MDS, or Multiple Displacement System, is a fuel-saving technology found in some HEMI vehicles, including Dodge Charger, Challenger, RAM 1500, & of course, Jeep Grand Cherokee.
When active, MDS shuts off half of the engine’s cylinders when they’re not needed, such as when cruising at highway speeds. This reduces fuel consumption and emissions, but it also reduces power and performance.
Fortunately, there’s a way to disable/delete MDS and restore your HEMI engine’s full potential!
This guide will walk you through the step-by-step process, so you can enjoy the row performance that HEMI is known for.
Keep reading to learn how to safely disable MDS on your HEMI vehicle.
What You’ll Need
Before you get started, there are a few things you’ll need to disable MDS on your HEMI engine:
- A compatible tuner or programmer (we’ll discuss this in more detail later)
- The appropriate software for your device
- A way to connect your device to the OBD-II port in your vehicle
Step 1: Prepare Your Vehicle
The first step is to prepare your vehicle for MDS disablement. This includes ensuring all the necessary components are in place and functioning correctly.
Start by ensuring that your fuel system is up to the task of supporting the increased power output. This means upgrading to a high-flow fuel pump and using high-quality fuel injectors. You should also ensure that your fuel filter is clean and in good condition.
Next, take a look at your ignition system. If you’re still running stock ignition components, now is the time to upgrade to aftermarket options. Aftermarket ignition coils and spark plugs will help ensure your engine gets the spark it needs to run at its best.
If you’re planning on making other vehicle modifications, such as installing a cold air intake or a new exhaust, now is the time to do it. These mods can also improve performance, so usually, it’s best to do them before you disable MDS. More on performance mods here.
Step 2: Choose a Tuner or Programmer
Now it’s time to choose a tuner or programmer compatible with your vehicle. There are a few different options on the market, so take some time to research your options and find the one that’s right for you.
Here’s our complete guide for the best tuner/programmers for HEMI to help you pick the best option.
Once you’ve chosen a device, make sure that you have the appropriate software installed. This software will be used to disable MDS on your HEMI engine.
Step 3: Connect your device to the OBD-II Port
The next step is connecting your device to your vehicle’s OBD-II port. This is typically located underneath the dash, near the steering column.
Once your device is connected, it should be recognized by the software. If not, refer to the user manual for troubleshooting tips.
Step 4: Disable MDS
With your device connected and recognized by the software, you’re now ready to disable MDS. This is typically done with a few simple clicks or taps of your fingertips.
Refer to the user manual for your specific device to find out how to disable MDS. Once you’ve done that, save the new settings and disconnect your device from the OBD-II port.
An alternative option if you want to temporarily disable MDS (without tuner)
This video guide from our friends at 1AAUTO will drive you through simple instructions as to how to disengage your HEMI truck’s MDS system temporarily.
Step 5: Enjoy the improved performance!
You’ve now successfully disabled MDS on your HEMI engine. This means you’ll enjoy increased power and performance without sacrificing fuel economy.
If you have any questions about the process or need help troubleshooting, feel free to contact a professional. With a few simple steps, you can enjoy the full potential of your HEMI engine!
With that said, let’s address some common questions that I think most of you will probably have.
Questions related to disabling MDS on HEMI vehicle
What year HEMI has MDS?
Strictly speaking, if you have HEMI V8, it has an MDS system. Chryslers first introduced MDS in 2006 with the induction of the V8 series of engines.
Some of the vehicles with an MDS system include:
- 2005– Chrysler 300C
- 2006– Dodge Charger
- 2005– Dodge Magnum
- 2005– Jeep Grand Cherokee
- 2006– Dodge Durango
- 2006– Dodge Ram (1500 only)
- 2006– Jeep Commander
- 2007– Chrysler Aspen
- 2009– Dodge Challenger
Models with manual transmission do not have an MDS system.
What are the benefits & drawbacks of disabling the HEMI MDS?
When MDS is activated, it deactivates four of the engine’s cylinders when they’re not needed, such as when you’re cruising on the highway. This saves fuel, but it also reduces power and can make your engine sound like it’s misfiring. Some people even find it irritating.
So, why would you want to disable the MDS? There are a few reasons.
- First, it’s a simple way to increase power. When the MDS is deactivated, all eight cylinders are always active, which means more power is available when needed.
- Second, it can make your engine sound better. With the MDS deactivated, your engine will have a deeper, throatier sound.
- It also makes downshifting so much smoother.
- And finally, it’s just fun to disable the MDS and see what your HEMI engine is capable of!
Of course, there is a drawback to disabling the MDS.
- You might notice a slight decrease in your fuel economy. With all 8 cylinders active all the time, the fuel consumption is obviously gonna go up a bit. Save fuel, and improve your HEMI MPG with this complete guide.
- Another thing is an increase in emissions as more fuel is burnt.
Should you turn off MDS on RAM?
With the benefits and drawbacks of the MDS system we discussed above, I hope the picture is clear to you now.
If you are tired of the speed limit forced upon you via MDS and feel the need for more power and torque, then I think you should turn off MDS on your RAM truck.
How much gas does MDS save?
When MDS is engaged, “The fuel saving could be as much as 10 to 20 percent”, according to Broomall. That, of course, also depends on driving style and all.