Exhaust Valve Disable

[doltmo]

The exhaust valves on the Huracan operate in a similar manner as on the Gallardo.

The exhaust valves are normally open muffler bypass valves that are held in the closed ("quiet") position by manifold vacuum. The vacuum is controlled by an electrical solenoid valve, which is, in turn, controlled by the ECU and the Anima switch. The electrical solenoid is normally closed, so when it is not energized it blocks manifold vacuum (and vents any vacuum downstream to the exhaust valves), making the car "loud". When energized, the solenoid opens and passes manifold vacuum (if present) on to the exhaust valves, closing them and making the car "quiet". When you stomp on the gas, manifold vacuum disappears and the exhaust valves open, making the car "loud" even if the solenoid is energized (in "quiet" mode).

So, the exhaust valves can be "locked" in the open position by depriving them of vacuum. This can be done two ways: unhook the vacuum lines from the exhaust valves, or disconnect the electrical cable to the solenoid valve. Accessing the exhaust valves requires getting your hands dirty. You must also plug both ends of the vacuum lines (on both sides) if you do this. Disconnecting the solenoid is much easier. It can be done "from the top" in about half an hour.

The solenoid is attached to a frame member in front of the right rear wheel, just inside the wheel well liner. You can probably remove the rear wheel and liner and get access to it. I went in from the top side, removing the right-side engine bay cover and reaching down to access the solenoid.

So here are the steps for a car with the carbon engine bay trim:

1. Remove the center trim panel (the one with "V10" label). It is held in place with 8 quarter-turn fasteners.

2. Loosen the 8 quarter-turn fasteners that hold the right-side engine bay trim in place. Do not try to remove the panel yet.



3. Remove the right-hand hood strut. Gently pry the "C" clips partially out (but do not remove them all the way) on each end - just enough to remove them from the ball stud. Be careful here. The C clips might fly off and be lost forever. The hood should stay up with only one strut, but it would be handy to have a wooden stick of the appropriate length within arm's reach if it doesn't.



4. Now remove the right-hand engine trim. It will require some maneuvering to get it out of the car. Be careful not to scratch any painted surfaces.

5. The solenoid valve is on the silver-colored frame member, down near the wheel well liner.



Removing the electrical connector is a bit tricky. Insert a small screwdriver into the rectangular clip and push in the direction shown. This action releases a barb that retains the connector on the solenoid. Don't force it. When you've released the barb, the connector will come off easily.



6. Protect the plug solenoid connector with a small plastic bag or similar cover. I used plastic wire-ties to hold them in place.





7. Replace the trim panels and hood strut. The side trim panel is a pain to get back in. Be careful that the rear end of it doesn't scratch the tail of the car.