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Related Topics Programming Decoders DCC Explained mfx Explained Digital Command Stations Choose a Locomotive Decoder Choose a Sound Decoder Decoder Finder Digital Decoders
Program realistic driving behaviour

Set Acceleration and Braking Delay | CV 3 & CV 4

Make shunting locomotives respond immediately, allow heavy freight trains to accelerate gradually and let express trains coast to a controlled stop before a signal. This guide explains CV 3, CV 4, switchable momentum, stopping distances and safe fine-tuning for all major model railway gauges.

Set the Momentum Calculate the Time Explore Digital Technology
ESU 53451 LokProgrammer for setting acceleration and braking delay PIKO 56415 SmartProgrammer for CV 3 and CV 4
The quick answer

How are acceleration and braking delays configured?

On a DCC locomotive decoder, the acceleration delay is normally configured in CV 3, while the braking or deceleration delay is configured in CV 4. Under the standard interpretation, a higher value produces a longer acceleration or braking period. On many DCC decoders, value 0 disables the programmed momentum.

The two values can be selected independently. A shunting locomotive may need to respond and stop quickly, while a heavy freight locomotive may accelerate slowly and coast for longer. With a sound decoder, the settings should also match engine revving, gear changes, brake sounds and changes in load.

Open locomotive or CV programming on your digital command station . Begin with small test values, drive over a defined test section and increase the values gradually. This makes it easier to identify which change produces the required result.

Important distinction
Momentum cannot repair jerky starting

If the locomotive already runs unevenly at the first speed step, check the current collection, mechanism, starting voltage and motor-control settings first. CV 3 controls the duration of acceleration, but it cannot correct dirty wheels or unsuitable motor parameters.

Decoders, command stations and programming systems

Manufacturers for configuring realistic driving behaviour

The basic functions of CV 3 and CV 4 are widely supported. However, value ranges, time factors, function-button assignments and additional braking methods may differ between decoder families.

Fine-tune acceleration and braking independently

What do CV 3 and CV 4 control in the decoder?

CV 3 – Acceleration delay

CV 3 determines how quickly the decoder accelerates after a higher speed command is selected. Small values produce a direct response, while larger values create a more gradual increase in speed.

CV 4 – Braking delay

CV 4 influences how quickly the decoder's internal speed step decreases after a lower controller setting is selected. The actual stopping distance also depends on the initial speed and vehicle.

Value 0 – Direct response

Under the standard DCC interpretation, value 0 means that no programmed momentum is applied. This is useful for shunting and diagnostic tests, but often looks unrealistic during normal train operation.

Function button for momentum

Many decoders allow acceleration and braking delays to be disabled using a function button. F4 is frequently used, although the actual assignment may be changed through function mapping or configured differently at the factory.

Additional momentum profiles

Modern decoders may offer several momentum profiles. This allows users to switch between settings for shunting, a light passenger train and a heavy freight train.

Sound and brake effects

With a sound decoder , suitable momentum settings help engine revving, idle sounds, load changes and brake squeal play more convincingly.

Vehicle or operation Acceleration Braking Practical adjustment
Shunting locomotive Short and direct Short to medium Make the momentum switchable for precise shunting movements.
Branch-line railcar Short to medium Medium Match the settings to short platforms and frequent stops.
Express locomotive Medium Medium to long Test from a realistic maximum speed.
Heavy freight locomotive Long Long Represent gradual load take-up and the mass of a heavy train.
Steam locomotive with sound Medium to long Medium Check exhaust beats, load changes and brake sounds together.
Multiple-unit consist As similar as possible As similar as possible Match all participating decoders to comparable times.
Reference value for NMRA DCC

Calculate an approximate acceleration and braking time

The basic DCC specification defines an approximate factor of 0.896 seconds for each value entered in CV 3 when the decoder passes through the complete speed-step range. CV 4 uses the same basic calculation for deceleration.

A value of 10 therefore represents approximately 8.96 seconds, while a value of 20 represents approximately 17.92 seconds. These figures are reference values. Manufacturers may use different scaling, internal speed steps, additional soft-start functions, alternative momentum profiles or special braking methods.

A test run is therefore always decisive. Measure the time from a standstill to the configured maximum speed and measure the stopping distance from a clearly defined speed step to a complete stop.

