How To Tell If Your 5.7 Hemi Has MDS

The hemispherical engine has been a fixture in the automotive industry since the extremely popular Chrysler 426 Hemi during the golden era of muscle cars, and we looked at every major Hemi engine and ranked them from least to most horsepower, as they aren't all created equal. Engineers have been toying with different combustion chamber shapes since the early 20th century, and looking back on the best and worst years for the Dodge 5.7L Hemi engine, it's certainly had some ups and downs. One factor that'll determine how your 5.7 Hemi performs is whether it comes with MDS or not.

MDS stands for Multiple Displacement System, a sophisticated method of improving engine efficiency and conserving fuel. Essentially, when this technology activates, it shuts down some of the engine's cylinders allowing it to run with less effort. First, the Electronic Control Module (ECM) stops fuel from going to certain cylinders. Then, the MDS solenoid disengages the lifters so that certain cylinders are sealed off and non-operating, leaving only four running. This system is designed to only engage when demand for output is low and usually will go unnoticed. Not every 5.7L Hemi engine has MDS, so how can you know if your vehicle includes it?

One of the easiest ways to identify whether your vehicle has MDS is by transmission type. MDS isn't possible in a vehicle with a manual transmission because it doesn't have a Transmission Control Module (TCM) that monitors shifting. In order to successfully turn off certain cylinders, and control other engine systems in a complex sequence, a Hemi with MDS needs fast modern processing modules with knowledge of all the engine systems.

The ECM facilitates several operations within the engine, including the MDS and doesn't have the same control or awareness in a car with a manual transmission. In other words, for MDS to work, the car needs to know what gear you're in, and it can't, unless it's an automatic transmission with a TCM unit. So, if you happen to have a 5.7L Hemi with a stick shift, you can rest assured you don't have this economy-boosting feature.

If your vehicle was produced before 2005, you won't have MDS on your 5.7L Hemi V8. However, since 2005, a variety of Chrysler, Dodge, Ram, and Jeep models that offer a 5.7L Hemi engine come with MDS. For example, a new Chrysler 300S V8 features the 5.7L Hemi with MDS, and it's also available on the 2024 Jeep Grand Cherokee L (3-row) with an automatic transmission. Other models that have featured MDS include the Dodge Charger, Magnum, Durango, and Ram 1500, among others.    

According to some owners, another way to tell if your Hemi has MDS is to look for an ECO light on your instrument cluster. This ECO light will illuminate when your vehicle has shut down four of the eight cylinders and is using MDS. If you're in a Ram 1500, for example, and enable the tow-haul mode, this should prohibit MDS from engaging as you need the full power of the engine when hauling.

One issue newer models may experience with MDS is lifter malfunctions. While you may achieve up to 20% improvement in fuel efficiency, between the MDS solenoid and lifters, there are more components involved that can fail with high-milage engines. If you discover your Hemi does in fact have MDS, there are a few options to disable it by switching to Sport or Manual mode or using a tuner, or you can remove it by using an MDS delete kit, which can run over $1,500.