How To Disable MDS on Hemi: Turning Off MDS of Ram Truck

Are you looking for how to disable MDS on Hemi? In this article, you will find the relevant information that you need to carry out this operation successfully.

The main functions of MDS on installed vehicles are to ensure the vehicle achieves higher fuel efficiency (you will save more on fuel) and as well as lower emissions while operating under light-load. This is achieved by deactivating some engine cylinders.

Many of the performance engines you see around today make use of some sort of cylinder deactivation technology, and the main aim is to increase fuel economy.

With the deactivation of half the engine’s cylinders, the fuel consumption rate reduces. The processes involved include shutting off the ignition source, closing the deactivated cylinders’ valves, and shutting off the fuel.

Although the MDS system ensures your vehicle’s engine uses less fuel by ensuring a 20% boost in fuel efficiency, it may affect its performance.

Whenever the engine tries to restart the deactivated cylinders- switching from 4 cylinders back to 8, this action sometimes results in response lag.

As a high-performance enthusiast, this may result in an irritating and frustrating experience, which may bring about the need to get rid of this system.

You may also want to disable the MDS on your vehicle if you use aftermarket exhaust. This is because of the goofy sound it produces when the engine switches from eight cylinders to four cylinders.

As you read further, we will find out about how you can eliminate or disable the MDS- the methods and steps involved in this operation will be carefully highlighted so that you can conduct this task on your own.

In the end, we hope you will find the most appropriate method that you can adopt to prevent the MDS from deactivating your Hemi engine cylinders.

What is MDS?

Multiple Displacement System (MDS) is also known as “Eco Mode” by many drivers or car owners. This system turns off 4 cylinders on the Hemi engine.

The aim of this operation is to ensure you use less gas while driving under light loads. MDS is present in several vehicle designs or models such as Chrysler 300, Charger, Challenger, Magnum, or Dodge.

In 2004, the 1st MDS Hemi 5.7 was commissioned. After the release, for a few years, the Hemi 5.7 was affected by short-term issues. These issues lasted for a few years.

5 years later (in 2009), an improved engine was released. This new engine’s components include 16 lifters- 8, which can disable valve action, and the remaining 8 are normal lifters.

Other components are a matchless camshaft, 4 solenoids, and a specially designed exhaust. The solenoids are responsible for initiating lifter action.

The cylinders are disabled with the aid of oil pressure. The MDS solenoids ensure oil pressure is directed to each of the 8 cylinder lifters.

This pressure drives in the locking pins, and as a result, collapses the lifters in an attempt to restrict the opening of the valves. Also, the engine control unit restricts spark and fuel to the cylinders.

The Hemi engine cylinders are numbered in the following firing order- 1, 8, 4, 3, 6, 5, 7, and 2. When the MDS is activated, it disables every 2nd cylinder.

So, 1, 4, 6, and 7 cylinders are deactivated accordingly to achieve rotational balance. Whenever the crankshaft rotates at 180°, each of the 4 cylinders gets deactivated in that order.

If you drive a Hemi-powered vehicle, at some point, you will have to choose between fuel efficiency and performance.

You will have to make this decision if you love driving on rough terrains such as hills and rocks where full power is required. So, if you think fuel economy isn’t a big concern or issue to you, you may decide to get rid of this system for high performance or RPM.

Note, Hemi-powered vehicles with manual transmissions do not have the Multiple Displacement System.

Methods of disabling MDS

The Multiple Displacement System can be disabled or eliminated through several methods. The most notable means are:

  • Using a tuner, which is more like software programming. This method allows you to modify several factory settings and parameters on your vehicle. As you read further, you will find out about the steps involved in executing this process successfully.
  • You can also eliminate, disable or bypass the MDS without making any form of modifications to the vehicle’s operation. In this case, the MDS is disabled using the gear. You will also find out more about this process as you read along.

How To Disable MDS on Hemi Without The Use of a Tuner

This option provides a temporary means of deactivating the MDS on your HEMI. This method doesn’t require any tools, and it doesn’t reprogram or modify the ECU- Engine Control Unit.

  • Put your truck in drive
  • Release your parking brake
  • Go to your steering wheel and push the gear down until it gets to 8
  • Leave your truck on 8, and you can drive around without your truck going on the ECO mode or the MDS being activated
  • You will have to repeat this process or steps every time you get in the truck or put it in park

 How to disable MDS on Hemi with a tuner

  • Get a private or custom tuner. E.g., i2 tuner
  • If you are using a tuner for the first time, you may have to take your time to go through the user manual
  • Plug the i2 tuner into the OBD2 port. Once it is plugged in, the tuner comes on automatically. Give it a few seconds to boot, and come on
  • Agree to the disclaimer displayed on the tuner’s screen
  • Turn the vehicle’s key into the run position. Do not start the engine at this point
  • Click on “tune vehicle,” and press the continue button
  • Choose between easy and advanced tuning. You may click on advanced tuning if you have a custom tune
  • Click on “tune select,” and choose “install custom tune”
  • Select your preferred PCM tune- your custom tune by clicking on Yes
  • Do not apply tune yet at this point. Instead, click on modify parameters
  • Click on MDS- this is most likely the last option from the list of options to choose from, and press the “Off” button
  • Confirm your option by clicking YES
  • Go back, and click on the “apply tune.” Once the installation is completed, turn off the vehicle and back on after a few seconds.

