Hendon Publishing - Article Archive Details
2006 Michigan State Police Patrol Vehicle Tests
Written by PFM Staff
Each year since the 1978 models, the Michigan State Police have tested a variety of police package (pursuit capable) and special service package (not intended for pursuit) patrol vehicles. These annual tests include acceleration to 100 mph, absolute top speed, braking from 60 mph after brake warm-up, road racing course lap times, an ergonomic and communications installation review, and EPA fuel economy ratings.
The acceleration, top speed, and braking phases are conducted at Chrysler’s Proving Grounds near Chelsea, MI. The vehicle dynamics testing has been performed on the 2.0-mile road course at Grattan Raceway near Grand Rapids, MI.
The police package cars included the 250 hp, 4.6L V-8 RWD Ford CVPI in both 3.55:1 and 3.27:1 rear axle ratios, the 240 hp, 3.9L V-6 FWD Chevy Impala, the 340 hp, 5.7L V-8 RWD Dodge Charger and Dodge Magnum, the 250 hp, 3.5L V-6 RWD Charger and Magnum, and the 295 hp, 5.3L V-8 2WD Chevy Tahoe.
The special service package (non-pursuit capable) included the 300 hp, 4.6L V-8 4x4 Ford Explorer, 300 hp, 5.4L V-8 4x4 Ford Expedition, the 295 hp, 5.3L V-8 4x4 Tahoe, and the 250 hp, 3.5L V-6 RWD Magnum.
The acceleration tests have maximum times allowed to reach 60 mph, 80 mph and 100 mph. The score for the event, however, is based on the zero to 100 mph times. The tests are conducted slick-top, no spotlights and with two troopers on-board.
Of the 2006 models, the fastest accelerating vehicles were the two Dodges powered by the Hemi V-8. The Charger V-8 and the Magnum V-8 both reached 60 mph in 6.5 seconds. The Hemi Charger took just 16.2 seconds to reach 100 mph, which is getting close to the Chevrolet Camaro’s time of 13.5 seconds. To reach 100 mph, the 2006 model, 3.55-geared CVPI took 23.4 seconds.
Apart from the two Hemi Dodges, the rest of the sedans all reached 60 mph within ½ second of one another, all clustered between 8.6 and 9.1 seconds. The 3.55-geared Ford CVPI was at the head of this second pack, followed by the Impala, the 3.27-geared CVPI, and the two V-6 powered Dodges. The two Tahoe SUVs, one gasoline powered, one E85 ethanol powered, were also in this same ½ second bracket…and near the front! For the record, the E85 (ethanol) powered Tahoe was a half second faster than the gasoline powered Tahoe.
Among the special service package SUVs, the 300 hp Ford Explorer was the hot rod. It reached 60 mph in 8.6 seconds, which was as fast as the 3.55-geared CVPI. While the Explorer was speed limited to 97 mph, it reached 90 mph just a quarter second slower than the faster of the two CVPI sedans. The other special service package vehicles (Magnum, Expedition, 4x4 Tahoe) all hit 60 mph in the 9-second bracket.
The second MSP test is top speed. At the end of the last acceleration run, the MSP troopers continue to accelerate the car around the 4.7-mile oval. The highest speed recorded anywhere on the course is the top speed of record. For one reason or another, all police and special service vehicles are electronically speed limited but not all vehicles actually reach that pre-set, limited speed.
This year, the top speed testing broke a record set in 1969. Those were the heady days of big block V-8s with massive carburetors and high compression ratios. The fastest officially timed police sedan was the 1969 440ci Dodge Polara with a top speed of 147 mph on this same Chelsea Proving Ground oval. The new record goes to the 2006 5.7L Dodge Charger with a top speed of 150 mph flat. The Camaros have reached speeds over 147 mph but this is a first for a 4-door police sedan. In fairness, this kind of performance was actually expected from the Hemi Charger.
What was not expected, or at least not outside of GM circles, was the incredible top speed of the new Impala. The 240 hp, 3.9L V-6 powered Impala reached 142 mph! That ties the best top speed from the old LT-1 powered Caprice. Actually, in most years, the Caprice ran in the high 130s. The V-6 Impala certainly does not have the torque-filled bottom end response of the V-8 Caprice but the acceleration to 60 mph is nearly as good (8.8 versus 8.2 seconds) and the top speed is the same.
