How To Deactivate Mds On Hemi

How to Deactivate MDS on Your Hemi Engine: A Comprehensive Guide

The Multi-Displacement System (MDS) in Chrysler's Hemi engines is designed to improve fuel economy by shutting down cylinders under light loads. While beneficial for saving gas, some drivers find MDS intrusive or prefer the performance characteristics of having all cylinders firing. This guide will walk you through understanding MDS and how to effectively deactivate it, focusing on different approaches and their implications.

Understanding Your Hemi's MDS

Before diving into deactivation, it's crucial to understand what MDS does and why it might be annoying to some. MDS, or Active Fuel Management (AFM) as it's sometimes called, seamlessly switches between 4-cylinder and 8-cylinder modes. This transition can sometimes be felt as a slight shudder or vibration, which some drivers find undesirable. Furthermore, some prefer the consistent power delivery of all eight cylinders, especially during acceleration.

Why Deactivate MDS?

Several reasons might lead you to deactivate MDS:

• Improved throttle response: With all cylinders firing, you'll experience quicker acceleration and a more responsive throttle.
• Smoother driving experience: Eliminating the cylinder deactivation transitions can result in a more refined and less jarring ride.
• Enhanced towing capability: While debated, some believe deactivating MDS offers a marginal improvement in towing performance.
• Personal preference: Simply put, some drivers prefer the feel of a consistently running V8 engine.

Methods for Deactivating MDS

There are several methods to deactivate your Hemi's MDS, each with its pros and cons:

1. Tuning/Performance Chip

This is generally the most effective method. A performance chip or ECU tune re-programs the engine's computer to disable MDS permanently. This method requires professional installation and may void your vehicle's warranty. It also offers the potential for additional performance enhancements beyond simply disabling MDS.

Pros: Permanent deactivation, potential performance gains. Cons: Costly, potential warranty issues, requires professional installation.

2. Using a Scanner Tool

Some advanced OBD-II scanner tools allow you to turn MDS on or off. This offers a temporary solution, and you'll have to repeat the process every time you start the car. This method requires a compatible scanner with the necessary functions.

Pros: Temporary solution, potentially cheaper than a tune. Cons: Not a permanent solution, requires specialized equipment.

3. Using the "Tow/Haul" Mode (If Available)

Certain Hemi models allow for the temporary deactivation of MDS using the Tow/Haul mode. Consult your vehicle's owner's manual to see if this feature is available and how to engage it. Note that this doesn't permanently disable MDS; it only disables it while the mode is activated.

Pros: Simple and readily available on some models. Cons: Only a temporary solution, doesn't offer full-time deactivation.

Choosing the Right Method

The best method depends on your budget, technical skills, and desired level of permanence. If you're looking for a permanent solution and are comfortable with the potential warranty implications and cost, a tune is the most effective. For a temporary solution or if you only want to disable MDS occasionally, an OBD-II scanner or the Tow/Haul mode might suffice.

Disclaimer: Modifying your vehicle's engine control system can affect performance, fuel economy, and potentially void your warranty. Always consult a qualified mechanic before undertaking any modifications. This information is for educational purposes only and does not constitute professional advice.