The scenario:
A 1.5:1 pulley ratio should give us a pressure ratio of 1.5 (coincidence only) and spin the blower to 9500rpm. The blower VE at this point is about 80% and it *should* be moving abut 180 m³/hr of air.
The problem:
Help me out with some math here and if im wrong correct me!
91kpa @ atmospheric x 1.5 Pressure Ratio = 135kpa on full boost
We took a reading and got 104kpa at full noise. 104kpa is not equal to 135kpa.
104kpa divided by 91kpa means the actual pressure ratio is around 1.14
Looking at the compressor map, this means we were really pushing 200m³/hr of air at 89% VE.
2 PSI at 6250 rpm is kinda defeating the purpose of the low end boost of a roots blower don't you think?
I would be a lot happier if it was making 2 psi at 1500rpm.
Now, if I told you the motor consumes 110m³/hr on its own normally aspirated and you factor the info above, what kind of pulley ratio should we have used? Can we safely run low boost at idle or would you recommend against it?
I'll see if I can post the compressor map somewhere. Here's some info on it in the meantime.
Max pressure ratio is 1.8, the graph starts at 4000rpm and finishes at 18,000rpm.
Flow starts at 80m³/hr and finishes at 400m³/hour.
Blower VE (not temp) is between 65% at the low end and 92% at the top end.
Your help is greatly appreciated - thanks!
Stevek
