Hemi engines are powerful and efficient, but they can also be a source of frustration if you don’t know how to disable MDS (Multi-Displacement System).
MDS is an advanced technology designed to improve fuel economy by automatically shutting off cylinders when they’re not needed.
If you’re looking for improved performance, disabling MDS can be the answer. In this article, we’ll explain how to disable MDS on Hemi engines and what benefits it could bring.
What is Hemi MDS?
Automakers can now take advantage of variable-displacement systems like Chrysler’s Multi-Displacement System (MDS). This feature first appeared on the 2006 5.7 L Hemi V8.
When the throttle is closed or at stable speeds, four of the V8’s cylinders are deactivated, much to the systems used by Mercedes-Benz, General Motors, and Honda: Active Cylinder Control, Active Fuel Management, and Variable Cylinder Management.
Since the system’s functionality would be compromised by the needs of trucks, it was initially only available on passenger automobiles. However, it was returned in 2006, and the 5.7 L engine was made available on all seven models, including SUVs and 1500 series pickups.
According to Chrysler, fuel economy might improve by 10% to 20% thanks to the new technology. On the interstate, the V8 and V6 Jeep Grand Cherokees with MDS have the same 21 mpg fuel economy (11.2 liters per 100 km).
Chrysler and Eberspaecher North America collaborated on an exhaust system for MDS-equipped vehicles that keeps the distinctive roar of V8 engines intact.
For the V8 mode, there are two enormous mufflers in the middle, and for the four-cylinder mode, there are two smaller mufflers near the tailpipes. The system is mechanically passive, unlike Eberspaecher’s similar technology used on Mercedes-Benz V12 engines.
How to Disable MDS On Hemi?
Some people believe that turning off the MDS is as simple as hitting the tow/haul button, but this is only true for 6-speed transmissions. In 8-speed transmissions, pressing this button will just alter the shift patterns.
A fuel-efficient pickup truck like a Ram with a Hemi will house the MDS. Turning off the MDS will allow you to use the full potential of the engine (all of its horsepower and torque).
Purchasing a tuner will permanently turn off the MDS. If not, turning it off momentarily will take only a short amount of time. It’s a simple and fast procedure that varies with the type of shifter and transmission you have. Follow the process outlined below:
- Move the centrally located shifter to the driver’s side of the car six times while in manual mode.
- The shifter for the 6-speed transmission is shown here for this 2013 Ram with a 5.7L Hemi engine.
- To switch to manual mode while driving, push the shifter to the floor, pull it to the driver’s side, and let go.
- The driver must then pull the shifter to the left and release it six times. To be accurate, the dash should display the number 6.
- Shift into manual mode with a knob shifter by pressing the down button, then use the up button to line up the gears.
- Instead of a traditional shifter stick, some cars have a knob on the center console.
- To switch to the manual transmission, press the down arrow on the steering wheel of a vehicle equipped with such a transmission. Then, keep pressing up until you’ve gone through all the gears your car offers.
- If your vehicle is equipped with a column shifter, you can match the gears by pressing the up button on the column shifter and pressing the down button on the steering wheel.
- If your vehicle has a column shifter, the end of the shifter will be equipped with buttons.
- Pressing the down button while in Drive will automatically engage the transmission’s shift mode; from there, you’ll want to push the up button until the maximum shift range number shows on the dashboard.
- The MDS system will not activate when the maximum number of gears has been selected in the instrument cluster. In other words, you’ll be using all of your engine’s potential hp and lb-ft of torque.
How MDS Works In Practice?
Injectors and these replacement Dorman MDS lifter transducers appear similar because they perform similar tasks. When they become clogged, it’s usually because of debris in the oil. Replacement of the solenoid is necessary to prevent the lifters from breaking.
It will take a lot of technical innovation to make cylinder deactivation a viable alternative. The hydraulic roller lifters in a Hemi engine are equipped with four control valve solenoids in the lube circuit; these solenoids are activated by the engine control module (ECM) via the harness and reroute pressurized oil to a locking pin in the lifter.
The roller can still move in accordance with the cam profile after this pin has been driven into the lifter body, but the plunger cannot move to engage the pushrod. When the ECM cuts power to the solenoid, the lifter’s pin springs back into place, re-aligning it with the plunger.
Failure of this procedure can occur for a variety of reasons, but oil contamination is by far the most common. Reduced ability to transition between states in a lifter is caused by dirt particles blocking the lubricating circuit.
Lifter disengagement occurs more frequently at higher rotational speeds in Hemis due to the MDS system. The internal locking pin in the lifter is disengaged, so the body of the lifter is not connected to the plunger.
When the engine speed exceeds the roller’s safe tracking range, the roller will repeatedly hit the cam lobe, finally breaking. There will come a time when the lobe surface, roller, lifter, and needle bearings all fail.
Does MDS Affect Performance?
Assuming the MDS is functioning normally, most current vehicles will only have minimal performance losses. Former versions of the MDS were more noticeable in their effect on performance drops in other vehicles.
The most serious problems with earlier MDS automobiles are their jerky shifts and power reduction at a constant speed. It has also been reported that the on/off cycling of the MDS can be disturbing to the driver. Furthermore, MDS problems are not always noticeable until after additional upgrades have been made to the car.
Do All Hemis Have MDS?
Although MDS isn’t standard on all Hemis, it has gained significant traction since 2005, when Chrysler first included it in the Dodge Caliber.
MDS is included in a large percentage of automatic automobiles manufactured during the last 15 years. In other words, the system is not available on vehicles that use a manual transmission.
When Does MDS Fail?
At this point in the narrative, it’s highly possible that the feared MDS lifter failure has already occurred to you. After the factory powertrain warranty on your Hemi has ended and you are ready to start customizing it, one option you have is to switch from MDS lifters to standard lifters.
The good news is that in addition to MDS lifters, you have access to a number of other lifter options, such as stock lifters that do not use MDS technology (similar to those used in your other four cylinders), Hellcat lifters, or high-performance lifters manufactured by Competitive Cams.
You will need not just a new set of non-MDS lifters and retainers, but also four plugs to put in the lifter valley in order to close off the space that the solenoids had previously occupied. As part number 53032221AA, this plug can be purchased from Mopar for use in non-MDS Hemi vehicles.
Because it is necessary to remove the heads in order to have access to the lifters, the following sets of tools are required: a head gasket set, a front timing cover gasket set, and a head bolt set. In order to get the Hemi engine to start, you are going to require an ECM flash that turns off the MDS.
Cars with V8 Chrysler or Dodge engines can benefit from the MDS displacement technology, which also reduces emissions. Many motorists are fine with the setup, but others would rather have their cars work at peak efficiency all the time.
The Ram 1500’s MDS can be disabled, however, doing so would reduce gas mileage. If you want to turn off the system for a little while, the highest gear will do the trick. You’ll need a tuner or a higher-performance camshaft to disable the system completely.