The 2.7 Liter V6 Mopar (Chrysler-Plymouth-Dodge) Engines
Willem Weertman wrote, in his engines book, that the 2.7 liter engine started with Francois Castaing’s believe that an advanced, lightweight, efficient engine was needed to secure Chrysler’s reputation. The engine was, therefore, a new design using aluminum blocks and heads, dual overhead cams, 24 valves, and other features to assure efficiency.
Released in 1998, it had a smaller bore and stroke than the 2-liter four-cylinder “Neon” engine; and, since the company already had bigger V6 engines, the cylinder spacing and deck height were both made much smaller, at 104 mm and 210 mm respectively, than those of the 3.2/3.5 engines. The aluminum block was protected from wear by iron bore liners, cast in place; six attaching bolts were used for each of the four main bearing caps, some also attaching a windage tray — which also did double duty, stabilizing the four caps to cut noise.
The 2.7 liter engine’s timing chain drove the water pump (the oil pump was direct-drive from the crank); the engine was an interference design, making the timing chain a prudent choice over a belt. The heads and block were extended to provide a cavity for the chain. The intake valves (inner) and exhaust valves (outer) were driven by separate camshafts, made of steel tubing and hardened steel lobes — a method that cut weight from the usual solid camshafts. Short roller chains connected each intake cam to its exhaust cam; the chains had hydraulic tensioners.
The combustion chamber of the 2.7 was a pent-roof design, with center-mounted spark plugs. Rocker arms with roller followers were similar to those of the 2.0 liter four-cylinder.
All the 2.7 engines had coil on plug ignition, with no spark plug cables, and sequential multiple point fuel injection.
The power output per liter ended up being the highest of any Chrysler V-engine, at 74 hp/liter, not far from the DOHC 2.0’s 75 hp/liter. The compression ratio was 9.7:1 at launch, with 200 hp (149kW) at 5,800 rpm and 190 lb-ft (258 Nm) at 4,850 rpm. The engine weighed 337 pounds.
A Magnum version of the 2.7 liter engine uses a variable intake system, building on Chrysler's work back in the 1950s and 60s (other automakers have also used variable intake systems). It varies the length of the intake manifold tubes to create a small, but useful, supercharging effect at different engine speeds. In the past, tuning the air tubes for a boost at one engine speed sacrificed power at another; this is similar to variable valve timing in that it avoids choosing one engine speed over another for performance increases. Regardless of Magnum or standard engine, the intake was reinforced nylon, with a far smoother surface than an iron intake, feeding a single throttle body.
The 2.7 in the LX had electronic throttle control and an enhancement to the intake manifold (described in greater detail below).
The 2.7 liter engine originally had a tendency to generate sludge which caused engine failure. Similar problems have been appearing on Toyota and Volkswagen engines. We were told that, shortly after the first reported cases, Chrysler isolated the problem to the crankcase ventilation system; hydrocarbons were entering the oil and breaking down the additives. This problem was solved (around 2002-2004), and the number of engine failures appears to be small.
Bob Sheaves suggested that the DOHC 2.7 engine was derived from the 3.5 liter V6 engine ("I refer to the development design and components, and not what eventually became production.") Specifically, he wrote that the 2.7 was developed from the 3.2, which was developed from the 3.5 all at Highland Park and later, at CTC. There were several changes, but the starting point for all was the 3.5. Willem Weertman’s Chrysler Engines book suggests that the 2.7 was based off the 3.5, but he agreed that it was in its own engine family.
The 2.7 V6 engine cut noise from 3.5 levels:
- The forged steel crankshaft, engineered using finite element analysis (FEA), had 26% greater torsional stiffness, and was the stiffest crankshaft Chrysler had analyzed up to that point
- The cast aluminum cylinder block had 28% greater torsional stiffness, thanks to FEA studies that focused on torsional frequency, lateral bending, and torsional bending. The block featured:
- Extensive ribbing
- Six bolt main bearing caps — four vertical, two transverse. For quietness, the natural frequency of the bearing caps exceeded the firing frequency of the engine. Stiff bearing caps reduced wear caused by deflection under load
- A structural beam windage tray added support to the main bearing caps to increase overall stiffness
- The air conditioning compressor and alternator mounted directly to the block and structural oil pan, rather than using brackets. Only the power steering pump, the lightest of the accessories, mounted on a bracket. This increased mounting stiffness compared to the 3.5:
- Air conditioning compressor: 68% stiffer
- Alternator mounting: 13% stiffer
- Power steering pump mounting: 5% stiffer
- More precise control of reciprocating masses and better balancing cut nominal engine unbalance by 27%. Pistons were 14% lighter than before, relative to their bore size.
