BrianG

Can someone explain the Evaporative Control system circuit on a S4??

heinrich

charcoal canister

BrianG

Thanks man!!

That's the most concise description of ANY system I've ever heard!!

I'll raise ya a gas tank, a plastic "Y" under the right fender liner, a vacuum controlled valve on the right fender in the engine compartment, a vacuum connection to the induction system somewhere, and more than a few yards of black rubber tubing.............

SharkSkin

Yep, that's pretty much it. Oh, there's an expansion tank just above the right rear wheel.

John Speake

...............and it feeds the filtered fumes back into the car engine inlet system via a solenoid valve that is triggered by the LH ECU. This system is defeated if engine temp is below 80degC, and also when the closed throttle switch is activated.

heinrich

See? All we needed was a lead-in and John took it all the way there

heinrich

The S4's vac line is one of the 4-splitter ones behind the intake.

BrianG

We're getting MUCH closer to the tid-bit that I seek!!

Where is this "feed...into the engine inlet" point??

Is the "solenoid valve that is triggered by the LH ECU" the unit clamped to the cross-bar over the engine??

And lastly ... what should be done with this system for a SuperModel installation?

John Speake

Hi Brian,
If you look on page 24-216 of the WS manual there's a diagram that might help.

This system has two valves in it, one is the electric valve I mentioned, and there also apprears to be a vac operated valve as well.. The vac valve is on the 24-216 diagram .

In the Tech Info for MY87 page 2.14 there is a picture of the electric "solenoid valve" and it appears to sit just above and slightly to the RHS of the dipstick.

I don't remember where the vac valve is, but a line for the filtered fumes runs direct from the vac valve to the solenoid valve . It seems from the very poor description given that the vac valve is fed from a point before the throttle plate, because they state that "there is no vacuum at idle". There is a simple hose/component diagram on the same page.

It appears that the vac valve acts as a gate for the carbon cannister fumes to be passed to the solenoid valve. The fact that when the throttle is closed the solenoid valve is switched off suggests to me that it feed after thet throttle plate.

Hope this helps. I can scan the page if you want. mail me at info@jdsporsche.com if you want. Easier than uploading here...

BrianG

Thanks John!! We're almost there!!

I have found that there is a "timed vacuum port" on the '85-86 throttle body, and it makes sense that this would provide the vacuum signal to the EvapControl system valve that sits on the right fender.

The ECU then provides the electrical to the valve on the right-front corner of the engine.

So:
1. The vapor line, then enters the engine compartment through the right fender and it connects to the vacuum controlled valve (which receives a timed vacuum signal from the TB)

2. The vapor line then runs to the electrically controlled valve ont the right-front corner of the engine (which get's its signal from the LH ECU).

3. The vapor line then runs to (somewhere???) on Andy's induction system.

Now.... what to do with the vapor-carrying line, after it leaves the electrically controlled valve, now that the '87 intake manifold is replaced with Andy's arrangement?

John Speake

Send me a mail if you want that diagram I have....