Реферат: Forced Air Induction Essay Research Paper The

"cruise" speed of the turbine is only 2000-6000 RPMs. It is this

latency of the turbo to accelerate to operating speeds that is referred to as

turbo lag. Although the small size of the turbine is ideal for a moderate

performance car, its size is a handicap in racing situations. Inherent with a

small compressor is its ability to quickly reach operating boost pressure. This

does not come with out a penalty. Effectively this small compressor trades

efficiency for speed. As any gas is compressed the temperature of it rises.

Smaller compressors will tend to heat the compressed air more than would a

larger turbo for a given pressure. Bernoulli’s principal states that as a gas is

compressed the temperature increases as the volume decreases. The inefficiency

of the VNT at pressures over 15 pounds per square inch increases the temperature

of the gas more than it is possible for it to compress, or decrease the volume.

The result is that the increase in boost pressure is inversely proportional to

the volume of air moved. As the compressor works to decrease the volume of air,

the rise in temperature works to increase the volume. Eventually the volume of

air is expanded by heat more than it can be compressed. The point at which this

happens is referred to as the stall speed. Because a larger turbo, although slow

to respond, is much more efficient at higher pressures it will result in a much

cooler charge at a given pressure. A smaller compressor also cannot move large

quantities of air at high pressures as would a larger turbo be able to. The size

of the VNT, although ideal for 12psi as it was intended for, suffers greatly in

high performance applications from stall speed of psi. The turbine also suffers

from a small and compact A/R ratio. The A/R is the ratio at which the turbine or

compressor housing is cast. The A/R is the ratio at which the volume of the

housing as gasses enter the housing to the volume it exits. For instance, the

size of connection on the intake side of the compressor is two and one quarter

inches inside diameter and has a volume of 323 cubic centimeters until it

reaches the compressor. The exit side is also two and one quarter inches inside

diameter and contains a volume of 155cc’s. The volume of each path to the