Chrysler - Dodge 3.5 Liter V-6 Engines
The 3.5 liter V6 has its roots in the 3.3 liter V6, launched in 1990; first used in the new LH platform, it was the basis of the 2.7 and 3.2 liter V6 engines. The 3.5 was Chrysler's premium V6 engine for cars for most of its long life, with its leadership ending only when the Pentastar V6 became available in the 2011 models.
As with the 3.3-liter engine, the 3.5 was manufactured at Chrysler's Trenton, (Mich.) Engine Plant. The oil pan is the only identical component between the 3.3 and 3.5. However, presumably to speed design or reduce tooling costs, the 3.5 had the same bore spacing and main journal and crankpin diameters as the 3.3 and 3.8.
Francois Castaing said:
It was a challenge because when we started the LH program in January, 1989, the only engine we knew we had for sure was the 3.3-liter V-6. But we felt if the car was to be a success, it needed a brand new, high power, high technology engine.
The engine people on the team knew they had never designed a new engine that quickly (40 months). Also, the investment would be quite high. There also was the fear that when you commit a lot of money for the company, you want to commit it right and not make a mistake. Still, the team and engine people within the team realized the LH would not be a success unless the new engine was there at the same time we launched the car.
So instead of giving in to the negatives that it couldn't be done, that we couldn't get the technology, the slickness, the power, the low emissions, the fellows said, 'let's go for it.' They challenged themselves, they were convinced the 3.5 engine was an absolute cornerstone for the car.
When introduced in 1993, the 3.5 hit 214 horsepower at 5,800 rpm, with 221 foot pounds of torque at 2,800 rpm. Mechanical noise levels were the lowest of any engine ever measured by Chrysler. This was an exciting engine compared to just about any competitor.
Like other major systems on the LH, the 3.5-liter engine was designed to meet or exceed the powerplant Chrysler engineers considered the best in this segment -- in this case, the 3.2-liter 24- valve engine in the Acura Legend. The executive engineer in charge of the engine was Gordon Rinschler; he specified a deep-skirt cast iron block and forged steel crank, due to the power involved.
Nestled in a compact, 60-degree block of cast iron with"over square" bore and stroke, Chrysler's 3.5-liter engine had the highest compression ratio -- 10.4:1 -- of any Chrysler-built engine in recent memory. It used bottom-feed fuel injectors, a first for high-volume passenger cars, to fit into the LH and improve hot restarts. Cross-bolts on the #2 and #3 main bearing caps added strength and cut noise.
'This truly is a premium engine and as 'bullet proof' as we could make it. At this stage, I'm more confident about the 3.5 than any engine I've ever been involved with," said Howard B. Padgham, powertrain engineer - who had at the time 28 years in Chrysler engineering, 15 devoted to engines, including Chrysler's 2.2, 2.2 Turbo and 2.5 four- cylinder engines, as well as the 318 V-8 and the 360 V-8 special, high-performance"police" engine package. "The 3.5 has the basic ingredients you'd expect from a premium engine: forged crankshaft, free-floating piston pins ... those sorts of things."
LH's trend-setting Cab Forward exterior design presented challenges, according to Padgham. "It's sloped like the hood to fit just like a hand in the underside of a glove. Notice the shape of the cylinder head, the design of the intake manifold. They reflect the space we had to work with."
The 3.5 liter engine was, at first, restricted to Chrysler brand LH models; it then spread to the Dodge Intrepid R/T, where it was dropped down to 242 horsepower (on regular gas; it had used midgrade in the Chryslers). It was later used in 242 - 250 hp form in the Chrysler Pacifica, Dodge Charger and Magnum, Chrysler 300C, and, with 232 hp due to the small engine bay, in the 2008 Dodge Avenger/2007 Chrysler Sebring.
