Aldous Voice

I recently saw a remote control kit to operate the exhaust valves for sale and thought I write out my thoughts. The kit is pictured below and, in my opinion, is potentially dangerous to fit to your car. I will try to explain why and will also describe a safer way of operating the exhaust valves.

First of all lets recap on what the valves do – the first part of this post explains the different exhaust systems fitted to the 360 and F430 models. In essence, at low engine speeds a valve closes off part of the exhaust system to reduce noise at idle and to promote back pressure in the system. At higher engine speeds the Motronics send a signal to the valves for them to open.

Many people prefer the extra noise that the open valves provide. It is easy to achieve this by simply disconnecting the plugs that connect to the valve solenoids. The following two pictures show which plugs to undo in a 360 (ringed in yellow) – they are situated under the rear lights.

Undoing these connectors will leave the valves permanently open – it should be noted that on an F430 unplugging the connectors is likely to result in P0475, P0477 or P0478 error codes being store in the Motronics.

Some people wish to be able to operate the valves remotely and there are several methods and kits out there to achieve this. I should start by saying that if you want a safe plug-and-play unit then I believe the Capristo unit to be the best solution and it manages to spoof the power drain at the soleniod so the F430 error codes above do not trigger.

However, it is an expensive unit and people may be tempted by the low cost unit shown at the start of this post – I have seen it advertised for £150. This unit is in fact just a cheap Chinese remote control switch with some connectors added to it. The unit is this one here <link> and is selling for a little over £5. In the event that this link stops working I have shown the picture from the eBay listing below and it can be found by searching for “12V Remote Control Switch”.

To know why fitting this unit is a bad idea we need to understand how the valve operation is triggered. The valve itself sprung open and is closed by a vacuum which is operated and controlled by an electrical solenoid. The solenoid is powered via the electrical connectors ringed in yellow above. Each of these connectors has two wires running to it – one is coloured Violet and is a permanent 12V supply (it is connected to the fuse board). The other is coloured Yellow & Blue and is connected directly to the Motronic (ECU). When the Motronic wishes to open the valve it sends a ground to this wire – the solenoid then has both 12V and ground and is forced to operate (close) the valve.

The way this unit is wired is that is interrupts the 12V signal between the fuse board and the solenoid. If the 12V is removed then the valve will remain open regardless of what the Motronic wishes to do. If the 12V is applied then the Motronic continues to operate as normal. The problem is that the 12V supply to the solenoid is also directly connected (ie: not protected by any fuses or diodes) to many other circuits.  In the 360 it is connected to all of the following:

• Variable Length Inlet Manifold Valves <link>
• Plenum Chamber Compensation Valve <link>
• Fuel Injectors
• Lambda (Oxygen) Sensors
• Mass Air Flow Meters (MAF) <link>
• Secondary Air Solenoid Valve (USA Only)

Normally, these circuits are separated between the two engine banks. This unit actually cross connects the power between the two banks. However this isn’t the main issue – there is a real danger that the unit could short out the 12V circuit. If this happens then at best all of the circuits listed above will be knocked out, at worst they will be damaged. Would you really trust a cheap Chinese electrical device costing just £5 mounted in the harsh environment of the engine bay not to malfunction? I certainly wouldn’t and the potential cost of rectifying the damage could be enormous.

A safer way to control these valves would be to use a relay on each of the ground signals to the exhaust valve solenoids. I would select an automotive relay that is rated for the environment found in the engine bay (in particular for the heat and vibration). Such a relay could then be controlled by a manual switch inside the cabin or even by one of these cheap eBay remote control units. In order to make the installation neat you could use 2 way Junior Power Timer connectors to fit into the existing loom.

Update (March 2014):  Fellow Ferrari owner Steve Bisel has created an exhaust valve control kit with the proper protection.  I am happy to endorse his product which can be seen here.

Other posts in this category: Engine & Drivetrain

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