The M84 cannot do proper knock monitoring. By "proper" I mean that you have a gated signal (like and Ignition signal) to the Knock device to tell when a particular cylinder is firing. This way you can close the window when nothing is happening so that it cuts down on noise that you are really not interested in in the first place. Secondly you can pin point which cylinder is detonating so that you only retard ignition advance to the cylinder that is weak.....why would you hinder the other cylinders and go down in HP for no reason? Hence 600 quid and an M400, M600, M800.
MoTeC Research Center Melbourne, Australia