Momentum Time Calculator

Approximate reference values for the standard DCC interpretation.

DCC Reference Values
Acceleration time 10.75 s
Braking time 14.34 s

The decoder instructions and a test run on your layout remain decisive. This calculator does not represent a constant stopping distance.

From direct response to realistic movement

Fine-tune acceleration and braking delay in eight steps

1

Identify the decoder and instructions

Check the manufacturer, decoder family and digital protocol. Determine the permitted value ranges for CV 3 and CV 4 and whether additional momentum profiles are available.

2

Define a test section

Mark a starting point and stopping point. The track should be straight, clean and long enough to assess a longer braking delay.

3

Check the technical condition

First test the locomotive with very low momentum values. Smooth low-speed running, reliable current collection and a free-running gearbox are essential.

4

Increase CV 3 carefully

Begin with a small value and accelerate to the usual operating speed. Increase CV 3 gradually until the vehicle accelerates convincingly.

5

Configure CV 4 separately

Approach the marked braking section from the same initial speed every time. Adjust CV 4 until the locomotive stops at the required point.

6

Consider the maximum speed

An excessively fast locomotive requires a longer distance even when the CV value remains unchanged. Set the maximum speed before completing the braking adjustment.

7

Check shunting mode

Test whether shunting mode and the momentum override are assigned to the required function buttons. The functions must not unintentionally interfere with lighting or sound.

8

Document the values

Save the decoder project or record the locomotive address, CV 3, CV 4, maximum speed and function button used for the momentum override.

From the smallest locomotive to a garden railway

Driving delays for H0, TT, N, Z, 0, 1 and G

CV 3 and CV 4 are not tied to a particular scale. Available space, train length, vehicle mass and layout dimensions nevertheless change the practical impression.

Gauge Typical challenge Recommended test
Z gauge Short layout distances and particularly sensitive current collection Work in small increments and do not conceal contact problems with high CV values.
N gauge Long trains on a compact layout Match the stopping distance to the longest train used regularly.
TT gauge A useful balance between train length and available space Test shunting and main-line operation with separate momentum settings.
H0 gauge Very different decoders, command stations and train types Document CV values by vehicle class and decoder family.
H0e / H0m Short stations, tight curves and frequent stops Combine moderate momentum with a safe stop before turnouts and the edge of the layout.
Gauge 0 Strong visual presence and numerous auxiliary functions Match sound, couplers and brake effects to the momentum settings.
Gauge 1 Large vehicles with long coasting distances Use a sufficiently long test section and leave a safety margin before the end of the track.
Gauge G Garden operation, large motors and changing train loads Test with light and heavy trains and on gradients.
Time delay, braking section and stopping point

Why does the same CV value not always produce the same stopping distance?

Initial speed

A train that begins braking at a high speed covers more distance during the same braking period than a slower train.

Maximum speed

CV 5, the speed curve or a speed limit configured in the command station changes the stopping distance. Set the maximum speed first.

Train load and mechanism

Digital momentum controls the motor. The flywheel, gearbox, rolling resistance and gradient still influence the visible driving behaviour.

ABC braking section

Compatible DCC decoders detect an asymmetrical track voltage and brake within the section. Depending on the decoder, CV 4 or a separate constant-braking-distance function may be used.

DC and Märklin braking sections

Multi-protocol decoders may respond to DC braking sections. Activation and direction are controlled using additional decoder parameters.

Constant braking distance

Some decoders offer a special stopping-distance function or calibration procedure. This is not the same as the simple time-based delay in CV 4.

Identify common causes quickly

Resolve problems after configuring CV 3 and CV 4

The locomotive still responds immediately

Check whether momentum has been disabled using a function button. Also verify that the writing process was successful and that the decoder supports CV 3 and CV 4.

The stopping distance is much too long

First reduce an unrealistically high maximum speed and then reduce CV 4. Always test from the same speed step.

The locomotive does not stop at the same point

A purely time-based delay does not produce an exactly constant stopping distance. Different speeds, loads and contact quality change the stopping point.

The locomotive starts with a jerk

Temporarily reduce CV 3 and check the starting voltage, motor control, wheels, pickup shoe and gearbox. Add the required momentum only after these issues have been resolved.

