ECV1 & 2 was known as the triflux. This was due to the design which had one exhaust and one inlet valve on each side of the cylinder head, with the resulting twin exhaust manifolds each feeding one turbocharger. At low engine speeds one turbocharger exhaust was shut-off, forcing all the exhaust gases through one unit and thus providing good low speed performance. As the engine speed rose, the second turbocharger was gradually introduced, until at high engine speeds both turbochargers ran in parallel.