There were no other top speed surprises. The 3.55-geared CVPI was speed limited to 120 mph, while the 3.27-geared CVPI reached 130 mph. The V-6 powered Dodges ran between 132 and 135 mph. The Hemi-powered Magnum was likewise limited to 135 mph. The 2WD Tahoe shut off at 124 mph. Braking
The MSP braking protocol involves two 90 mph full pedal stops to warm the brakes, followed by six 60 mph full pedal stops for score. After a heat soak period, these two 90 mph and six 60 mph stops are repeated. The best ten out of 12 stops from 60 mph are averaged for the final deceleration rate. This is then converted to a projected stopping distance from 60 mph.
The MSP has established a maximum stopping distance for their large patrol sedans, both RWD (Ford CVPI, Dodge Charger) and FWD (Impala). The standard is roughly the same at 149.7 feet and 149.1 feet, respectively.
The V-6 and V-8 Charger and the V-6 and V-8 Magnum all stopped in the 128 to 134 foot range. The V-6 Charger took the honors for the shortest stops from a 4-door police sedan. The 3.27-geared CVPI and the 3.55-geared CVPI were next with 143 foot stops. This was about a ½-car length longer than the Dodges. Compared to the 2005 CVPI, this was about a 4-foot improvement.
Ford Fleet had hoped the change to a 17-inch wheel would provide even better braking performance. By providing a little more air space around the rotors and calipers, the goal was for cooler brakes and even shorter stops. In reality, the better braking results for the 2006 CVPI was attributed as much to the 17-inch version of the Goodyear Eagle RS-A as any change in brake cooling due to the larger wheels or wheel vents.
The 2000 to 2005 model Impala has traditionally had the best brakes of any police sedan. The stops from 60 mph are usually in the low-130s. With basically the same rotors, calipers and pads, the 2006 Impala stopped in 151 feet. This slightly exceeds the maximum allowed by the MSP.
GM Fleet attributed the long stopping distance, an average of 12 stops, to a change in ABS software and hardware, and a lack of development time for the prototype police-specific braking system. While the retail Impala in on the market, the police package Impala had not yet gone into production. A retest was requested by GM Fleet, and these retests are occasionally performed on a case-by-case basis.
A few weeks after the MSP test, on the same Chelsea road surface and under similar ambient temperatures, the Impala was retested. The tweak was to the ABS software calibration which controlled the stop at speeds under 20 mph, i.e., the very end of the emergency braking. The Impala stopped in 142.5 feet, well within the MSP limits and 5-inches shorter than the Ford CVPI.
Most of the SUVs, whether police package or special service package, stopped from 60 mph in the 143 to 150 foot range. The 4x4 Tahoe took 156 feet. The heaviest SUV (Expedition) and the pursuit rated 2WD Tahoe produced the shortest stops at 143 feet.
The Grattan Raceway is a 2-mile, 13-turn road-racing course with a 3200-foot front straightaway. By the end of the straight, the Ford CVPI, for example, reaches 110 mph. The course also has a number of twists and off-camber turns. On some parts of the track, the cars get nearly airborne while on other sections of track the suspension almost completely bottoms out. Each car is driven five laps by four different MSP troopers from their Precision Driving Unit.
On the road course, the fastest two police package vehicles were Hemi-powered: the Dodge Charger V-8 was one-third second faster than the Dodge Magnum V-8. These vehicles were three seconds quicker than the next closest cars, the 3.55-gear Ford CVPI and the 3.27-geared Ford CVPI. With one minute, 40 second lap times, that three second interval between the Hemi cars and the CVPIs equates to a 15 car-length difference.
The 3.5L Dodge Charger and Dodge Magnum were ½-second behind the two Ford CVPIs. The 3.9L Chevy Impala was two seconds, or 10 car-lengths behind the two V-6 powered Dodges and the police package Tahoe 2WD was three seconds behind the new Impala.