The brake sound is missing

Some sound projects play brake squeal only when the locomotive has reached a sufficient speed, decelerates noticeably and reaches speed step 0.

A multiple-unit consist is under tension

Match the maximum speed, speed curve, CV 3 and CV 4 of all locomotives. One decoder must not accelerate or brake significantly faster than the other.

Suitable digital technology at Modellbahnshop

Command stations, programmers and decoders for realistic driving

Digital command stations provide direct CV programming, while manufacturer-specific programmers offer convenient graphical configuration. A new decoder must match the model's interface, protocol, dimensions, motor current and required functions.

Read, write and test CV values

Digital command stations and programming devices

For CV 3, CV 4, speed curves, function mapping and sound projects.

Wide selection of interfaces

Locomotive decoders for H0 gauge

Decoders for NEM 652, 21MTC and PluX22 and several digital protocols.

Compact decoder designs

Locomotive decoders for TT, N, Z, H0e and H0m

Micro decoders for restricted installation space and small vehicle bodies.

More power for larger motors

Decoders for Gauges 0, 1 and G

High-output drive and sound decoders for large-scale vehicles.

Optimise driving behaviour further

Related guides to decoders, command stations and digital operation

CV basics

Programming digital decoders

Configure addresses, speed, lighting, mapping and sound safely.

Open guide → Digital protocol

DCC explained simply

Understand speed steps, addresses, functions and Configuration Variables.

Open the DCC guide → Automatic registration

mfx explained simply

Understand locomotive registration, driving parameters and function symbols.

Open the mfx guide → Buying guide

Which digital command station is right for you?

Choose a control system according to the protocol, layout and preferred operating method.

Open comparison → Sound and driving dynamics

Choose a sound decoder

Combine the decoder, loudspeaker, driving behaviour and sound project correctly.

Open buying guide → Installation and compatibility

Compare decoder interfaces

Understand the differences between Next18, PluX, 21MTC, NEM 651 and NEM 652.

Open interface guide →
Frequently asked questions from the digital workshop

FAQ about acceleration and braking delay

Which CV controls the acceleration delay?

On DCC locomotive decoders, the standard acceleration delay is normally configured in CV 3. Manufacturers may also provide additional momentum profiles or a separate soft-start function.

Which CV controls the braking delay?

The standard DCC braking or deceleration delay is normally stored in CV 4. A higher value usually produces a longer deceleration period.

What does value 0 mean in CV 3 and CV 4?

Under the basic NMRA definition, value 0 means that no programmed acceleration or braking momentum is applied. The decoder instructions and additional functions remain decisive.

Which values are realistic for a locomotive?

There is no universal value because decoder manufacturers may use different scaling. Begin with low values and increase them gradually on a defined test section.

Why is the stopping distance longer at a higher speed?

CV 4 normally defines a deceleration period. A faster train covers more distance during the same period than a slower train.

Can momentum be disabled using a function button?

Many locomotive decoders provide switchable acceleration and braking momentum. F4 is frequently used, but the button may be assigned differently through function mapping.

What is the difference between shunting mode and momentum override?

Shunting mode normally reduces the maximum speed or expands the lower speed-step range. The momentum override removes the programmed time delay. Both functions may be activated together.

How is a constant stopping distance configured?

A constant stopping distance is an additional decoder function and is not created solely through CV 4. The required CVs and any calibration procedure are manufacturer-specific.

Does CV 4 also apply in an ABC braking section?

This depends on the decoder and its configuration. Some decoders use the standard braking delay, while others use a separate constant stopping distance or additional braking parameters.

Why does the locomotive start jerkily despite a high CV 3 value?

Possible causes include poor current collection, mechanical problems, an unsuitable starting voltage or incorrect motor-control parameters. A long acceleration delay merely conceals the fault.

How do I match two locomotives for double heading?

First match the minimum, mid-range and maximum speeds. Then give both vehicles comparable acceleration and braking times. Test the locomotives both coupled and uncoupled.

Can CV 3 and CV 4 be changed on the main track?

Many DCC decoders support Programming on Main. A separate programming track is safer for initial tests and unfamiliar vehicles.

Suitable momentum makes every train look more convincing

Further instructions, comparisons, decoder guides and product recommendations are available in the central model railway guide.

Open the Model Railway Guide