Javelin exhaust

[BobCulver]

The car with branch exh is back on road but no reports yet.
Whilst it may look like a traditional 4 into 2 into 1 it is of course not as consecutive firing cylinders join early. Any separation of these cyls is better than none, and evident on all moderns, but the normal 4,2,1 theory does not apply.
It is a while since I read up on exh sytems. Most books adequately explain the tuned single pipe but I do not recall any clear description of the exact operation of others ie the favoured racing set up of 4 pipes into a large single instead of leaving separate. One would expect the pos pulses from other pipes discharging would be detrimental but possibly some overriding non resonant gas flow extractor effect is added by grouping.
In the book Sports Car, Campbell reckons that with a common manifold a length can be chosen so that the return pulse from 1st major expansion arrives btdc, before consecutive cyl exhausts. My experience is that on old conventional fours, such a resonance does occur with a suitably located silencer.
I suspect with the Javelin the pulse reflected from the blind branch adds to the end of, or the beginning of the next firing discharge pulse, giving the odd beat and pronounced brief crackle when not fully silenced.
Bob Culver