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Discussion Starter #1
For a long time, I've been noticing a sound like the A/C compressor kicking in, and then a different tone to the exhaust like it's under load. This is happening on light acceleration from a stop. I finally figured out that it's the MDS kicking in - I've got to give it more gas to turn it back off. Is this normal? I'm referring to the audible "kicking in" sound, and the fact that it turns on when I'm accelerating - even if it is a grandpa acceleration, it doesn't seem like the MDS should engage.

is there a way to turn it off for in town driving, and turn it back on for highway driving?
 

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If you drive in autostick, MDS will not engage. MDS can also be turned off via a tuner.
 

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^^^what he said^^^
I would just shut it off completely. I never felt the savings was significant enough. When my MDS kicked in under the 91 Oct. tune (via Predator), it felt like the fuel supply was cutting in and out - horrible. I just shut it off completely. I really notice a weird sound when I altered the stock exhaust as well (with MDS on).
 

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As noted above, there isn't anything you can do to "turn off" MDS except through software modification. Below is some information about how MDS works to help forum members better understand MDS operation.

The Multiple Displacement System (MDS) provides cylinder deactivation during steady-speed, low-acceleration and shallow grade climbing conditions to increase fuel economy. The Powertrain Control Module controls the operation of the MDS system. Primarily the engine must be warmed up to at least at normal operating temperature. This assures the oil is at the correct viscosity to flow to the solenoids properly. The PCM will determine if the required engine load will permit MDS operation.

MDS operates between 1,000 and 3,000 rpm. It will operate in four-cylinder mode when the torque requirement is less than 95 percent of the maximum available from four cylinders. It provides full-rated power in V8 form with an increased fuel economy benefit when operating in four-cylinder mode, depending on driving habits and vehicle usage. It is integrated into the basic engine architecture and is more reliable than add-on systems. Deactivation and activation of the cylinder is transparent to the driver.

Deactivation occurs during the compression stroke of each cylinder, after air and fuel enter the cylinder. Ignition then occurs, but the combustion products remain trapped in the cylinder under high pressure, because the valves no longer open. No air enters or leaves. During subsequent piston strokes, this high-pressure gas is repeatedly compressed and expanded like an air spring, but fuel is not injected.

Special hydraulic lifters are used on four of the cylinders. They are controlled by solenoids. Each of the designated cylinders has its own solenoid which controls two lifters. When the solenoid is energized, oil under pressure is permitted to flow to the side of the lifter. This causes a lock pin inside the lifter to compress. When the lock pin is compressed the lifter contracts and its length is reduced. At its reduced length the lifter is no longer able to open the engine valve.

Both four- and eight-cylinder configurations have even firing intervals, providing smooth operation. Two cylinders on each bank are active when the engine is in four-cylinder mode – every other cylinder in the firing order. All of the cylinders that are deactivated have unique hydraulic valve lifters that collapse when deactivated to prevent the valves from opening. Engine oil pressure is used to activate and deactivate the valves. It is delivered through special oil passages drilled into the cylinder block. Solenoid valves control the flow. When activated, pressurized oil pushes a latching pin on each valve lifter, which then becomes a “lost motion” link. Its base follows the camshaft, but its top remains stationary, held in place against the pushrod by light spring pressure but unable to move because of the much higher force of the valve spring.

720 degrees of crankshaft revolution is required to fire all cylinders. This is the same for all four stroke engines. When this number is divided by the number of cylinders, it produces, 90 for eight cylinders, 120 for six cylinders and 180 for four cylinders. Combinations of 90 and 180 work well together. The change occurs within two revolutions of the crankshaft. When operating in the economy mode, the engine is operating like an efficient four cylinder engine. With drive by wire there will be no change in the accelerator pedal position.

MDS can provide a 5-20 percent fuel economy benefit when operating in four-cylinder mode, depending on driving habits and vehicle usage. For EPA rating purposes, fuel economy is 8-15 percent higher than if the engine was operating on eight cylinders at all times.

MDS is integrated into the basic engine architecture, requiring a minimum of additional parts - four additional solenoids, an oil temperature sensor and a wire harness. Eight unique valve lifters and a modified camshaft are also required.

NOTE: It is critical to use the recommended oil viscosity in 5.7L HEMI engines that use MDS. Vehicles with 5.7L HEMI engines equipped with Multiple Displacement System (MDS) must use SAE 5W-20 oil. Failure to do so may result in improper operation of the Multiple Displacement System (MDS).

