Another engine theory Q - Blowers?


Well-Known Member
Oct 21, 2019
I'm aware of the energy value (efficiencies) of turbo prop systems. Especially for normalize HP maintenance high up.
This Q is not about that. :)

When converting small auto engines, we all tend to need high torque at lower rpm than original design rpm's for optimal HP range & peak torque in the original engine.

PSRU's are a common solution.
Especially if we hope for higher speeds yet good take-off and climb performance with longer props than the un-aided engine can swing.

So: now that small (relatively light) roots blowers are available somewhat economically,
Which is "harder" on a 4 stroke IC engine -
1.) gain HP & convert to torque by running the engine fast and reducing the output rpm with a PSRU?
2.) install a blower and run the engine at same rpm as above PSRU output, but with more available torque (More HP at same rpm)?

Both add heat to the base engine which has to be rejected.
Which system is theoretically (practical problems can be solved) "worse"?