- Low rumble intake manifold had three tuned intake runners from each bank of cylinders, connected to its plenum chamber in a cluster or focal point. Standing air pressure waves at the mouth of each runner were essentially in phase, while prior manifolds had waves out of phase at low speed, resulting in rumbling noises.
- While providing overall stiffness to the block, ribbed block sides broke up flat surfaces into small sections that are too stiff to resonate with engine internal noises
- Isolated composite valve covers prevented vibration in resonance with the internal noise in the cylinder head; the composite material had inherent damping characteristics.
The following information was provided by Chrysler.
Chrysler 2.7 liter V6 engine specifications: 2004 revisions
In 2004, the 2.7 liter engine was modified for the LX series to produce more low-speed torque at launch and during mid-range operation for strong performance in everyday driving. The engine produced 190 hp at 6400 rpm, and 190 lb.-ft. of torque at 4000 rpm. This was done by using a new active dual-plenum intake manifold tuned for improved low-speed torque.
The manifold included a manifold tuning valve added to low-speed torque — increasing part-throttle torque by 8-10% in the primary driving range of 2100 to 3400 rpm, giving better performance in normal driving; and also adding to torque under full throttle.
Another addition for the LX cars was electronic throttle control ("drive by wire"), which allowed more consistent speeds on rolling grades with cruise control; it interacted with the transmission control system to cut gear hunting, and tailored throttle response to pedal movement based on operating conditions. For example, a large pedal motion at a standing start may open the throttle less than the same pedal movement at highway speeds.
The 2.7 liter engine was used in this configuration on the 2008 Chrysler Sebring and Dodge Avenger, and on the 2009 Dodge Journey.
Chrysler V6 engines compared with those of competitive cars, 1998
|Vehicle||Engine||BHP||RPM||Octane||Cost As Tested|
|Acura 25TL, 1997||2.5L||176||6300||Premium||$30,478|
|Ford Taurus, 1996||3.0L||200||5750||Regular||$24,205|
|Cadillac Catera, 1997||3.0L||200||6000||Premium||$34,750|
|Nissan Maxima, 1997||3.0L||190||5600||Regular||$24,675|
|LH series, '93-'97||3.5L||214||5850||Mid-Grade||$24,270|
|Mitsubishi Diamante, '97||3.5L||210||5000||Premium||N/A|
Competitive information from manufacter's press kits and data books - sorted in order of output per liter. Fuel mileage not available.
Chrysler V6 engine specifications - “LH” series, 1998-2007
|Category||2.7 Liter (a)||2.7 liter (b)||3.2 liter (to 2002)|
|Bore x Stroke||3.39 x 3.09 (86 x 78.5mm)||3.66 x 3.19 (92 x 81)|
|Power: hp (kW)||
200 (149) @ 6000
|190 (142) @ 6,400||220 (164) @ 6600|
|Torque: lb-ft (Nm)||
188 (254) @ 4900
|190 (258) @ 4,000||222 (301) @ 4000|
|Max. RPM||6464||6,600||6800 rpm|
|Fuel||Unleaded regular, 87 octane|
| (a) at launch
(b) this setup started in 2004 and was completely phased in by 2007.
Emissions: all use at least one three-way catalytic converter, quad-heated oxygen sensors, EGR, and internal engine features. 3.8 meets Tier 2 bin 5 (federal) and LEV 2 (CA) specs; 4.0 meets Federal tier 2, bin 8 and ULEV1 (CA) specs.
The 2.7 liter engine was phased out in favor of the Pentastar V6 starting with model-year 2011.