Just a few simple tips can help owners of Chrysler Group engines with Multi-Displacement System (MDS) get the most fuel mileage possible from their 5.7L HEMI V8 engine. The customer does not need to drive in a certain way to realize a fuel economy improvement with MDS but these driving habits can maximize their fuel savings with this technology.

•Keeping speeds to 65 mph or below - MDS uses four cylinder mode most at these speeds
•Use cruise control -- this helps maintain a steady speed generally allowing the HEMI to run on four cylinders for longer periods
•Accelerate more gradually - the HEMI will provide V8 power whenever it is requested by the driver
•Use a steady throttle whenever possible - this maximizes four cylinder mode
 

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Discussion Starter #5
Thanks for the explanation! Mine, though, is definitely not "transparent" to the driver. I guess I am hearing the solenoids kicking in, as it is a loud noise - not really loud, but like the noise you hear when the A/C compressor kicks in. Is that normal? BTW, I cannot hear it at highway speeds, only when I first take off from a stop and it kicks in. I know that it is the MDS, because I watched the EVIC display, and the noise and MDS application happen at the same time.
 

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RDT do you have a tune on your car?
 

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Discussion Starter #7
No tune - stock. The only changes in the engine compartment are a cone filter and catch can.
 

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Is there, or was there, a check engine light showing?
Are there any stored diagnostic trouble codes?
Are you using the correct weight engine oil?
 

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It should be fairly transparent to the driver. If it's not, it may be a malfunctioning solenoid possibly caused by the wrong oil weight.

Check for codes that may not be lighting up the CEL.
 

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It should be fairly transparent to the driver. If it's not, it may be a malfunctioning solenoid possibly caused by the wrong oil weight.

Check for codes that may not be lighting up the CEL.
................great minds think alike....................
 

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I am new to the forum and have a question on an issue I experienced today. My 2008 300C AWD stalled at every red light on the way to work. I ran the error codes and see that the crankshaft position sensor is the issue at hand. From all the reading I have been doing, the CPS should be behind the starter on the passenger side. I was under my car and the starter is on the drivers side. Does anyone have an exploded view of where the CPS is located on an AWD. Thank you in advance for any assistance you can provide.
 

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The crank position sensor is mounted into the right rear side of the cylinder block. It is positioned and bolted into a machined hole.

1. Disconnect and isolate the negative battery cable.
2. Raise and support the vehicle.
3. Remove the starter motor
4. Disconnect the CP sensor electrical connector.
5. Remove the CP sensor mounting bolt.
6. Using a slight twisting motion, remove the CP sensor from the engine block.
7. Check the condition of the sensor O-ring and replace if necessary.
 

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Discussion Starter #14
Is there, or was there, a check engine light showing?
Are there any stored diagnostic trouble codes?
Are you using the correct weight engine oil?
no check engine light
I'll have the codes checked
Always have my oil changed at Michel Tire, and assume they use the right weight (you know what they say about assuming - I'll check into this!

I don't really think the MDS is operating incorrectly, it's just louder (at slow speeds) than I expected.

Thanks for the input!
 

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:aargh4: MDS SUCKS! I think that the noise that you are hearing is the sound of the exhaust when the transmission does what I call a slow downshift, like when you are cruising at 40 in fifth gear and give it a little gas and it makes a loud droning noise before it downshifts. One of the main reasons that I HATE MDS. Many thanks to Diablo Sport for allowing me to turn it off. I swear that if it wasn't for my Trinity tuner I would have the MDS lifters replaced and turn it off forever.
 

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I will follow the instructions provided for replacing the crankshaft PS tonight. I am just confused how everyone says the starter is located on the passenger. But when I was under the car last night. It was on the drivers side.
 

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I will follow the instructions provided for replacing the crankshaft PS tonight. I am just confused how everyone says the starter is located on the passenger. But when I was under the car last night. It was on the drivers side.
After looking into the service manual I concur that the starter motor is on the driver's side (left side) in the AWD cars. It is on the passenger's side (right side) in the RWD cars. Strange but true. Must have something to do with getting all of that AWD stuffed in there requiring the starter motor to take a 180-degree flip around the bellhousing.
 

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Yeah it's opposite in an awd, transfer case hangs out to the passenger side and the front drive shaft will run up where the starter would have been and through the funky oil pan. However as the motor is the same and the sensor mounts into the block I would assume it stays stage right on the passenger side...the awd runs the same Hemi!

Sent from AutoGuide.com Free App
 

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As noted above, there isn't anything you can do to "turn off" MDS except through software modification. Below is some information about how MDS works to help forum members better understand MDS operation.

