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Concept Police Cars and Future Drivetrains
Written by PFM Staff
The Michigan State Police (MSP) tested three promising prototypes during the annual Patrol Vehicle Evaluation. One was the Ford Crown Victoria Police Interceptor (CVPI) powered by a version of the Marauder DOHC V-8. Another was the standard CVPI fitted with a more aggressive rear gear ratio. The third was a pursuit-rated Chevrolet Tahoe.
The prototype CVPI used the 4.6L 4-valve, 4-cam engine detuned slightly to run on regular gas. The premium gas version used in the Marauder produces 302hp. With the knock sensor calibrated to run on regular gas, the double overhead cam V-8 produces an estimated 275hp. The slight power loss was deemed worth a $.10–15 per gallon cost avoidance for premium.
In acceleration and top speed, the 4-valve, DOHC powered CVPI was much faster than the 2-valve, SOHC powered production CVPI. The 4-valve car was a full second faster to 60mph, more than five seconds faster to 100mph and had a top speed of 141mph, which is 13mph higher than the production unit.
On the ultimate measure of police vehicle performance, the 13-turn road racing course, the Marauder-powered CVPI was a full two seconds faster than the standard CVPI, or 11 car-lengths over the distance of two miles.
The Ford 4-valve CVPI is fully as fast, or perhaps a click faster than the legendary Chevrolet Caprice powered by the LT-1 V-8. However, the 4-valve engine is not yet released for production in the CVPI. Nor has the price surcharge been established for the optional engine. Price adders between $1600 and $2400 have been discussed with some fleet managers.
The 4-valve CVPI used a standard 3.27 rear gear and was speed limited to 143mph. The higher top speeds were made possible by the use of a metal matrix driveshaft from a 2000 CVPI. The driveshaft remains an engineering and purchasing challenge. The four-inch Marauder driveshaft presents packaging (clearance) problems when used in the CVPI.
The other prototype from Ford was a standard CVPI modified with some off-the-shelf parts. It had a 3.55 rear gear, instead of 3.27 gears, to improve acceleration. It also used the larger air intake box from the Marauder for an estimated 7hp increase. The 3.55 gear required the same out-of-production metal matrix driveshaft, and was speed limited to 129mph. The production CVPI used these same 3.55 rear gears in 1999 and 2000, but was then mated to a 215hp engine. The current CVPI engine is rated at 239hp.
Compared to the standard 3.27 geared CVPI, the 3.55 geared CVPI was one third of a second faster to 60mph and 1.8 seconds faster to 100mph. Interestingly, the 3.55 geared CVPI was no faster around the road course than the production CVPI. We will know more about the availability of the 3.55-geared CVPI in six months.
Don’t even think of a 5.4L V-8 in the CVPI. The frame of the Police Interceptor will now accept the taller 5.4L V-8. And the earlier windshield wiper motor interference was solved for 2001. The SOHC 5.4L V-8 is no more costly from an initial purchase or operating expense view (except gas mileage), or more complicated from a maintenance and repairs view, than the SOHC 4.6L V-8. However, the high-torque 5.4L V-8 is limited by production capacity. Every 5.4L engine Ford makes goes into a truck. If they could make more of these engines, more trucks would get the 5.4L.
While the powertrain for the CVPI in the next few years is still uncertain, the long-term future of the V-8 powered, rear wheel drive Panther platform is very bright. It is reported to be in Ford’s production planning cycle through 2011.
The third concept vehicle at the MSP tests was Chevrolet’s pursuit-capable Tahoe. Pursuit-rated SUVs are a fast-changing and perhaps controversial area of police fleets. For the 2003 model year, except for the GM Hummer H1, no police vehicle manufacturer produces a police package (pursuit-capable) SUV. The Tahoe, Explorer, Expedition and Excursion are all special-service vehicles. All are sold with disclaimers like, “Not designed nor intended to be used at high speeds, for emergency driving or as a pursuit vehicle.”
Ford is looking at its pursuit-capable SUV options, considering the Explorer, and acknowledging a need exists for such a vehicle. While a Roush-prepared Expedition was displayed at the 2002 model year MSP tests, this is not an active project at Ford.
Dodge is also researching a pursuit SUV. DaimlerChrysler dropped the Jeep Cherokee after the 2001 model year. These 2WD and 4WD police vehicles were replaced for 2002 by the Dodge Durango in 2WD and 4WD, with the special service package. In the retail market, the Jeep Cherokee has been replaced by the Jeep Liberty. While the Liberty looks smaller than the Cherokee, it is actually larger. DaimlerChrysler ruled out the Liberty as a police vehicle because it had an external spare tire. However, a number of police departments have expressed interest in a police version of the Liberty. DaimlerChrysler is currently reconsidering a police or special service package for the Liberty.
The Dodge Durango was originally released as a pursuit-capable police package but was later downgraded to special service due to development costs. Dodge will not produce a pursuit-capable or special service package Durango SUV until the current model is redesigned for 2005.
Chevrolet is the closest to making a police package SUV. They had a hot rod prototype of the Tahoe 2WD at the 2002 MSP tests. It accelerated to 100mph five seconds faster than the Dodge Durango and lapped the Grattan Raceway one second faster than the Chevrolet Impala.
