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Jeep Engineering Innovation: '07 Patriot

One of the most remarkable exercises in automotive engineering that has occurred of late is the development of the 2007 Jeep Patriot.

One of the most remarkable exercises in automotive engineering that has occurred of late is the development of the 2007 Jeep Patriot. This is not because the Patriot is the most economical product in the brand’s lineup (staring @ $14,985, including $560 destination), but there is that. It’s not because the Patriot can be optioned so that it has the kind of off-road capability that one would expect from a vehicle carrying the “Jeep” badge (e.g., the Patriot Limited with the Freedom Drive II and Off-road Package is “Trail-Rated”). No, that’s not it. What is truly remarkable is that the Patriot is based on the same platform and is built in the same assembly plant (Belvidere [IL] Assembly) as the Jeep Compass and the Dodge Caliber (the Belvidere plant has the ability to completely flex the production of any of the three vehicles from 0 to 100%, and it also would permit the piloting of a fourth model while the other three are being built). That’s right: a serious SUV shares architecture with its somewhat soft brand-mate and a five-door hatchback. That’s respectable engineering.

To assure that it is a solid vehicle, there is extensive use of high-strength and hot-stamped steel. They account for 40% of the vehicle mass. Essentially, a structural safety cage is created with the steels. For example, the B-pillar is fabricated with a lower section consisting of mild steel to assist in energy absorption in case of a collision and the upper with an ultra high-strength steel. The hot-stamped cross car beam bolted to the body structure is designed to take up to 60% of the load during side impact. Dual-phase steel is used for the front and rear rails, tunnel reinforcements, and floor cross-members. The front closure and upper cross members are hydroformed. Benefits of using these steel structural elements include, in addition to the impact performance, better NVH characteristics and weight reduction. For example, according to Matt Liddane, chief engineer for the Patriot, using hot-stamped high-strength steel for the A- and B-pillar and roof-rail reinforcements saved 44 lb. compared with conventional steel. (The curb weight ranges from 3,108 lb. for a Sport 2WD to 3,316 lb. for a Limited 4WD.)

The base engine is a 2.4-liter 172-hp (at 6,000 rpm) all-aluminum inline four that provides 165 lb-ft of torque at 4,400 rpm. The option is an all-aluminum inline four, a 2.0-liter that provides 158 hp at 6,400 rpm and 141 lb-ft of torque at 5,000 rpm. Both of these engines are members of the “World Engine” family produced by the Global Engine Manufacturing Alliance (GEMA) at its plant in Dundee, MI. GEMA is equally owned by DaimlerChrysler, Mitsubishi Motors, and Hyundai Motor. The standard transmission for the 2.4-liter is a five-speed manual, a Magna Driveline T355. The standard transmission for the 2.0-liter is a JATCO CVT2 continuously variable transmission. And for those who opt for the fully off-road setup Patriot, the version with the 2.4-liter engine and four-wheel-drive, there is the JATCO CVT2L, which features an integral low-ratio, or a “first gear” with an effective ratio of 19:1 for the torque required for extrapavement activities. (While on this subject: Freedom Drive I and Freedom Drive II both use an electronically controlled coupling (ECC) that is attached to the rear differential. Torque is transferred to the rear wheels through a two-stage clutch system; an electromagnet operates a low-torque clutch; its force is amplified by a cam-and-ball mechanism which, in turn, applies the main clutch for torque transmission to the rear wheels, based on input from the ECC. Freedom Drive II, in addition to ESP, ABS, and Brake Traction Control, deploys Hill-descent control, which modulates hydraulic brake pressure. There are also brake lock differentials to apply brake force to a wheel that is spinning faster than its mate on the same axle.)