FEATURE Carol Stream Justifi es V8
CYLINDER DEACTIVATION – URBAN MYTH M
any police departments point to cylinder deactivation as a way to justify a larger engine over a smaller engine. “The
V8 will idle on 4 cylinders, saving more gas during idling than a V6.” That is a very persuasive argument to chief, sheriff or muni council who are all about anti-idle policies and totally skeptical about any V8 police engine. Nice try. Not true. Chevrolet calls it Active Fuel Management. Dodge calls it
Multiple Displacement System. These systems do not engage during idle with the trans in Park. They do not engage during idle at a stop with the trans in Drive. At idle, V8 engines remain V8 engines running on all eight cylinders. With current engine technology, lots of reasons exist for this. One is a very rough idle from a V8 operating on only four cylinders at idle. The V8 has enough torque to idle in V4 mode, but the idle is rough enough that no automaker wants to be associated with it. The idle is so uneven that most drivers will notice it and think something is wrong. Even though nothing is wrong with the engine, it certainly feels like it. Trying to educate
the offi cer that a rough running engine is OK is exactly the op- posite of most fl eet maintenance strategies. Another reason is a technical hurdle. Cylinders are activated or deactivated by oil pressure changes in special hydraulic lifters. At idle, the oil pressure is too low to properly operate the pressure- controlled lifters. While cruising at 2000 rpm, the oil pressure is 55 psi. However, idling at 700 rpm, the pressure is just 30 psi. Extended operation at low oil pressure also raises both wear and cooling concerns. As for the V6, it doesn’t have enough torque in V3 mode to overcome friction and other pumping losses at idle. The idle speed needs to be increased just to keep the engine running. Increasing the idle rpm cancels the fuel savings from shutting off cylinders. How about cylinder deactivation during normal patrol? Cylin-
der deactivation only happens during fairly steady throttle under fairly steady loads. That is defi nitely not the typical police driving style. Bottom line? The benefi ts of cylinder deactivation just are not seen in law enforcement use.
than—the Ford CVPI. Like virtually every study, the Carol Stream Police evaluation is a snapshot in time. T is is a credit to the police automakers that are constantly responding to the voice of the customer. Some depart- ments were required to make purchase decisions before the pow- ertrain or feature that disqualifi ed a certain vehicle became available. Of course, the best example of this is the now-available, 3.5L EcoBoost V6 in the Ford PI Utility. However, lesser examples exist, i.e., the upgrade from 3.5L V6 to 3.7L V6 in the Ford PI Sedan, the availability of a 4x4 police package in the Chevrolet Tahoe, the column-mounted shifter in the Chevrolet Caprice, the availability of a V6 in the Caprice. T e police always need to go with the best information available at the time.
Patrol Evaluation T e Carol Stream Police did their evaluation the right way—they got test vehicles, put them in-service, and asked for feedback from patrol and senior offi cers. T e subjective high-speed handling com- ments from the LASD/LAPD test drivers were compared and con- trasted with their own patrol-oriented driving impressions on the streets of this urban city. In most cases, multiple offi cers from all platoons drove the ve-
The Ford PI Sedan with the 3.5L EcoBoost V6 may have a residual value more like a Taurus SHO, while the PI Utility with the same engine may have a residual closer to the Explorer Sport.
hicles for a number of patrol shifts. In addition to patrol, the ve- hicles were driven by command staff , detectives, crime scene techs, and others involved in fl eet operations. T e driving impressions included such patrol-specifi c drills as drawing a holstered duty gun while seated in the vehicle. T e road conditions during the evalua- tion period were both dry and wet.
Carefully Considered A couple of other aspects of the Carol Stream Police study stand out as exemplary. First, they gave special attention to the order-to-
48 Police Fleet Manager Mar-Apr 2014
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