Powerforum

A question that sometimes arises is the idea of having a balance pipe, or cross-over, between the two sides of the engine - the thinking being that if it works on a V8 it must do something for a V12.

It is true that a cross-over can benefit conventional V8 engines (with two plane crankshaft) but only because they have an uneven firing sequence along each cylinder bank, which creates the rather delightful V8 exhaust note. A consequence of having two cylinders firing consecutively on each bank is that the flow rate is briefly doubled, then later in the cycle the long gap between firing impulses causes it to be halved, compared to the average flow rate. The temporary high flow rate means the V8 can benefit from using larger pipe sizes than other engines and a cross-over pipe can help to even out the impulses. It is not obvious to the eye but the Jaguar V8 incorporates a cross-over within the main silencer box.

A V12, on the other hand, has equally spaced firing impulses along each bank creating an even sequence of pulses. There is no flow variation to require a balance pipe and the system does not have to contend with brief periods of peak flow so pipe sizes can be smaller. The only reason the V12 E Type had a balance pipe was simply to tune the exhaust note.