Phase variator mapping?

Posted By: Anonymous

Phase variator mapping? - 26/10/2011 09:20

Those of you that have run a standalone ECU, did you ever try sending a PWM signal to the variator and varying it's duty?

Posted By: Anonymous

Re: Phase variator mapping? - 26/10/2011 11:45

The variator action isn't directly electronically controlled, it's hydraulic. The valve (solenoid) is opened electrically and then engine oil pressure acts on a piston to alter the cam angle, so by using PWM on the solenoid valve to have it partially open instead of fully open I doubt that would give you enough precise control over the oil pressure at the piston to allow continously variable cam timing, it would probably just delay the piston action slightly.

Posted By: Anonymous

Re: Phase variator mapping? - 26/10/2011 15:39

Yeah I thought that may be the case. I'll have a play when the time comes and see what happens. Might see about plumbing in a valve that can vary the pressure instead of just switching between the galleries.

Posted By: Anonymous

Re: Phase variator mapping? - 26/10/2011 15:58

Yes, that may be possible, but the engine oil pressure will change with revs too so it may get complicated.

My grande punto has continuously variable valve timing and I think it uses variable oil pressure to alter the cam angle, so may be worth looking at how it's implemented there.

Posted By: Anonymous

Re: Phase variator mapping? - 26/10/2011 16:00

I remember JohnS looking into altering the point where the variator changes (later up the RPM?) - that was with his MOTEC though.

I wonder if Flea has experimented too.

Posted By: Anonymous

Re: Phase variator mapping? - 26/10/2011 16:11

Yup, it's possible to change the variator point by altering that map in the firmware, flea should be able to do that I would think.

The grande punto system is implemented by oil pressure, found this description:

Quote:

The phase transformer actuator comprises a rotor in one piece with the camshaft that can rotate in relation to the pulley (stator) moved by the crankshaft. The rotor is equipped with vanes and moves through the effect of the engine oil pressure on the vanes.

There are two compartments (the advance compartment and the delay compartment) created at the two sides of each of these vanes: the oil can flow into one compartment or the other.

The pressure of the oil entering a compartment pushes the vane to one side and the oil in the other compartment is discharged to the cylinder head. The rotor and consequently the camshaft are thereby rotated in a certain direction (advance or delay).

If the engine oil alternatively enters one compartment and the other continuously for the same time, the pressures at the two sides of the rotor are dynamically balanced and it remains still.

The flow of engine oil is activated by a cassette solenoid valve which places the oil ducts in the cylinder head in contact with the advance or delay compartments.

So they're using oil pressure on both sides to balance it, which neatly gets around the problem of oil pressure increasing with engine revs, whereas in the coupe you'd just have the variable oil pressure pushing against the return spring... sounds unlikely it would be accurate enough.

Posted By: Anonymous

Re: Phase variator mapping? - 26/10/2011 18:38

The VVT in the coupe is just an open loop valve. You can only open and close it you cannot constantly adjust. I doubt you will ever add this feature, and even if you did you would probably see very little gain anyway. You would need vvt cam measurement approx four edges as well a cam phase with latch angles being subtracted to know the cam position at all times, with PID closed loop control.

On a morden engine twin VVT is used and the only real reason for this is passing Euro 5 emissions rather than performance. You will find at the 100% TPS top line the cam is fully retarded anyhow.

Simple way to get rpm right on the coupe is power run with valve off then power run with valve on where they cross is change over point. With standalone you could also play with coolant, TPS and MAP/MAF switchover points etc...

Posted By: Flea

Re: Phase variator mapping? - 02/11/2011 17:11

Originally Posted By: Nobby

I remember JohnS looking into altering the point where the variator changes (later up the RPM?) - that was with his MOTEC though.

I wonder if Flea has experimented too.

Yes I do change the VVT in the 20v, although it is a little more complex than simply changing the switch point. The gains are significant, so it is certainly a requirement to good tuning.

Posted By: JohnS

Re: Phase variator mapping? - 11/11/2011 07:19

Originally Posted By: TurboJ

Simple way to get rpm right on the coupe is power run with valve off then power run with valve on where they cross is change over point. With standalone you could also play with coolant, TPS and MAP/MAF switchover points etc...

If you want to get more out of it then you can also adjust the cam timing to optimise it in conjunction with this. Both the inlet and exhaust cams have adjusters and it does significantly impact the engines behaviour and to some extent you can get the best of both worlds.
Has anyone tried using the variator from the 2.4 VIS engine as I think it has much more 'adjust'. The 1.8/2.0TS ones are also compatible with the cams I think (the ones that were on Watchdog for going wrong!!!)

Posted By: Anonymous

Re: Phase variator mapping? - 30/11/2011 12:54

my variator is from the 2.4 and it seems the same as the 2.0 (18 degrees) - although it seems to lack all the extra bits that wore out on the 2.0 variators. the 2.0/1.8ts variators are 25 degrees - not sure if they're a straight swap.