by Dave Koehler
We recently installed a racepak
into our car, which includes the
exhaust temp sensors. But I cannot
find any info anywhere as to the
heat range that the exhaust header
temps should be. The basic info
on the motor is as follows ...
1471 Littlefield blower
Alcohol injected ...
Approx. 1800 hp
Truck weighs 3200 lbs. and ran
a 7.87 at 165 mph last year before
the new updates.
Anywhere you could direct me or
any info. you could give me would
Arthur H Irwin IV
Arthur, This is a good news/bad news thing.
The bad news is that there is no magic number
to shoot for. The good news is that you won't
have to worry about comparing numbers with your
pit neighbor. Due to probe placement, type of
probe, camshaft, engine load and overall engine
design there will not be two engines with the
same egt numbers. If you are currently running
well and like the looks for your spark plugs
then whatever number comes up is your baseline
reading. Now ... exhaust temp numbers are great
for balancing cylinder to cylinder power via
nozzle changes or individual cylinder timing
changes. They are also useful as an early warning
system for catching something going south on
any particular cylinder, bad plug wires, etc.
Watch for overall changes in the graph. If one
is trying to climb faster than the others or
a lot slower than the others but ends up about
the same temperature, then that particular cylinder
should be looked
at. Hope this helps.
Have a safe race,
I am new to the world of "Pro-Mod"
racing. I have seen a few at the
NHRA races. Would you tell me the
purpose of the mist or spray coming
under the hood by the windshield
on nitrous cars before they launch?
Thanks ahead of time.
Drag Racing Fan,
Hank, Good question. Nitrous is a steady rate
system. The racers can keep their fuel pressure
relatively steady but at the moment there is
not a regulator that can handle the volume of
compressed nitrous correctly. The racers want
to leave the line with the same nitrous pressure
each time. What they do is warm the bottle so
that they have about 950 lbs. of pressure before
staging. When they are done with the burnout
and ready to stage they activate an auxiliary
solenoid that is tied into the hose leading
from the nitrous bottle. They let off enough
pressure to bring their launch pressure down
to 900 lbs. each time and then stage. The spray
you see is nitrous being expelled and the process
is called "The Purge". It also makes
for a neat show and announces to the world that
"yup I am bad, don't fool with me."
Keep watching and reading. There is much to
Have a safe race,
Dave Koehler answers your
nitrous & fuel-injection