If an MDS-equipped engine has been mechanically converted to non-MDS lifters and a compatible non-MDS valvetrain configuration, the PCM generally needs a calibration that no longer commands cylinder deactivation. The mechanical parts and the electronic strategy must agree. Simply installing an MDS delete kit does not change what the PCM is programmed to request.
Key Takeaways
- A mechanical MDS delete and an electronic MDS disable are different jobs.
- After a hardware conversion, the calibration should match the installed camshaft, lifters, and supported engine configuration.
- Turning off MDS commands does not repair a failed lifter, damaged camshaft, oiling fault, wiring problem, or low compression.
- Not every HEMI or Chrysler-family application uses MDS or is supported.
- MoPower coverage is equipment-specific and extends through model year 2025 only for actual supported MDS-equipped applications.
What an MDS Delete Kit Changes
Chrysler's Multi-Displacement System uses cylinder deactivation during selected light-load operating conditions. On an MDS-equipped HEMI, the system relies on specific lifters, oil-control hardware, PCM commands, and a calibration designed around that valvetrain. The purpose is to deactivate selected cylinders when operating conditions permit and return to full-cylinder operation when load increases.
A mechanical delete kit typically replaces MDS-specific valvetrain components with a compatible non-MDS arrangement. The exact parts vary by engine and build, but may include non-MDS lifters, related trays or hardware, and a camshaft selected for the final combination. This is engine work. It should be planned and performed with the correct service information and parts for the application.
For the system-level background, see What Is MDS Delete and When Is It Used?
Why the Factory Calibration No Longer Matches
Before the conversion, the PCM may command MDS solenoids and apply diagnostics based on the factory system. After the hardware is removed or changed, those commands and expectations no longer describe the engine. A compatible calibration disables the supported MDS operating strategy and related diagnostics so the controller is not trying to operate hardware that is no longer present.
If the build includes a non-stock camshaft, injector change, airflow change, or other engine modification, additional calibration work may be required beyond an MDS switch. The tune must be selected around the complete combination, not the kit name alone.
Electronic MDS Disable vs Mechanical MDS Delete
An electronic MDS disable changes supported PCM behavior so cylinder deactivation is not commanded. The MDS lifters and related hardware remain in the engine. A mechanical MDS delete changes the valvetrain so the engine no longer has the original MDS hardware configuration.
Electronic disable can be appropriate for certain supported stock-hardware goals, but it does not physically convert the valvetrain. Mechanical conversion addresses hardware, but it does not automatically update PCM software. The complete job may require both mechanical work and calibration.
Can You Start the Engine Before Tuning?
Whether a freshly built engine should be started on the existing calibration depends on the exact combination and the engine builder's startup plan. MoPower does not recommend assuming that a factory MDS calibration is appropriate for a non-MDS build. Incorrect expectations about cylinder-deactivation hardware, camshaft behavior, airflow, or diagnostics can complicate first start and break-in.
Arrange the programming path before final assembly when possible. That allows time to identify the controller, verify support, and gather the final parts specification. It also avoids discovering after installation that the supplied PCM or calibration path does not support the application.
What Information the Calibration Provider Needs
- Year, make, model, engine displacement, and transmission
- Whether the original engine was actually equipped with MDS
- PCM part number and software information when available
- Camshaft manufacturer and exact part number
- Lifter and valvetrain configuration
- Injector, intake, exhaust, displacement, and compression changes
- Whether the vehicle retains factory emissions-related hardware
- Any existing tune or unlocked/replacement controller
“MDS delete kit” is not a complete build specification. Two engines using that phrase can have very different camshafts and airflow requirements.
Stock-Profile vs Aftermarket Camshaft Builds
A conversion that retains a stock-like camshaft profile may need a narrower set of calibration changes than a build using an aggressive aftermarket camshaft, but both still require the final hardware to be identified. An aftermarket cam can change idle airflow, manifold pressure, torque output, and transmission behavior. Valve springs, pushrods, injectors, cylinder heads, and displacement changes can further affect the appropriate strategy.
Do not select a tune from the phrase “non-MDS cam” alone. Supply the exact camshaft part number or specifications and describe the complete engine. That helps determine whether the build fits a supported fixed MDS mail-in service or has additional tuning needs that should be addressed separately with the customer's engine builder or tuner.
What the Tune Does Not Fix
A calibration cannot restore a wiped cam lobe, collapsed lifter, bent pushrod, damaged rocker, blocked oil passage, low oil pressure, broken wiring, poor ground, or low cylinder compression. It also cannot correct incorrect mechanical timing or incompatible parts.
If the engine had a tick, misfire, metal in the oil, or low oil pressure before disassembly, inspect and repair the cause. Do not use an MDS-off calibration as a substitute for mechanical diagnosis. The related guide, Can MDS Delete Fix a HEMI Tick?, explains why noise alone is not enough to choose a service.
Does Every HEMI Need the Same MDS Tune?
No. Some HEMI applications were not equipped with MDS, and supported strategies vary by engine, year, controller, transmission, and installed equipment. A tune for one truck, SUV, or passenger-car configuration should not be assumed to fit another.
MoPower MDS coverage is limited to actual supported MDS-equipped applications through model year 2025. That statement does not include every HEMI through 2025. The 2024–2025 electric Dodge Charger is not supported by MoPower services and is not an MDS application.
MoPower's MDS Service Is Mail-In Only
For supported applications, MoPower's MDS programming is handled as a mail-in controller service. It is not an iterative remote MDS tuning service delivered through a handheld device.
A heavily modified engine combination may have tuning needs beyond the supported MDS programming change. Those additional needs should be evaluated separately with the customer's engine builder or tuner and are not part of MoPower's MDS service path. The general differences between service methods are explained in Mail-In PCM Programming vs Handheld Tuning.
Before Ordering Calibration Work
- Confirm that the engine was originally MDS-equipped.
- Finalize the camshaft, lifter, and valvetrain combination.
- Record the vehicle and PCM identifiers.
- List every relevant airflow, fuel, displacement, and transmission change.
- Check the exact application in the Vehicle Finder.
- Confirm the mail-in controller requirements and current shipping instructions.
Frequently Asked Questions
Can I install non-MDS lifters and leave MDS enabled in the PCM?
The calibration should match the final hardware. Leaving an MDS strategy active after a mechanical non-MDS conversion is not the correct finished configuration.
Is turning off MDS enough for a camshaft upgrade?
Not necessarily. A non-stock camshaft can require changes beyond MDS behavior, including airflow, idle, torque, and transmission-related calibration depending on the build.
Will an MDS tune repair a misfire?
No. A misfire can come from valvetrain damage, ignition, fuel, compression, wiring, or other causes. Diagnose and repair the fault.
Can MDS be disabled without removing the hardware?
On specific supported applications, electronic disable may be available while the original hardware remains installed. That is not a mechanical delete and does not repair failing components.
Does MoPower support every 5.7L or 6.4L HEMI?
No. Support depends on year, controller, vehicle, software, and installed equipment. Confirm exact compatibility.
Should I order programming before or after assembling the engine?
Confirm the service path before assembly, then provide the final component list. That reduces delays and makes sure the calibration request matches the completed build.
Make the Hardware and Software Agree
A reliable MDS-delete build starts with compatible mechanical parts and finishes with a calibration suited to the actual combination. Use the MoPower Vehicle Finder to check support, or contact MoPower with the PCM number and complete engine-build details.