Mechanical Speed Limiter Guide (Limitador de Velocidad Mecánico)

Plenty of working trucks and buses across Latin America are older diesels with mechanical fuel control. No electronic throttle, no pedal sensor, nothing for an electronic unit to read. If you run vehicles like that and want a limitador de velocidad (or gobernador de velocidad) on them, a limitador de velocidad mecánico is the answer. In Brazil the same thing is a limitador de velocidade mecanico.

This guide explains how a mechanical speed limiter works, what accuracy to expect, which vehicles it suits, and when you should choose an electronic unit instead.

What is a mechanical speed limiter?

A mechanical speed limiter caps road speed by acting on the fuel supply, not on an electronic signal. When the vehicle reaches the set speed, the limiter restricts the fuel reaching the engine, so extra pedal travel produces no extra speed. The driver can still drive at any speed below the set limit.

AutoKontrol’s mechanical unit is the System 80. It is a mechanical device that works on the fuel line, made for older, mechanically governed diesel vehicles.

Why mechanical vehicles need a mechanical limiter

An electronic limiter works by sitting in the signal path between the pedal and the engine control unit. On a modern drive-by-wire truck that is straightforward, because the pedal sends an electrical signal to the ECU.

An older mechanically governed diesel has no such path. The pedal moves fuel control through linkages and the fuel system, and there is no signal to intercept. A unit that depends on one has nothing to connect to. That is the job System 80 was built for: it works on the fuel line, so it does not depend on any electronics in the throttle.

System 80 at a glance

	System 80
Type	Mechanical
Works on	The fuel line
Suits	Older, mechanically governed diesel vehicles
Fit time	About 60 minutes
Accuracy	Within +/-1-2 km/h

A fit time of about 60 minutes means a truck is off the road for part of a working day. Accuracy to within +/-1-2 km/h is more than adequate for the usual reasons fleets limit speed: fuel use, tyre and brake wear, driver behaviour and site rules.

Which vehicles it suits

System 80 is aimed at:

• trucks and tractor units with mechanical diesel fuel control;
• older buses and coaches with mechanical fuel systems;
• volquetas, camiones and other working vehicles that stay in service for many years;
• fleets that keep older units running because they are reliable and paid for.

Many of these vehicles have been running for years and will run for years more. Fitting a limiter to them is often easier than replacing them, and it brings them in line with the speed policy of the rest of the fleet.

When to choose a DBW instead

Not every diesel is mechanical, and age alone does not tell you. The question is how the throttle is controlled.

• Pedal sends an electrical signal to the ECU (drive-by-wire): choose the DBW speed limiter. It is electronic, works on the throttle signal, and takes about 1.5 hours to fit.
• Fuel controlled mechanically: choose System 80.
• Vehicle uses the SENT protocol on its throttle sensor: the SENT speed limiter is the one for that.
• You want tracking and proof of speed compliance: TrackSpeed combines a limiter with ScorpionTrack GNSS tracking and takes about 60 minutes to fit.
• Different speed limits in different zones: GeoKontrol applies GPS geofenced limits.

If you cannot tell which your truck is, do not guess. Send us the make, model, year, engine and throttle type, and we will tell you which unit fits. Many fleets run a mix, with System 80 on the older vehicles and DBW on newer ones, and we can quote across both in one go.

For a fuller comparison of the two approaches, see electronic vs mechanical speed limiters.

Fitting a mechanical limiter

We ship direct to your fleet with fitting instructions. Your own workshop team can fit System 80, or you can use a local auto-electrician or workshop of your choice. Plan on about 60 minutes per vehicle. Our technical team supports you remotely. For general guidance on preparing and checking a fit, see the speed limiter installation guide, and for the options on who does the work, fit a speed limiter yourself or with a local installer.

After fitting, check the vehicle on the road at the set speed. The limiter should hold it steadily, within the +/-1-2 km/h accuracy.

Why limit older vehicles at all?

Older trucks are often the ones that get driven hardest, because they are the cheapest to run into the ground. A limiter on those vehicles does the same things it does on a new one:

• Fuel. Diesel use climbs steeply at higher speeds. Our HGV fuel consumption calculator lets you put numbers on it.
• Tyres and brakes. Lower peak speeds mean less wear.
• Safety. Heavy vehicles need much more distance to stop at speed, and older vehicles may have older braking systems.
• Client and site rules. Mining, port and construction sites often set speed rules for contractor vehicles.

AutoKontrol units are designed and manufactured in the UK and are ECE R89 type-approved. We are part of Scorpion Group, in vehicle electronics since 1973.

Frequently Asked Questions

What is a limitador de velocidad mecánico?

A speed limiter that caps road speed by acting on the fuel supply rather than on an electronic signal. AutoKontrol’s System 80 is a mechanical limiter that works on the fuel line.

Is System 80 electronic?

No. System 80 is mechanical and works on the fuel line. For electronic-throttle vehicles we make the DBW, which is electronic.

How accurate is a mechanical speed limiter?

System 80 holds speed to within +/-1-2 km/h.

How long does it take to fit?

About 60 minutes. A DBW takes about 1.5 hours.

Can my own workshop fit it?

Yes. We ship direct with fitting instructions, and your own workshop or a local auto-electrician can fit it. We support remotely.

How do I know whether my truck needs mechanical or electronic?

It depends on how the throttle is controlled, not only on age. Send us the make, model, year, engine and throttle type and we will confirm the right unit.

Get a quote

Tell us the make, model, year and engine of your trucks and buses and how many you run. We will match each vehicle to System 80, DBW or another unit. Request a quote or email international@autokontrol.com.