The pursuit-rated concept Tahoe was back for the 2003 MSP tests. Again, it was a 2WD. Chevrolet has no plans for a pursuit-capable 4WD vehicle. The concept Tahoe shares the same 5.3L V-8 powertrain as the 2WD special service Tahoe and the acceleration times were virtually identical. However, the pursuit-capable SUV was not speed limited to 98mph like the standard Tahoe. The pursuit concept reached 127mph, comparable to the police Impala and Ford CVPI.
The pursuit concept Tahoe has a very different suspension from the special service Tahoe. It has stiffer springs, which also lowers the Tahoe, and shocks to match the springs.
The MSP did not run the standard Tahoe on the road course, since they do not run any special service vehicles under pursuit-like conditions. This makes direct comparison with the pursuit-capable Tahoe impossible. However, the pursuit Tahoe was almost a second faster around the road course than the police package, pursuit-rated Impala and about one and a half seconds from the Ford CVPI.
Ford’s 3-valve Modular V-8
For 2004, the 5.4L V-8 used in the Ford Expedition will be upgraded to a 3-valve combustion chamber and variable cam timing: two intake valves and one exhaust valve along with a center mounted spark plug. The engine that breathes better produces the three-way win of more horsepower and torque, better fuel economy and cleaner emissions. Normally, one or two of these must be given up to gain the other. The engine currently produces 260hp and 350lb-ft of torque. The current 5.4L 2-valve engine produces 260 hp and 350 lb-ft of torque. The 2004 5.4L 3-valve engine will deliver 300 hp and 365 lb-ft of torque, a 15% increase in horsepower and five percent increase in torque.
According to Ford Powertrain, the extra intake valve in the 3-valve layout adds performance at the low and mid rpm range. At lower rpms, getting air in the engine is the problem; at higher rpms, getting air out of the engine is the problem. The second exhaust valve in a 4-valve engine only significantly helps at engine speeds above 5000 rpm. The 3-valve engine acts like a 4-valve engine for most of the powerband used by law enforcement.
The more valves the engine has, the better it breathes. It is simple geometry. Draw a circle that represents the cylinder. Then draw the two largest circles (valves) that will fit inside the circle (cylinder). You will see lots of wasted area. Now, draw the three largest circles that will fit. Then draw the four largest circles that will fit. The more valves, the more area is available for airflow.
All of this is important to law enforcement because, for emissions and fuel economy reasons, Ford has plans to eventually convert all of its Modular V-8 engines from 2-valve to 3-valve. And that includes the 4.6L V-8 used in the CVPI. The timing is uncertain. What is certain is the CVPI will get a considerably more powerful engine in the next few model years. Maybe a regular fuel version of the Marauder 4-valve V-8 producing 275 hp, as an option. Maybe a 275 hp (remember 15% more), 3-valve V-8 used across the board.
Dodge RWD V-8
Rumors of a RWD Dodge Intrepid have circulated in police circles ever since the FWD vehicle was first tested by the MSP in 1993. Fueled by an LH platform design that would technically allow a FWD, RWD or all-wheel drive layout, and fanned by Mopar enthusiasts who remember the Dodge and Plymouth police cars of old, the rumors have been kept alive for a decade.
After the debut of the 2004 Chrysler 300N during the Detroit Auto Show in January 2003, denying the return of a rear wheel drive, V-8 powered Mopar police car will no longer be possible. The 300N will be DaimlerChrysler’s new large car with a three-inch longer wheelbase. The police powertrain is, of course, uncertain at this point. Even if the Chrysler 300N gets the 350hp 5.7L Hemi V-8 from the truck line, there is no assurance that the V-8 will be used in either the long-awaited large Dodge passenger car or Dodge police car.
The likely standard engine is the 300hp version of the 3.5L V-6, which is 50hp more than the present Intrepid police engine. The V-8 may be optional in the police Dodge. A large Dodge sedan is a likely bet for late in the 2004 model year or early in 2005, since all of the LH platform cars are made at the same assembly plant in Brampton, Ontario.
As for the Chevrolet Impala, the slowest of the police sedans, do not expect the Impala to get a V-8. The V-8 program for the Impala/Monte Carlo platform has been shelved. The Pontiac Division has a 3800 V-6 in the Grand Prix sister, which achieves 230hp by the use of a supercharger. Interestingly, Chevrolet Fleet did not rule out supercharging as an option to improve acceleration. Put another way, the supercharger will happen on the Impala before a V-8 of any size. Since questions about the return of the Caprice are raised every time fleet managers gather, no matter what powertrain enhancements are made, the Impala will remain front wheel drive. Of course, rumors and questions about the Australian-made Holden keeps coming up in those same gatherings.
Published in Police Fleet Manager, Jan/Feb 2002
Rating : Not Yet Rated
Related CompaniesChevroletDaimlerChryslerDodgeFord Motor Company
Related ProductsChevy TahoeDodge DurangoDodge IntrepidFord CVPI (Crown Victoria Police Interceptor)Ford ExpeditionFord ExplorerMarauderMSP TestingVehicle Performance
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