MACS Service Reports - 2016 - AUG1

©

Total Vehicle Climate and Thermal ManagementTM

August 2016

By Dave Hobbs, MACS Technical Correspondent

In our July MSR we discussed OBD II thermostat look up table for the best fuel injector pulse width.
monitors and ECT sensors. You may recall the men- The same for spark timing with RPM's and engine
tion of there not being much new when it comes load to determine exactly the best to produce the
to thermostats other than their OBD II monitors spark during those conditions. The same is now
(which we covered in depth) and electric assisted true for the engine cooling system's electric therthermostats. We'll take on those electric thermo- mostat. Engine load and VSS (Vehicle Speed Senstats in this month's MACS Service Report.
sor) are now being mapped (Fig. 1) into the PCM's
If you are an Audi / VW savvy technician you've / ECM's 3D software look up table to determine the
encountered electric stats for several years now. An PWM (Pulse Width Modulated) output to the heatidea good for one OEM is often likely to spread to ing element inside of today's electric thermostats.
another so chances are very
good you'll be seeing these
electrified stats showing up
on the Chevy pulling into
your service bay. The 2011
Cruze is one of the first GM
adopters of what engineers
call "Thermal Mapping." If
you're thinking mapping is
something you did before GPS
apps popped up on your smart
phone you'd only be partially
correct. Software mapping is
something engine tuners have
been doing for years with engine management. Using 3D
maps of points for different
variables you can, by trial and
error, determine what an ECM
output such as spark timing
or fuel injector pulse width
should be. For example, engineers and serious hobbyists /
tuners program RPMs, engine
load and coolant temp vari- Figure 1: The electric thermostat can be opened more quickly compared to a traditional thermostat allowables into a 3D software map / ing for software 'mapping' control by the ECM. Software mapping is used for many engine management
functions including fuel control and spark advance. Coolant mapping table shown is for a performance
application.

MACS Service Reports is the official technical publication of the
Mobile Air Conditioning Society Worldwide, Inc., P.O. Box 88,
Lansdale, PA 19446. The material published in MACS Service
Reports expresses the views of the contributors and not necessarily that of MACS. Every attempt has been made to ensure

August 2016

the accuracy of the content of MACS Service Reports. MACS,
however, will not be responsible for the accuracy of the information published nor will MACS Worldwide be liable in any way for
injury, labor, parts or other expenses resulting from the use of
information appearing in MACS Service Reports.

1

MACS Service Reports

Chart courtesy Mahle

ELECTRIC THERMOSTATS



Table of Contents for the Digital Edition of MACS Service Reports - 2016

MACS Service Reports - 2016 - JAN1
MACS Service Reports - 2016 - JAN2
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MACS Service Reports - 2016 - AUG1
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MACS Service Reports - 2016 - OCT1
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MACS Service Reports - 2016 - NOV1
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MACS Service Reports - 2016 - DEC1
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MACS Service Reports - 2016 - DEC7
MACS Service Reports - 2016 - DEC8
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