The first generation 3.5 was a single overhead cam, 24-valve design, with a deep skirt and cross-bolted mains, with a 96 mm bore and 81 mm stroke. The engine was always a single cam design, unlike the DOHC 2.7 liter V6 that was launched at the same time as the second-generation 3.5. All 3.5 liter V6 engines from Chrysler had distributorless ignition (shifting from coil packs to coil-on-plug in later years) and sequential multiple port fuel injection.
John Hurst designed a single-cam-per-head setup with dual valve rocker arm shafts, a design that cut costs for the four-valve-per-cylinder setup. Spark plugs were centered in the combustion chambers, and the intake valves were 35 mm with 29 mm exhaust valves. The engine was free wheeling, to avoid damage if the timing belt (which also drove the water pump) broke. The aluminum intake manifold was built in two sections, with two throttle bodies. The intake branch length, 315 mm, was tuned to increase torque.
Two plenums were used in the first generation; a valve, normally closed, allowed them to connect quickly during wide open throttle in the 3,200 to 4,000 rpm range, for extra torque.
Chrysler - Mopar 3.5 V6 vs Mercedes V6
In 1998, both Chrysler and Mercedes produced 3.5 liter V6 engines. Burke Brown wrote:
... [Mercedes] had done an aluminum block 3.5 and so had we. ... The only real difference is that ours was what we called semi-permanent mold, and we had cast in liners, casting in cast iron liners. So at least by our view we had the best of both worlds. We had a perfectly round iron bore, unlike a cast iron block, where the water jacket isn’t always the same thickness, so the water cooling for the cylinder isn’t as perfect as we could get it because everything was just the same.
... They had no liners. But they were doing a process where they would treat the aluminum and harden it. They were etching away the soft stuff until just the hard part of the aluminum cell structure was there. I forget all the fancy details, but it was working for them, but it was a more expensive process than our kind of brute force way.
But ours was bulletproof. To this day, I’ve never heard anybody talk about an aluminum engine that’s had a liner come loose or leak or anything like that. Never. I mean, I’ve talked to guys with 3.5s with 150 to 200,000 miles on them and never had to take anything apart.
The second generation 3.5 liter V6 engine: 1999 to 2010
The 3.5 liter V6 engine was modified and switched to an aluminum block; it produced 232 to 253 horsepower in its second generation, and was most often rated at 250 horsepower. When launched, Chrysler wrote:
The new high output 3.5-liter engine is the best performing V6 available today in terms of total horsepower and torque — more than the BMW M3 [I6], Ford Taurus SHO [V8], Lexus GS300, or Mercedes E320 — with 250 horsepower at 6600 rpm, 250 pound-feet of torque and a compression ratio of 10.1:1 The high output 3.5-liter also is among the leaders in specific torque and the only one to optimally run using mid-grade fuel.
Engineers optimized a combination of components from air intake to tailpipe exhaust to maximize air-flow. [It was] designed with low induction restriction, a larger throttle body, large intake valves and a large throat area to support the high flow intake port and chamber allowing more air to enter the system. Smooth intake manifold runner surfaces — made possible by using a composite material — eliminate air friction and allow more air to flow through the system.
The size of the exhaust valves and the shape of the exhaust ports, manifold and catalytic converter entrance were optimized for maximum flow exiting the engine. The diameter of the exhaust system pipe was increased to decrease backpressure, allowing more outward flow.
The high output 3.5-liter engines have a three plenum intake manifold design with short runner valves and a manifold tuning valve to regulate the air-flow needed, and a higher lift camshaft for increased air flow.
Fuel economy will improve as much as 10 percent on our new sedans using the new engines, due partly to the use of aluminum and computer simulations to optimize air flow. These engines have the potential to reduce hydrocarbon emissions by 30 percent. They will meet Tier 2 federal emission standards and California's Transitional Low Emission Vehicle (TLEV) standards in 1998. They also will meet California's stringent Low Emission Vehicle (LEV) standards by the year 2000.
The new family of engines was developed faster than any engines in the history of the industry. Development time was cut by 26 weeks by creating the industry's first "paperless" engine, using CATIA-based computer software for predictive modeling and a rapid prototyping process.
