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LP Engine G430 (3.0L)
General Information
1.3 Air Temperature Versus
Power Output
The temperature of the air entering an engine is
very important for two reasons.
1. Hot air entering an engine can lead to detonation
and pre-ignition, which will injure or destroy an
engine in short order. The cooler the temperature
of the incoming air the healthier it is for the
engine.
2. As the temperature of air entering an engine
increases it expands becoming less dense and
lighter. This reduces the volumetric efficiency
and therefore the horsepower output of the
engine. For every 10-degree increase of engine
intake air temperature the horsepower output
drops 1%. Since under hood air temperature can
easily reach 200 degrees it is very important that
the engine air intake be ducted outside the
engine
compartment. As an example an engine that makes
100 HP breathing air at 60 degrees will only make
86 horsepower breathing air at 200 degrees. This
decrease in power can be explained by the fact that
an engine requires 7lbs. of air to make 1
horsepower for 1 hour. As air is heated it expands
and becomes less dense and lighter (as in a hot air
balloon). A greater volume of air is required to
weight 7lbs. An engine running at rated full load
RPM can only breath a fixed volume of air. The
number of available pounds of air is reduced by
using hot air (a 100 cubic inch displacement 4
stroke engine will only pass 100 cubic inches of air
and fuel for every 2 revolutions of the crankshaft.
The displacement is fixed by the bore and stroke.
The displacement cannot increase to allow for the
high temperature and lower density of the incoming
air).
Intake Air Temperature vs Horse Power
00
20
20
40
40
60
60
80
80
100
100
120
120
50
50 60
60 70
70 80
80 90
90 100
100 110
110120
120 130
130140
140 150
150160
160170
170 180
180 190
190 200
200 210
210220
220230
230 240
240 250
250
Temperature in Fahrenheit
Power(%)
Power(%)
Air Temperature Versus Power Output
