Hopefully the manifold problem isn't too bad?

What do you guys reckon?
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Old 13th January 2018, 00:23   #10
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Originally Posted by SD1too View Post
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.

Simon
So.. No chance on the idea of a live remap on a gutted inlet manifold to try and compensate for the loss of drivability under 3k rpm? Has this approach been tried at all?
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