ProCharger winning but unsure if we are comparing apples with apples...

Comparison of Specs

	Rotrex C8-8	Rotrex C15-20	Procharger A-1 (range of models?*)
MSRP	AUS$1,750 (if bought from the UK)	AUS$2,030 (if bought from the UK)	US$1,599 (AUS$1,530)
Base HP Range (Naturally Aspirated)			25-100
Max Supercharged HP	41-75hp	68-163hp	150hp
Max Flow (cfm)			450 cfm
Max Boost (psi)			15 psi
Max Set-up Ratio	12.52:1	12.67:1	4.1:1
Volute Diameter			7”
Outlet Diameter			2”
Oil Capacity (oz)			2.5
Max Impeller RPM	240,000 rpm	180,000 rpm	75,000 rpm
Inlet Diameter			3”
Self-Contained			Yes
Reverse Rotation Available			Yes
Weight	1.4 Kg	2.9 Kg	5.6Kg (estimated)

* ProCharger provide less info than Rotrex - I suspect that A-1 is a group of superchargers like the "C8". Rotrex provide info for each model (e.g. C8-6, C8-8, etc) but it looks like ProCharger just give info in a range and pick the best value.

Using a 1/1 model we see that the Rotrex is the only choice based on size.

ProCharger requires:

Flow Rate

The rule of thumb for flow is:

So for 50Hp we need: 0.042 kg/s

Pressure Ratio

The rule of thumb for pressure ratio is:

So for 50Hp from 40Hp we need: 1.44

Flow Rate

Bell states for a 4 stroke:

Airflow rate = (cid x rpm x 0.5 x Ev)/ 1,728

So for a metric two stroke:

1 cubic centimetre = 0.0610237441 cubic inches

Pressure Ratio

The compressor map below shows that the C8-8 will give this at 160K-200K rpm (~13K-~17K input rpm) - though I need to understand pressure maps more (off to do some reading).