Bully Dog 40390 PCH with Pyrometer Lead - Manual (Page 6)

5
installation Pre-vs-Post
pOST-TURBO vS. pRE-TURBO
What are the determining factors in deciding whether to install the pyrometer probe in a pre-turbo
location or a post-turbo location?
The location of the pyrometer probe along the stream of exhaust gas will make a considerable dif-
ference in the temperatures that will display on the GT or PMT. An incorrect interpretation of the
readings can lead to vehicle damage, so it is very important to have a clear understanding of the
differences between Pre-turbo and Post-turbo.
Consider these factors:
1. Difficulty of the install: Before installing inspect the exhaust manifold and the turbo down pipe of
the vehicle and determine which location will make for the easiest install. Consider while inspecting
these locations that the pyrometer probe should be installed 3” from the turbo inlet or exit give or
take 1”. Many vehicles will have an obviously easier position for installation.
2. What is the vehicle engine configuration: If the vehicle is a V8, and the intention is to install a
pre-turbo pyrometer, then really two pyrometers should be installed, one pyrometer in each exhaust
manifold bank to detect any difference between each bank of cylinders. If the vehicle engine is a
strait six like the Dodge Cummins then installing pre-turbo or post turbo can be done easily and
mounting in both locations is also very possible.
3. How much horsepower is the vehicle running: If the vehicle is running significantly more horse-
power than stock (100+ horsepower) it is strongly advised that both a pre-turbo pyro probe and
post-turbo pyro probe be installed. Both pyrometers should be installed within the recommended
parameters distances from the turbo charger.
What is a safe temperature range when watching either pre-turbo or post-turbo temperatures?
We always recommend that the driver use our pyrometer calibration procedure to determine safe
temperatures for their vehicle. The pyrometer calibration procedure allows the driver to see the max-
imum temperatures achievable with a stock vehicle and from there helps determine a safe range of
temperatures to use while the vehicle has performance enhancing tunes installed. The pyrometer
calibration procedure would also be used to determining where to set safety defueling points if us-
ing the pyrometer on a GT diesel or PMT.
Is mounting the pyrometer in the Pre-turbo location recommended over the post-turbo location?
Mounting the pyrometer probe pre-turbo is generally recommended because it provides more ac-
curate EGT readings. Mounting the pyrometer probe pre-turbo actually provides closer to real time
temperatures and more accurate temperatures because it is closer to the actual combustion event
taking place inside the engine. Pre-turbo temperatures will display the intensity of the heat coming
out of the engine and will indicate the temperature of the exhaust gas that is entering the turbo
charger. A post turbo pyrometer probe will only indicate the temperature of gas exiting the turbo
charger.