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Chrysler - Dodge - Jeep 3.8 liter V6 engines

The 3.8 liter V6 was a conservatively designed, wider-bore, longer-stroke version of the then-new 3.3-liter V6. It was a good, solid engine from the start — not the highest performer or the lowest, but relatively quiet, driveable, and reliable.

3.8 liter V6

The 3.8 was first used in the 1991 Chrysler New Yorker, Chrysler Imperial, and Dodge Dynasty. It was extremely similar to the 3.3, except for the bore and stroke — which required different pistons and connecting rods, a different upper intake manifold, and a revised crankshaft (the valves were the same). Low-end torque was good for an engine of its size, but it had a fairly low redline; the 3.3 could feel sportier as it wound higher.

1991 3.8 V6 engine diagram

In its first three years, the 3.8 produced 150 horsepower at 4,400 rpm — the same as the 3.3 (and more than the 5.2 V8 of the time) — with 204 lb-ft @ 3,200, 15% more than the 3.3. It would eventually hit 205 hp and 240 lb-ft of torque.

The 3.8’s heads had alternating intake and exhaust valves, with symmetrical ports; pushrods (rather than an overhead cam) acted on two valves per cylinder throughout its life. To cut maintenance costs, the 3.8, like the 3.3, had a chain-driven valvetrain (the newer 3.5 and 4.0 engines would use belts).

3.3 and 3.8 engines

The first version had two squish areas, around a third of the bore area; cylinders were fed by multiple point fuel injection and a two-piece cast aluminum intake.

Why pushrods? One engineer wrote that management took the cost-effective approach, after a survey of potential customers showed no clear preference. “Ford’s Taurus engines and GM’s 3.8 used pushrods, so why not us?”

3.8 photo

The 3.8 had distributorless ignition for its full run, using Hall Effect sensors on the transaxle and engine (front cover module) to find crankshaft position and speed; the computer could figure out the injection/ignition sequence within a single crank for fast starting. It had three coils, firing two plugs at once (one fired during the exhaust cycle, so they would not need six coils). Spark plugs were gapped to 0.050 inches. When launched, EGR was only needed in California; and there was no need for an air pump or aspirator.

engine

Regular upgrades kept the engine competitive. All the cars it was used in were dropped after the 1993 model year, but the minivan was given a revised intake plenum and sequential fuel injection for the 1994 minivans, where it provided a much-needed torque boost. It would remain a minivan engine until the end.

The intake and exhaust were updated for the 1996 minivan redesign, adding just 4 hp but boosting torque by 14 lb-ft — coming in at 3,100 rpm instead of 3,600. The company also dropped noise at wide-open-thrttle by 4 dBA, and added 100,000-mile platinum-tipped spark plugs. (See full details on our 1996 minivan changes page.)

jeep 3.8 liter V6 engine

For this model-year, both the 3.3 and 3.8 gained a much broader torque curve, emphasizing the 2,400-4,800 range. This was done by retuning the intake manifold with longer primary runners (16 inches long); reducing restrictings to the air intake; cutting exhaust resistance; coating pistons to reduce friction (late in the 1996 model-year); and recalibrating ignition and fuel injection.

Chrysler also cut the idle speed, for better city mileage, and added a knock sensor so the spark advance curve could be advanced further without risking detonation from bad gasoline.

final 3.8 engine

Power and torque both went up again for the 1998 minivans; the addition of a two-length variable intake, 24% larger throttle bore, smoother cylinder bores, and new heads with higher compression, provided a hefty horsepower gain for the 2001s, up to 215 hp, with torque rising by 5 lb-ft to 245. Emissions dropped by 17% at the same time.

Adjustments made for 1999 cut hydrocarbon emissions by around 69%, while dropping NOx emissions by 43%, compared with the 1998 design, according to Chrysler, due to “base engine, calibration, and exhaust after-treatment refinements.”

Years bhp Torque
(lb-ft)
Notes
1991-93 150 203 First year (9.0:1 c/r)
1994-95 162 213 New intake plenum, SMPI
1996-97 166 227 Revised intake and exhaust
1998-2000 180 240  
2001-04 215 245 Variable intake, other changes
2005 207 238  
2006 205 240  
2007 200 235 Minivan/Pacifica
2007-08 202 237 Jeep version
2009-10 205 240 Jeep version
2008-10 197 230 Minivan/Pacifica version

The 3.8 was added to the 2005 Chrysler Pacifica crossover as a base engine.

The 2007-or-so retuning dropped power ratings, but flattened the torque curve for more of a punchy feel.

last engine

As for the Jeep Wrangler version — launched in 2007, to replace the aged AMC 4.0 liter straight-six — it out-powered (at peak) both its predecessor and the minivan version. The 3.8 was also lighter and shorter, and had higher torque when above 3400 rpm. The old 4.0 had stronger low-end torque.

The Dodge web site listed 202 horsepower and 237 lb-ft of torque for the Nitro version.

Years Compression
1991-95 9.0:1
1996- 8.9:1
2001-10 9.6:1

Redline was set at a low 5,400 rpm. The oil capacity was four quarts.

Category 3.8 Liter
Bore x Stroke
3.78 x 3.43 (96mm x 87mm)
Valve System
12 valves, roller followers, hydraulic lifters
Fuel
Regular (US: 87 octane)

One problem, relatively common but still rare, is rocker arm pedestal breakage. Repair information is at the 3.3 page. This may have been resolved by Chrysler.

The Trenton Engine plant made its last 3.8 liter engine on May 20, 2011.

What might have been?

Doug Miske wrote (around 2001) that a special project engineer at the Brampton plant had said:

One 24-valve 3.8L V6 showed up for a special installation into a “300M - II” mule, needing a modification to the hoodline of the 300M (the 3.8 is a bit taller). Output was estimated at about 290 hp @ 6200 rpm, 290 lb-ft @ 4200 running on 91 octane (not 89 as on the 3.5L). Maintaining traction on full-throttle launches was a challenge and generated some nice stripes when the traction control was switched off. The 300M - II had P225 55ZR17 Michelin Pilot XGTZ4 tires.

The other 3.8 was installed in a 1999 SWB Caravan Sport, and was tuned to run on 87 octane unleaded. Output was estimated in the 240 hp, 260 lb-ft area. The 3.8 burned less fuel than the current 3.3L, with lower emissions. [The company appears to have made a 24-valve 4.0 instead.]

last 3.8 liter V6 head

Some engine creators: Willem WeertmanPete Hagenbuch • Marc Rozman


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