Volumex Compressor Map

[Grundo Farb]

Is anyone aware of a compressor map for the the volumex unit? From this you can change the parameters of the boost, inlet temperature, fuel flow etc and check the impact on the engine. A friend used this technique to size the correct turbo chargers for a V8 in order to get the best response - it would be interesting to see how the base unit fits with the engine as is.

A compressor map has pressure ratio on the y axis with air flow on the x axis.

[Will]

Turbos have compressor maps, superchargers (generally) don't.
This is because a supercharger puts out a fairly linear boost curve vs. RPM, since it is geared directly to the motor.
You'll find most sources quote the Vx as putting out around 4.5lbs at 2500RPM, and climbing steadily to around 6.5lbs at 6000RPM, with a corresponding increase in engine output.

-Will

[Pope1]

What's pressure ratio? Ratio of what to what?

[Will]

Chris; I assume he means in a turbo, ratio of inlet and exhaust mani pressures- not applicable for superchargers.

-Will

[Pope1]

Thanks Will. Just trying to make sense of a few things myself. Since fitting my overdrive pulley, boost has not increased (a constant 0.4 bar right across the mid-range at WOT) but it feels as if its flowing more air and breathing better. Does that make sense?

[Tom McGaffigan]

Pressure ratio is an appropriate term for engines that are either turbocharged or supercharged. There are maps for positive displacement superchargers like the Volumex but they do differ from turbo compressor maps. Positive displacement supercharger maps typically plot pressure ratio on the y axis and volumetric flow rate on the x axis. Additional data such as inlet flow versus supercharger RPM, Delta T (temp increase of compressed air) versus RPM and power required to drive the supercharger versus RPM is also graphed. The below site has graphs for Eaton superchargers. I have not seen any data for the Volumex.
http://www.capa.com.au/eaton_m45data.htm
Tom McGaffigan

[SteveNZ]

What's pressure ratio? Ratio of what to what?

Ratio of absolute air pressure on either side of the compressor.

You can assume there is 1 Atmosphere (14.7psi) before the compressor. PR=2 means there is twice the absolute pressure after the compressor than there is before it.