VIS To a newbie

ViT · 5th August 2012, 08:22

I'm really sorry to create a thread like this as I know the subject of the VIS and its motors has been done to death. But, after owning the 190 for just over a week, I'm trying to get a really good understanding of the system and how it works.

There are lots and lots of threads all over the net on the subject but not one thread explains what its for, and how to tell when its not working. To somebody who's on his first KV6 engine car, it's a minefield!

OK, so here are my questions:

1) Why does the KV6 have a VIS system? What's the point?
2) What is a balance motor, and what is a power motor?
3) Under what circumstances do these motors typically work? (For example, do they operate consistantly at specific engine speeds or are there other factors?)
4) How can I tell if one or both motors aren't working?
5) Is there a test kit on the market?

Thanks again, I'm really sorry to create a thread like this, but it's all little overswhelming for a new guy!

lovema75 · 5th August 2012, 08:40

I am hardly an expert myself, but basically they open and close valves inside the manifold to alter the airflow into the engine. In particular, by altering the distance the air flows, they basically create a variable length inlet tract.

As the v6 develops most of its power high in the rev range the low down torque would be limited, so the the motors operate the valves creating a longer air tract which boosts low down torque.

But an engine with longer inlet tracts for torque can't rev as well higher up the rev range, so the VIS motors operate the flaps in the manifold to shorten the air tracts and allow the engine to rev more freely at high speed. So it's a "best of both worlds" solution. Until it stops working.

Then while the engine will still run, its efficiency will be affected, it will be sluggish pulling away, and fuel economy can be badly affected.

Yes the club had a tester available for paid up members, and Stocktake is the guru on repairing them.

Rattling from your manifold is also a sign that the flaps inside are worn- the only cure is a replacement manifold.

The motors are controlled by the ECU operate at certain speeds and load conditions, with the balance valve effectively controlling the airflow between the 2 cylinder banks, sometimes making them breath as 2 3-cylinder heads or mixing the flow together. The power flaps (I believe) alter the length of the inlet tract and open at about 3000rpm, hence you should feel an extra surge about then.

Sorry experts if the above is drivel, please correct as needed.

SD1too · 5th August 2012, 08:43

Quote:

Originally Posted by ViT

1) Why does the KV6 have a VIS system? What's the point?

To smooth out the torque curve resulting in more consistent performance over the entire rev. range.

Quote:

2) What is a balance motor, and what is a power motor?

They're both basically the same technical design, with different physical layouts. They're a module containing an electric motor, two microswitches, a relay, and a small PCB. They operate the balance valve and power valves.

Quote:

3) Under what circumstances do these motors typically work? (For example, do they operate consistantly at specific engine speeds or are there other factors?)

Engine speed and throttle position.

Quote:

4) How can I tell if one or both motors aren't working?

Subscribe to the club and borrow the VIS actuator testing equipment.

Quote:

5) Is there a test kit on the market?

No.

Simon.

ViT · 5th August 2012, 08:46

THANK YOU

If the system relies on engine speed and throttle position, would it be a fair argument to make that if I'm gently squeezing the trottle and not planting it, i'm not likely to feel any surge of torque when the magic rpm thresholds are hit? (unlike a turbo system for example)

Quote:

Originally Posted by SD1too

Subscribe to the club and borrow the VIS actuator testing equipment.

Thanks for that encouragement and reminder! Done

How do I go about arrange the use of this?

Typhoon190 · 5th August 2012, 09:42

http://www.the75andztclub.co.uk/foru...ad.php?t=63063

Rocket · 5th August 2012, 10:05

Quote:

Originally Posted by ViT

THANK YOU

If the system relies on engine speed and throttle position, would it be a fair argument to make that if I'm gently squeezing the trottle and not planting it, i'm not likely to feel any surge of torque when the magic rpm thresholds are hit? (unlike a turbo system for example)

Thanks for that encouragement and reminder! Done

How do I go about arrange the use of this?

Try this

http://www.the75andztclub.co.uk/foru...0984&page=8#72

Which links to this
http://www.the75andztclub.co.uk/foru....php?t=38545#5

SD1too · 5th August 2012, 10:13

Quote:

Originally Posted by ViT

... would it be a fair argument to make that if I'm gently squeezing the throttle and not planting it, i'm not likely to feel any surge of torque when the magic rpm thresholds are hit? (unlike a turbo system for example)

Yes, I'd say that's a fair conclusion. Although if your balance actuator has failed, and the flap stuck (both common faults) you'll notice that normal acceleration becomes distinctly lacklustre at around 3,000 rpm.

Simon.

stocktake · 5th August 2012, 15:16

Quote:

Originally Posted by ViT

Thanks for that encouragement and reminder! Done

How do I go about arrange the use of this?

