Which car has better mileage? A Jeep Grand Cherokee 2006 with?

Question

a V8 4.7L engine or a Hemi 5.7 L engine? I heard that the Hemi has less fuel consumption due to higher technology ( Shutting 4 cylinders when RPM is less than 3) , any Hemi owners answers?

Answer 1

I would suspect that you would obtain better fuel mileage with the smaller 4.7 engine. While I do not have any personal experience with either engine, one of my associates does have a new Chrysler 300C equipped with the 5.7 engine you describe. The car is certainly lighter in weight and easier to propel than is a Grand Cherokee. He is only able to obtain a dismal 17MPG on the highway in this car, even though it is equipped with the cylinder shutdown feature you describe. In other words, the shutdown feature doesn't do much to improve mileage.

A car the size of the 300C should be capable of well over 20MPG with an appropriate engine.

Answer 2

The 4.7-liter V-8 was updated for the 2005 model year and was the mid-range engine in 2005-2007 model Grand Cherokees. The engine produces 235 hp (172 kW) @ 4700 rpm and 290 lb-ft (393 N•m) of torque @ 3700. Dual knock sensors have been added for 2005 and enable improved engine calibration for both fuel economy and power output. The updated engine has improved NVH characteristics, realized through the use of composite valve covers, structural improvements to the air box and resonator and improved dampening of the heat shields. An EGR valve is now used to reduce NOX emissions while improving fuel economy by replacing some of the incoming fuel/air mixture with inert exhaust gas.

The Dana corporation supplied the new reduced-tension piston rings and the rod bearings. Dana also supplied the new cylinder-head, cam-cover module. The new thermoset plastic cylinder-head cover module was developed in just 12 months and replaces a magnesium component. Due to innovative manufacturing processes, Dana was able to reduce the overall cost of the module, while incrementally improving noise, vibration, and harshness, or NVH.

The vinyl ester glass-reinforced thermoset plastic modules, which are unique to the left- and right-side cylinders, include the cover, gasket, and fasteners. These components are produced at Dana's Composite Sealing Center in Paris, Tenn. With this new sealing system, Dana developed a custom compound material for gaskets and grommets. Dana also provided prototyping for the gasket and isolator molds to ensure the design met all of Jeep's specifications. The system relies on a self-retaining, "press-in-place" gasket to improve function and quality consistency. This innovation eliminates the time- consuming and costly steps of precisely aligning and attaching the gasket to the valve cover with adhesive.
2008 models of the Grand Cherokee and Commander will feature a new updated 4.7-liter V-8. The new engine offers better fuel economy, power, and torque than the previous 4.7-liter engine, while increasing refinement, thanks to dual spark plugs per cylinder, increased compression, better cylinder-head port flow, and a new combustion system. The result is 290 horsepower, a 25 percent increase; and 320 lb.-ft. of torque, a 10 percent increase. The engine is still capable of operating on E85 ethanol fuel. Smoother and quieter running came from revisions to the induction system, a lightweight piston/rod assembly, reduced accessory drive noise through lower accessory drive speed, and a new valve-lash adjuster system. The new 4.7-liter V-8 is also equipped with Electronic Throttle Control.



The 5.7-Liter V-8 HEMI engine that powers the 2005 Jeep Grand Cherokee uses aluminum cylinder heads with hemispherical combustion chambers, creating outstanding airflow leading to high power and torque. The engine produces 330 hp (246 kW) @5000 rpm and 375 lb-ft (502 N•m) @4000 rpm. Dual ignition (two spark plugs per cylinder) increases peak power and torque, reduces exhaust emissions, increases fuel economy and provides a smooth idle. The combustion system has been refined and the engine uses direct-mount accessories for quieter operation.

“Two legends combine with the introduction of the modern HEMI V-8 in the 2005 Jeep Grand Cherokee,” said Eric Ridenour, Executive Vice President—Product Development. “The HEMI is the most powerful engine ever offered in a Grand Cherokee and easily gives the vehicle best-in-class power.”

Fuel economy has also been improved, but not at the expense of HEMI performance. Chrysler Group has developed the Multi-Displacement System (MDS) that deactivates four cylinders when the V-8 is not needed. The 2005 Grand Cherokee is the first SUV to offer fuel-conserving MDS.

The Chrysler Group MDS seamlessly alternates between smooth and economic four-cylinder mode when less power is needed and V-8 mode when more power from the 5.7-liter HEMI engine is in demand. This optimizes fuel economy when V-8 power is not needed without sacrificing vehicle performance or towing capability.

“The MDS was part of the engine’s original design,” said Bob Lee, Vice President—Powertrain Product Team. “This results in a cylinder deactivation system that is elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost.”

Some of the significant technologies enabling the MDS are the speed of electronic controls, the sophistication of the algorithms controlling the systems and the use of Electronic Throttle Control. The HEMI is able to transition from eight cylinders to four in 40 milliseconds.

This engine and MDS has completed over 6.5 million customer-equivalent miles through Chrysler Group’s development and durability testing. It is covered by the seven-year/70,000-mile Limited Powertrain warranty.

The HEMI engine that powers the 2005 Jeep Grand Cherokee uses aluminum cylinder heads with hemispherical combustion chambers, creating outstanding airflow leading to high power and torque. Dual ignition (two spark plugs per cylinder) increases peak power and torque, reduces exhaust emissions, increases fuel economy and provides a smooth idle. The combustion system has been refined and the engine uses direct-mount accessories for quieter operation.