Many 3.5 V6 engines were shipped with a variable intake system, building on Chrysler's work back in the 1950s and 60s. It varied the length of the intake manifold tubes to create a supercharging effect at different engine speeds. Tuning the air tubes for a boost at one engine speed had, in the past, sacrificed power at another; the variable system provided benefits at multiple speeds.
Marcel wrote in 2008, regarding the Dodge Challenger’s implementation of the 3.5 liter V6:
What you've seen before on these 3.5 engines is the Dual Plenum/Dual Throttle Body setup, where each three-cylinder bank had its own intake manifold and separate throttle body.
Now they've changed that to a Triple Plenum / Dual Runner Manifold fed by a single throttle body. This system is basically two different manifolds in one, controlled by runner valves. The long runner flow path is used at low rpms to gain additional torque. The short runner flow path is used at high rpms to gain additional horsepower. The dual Runner manifold is mentioned on the website but the benefits are not explained.
To eliminate oil leaks and other reliability issues:
The cylinders are lined with cast iron, with an industry-first process that permanently holds the liner in place and assures proper cooling of the cylinder walls.
1990-97 1999 Compression 10.44:1 9.9 or 10.1:1 HP @ rpm 214 @ 5,800 250 hp @ 6400 Lb-ft @ rpm 221 @ 2,800 250 lb-ft @ 3900 Valves SOHC, 24 SOHC, 24 Valve head diameter Intake 35, exhaust 29 Not provided
The aluminum engine blocks are heat treated to make them stronger than engine blocks made of cast iron. To make the engines last even longer, the crankshafts were made of forged steel rather than nodular iron.
Oil drain passages are cast right into the block to improve lubrication by getting the oil back to the oil pan quickly, even under severe high-speed conditions.
Long and fragile secondary cables, traditionally the weak link in an ignition system, have been eliminated. Instead, individual coils are placed directly above each spark plug. This "coil-on-plug" ignition system, along with spark plugs with platinum tips, provide a maintenance-free ignition system for 100,000 miles.
The 3.5 liter V6 engine was created for the first generation LH series, debuting in 1993; it got a boost to 250 horsepower in 1999; and it finished production in 2010, still making 250 horsepower, as the standard powerplant in the Dodge Charger, Dodge Challenger, and Chrysler 300, maintaining a reputation as a solid motor the entire time.
Maintenance and repairs
Jim Gathmann wrote: The coil pack on the first generation had three coils; the PCM (computer) sent one timing signal to each coil which fired two plugs. This way, the PCM could have a different signal for each grouping of cylinders. Early PCMs lacked knock detector circuits.
Douglas Miske wrote that the change interval for the timing belt is 84 months or 105,000 miles / 170,000 km.
For those who believe the 3.5 was a Mitsubishi engine, Kevin Cobabe sent us the following chart:
|Chrysler 3.5||Mitsubishi 3.5 (e.g. Diamonte)|
|Power||250 hp @ 6400
250 lb-ft @ 3900
|205 hp @ 5000
231 lb-ft @ 4000
|Bore x Stroke||3.78 x 3.19||3.66 x 3.38|
|Compression||9.9:1 / 10.1:1||9.0:1|
"91redbaron" wrote: The 3.5 had a rather interesting intake setup. There were two separate intake manifolds for the left and right side cylinders with their own throttle-bodies (interesting throttle linkage and cabling there). So in a way it was like two in-line 3-cylinders that were joined at the crank.
Transmission fluid leak
Transmission fluid can leak from the hose between the cooler integrated into the radiator and the transmission; this seems common with 3.5 liter engines. SAE mechanic “ImperialCrown” wrote, “Many times the hoses are okay, the clamps may just need re-tightening. The brace plate above the radiator unbolts and tips forward. Match up the washer paint marks when putting it back together for proper alignment. The lower clamps are harder to get at and you may need to jack the car up and have a jackstand in place.” (Bob Lincoln added that the hose must be rated for transmission oil; regular rubber hose can rupture fairly quickly when exposed to transmission fluid.)
