Variator redesign?? - Page 2 - Alfa Romeo Forum
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Re: Variator redesign??

Originally Posted by norbert
Thats not strictly true, the Variator not functioning correctly will affect performance, particularly above 5k revs.


The variator is called into action on low and medium revs, to provide extra torque. It's not in use in high revs at all!!!

Transcription from eLearn Workshop Manual:

Timing variator
Controlled directly by the fuel injection control unit, the purpose of the timing variator is to vary the timing of the inlet valves in accordance with the engine load and required rpm.


When the closed stage is required (idle speed and maximum power zone), the solenoid (1) is de-energized, so the slide valve (2), pushed by the return spring (3), remains raised, preventing the oil coming from the duct (A) from reaching the variator.

In this case the timing of the inlet valves remains unchanged (closed).


When the open stage is required (medium rpm with high torque). The solenoid (1) is energized, thus pushing the slide valve (2) downwards.

In this position, the oil coming from the duct (A) enters the chamber (B) of the piston, and from here, through a special hole, goes into the duct (C) in the piston.

The oil can only emerge from this duct through the top hole (in communication with the delivery pipe (D) to the variator), since the bottom hole, as the slide valve (2) has lowered, is not in communication with the discharge pipe (E).

The oil passes through the duct (D) and (F) and reaches the chamber (G), pushing in an axial direction towards the engine the piston (4), which comprises outer helical teeth, forcing it to rotate clockwise.

Its rotation is transmitted via a straight-teeth splined profile to the pinion (5) which, screwed onto the threaded end of the camshaft (6), transmits rotation to the camshaft, thus varying by 25° engine the timing of the inlet valves.

When the solenoid is de-energized, the slide valve (2) returns to its initial position, cutting off the flow of pressurized oil to the piston (4), but allowing oil to return to the discharge, thanks to the force of the return spring (7).

The duct (D) lubricates the camshaft journal in the various operating conditions.

The oil which leaks into the chamber (H) of the solenoid is discharged through the drain duct (E).

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Last edited by LEO175; 26-12-06 at 23:08.
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Re: Variator redesign??

That seems to say that the variator opens the valves more at higher revs to give better torque, thus a failed one (ie. one where the teeth were worn) would open the valves less and thus the power would be less.

Am I right about that? thats how it reads to me.
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Re: Variator redesign??

I'm afraid you are not reading right, Rob...

"When the open stage is required (medium rpm with high torque)."
"...transmits rotation to the camshaft, thus varying by 25° engine the timing of the inlet valves."

So, it works at medium revs (somewhere near 3-4krpm...), not at high revs...

The purpose of it is to assure good torque without compromising good power.
Normally, the more torque you have, the less top power you get and vice-versa.
That's why a Honda Type R has 200bhp, but poor torque at medium revs, for example...
The variator helps contradicting that rule... it gives torque, not power...

A worn variator would have some slack on the inner gears, but it would be very difficult for that slack to be big enough to affect it's action at the point you could notice it... and in that case it should make a hell of a noise, permanently!!!

Have a look at one of those dismounted:


Last edited by LEO175; 27-12-06 at 13:59.
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