The Multiple Displacement System (MDS) provides cylinder deactivation during steady-speed, low-acceleration and shallow grade climbing conditions to increase fuel economy. The Powertrain Control Module controls the operation of the MDS system. Primarily the engine must be warmed up to at least at normal operating temperature. This assures the oil is at the correct viscosity to flow to the solenoids properly. The PCM will determine if the required engine load will permit MDS operation.

MDS operates between 1,000 and 3,000 rpm. It will operate in four-cylinder mode when the torque requirement is less than 95 percent of the maximum available from four cylinders. It provides full-rated power in V8 form with an increased fuel economy benefit when operating in four-cylinder mode, depending on driving habits and vehicle usage. It is integrated into the basic engine architecture and is more reliable than add-on systems. Deactivation and activation of the cylinder is transparent to the driver.

Deactivation occurs during the compression stroke of each cylinder, after air and fuel enter the cylinder. Ignition then occurs, but the combustion products remain trapped in the cylinder under high pressure, because the valves no longer open. No air enters or leaves. During subsequent piston strokes, this high-pressure gas is repeatedly compressed and expanded like an air spring, but fuel is not injected.

Special hydraulic lifters are used on four of the cylinders. They are controlled by solenoids. Each of the designated cylinders has its own solenoid which controls two lifters. When the solenoid is energized, oil under pressure is permitted to flow to the side of the lifter. This causes a lock pin inside the lifter to compress. When the lock pin is compressed the lifter contracts and its length is reduced. At its reduced length the lifter is no longer able to open the engine valve.

Both four- and eight-cylinder configurations have even firing intervals, providing smooth operation. Two cylinders on each bank are active when the engine is in four-cylinder mode – every other cylinder in the firing order. All of the cylinders that are deactivated have unique hydraulic valve lifters that collapse when deactivated to prevent the valves from opening. Engine oil pressure is used to activate and deactivate the valves. It is delivered through special oil passages drilled into the cylinder block. Solenoid valves control the flow. When activated, pressurized oil pushes a latching pin on each valve lifter, which then becomes a “lost motion” link. Its base follows the camshaft, but its top remains stationary, held in place against the pushrod by light spring pressure but unable to move because of the much higher force of the valve spring.

720 degrees of crankshaft revolution is required to fire all cylinders. This is the same for all four stroke engines. When this number is divided by the number of cylinders, it produces, 90 for eight cylinders, 120 for six cylinders and 180 for four cylinders. Combinations of 90 and 180 work well together. The change occurs within two revolutions of the crankshaft. When operating in the economy mode, the engine is operating like an efficient four cylinder engine. With drive by wire there will be no change in the accelerator pedal position.

MDS can provide a 5-20 percent fuel economy benefit when operating in four-cylinder mode, depending on driving habits and vehicle usage. For EPA rating purposes, fuel economy is 8-15 percent higher than if the engine was operating on eight cylinders at all times.

MDS is integrated into the basic engine architecture, requiring a minimum of additional parts - four additional solenoids, an oil temperature sensor and a wire harness. Eight unique valve lifters and a modified camshaft are also required.

NOTE: It is critical to use the recommended oil viscosity in 5.7L HEMI engines that use MDS. Vehicles with 5.7L HEMI engines equipped with Multiple Displacement System (MDS) must use SAE 5W-20 oil. Failure to do so may result in improper operation of the Multiple Displacement System (MDS).

Just a few simple tips can help owners of Chrysler Group engines with Multi-Displacement System (MDS) get the most fuel mileage possible from their 5.7L HEMI V8 engine. The customer does not need to drive in a certain way to realize a fuel economy improvement with MDS but these driving habits can maximize their fuel savings with this technology.

•Keeping speeds to 65 mph or below - MDS uses four cylinder mode most at these speeds
•Use cruise control -- this helps maintain a steady speed generally allowing the HEMI to run on four cylinders for longer periods
•Accelerate more gradually - the HEMI will provide V8 power whenever it is requested by the driver
•Use a steady throttle whenever possible - this maximizes four cylinder mode
Something very strange is happening with my 300c. Whenever I just touch the door handle or open the door a rapid loud clicking sound starts from the car! Sometimes when I'm driving the same clicking sound happens! Sometimes it happens when the A/C is being used in fact the A/C won't turn on till after the clicking sound stops! Plus I'm getting a code that my number 7 cylinder is deactivated! I was told that I may have a MDS issue?? Can someone please help me understand whats going on or what needs to be done?
 

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Hard to guess, I suggest you start a thread so the thread is only one subject. And in it list the code, info on car(year, engine, awd, etc) and if you can get a recording of the sound.
 
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