Whether it was track conditions, air temperature, or the more responsive 17-inch wheels and tires, the Ford CVPIs were a little more than a 1-second faster than last year’s cars. The 3.9L Impala was a little more than a half-second faster than the 3.8L Impala from 2005. The Tahoe times were about the same.
On the road course, the two Hemi-powered Dodges, and especially the 2WD Tahoe, showed lots of wheelspin. On the police cars, the DaimlerChrysler Electronic Stability Program (stability control) is tuned for more aggressive driving than the special service or retail cars. As such, the ESP allows a little more wheelspin, a little more understeer, and a little more throttle-induced oversteer.
The Tahoe, however, is designed to allow wheelspin under heavy acceleration, which limits oversteer. This is why it is important to put the exact same General tires back on the Tahoe. It is important for the overall handling not to change the amount of traction (either more or less) given by the tires. The 2WD Police Tahoe is not equipped with GM’s StabiliTrak stability control system.
The MSP does not test special service package vehicles, like the Dodge Magnum, Ford Explorer, Chevrolet Tahoe 4X4, Ford Expedition, or Chevrolet Silverado on the road course. This is an emphasis that, in addition to clear and frequent written disclaimers from each manufacturer, these vehicles are not designed nor intended for high-speed or pursuit-style driving.
The Michigan State Police base their fuel economy rating on the EPA City mileage results. Fuel economy matters. Since fuel economy is a tangible cost, unlike acceleration to 100 mph, for example, some fleet managers consider this operating expense on equal footing with the initial expense of the vehicle. They are not going to spend $0.15/gallon difference for a car that runs on premium fuel. Yet selecting a patrol vehicle with a 1.7-mpg difference in mileage is (cost-wise) the same as selecting an engine that runs on premium.
The Ford CVPI, the V-8 powered Dodge Charger and Magnum are all rated at 17 mpg (EPA City). The Chevy Impala and the V-6 powered Charger and Magnum are all rated at 19 mpg (EPA City). The Tahoe in both 2WD and 4X4 is rated at 15 mpg (EPA City) while the 4.6L Explorer and 5.4L Expedition are both rated at 14 mpg (EPA City).
No police patrol vehicle ever gets EPA Highway mileage and only the easiest driven admin cars ever get EPA City mileage. Based on research conducted by the Illinois State Police, the patrol vehicles get between 70 and 75% of the EPA City rating.
As fleet managers divide police cars into so many categories, it is extremely difficult to point to any one car as a “winner” based on the NIJ-funded MSP tests. Across the nation, fleet bid categories are divided into FWD and RWD, into V-6 and V-8, and into body on frame and unitized body. In fact, these distinctions may do our municipalities a disservice. We should be specifying performance, not components.
For their part, regardless of vehicle platform, the MSP is careful to point out that these tests (the minimums, the maximums, and the category weights) are all designed for the way the MSP uses their patrol vehicles. Other departments will certainly use their patrol vehicles in a different way and this should put a different emphasis on the test results.
If some of the artificial bid distinctions are removed, and instead “police package sedan” is used, a winner in each category is obvious. The Charger V-8 has the fastest acceleration, the highest top speed, the quickest road course times, and the shortest braking distances. In the shootout among the V-6 police sedans, the results were evenly split between the V-6 Impala and the V-6 Charger.
Weighing the Test Phases
The MSP weighs the six test phases to suit the needs of a state police or highway patrol. The needs of city or county law enforcement agencies may be (and probably are) very different. While subtle changes have taken place, from time to time, the MSP typically weighs the tests as Road course: 30%, Acceleration: 20%, Braking: 20%, Top speed: 15%, Ergonomics: 10%, and Fuel economy: 5%. These numbers are plugged into a bid adjustment formula. This formula may be used by any agency and is available at the NLECTC website.
Different weightings may be selected. For example, an urban department may want to emphasize fuel economy, ergonomics, and braking while deemphasizing road course, acceleration, and top speed. Since most bids are close, this change in weighting may point to a different “most bang for the buck” police vehicle.
Published in Police Fleet Manager, Nov/Dec 2005
Rating : Not Yet Rated
Related ProductsRide and DriveSafetyTraffic, SafetyVehicle TechnologyVehicle Training
Click to enlarge images.