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(Post Link) post #1 of 12 Old 16-02-08 Thread Starter
Status: R.I.P Allan Simonsen
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n00b alfa question - variator....

i hear about something called a variator on the alfa twin spark engines, as i'm looking at buying a 147 2002 - 2003, hopefully the 2.0 is it something i need to check and how do i check it?

the car will be getting a cam belt change regardless of mileage as soon as i buy it, but i'm struggling for info on the variator...
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Re: n00b alfa question - variator....

Just get the variator changed with the cambelt, ay an extra £100.00 or so. Its good practice.

If you start the engine from stone cold it rattles like a diesel for a few seconds if its on its way out.

Most people change them with the belts to be on the safe side.

Also get the tensioner and the balance belt swapped too Phil.
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(Post Link) post #3 of 12 Old 19-02-08 Thread Starter
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Re: n00b alfa question - variator....

i plan to take the car straight to Northants Alfa for a full service as soon as i buy it, that includes the variator.
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Re: n00b alfa question - variator....

I expect you've read up on the cam belt issues, but get the belt & tensioners done at least every 36K or I think 3 years (but check that). Ignore what the service book says as it will probably say 72K. As far as the variator is concerned it's prudent to change at the same time as you have to remove the cambelt to get to it (I understand). Therefore if it needs doing between belt changes you'#ll end up with an early belt change! A good independant should do the whole job at a reasonable charge. I paid about £ 450 for 72K service, belts, tensioners, variator, rear torsion bars & a few other bits (didn't need plugs as they were done at 60K)
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Re: n00b alfa question - variator....

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Originally Posted by cj romeo View Post
Just get the variator changed with the cambelt, ay an extra £100.00 or so. Its good practice.

If you start the engine from stone cold it rattles like a diesel for a few seconds if its on its way out.
What does the variator actually do? What are the implications of it going? My 145 does sound a bit diesel like on a cold start for about two seconds despite having had the belt done at 40k.

Worried now....
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Re: n00b alfa question - variator....

Hi

I am also interested to find out what the impact of not acting on this would be; I've just bought a 156 2.O TS SW and I've noticed she sounds a bit like a diesel on start up; didn't notice it when i bought her but I sure do now. My belts were done 20k miles/2 years ago so I was hoping to hold out for another year. Will this be an option or am I going to find myself with bigger problems if I try and live with it?

cheers

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Re: n00b alfa question - variator....

the variator adjusts the valve timing on the inlet. why is that good? variable valve timing gives you the best of both worlds in terms of low rpm torque and high rpm power.

the variator works by moving the cam pulley when oil pressure (rpm) gets high enough to force the variator against its spring. as the oil pressure (rpm) drops the variator is pushed back into the low rpm position by its spring.

how does a moving cam pulley adjust valve timing? when the pulley moves it effectively changes the position of the pulley on the timing belt, closer or further away from the crank pulley, that will advance and retard the time at which the valves open and close in relation to the crankshaft.

the default position is set for low rpm torque, as most engines are, however this means at high rpm the intake valves close before the total requirement of air is able to enter the cylinder, that means a power loss, but the variator makes sure the inlet valves close later, allowing more air to enter.

why dont they just have it so they close later all the time? at lower rpm this would cause scavenging where unburnt fuel and air enter the exhaust, killing torque & reducing mpg.

when the variator fails it is almost always its spring that snaps (it can be replaced seperately to save a few quid ). this means the variator will stay in the high rpm position, which leads to scavenging at low rpm.
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Re: n00b alfa question - variator....

Nice clear explanation

cheers jug
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Re: n00b alfa question - variator....

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Originally Posted by jug View Post
the variator adjusts the valve timing on the inlet. why is that good? variable valve timing gives you the best of both worlds in terms of low rpm torque and high rpm power.

the variator works by moving the cam pulley when oil pressure (rpm) gets high enough to force the variator against its spring. as the oil pressure (rpm) drops the variator is pushed back into the low rpm position by its spring.

how does a moving cam pulley adjust valve timing? when the pulley moves it effectively changes the position of the pulley on the timing belt, closer or further away from the crank pulley, that will advance and retard the time at which the valves open and close in relation to the crankshaft.

the default position is set for low rpm torque, as most engines are, however this means at high rpm the intake valves close before the total requirement of air is able to enter the cylinder, that means a power loss, but the variator makes sure the inlet valves close later, allowing more air to enter.

why dont they just have it so they close later all the time? at lower rpm this would cause scavenging where unburnt fuel and air enter the exhaust, killing torque & reducing mpg.

when the variator fails it is almost always its spring that snaps (it can be replaced seperately to save a few quid ). this means the variator will stay in the high rpm position, which leads to scavenging at low rpm.

best explanation i have read.

nice one
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Re: n00b alfa question - variator....

Good explaination jug. Thhe oil seal inside the Variator also fails, this allows the oil to leak out back into the engine when the engine is stopped, hence the rattle when you start the car until it has filled back up.
When the seal gets really bad it will rattle all of the time, and you will have no variable valve timing, because just as Jug says it operates on oil pressure.
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(Post Link) post #11 of 12 Old 21-02-08 Thread Starter
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Re: n00b alfa question - variator....

ahh, thanks for the excellent explanation, that makes total sense..

the service i plan on doing will be the full 72k service, regardless of if it needs it or not, that includes the variator.

my rather sick mustang is going to an American car specialist in Birmingham tomorrow to have everything sorted, as soon as its back its on ebay, and in auto trader..

anyone want a 96 mustang 3.8? £4k takes it!!
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Re: n00b alfa question - variator....

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Originally Posted by philoldsmobile View Post
anyone want a 96 mustang 3.8? £4k takes it!!
no thanks, british roads have corners so it isnt really suitable
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