Kestas: If the rough idle is accompanied by a drop in engine speed when the air conditioner goes on, it may be that the engine is not getting enough air. Clean the throttle body, then check to make sure the idle air controller is clean and has full travel to the open position. (Take off the idle air controller, check for free movement, and give it a good visual inspection to make sure it is clean. It may need a shot of carb cleaner on the moving surfaces.
FCT: Check to make sure that the fuel rail recall was done (where applicable).
Mark: The engine is prone to intake manifold gasket problems that can cause a rough idle.
"Mopar Man and Woman:" "Remove and clean both throttle bodies. Synchronize throttle bodies. Remove IAC (ASI) [idle air speed/automatic idle speed] motor, but do not spray or soak with cleaner. Wipe tip off with cleaner on shop towel. Spray cleaner into bore in manifold. Make sure that hose that goes to air cleaner duct to intake right behind IAC is not blocked, collapsed etc. This is the source for air flow to the IAC on the 3.5L.
Perform minimum air flow test with DRB or other Scanner - should be 500-650rpm. If above, suspect vac leak, if low you have throttle body problems. At full operating temp, curb idle, what are desired IAC steps? Try cylinder balance test with scanner. If one or two cylinders are slightly different than rest, suspect intake manifold gasket failure. Also, after each repair, before starting, reset adaptive memory in PCM with scanner."
Cesar: "Just thought I share a similar problem I had with my 97 Eagle Vision w/3.5L that drove a lot technicians crazy, including field support folks, for 8 working days! The problem was one of the camshaft was slightly out of alignment in respect to its sprocket. This problem started after a water pump housing ("rear timing belt cover") was replaced and fuel rail recall performed. The symptoms I had after this effort was rough idle similar to the problem you've described. To verify valve timing on this engine there is a camshaft alignment special tool 6642 that must be used."
There may also be a problem with the MAP sensor (instructions on diagnosing).
There may also be a problem with the EGR sensor (replacement guide)
Chrysler compared well to the competition in 1998, particularly when looking at cost.
|Vehicle||Engine||BHP||RPM||Octane||Cost As Tested|
|Mercedes E420, 1997||4.2L||275||5500||Premium||$53,522|
|Ford SHO (V8), 1996||3.4L||235||6100||Premium||$28,250|
|LH series, '93-'97||3.5L||214||5850||Mid-Grade||$24,270|
|Mitsubishi Diamante, '97||3.5L||210||5000||Premium||N/A|
|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|
|Acura 25TL, 1997||2.5L||176||6300||Premium||$30,478|
|3.5 Liter (LX)||3.5 Liter|
|Bore x Stroke||
3.39 x 3.09 |
(86 x 78.5mm)
3.66 x 3.19 |
(92 x 81mm)
|3.78 x 3.19|
(96 x 81mm)
|3.78 x 3.58 |
(96 x 91)
|Valves||24 valves (4 per cylinder)|
|Valve System||Hydraulic end-pivot roller followers, hydraulic lifters|
|Fuel Injection||Electronic sequential multi-port injection (SMPI)|
|Construction|| Semi-permanent-mold aluminum block with cast-in iron liners, |
cross-bolted main bearing caps, cast aluminum heads
in hp (kW)
220 (164) |
|250 @6400||235 (186) @ 6,400||255 (190) @ 5,800|
in lb-ft (Nm)
188 (254) @ 4900*
222 (301) |
|250 @ 3900||232 (339) @ 4,000||275 (360) @ 4,000|
|Max. RPM||6464*||6800 rpm||?||6,800 rpm||5,800 rpm|
|Fuel||Unleaded regular, 87 octane||89 preferred, 87 OK|
|* Later retuned to 190 hp (142 kW) at 6,400 rpm and 190 lb-ft (258 Nm) at 4,000 rpm, |
with a redline of 6,600 rpm and a compression ratio of 9.9:1.