Disconnecting the MGTF Exhaust volume control valve

Want more noise?

In other sections of this site I've already mentioned 'drive-by' noise regulations. Since the release of the MGF in 1995, these regulations have become more stringent - as much of a problem to sports car manufacturers as exotic as Ferrari as it is to our own more humble MG brand. The commonest way around this problem is the use of a flap in the exhaust system (an exhaust noise control valve, or evc). When closed, the valve makes the exhaust gasses travel through the whole silencer, making it quieter. It is under these conditions that the drive-by noise measurements are made. However, to give the exhaust more noise, the flap valve opens - giving a more direct opening for the exhaust gases - and a sportier, louder exhaust note.

This is a great system - although this can mean that your exhaust looks a little odd in the morning as the gas only appears to be exiting through one tail pipe! (The left one).

An interesting discovery was that when deactivated, the flap defaults to the "open" position. Evidently, someone inside MG Rover is a true motoring enthusiast! This means that the full sound of the TF's exhaust can be heard from idle by simply disconnecting an electrical connector!!!

Here's how:

1	First remove the inspection cover above the engine bay - as described here
2	Now identify the evc on a shelf on the left side of the engine bay, and pictured here: Components, from left to right are: Vacuum canister Electrical plug that provides ECU control over evc Electro-mechanical 'switch' for opening and shutting of evc Vacuum hoses (2) - one from vacuum canister, the other to the exhaust flap valve
3	Next, identify the electrical plug to the electromechanical vacuum exhaust flap actuator. This plug provides control over the flap by the ECU. It is held in place by a spring 'circlip'. It can be readily released by depressing the exposed wire at the top of the plug, as arrowed in the picture opposite.
4	Now the connector can be withdrawn. The plug can be simply left disconnected, and will not result in any harm to the electrical system or exhaust. Best still, the ECU will not register the fault... Note that prolonged periods of in-operation will lead to the flap seizing up. Good news if you don't want the flap to operate and you wish to return the wiring to standard configuration. Not such great news otherwise!

Does this mod result in more power?

In the interests of completeness, we tried comparing the before and after power curves on a TF135 to see if disconnecting the evc would have any effect on engine power. Given that even sports exhausts struggle to liberate 5bhp, we didn't hold out much hope of seeing a gain... Off to Dave Walker's Rolling road, we tried this simple modification. No differences whatsoever in either the torque or power curves at any point in the rev-range. Sorry chaps. But the cheekier exhaust note was worth it - as was the aesthetic of seeing exhaust gases from both tail pipes!