Compound Charging

[derekf]

There was a Lancia rally car in the late 80s that was both super- and turbo-charged. If memory serves, there was an RPM where the intake changed over from the SC to the TC.

A google search found some info:
(from http://www.carsfromitaly.com/lancia/deltas4.html - you'll have to click the "Delta S4" link, their page redirects if it's outside its frames)

The unusual route of using a supercharger and turbocharger together was to avoid the poor performance of the large turbochargers at low engine speeds. On the S4 the order, from the air intake was turbocharger, intercooler, supercharger, intercooler, inlet manifold. Once the supercharger became less efficient, at higher engine speeds where the turbo performed better, a bypass allowed the turbo to feed the engine directly.

http://www.lanciaaustralia.com.au/pa...es/rallyhq.htm says



A special bypass valve cut out the supercharger after 5000 rpm. On gravel the two forced induction systems worked together up to those revs when the turbo took over. The benefit was the low rev torque by the supercharger assisted in removing the turbo lag which had made some developing turbo cars difficult to drive.