How to wire AVCS actuator?

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EMS
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How to wire AVCS actuator?

Post by EMS »

How to wire the AVCS actuators?

In a stock AVCS equiped car, both wires come from the ECU, but I need to know how to wire the AVCS actuators with a MY99 S6PNP. The control wire (PWM?) is clear to me, but the other wire... Is it 12V+? Is it 5V+? It's not direct battery voltage I assume, as in the stock car this wire comes from the ECU and not from a relay.

Hope someone can help.

Mark.
pat
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Re: How to wire AVCS actuator?

Post by pat »

Mark,

The AVCS OCV is a linear hydraulic control valve which needs to be driven with a PWM signal at around 300Hz. We recommend the installation of schottky flyback diodes to keep heat dissipation in the S6 output stages to a more sensible level (the output devices limit at 60V, so between the transistor, coil inductance and flyback clamp there is effectively a switched mode "boost" converter with the load being the flyback clamp).

You will need to provide an ignition switched live to one side of the OCV and also connect the cathode of the flyback diode to this wire. The other end of the OCV should be driven by a spare AUX or INJ output on the S6, with the anode of the flyback diode to this wire. You can probably find ignition switched live from something like the pressure sources switching solenoid or the canister purge solenoid. The MY99/00 is fairly loaded output wise due to the stepper idle. If you intend to use the MY99/00 manifold then you'll need to have a look what outputs could be used BUT the manifold is a bad fit with AVCS heads; I would recommend swapping over to MY01- manifold which will free up 3 of the 4 idle outputs which can then be used for AVCS OCV control.

You'll need to bring the two AVCS sensor signals into the ECU. A signal ground may be found on the AUX connector, but the sensors will need to be connected to AB3 and AB4 (if they are early AVCS heads with VR sensors, if they late heads with Hall Effect sensors then AU3 and AU4 would be the inputs of choice, but you will also need to configure a Manual Cam Checklist for the late G11 pattern to detect phase correctly).

Furthermore please note that you cannot use the G10 crank pulley with the later heads at this time. We haven't implemented a hybrid G10/G11 pattern, mostly because it doesn't make sense to use the inferior G10 pulley. You can freely use hybrid G11/G10 setups, and indeed 36-1/G10 , 36-1/G11, 36-1/G11 Late.

Hope this helps / makes sense,

Pat.
EMS
Posts: 41
Joined: Tue Oct 12, 2010 2:24 pm

Re: How to wire AVCS actuator?

Post by EMS »

Thanks Pat,

I need to look which output to take, as the car has standard MY99 inlet manifold and idle control...

Can you give me any part no. for the Diodes you recommend?

Thanks again,

Mark.
Jasper K
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Re: How to wire AVCS actuator?

Post by Jasper K »

Hi Mark,

You are best off choosing Schottky diodes of the MBR range or SB range. Something along the lines of 5A, 60V is plenty beefy for what you want.
You can buy SB560 diodes for example from Farnell, Digikey, RS, etc. You could perhaps suffice with 40V devices which have a lower Forward Vdrop but then again it isn't that critical as it's only spikes they clamp to the Supply line.

Cheers,

Jasper.
EMS
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Re: How to wire AVCS actuator?

Post by EMS »

Thanks Jasper!
TimH
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Re: How to wire AVCS actuator?

Post by TimH »

What sort of power dissipation is there in the flyback diodes? Wondering whether they can simply be soldered inline with the +12V wire, with heatshrink over them, or if that's going to be a problem?
Jasper K
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Re: How to wire AVCS actuator?

Post by Jasper K »

Hi Tim,

For AVCS solenoids having the Schottky diodes soldered inline with heatshrink over them will work just fine.


Cheers,

Jasper.
TimH
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Re: How to wire AVCS actuator?

Post by TimH »

Thanks Jasper :D
pat
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Re: How to wire AVCS actuator?

Post by pat »

Tim,

Although a nonlinear element, the diode is still subject to the same laws that other elements are, POWER = VI cos phi. The phase angle will be around zero so it's a straight POWER = VI. But of course it is not continually conducting so POWER (rms) = V (rms) * I (rms). The forward drop of a Schottky diode will be in the region of 0.3V and the current cannot be any higher than the DC resistance of the solenoid would allow, and most likely somewhat less. Let's say, for argument sake, it is 500mA, then the power dissipation would be 0.3V * 0.5A * 65% duty = 0.0975 watts, or 0.1 watts. Not exactly likely to get hot as Jasper has already said, heatshrink will be just fine :)

Cheers,

Pat.
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Re: How to wire AVCS actuator?

Post by pat »

Tim,

the cathode of the diode will be facing VBAT, ergo clamping flyback voltage across it to around 0.3V so we should not see any more than about VBAT+0.3V on the output pin. Of course there is parasitic inductance in the wires etc and it does take a finite amount of time for a diode that is reverse biased and which becomes forward biased to actually start conducting. Compared to the PWM period, though, these are of little significance.

Were you thinking that the diodes were being used as a voltage clamp in the sense of a Zener ? That's not how they are employed, they are there to reduce power dissipation in the output transistors, which would have clamped at about 60V.

Cheers,

Pat.
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