Get yourself to the midland Nano meet in around 4 weeks time (15th 16th Sept)

It's all free

Join us round the camp fire on Sat night, bring your tent if you can

. Get to know the cars and the people. I will have a look at your VIS motors for free at these meets.

See here

http://www.wolverhamptonnanomeets.com/last-meet.html

well over 30 cars on both days at the last one

ViT · 5th August 2012, 17:58

Quote:

Originally Posted by stocktake

Get yourself to the midland Nano meet in around 4 weeks time (15th 16th Sept)

It's all free

Join us round the camp fire on Sat night, bring your tent if you can

. Get to know the cars and the people. I will have a look at your VIS motors for free at these meets.

See here

http://www.wolverhamptonnanomeets.com/last-meet.html

well over 30 cars on both days at the last one

I'll be there! It will be a pleasure to meet you all

kaiser · 5th August 2012, 18:05

You are asking a really good question. Why it is there, I must say, I have no idea.

There are claims of improved performance, and reduced fuel consumption.

I got tired of my inlet manifold making my engine sounding like a bad diesel, so I opened the manifold and ripped the actuators and the butterflies out.

I have a far more responsive engine, and I guess the process has netted me about 20 hp, for free.

So indeed, why did they bother.?

I haven't got a clue.

5th August 2012, 08:22	#1
ViT Avid contributor Trophy Blue MG ZT 190+, Union Blue MG6 Magnette TSE and Orange Marmalade MG3 3Style Join Date: Dec 2009 Location: Tenbury Wells Posts: 191 Thanks: 17 Thanked 3 Times in 3 Posts	VIS To a newbie I'm really sorry to create a thread like this as I know the subject of the VIS and its motors has been done to death. But, after owning the 190 for just over a week, I'm trying to get a really good understanding of the system and how it works. There are lots and lots of threads all over the net on the subject but not one thread explains what its for, and how to tell when its not working. To somebody who's on his first KV6 engine car, it's a minefield! OK, so here are my questions: 1) Why does the KV6 have a VIS system? What's the point? 2) What is a balance motor, and what is a power motor? 3) Under what circumstances do these motors typically work? (For example, do they operate consistantly at specific engine speeds or are there other factors?) 4) How can I tell if one or both motors aren't working? 5) Is there a test kit on the market? Thanks again, I'm really sorry to create a thread like this, but it's all little overswhelming for a new guy! __________________ http://badges.fuelly.com/images/sig-uk/202608.png

5th August 2012, 08:40	#2
lovema75 This is my second home 75 Tourer CDT Join Date: Dec 2011 Location: Enfield Posts: 3,925 Thanks: 63 Thanked 431 Times in 237 Posts	I am hardly an expert myself, but basically they open and close valves inside the manifold to alter the airflow into the engine. In particular, by altering the distance the air flows, they basically create a variable length inlet tract. As the v6 develops most of its power high in the rev range the low down torque would be limited, so the the motors operate the valves creating a longer air tract which boosts low down torque. But an engine with longer inlet tracts for torque can't rev as well higher up the rev range, so the VIS motors operate the flaps in the manifold to shorten the air tracts and allow the engine to rev more freely at high speed. So it's a "best of both worlds" solution. Until it stops working. Then while the engine will still run, its efficiency will be affected, it will be sluggish pulling away, and fuel economy can be badly affected. Yes the club had a tester available for paid up members, and Stocktake is the guru on repairing them. Rattling from your manifold is also a sign that the flaps inside are worn- the only cure is a replacement manifold. The motors are controlled by the ECU operate at certain speeds and load conditions, with the balance valve effectively controlling the airflow between the 2 cylinder banks, sometimes making them breath as 2 3-cylinder heads or mixing the flow together. The power flaps (I believe) alter the length of the inlet tract and open at about 3000rpm, hence you should feel an extra surge about then. Sorry experts if the above is drivel, please correct as needed. Last edited by lovema75; 5th August 2012 at 08:48..

5th August 2012, 09:42	#5
Typhoon190 This is my second home MG ZT-T 190 Monogram Typhoon Join Date: Jan 2009 Location: Oxfordshire Posts: 4,716 Thanks: 328 Thanked 557 Times in 443 Posts	http://www.the75andztclub.co.uk/foru...ad.php?t=63063

5th August 2012, 18:05	#10
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	You are asking a really good question. Why it is there, I must say, I have no idea. There are claims of improved performance, and reduced fuel consumption. I got tired of my inlet manifold making my engine sounding like a bad diesel, so I opened the manifold and ripped the actuators and the butterflies out. I have a far more responsive engine, and I guess the process has netted me about 20 hp, for free. So indeed, why did they bother.? I haven't got a clue.