[Tom Vaught]

Time for a bit of Airflow Math.

Lets calculate the pounds of air flowing into an 455 Pontiac Engine for two different Boosted Vehicles.
(one that is NOT Inter-cooled and the other one is Inter-cooled).

For both cars we will use a Volumetric Efficiency of 0.85 and will limit the engine rpm to 5500 rpm.

Volume, in cu.ft per minute = (5500 rpm x 455 cubic inches) / (1728 x 2) = Engine CFM.

(5500 x 455) divided by (1728 x 2 ) = 2502500 / 3456= 724.1 cfm.

This holds true for both cars, both intercooled and non-intercooled will be moving 724.1 cfm of air into the cylinders at 5500 rpm.

As we will see however, the "MASS OF AIR FLOW" flowing into the engine will not be the same.

We will also assume that the Discharge Air Temp is about 250 degrees (actual will be 258 degrees F which we will see below).

How we got an actual temp of 258 degrees F:

Temp into engine= 70 deg F + 460 = 530 deg R

Pressure into engine= -0.5 psig + 14.7 = 14.2 psia. The -0.5 psig is the Air Inlet Restriction from the Air Filter and Inlet Pipe Losses.

Pressure out (or the Boosting Device Pressure) = 19 psig + 14.7 = 33.7 psia. psia is pressure in square inches absolute.

Pressure out / Pressure in = 33.7/14.2 = 2.373 (this is the compression ratio). Also called the "Pressure Ratio" of the Boosted Air going into the engine.

Temperature out = 530 + 530 x (-1+2.3730.263 ) = 717.8 deg R - 460 = 257.8 deg F.

That is how hot the air would be with the 19 psi of boost pressure and no inter-cooler. That Holley Carb WOULD BE HOT.

Later I will calculate the Non-Inter-cooled Air vs the Inter-cooled Air and give you the Horsepower Difference (assuming we can lower the Inter-cooled air temp to 130 degrees F.

Tom V.