The 4.0, an engine used for a fairly brief period, had 253-255 hp (190 kW), barely more than the 3.5, but with 262-275 lb-ft of torque (the 3.5 had 250), and a wider torque curve for greater driveability. Gas mileage was, after its first year, actually higher than the 3.3 or 3.8 liter engines, when used in minivans.
Chrysler wrote: With 205 horsepower and 240 lb.-ft. of torque, the 3.8-liter V-6 engine produces more horsepower and torque than its predecessor (the 4.0 liter straight-six used by AMC and Jeep, not the 3.8 V6 long used on minivans and the Imperial). Compared to the 4.0-liter inline six-cylinder engine, the 3.8-liter is lighter and shorter, and maintains higher torque at speeds above 3400 rpm, allowing for an expanded operating range. [In the 2007 Pacifica, the 3.8 puts out 235 lb-ft of torque. It does not appear for the moment that the 3.8 has been revised; rather, it seems to have been put into higher production and used to replace the 4.0 I-6.]
The 4.0 engine is paired in the Pacifica (and most likely will be paired in minivans) with a new six-speed automatic (62TE) based on the current 41TE, which is also used with the 3.5 V6 in the new Sebring/Avenger. Quality is one of the key goals of the new transmission, according to sources. In the Dodge Nitro at least, the 4.0 is being paired with a five-speed automatic.
The engines are essentially stopgaps. The 4.0 line closed in 2010 and the 3.8 shut down in May 2011. The engines, based on the original 3.3 liter V6 launched in 1990, were the last of the original family of Chrysler V6s. They were produced at Trenton Engine North.
Horsepower and torque figures vary depending on the source and application. See the independent vehicle pages for exact figures.
The new engine uses a long stroke for improved low rpm torque, which provides quick and impressive engine response around town. The 4.0-liter V-6 engine produces 255 hp @ 6000 rpm and 265 lb. ft. of torque @ 4200 rpm, which is 15 more lb. ft. of torque at peak power rpm, and as much as 35 lb. ft. more torque throughout the power curve than the previous 3.5-liter V-6 engine.
“The 2007 Pacifica’s new 4.0-liter, V-6 engine improves the torque curve in the low- to mid-range for more pep during acceleration from idle,” said Bob Lee, Vice President – Powertrain Engineering. “Reductions in powertrain noise, vibration and harshness (NVH) also rank the new Pacifica among the best-in-class.”
When developing the 4.0-liter engine, Chrysler Group engineers focused on five primary Noise, Vibration and Harshness (NVH) metrics: engine vibration at the powertrain mounts, radiated noise, crank shaft torsionals, induction snorkel noise and sound quality. Attention to these metrics resulted in an improved engine design, which includes new main bearing diameters on the crankshaft, lower reciprocating mass piston and rod assemblies, an improved block and oil pan structure, reduced bearing clearance, low rumble intake manifold and an equal-length dual exhaust. During development of the 4.0-liter engine for the 2007 Chrysler Pacifica, the following design changes were made:
The 4.0-liter V-6 is a single overhead camshaft, 24-valve engine that utilizes a semi-permanent mold cast aluminum block with iron liners and cast aluminum cylinder heads.
"superduckie" wrote that Kenosha would make the 3.5 liter aluminum engine and the 2.7 V6, in addition to (for a while) the 4.0 liter AMC six. Trenton will make the 3.3 and 3.8 engines as well as the new 4.0 liter V6. The 4.0 is based off the 3.5 liter engine, while the 3.8 is based off the 3.3 — keeping in mind that these engines are all in the same basic family. It does not appear as though the new 3.8 liter engine is any different (other than minor tuning) from past 3.8s; the “new” part may just be application in Jeeps and a revised torque curve.
Until 2004, the 3.5 engine was made at Trenton along with a 3.2 liter version of the same block. The 4.0L V6 is being machined on the same machines as the 3.5L was at Trenton, with an enlarged assembly line. This is not being built at Kenosha. (Chrysler acknowledged that the 4.0 is based on the 3.5). Neither of these engines is related in any way to the 4.0 liter AMC straight-six.
Emissions: all use three-way catalytic converters, heated oxygen sensors, EGR, and internal engine features. Thanks, Doug Hetrick, for the horsepower rating updates.
All have electronic sequential multi-port injection (SMPI); engines are all semi-permanent mold aluminum block with cast-in iron liners, cross-bolted main bearing caps, and cast aluminum heads.
* That's in a Caravan. In the Wrangler, the 3.8 gets 205 horsepower and 240 lb-ft of torque - possibly due to tuning for more torque at lower engine speeds. (Thanks, Doug Hetrick.) (Or does it get 202 horsepower and 237 lb-ft of torque? The Dodge web site has both listed. Thanks again, guys!) ... the Wrangler Rubicon provides 16 mpg city, 19 highway, a far cry from the much-larger Grand Caravan's 18/25.
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