03-05-2012, 07:44 AM
Join Date: Feb 2010
Total Cats: 0
Yes, there will be about a 4% loss. Corky Bell as usual was kind enough to give me a "guesstimation" based on what info he has. Here's his figures:
No, not quite right. Two things; the added power must take some of the added power to run the blower faster and at a higher pressure. Second, the air will be heated more because of more compression to a higher pressure. Heating the air will move the air molecules a little farther apart, thus a few less per CFM.
An approximation would be about 8% of the intended gain power the SC, or: 8% 0f 18 = 1.5% That drops your expected gain to 16.5%.
The heating of additional compression will reduce the air density proportional to the absolute temperature. “Absolute” means all the way down to no heat, which is about 460 F below or normally referred to “0” which is just 32F below freezing.
Guessing that your SC produced 6 psi boost, the boost change would be about 4.5 psi. This will create a temp increase of approximately 17F for every psi, or about 75 F.
The temp change of the first 6 psi would be about 6 x 17 = 102F. That drops the air density by approx;
On an 80 F day:
Change = (460 = 80 + 102 )/(460 + ambient of 80) = 12%
For the next 4.5 psi, with the additional temp of 75F:
Change will be about (642 + 75)/ 642 = another 12% of the expected gain.
So, of the 18%,, down to 16.5% due to powering the blower, another 12% drops due to the air density change.
Or: 16.5% x (1 - .12 ) or 16.5% x .88 = 14.5%
So, instead of expecting 18%, or 32 hp, you should see something closer to 14.5% or about 27hp.