In case you do not have a custom tune, click on EASY TUNE, and select the 93-OCTANE, click on YES, followed by MODIFY STOCK TUNE, select YES, and click on MDS from the menu displayed.

Pros and Cons of disabling MDS on Hemi engine

Pros

  • You will be able to drive your vehicle on eight cylinders
  • Guarantees optimum power delivery- 100% of your Hemi engine power all the time
  • The valve lifters won’t have to be collapsed and reactivated consistently. In the end, you will save money on costly repairs
  • The vehicle runs a lot smoother once you turn off the MDS- Guarantees full reliability and improved drivability
  • Helps prevent loud and annoying ticking sound. Especially if you have an aftermarket exhaust installed on your vehicle
  • Downshift becomes quicker, and throttle response is enhanced
  • Eradicates durability issues by ensuring an improved working order of the Hemi engine
  • Eliminates shuddering- Your engine won’t have to cycle between operating on 4 or 8 cylinders
  • Allows you to drive on all terrains- No matter how rough the roads are, especially during extreme weather conditions, you will have the needed power to drive through and find your way home
  • Allows you to haul hefty loads by ensuring you get the control and power that you need

Cons

  • You will lose gas mileage, thereby spending more on fuel, especially when you often drive in the city or on highways
  • Disabling the MDS on Hemi using a tuner is a bit expensive. This may cost between $300 and $600

FAQ’s About Disable of Hemi MDS

How does the MDS work?

When MDS is activated on your vehicle, what happens is that some vital controls in one or more cylinders are disabled. During this period, the fuel injection system, the valve action, and the spark ignition are deactivated.

Although the engine works as normal, this time with limited numbers of cylinders. This operation eliminates pumping losses and also improves cylinder pressure in the other cylinders that are still active.

Why was MDS introduced on Hemi

MDS was introduced on Hemi engines to disconnect multiple cylinders when there is not much of an engine load. This way, you save more on fuel consumption. It takes about 0.04 seconds to disable the cylinders.

How does MDS help lower emissions?

When the MDS is activated, it ensures the exhaust gas temperature is constant. This helps to improve the performance of the emissions system.

How does the engine switch from eight cylinders to four?

The switch occurs automatically. Whenever your vehicle attains highway speed, the MDS disables 4 cylinders out of the total number of 8 as a fuel-saving measure.

How does the engine switch from four cylinders back to eight?

The switch occurs whenever a drive desires extra power than what the 4 cylinders can give or offer. In this case, the collapsed lifters are reactivated in about 4 milliseconds, thereby allowing the full operation of the 8 cylinders.

Would MDS affect my engine?

When you look around today, the 5.7L and 6.4L make use of MDS, and the users of this Hemi engine have not reported any problem or issue with their engine.

Suppose you have an MDS Hemi engine built from 2009 upward. In that case, the decision to turn off the MDS is solely dependent on preference, operation, and driving habits.

In essence, drivers disable the MDS on their vehicles not because it affects the engine but because they see it as important.

What is the difference between Hemi 5.7 and 6.4 engines?

Although the 5.7L and 6.4L Hemi have different stroke lengths- 3.58-inches and 3.72-inches respectively, they are both durable and reliable engines. Well. Since the 6.4 engine has a longer stroke length, it certainly gives out more power than its counterpart, the 5.4 Hemi.

What is the life-span of a Hemi?

The 5.7 and 6.4 Hemi can cover up to about 300,000 miles. Although the Hemi engines are made to last for a very long time, the owner must ensure proper maintenance culture is adopted.

If you own a vehicle that runs on a Hemi engine, ensure you regularly take care of the engine for best performance and longevity.

How do you know if MDS is activated?

When the MDS is active, the Eco light comes on. Another way to find out if this system is ON or OFF is through your vehicle’s sound and feel.

It is easy to notice when your vehicle is running on 4 cylinders instead of 8 if you have a very loud exhaust installed. This is because the vehicle sounds totally different.

Verdict

We have discussed and answered the question, “How to disable MDS on Hemi,” by providing various methods that Hemi engine owners can adopt if they decide to disable or get rid of this fuel-saving system from their vehicle.

Depending on your choice, you can either choose to deactivate the MDS temporarily or permanently. Before you make up your mind on the method to adopt, you may need to consider some factors.

Most importantly, ensure you consider your driving habit. Know if you prefer performance over fuel economy, and consider your terrain. Suppose you drive more on a smooth terrain- around the city or highways.

In that case, you may decide not to eliminate with the MDS and only disable it temporarily during extreme conditions such as when it snows, using your gear.

If you drive on the rough terrains more often- around the hills and rocks, or you haul/tow with your vehicle regularly, you may decide to disable the MDS permanently, thereby running the engine on 100% at all times.

Finally, the process of disabling the MDS is easy and fast, irrespective of the method you choose to adopt.