DaveKillens wrote:This type of forced induction is used a lot in dragsters, in the form of the Roots type blower. The reason why they are not used in Formula One engines is evident in these graphs, comparing a roots blower against a turbo. In a turbo, efficiency is higher at higher RPM.Fundamentally, in a Roots type blower, as RPM and boost increase efficiency drops off. In a turbo, it gets better as RPM and boost increase.
DaveKillens,
A Roots "blower" is different in principle from a Lysholm or a turbocharger centrifugal compressor. The Roots blower is not a compressor. Instead its function is more like that of a gear pump. The Roots creates manifold pressure by pumping more air volume than the engine is consuming. And it's precisely because of the fact that the Roots blower produces no internal compression work that it tends to have low efficiency.
