Speed ​​converter for tuning EURO4 & EURO5 scooters with Rongmao ECU (45 km/h to Unlimited)

Want to increase the speed of your EURO4 & EURO5 scooter? This Speed ​​converter is the ideal solution for scooters with a Rongmao ECU EFI system, such as models from La Souris, Senzo, and other popular brands. The system is plug & play, which means you can easily install it without any complicated software modifications.

Most important features:

🚀 Speed ​​options:

• 45 km / h (limited)
• 60 km / h (unlimited) for EURO 4-compliant vehicles scooters
• Maximum 55 km/h before and after, EURO 5-compliant vehicles scooters (There are Euro 5 models that barely drive faster than 45 unlimited, explanation is at the bottom of the page)

📲 Remote control:

• Easily switch between 45 km / h en unlimited with the supplied remote control.
• Easy to use, so you can quickly adjust the speed.

🔧 Easy Installation:

• The system is complete plug & play. Plug it in and your scooter will work right away.
• No software adjustments needed – the original ECU remains intact.

Compatibility:

This speed converter is suitable for scooters with a Rongmao ECU and is compatible with the following models:

✅ La Souris EURO4 & EURO5

• Sourini RS
• City
• Desingo
• Valexim

✅ Senzo EURO4 & EURO5

• SP50
• GRACE
• RIVALUX R
• RIVALUX S
• GT2 Grande Retro

✅ Santini EURO4 & EURO5

• SAINT REMO
• FLORENCE
• CAPRI (small & large models)

✅ FAST Scooters EURO4 & EURO5

• Fast Riva
• Leopard Scooter

✅ LeopardForza (EURO4 & EURO5)
✅ RSO Scooters (EURO4 & EURO5)
✅ GT Union Scooters (Germany models, EURO4 & EURO5)

What's in the box?

• Speed ​​converter
• 2x Remote controls
• Cable and 2 adapters
• Assembly instructies (Instructional video available)

Installation instructions:

1. Dismantle the saddle box to access the necessary parts.
2. Remove it cap of the readout plug (OBD2).
3. close the adapter on on the readout plug of your scooter, so that the speed converter is supplied with power.
4. Connect the adapter with the cable from the crankcase cover (kickstart cover) and the ECU.
5. close the speed converter on on the white plug of the adapter.
6. After installation, you can easily switch between limited and unlimited speed settings via the remote control.

Please note: The system only works if the scooter is original and has not already been modified. If your scooter has already been modified, you must first restore it to its original state before installing the speed converter.

Why this Speedconverter?

• Increase your speed up to 60 km/h (EURO4) or maximum 55 km/h (EURO5) without your ECU to replace.
• Simple to install with the plug & play technology.
• User-friendly remote control for easy switching between speeds.
• Suitable for EURO 4-compliant vehicles en EURO5 scooters from well-known brands.

(I.e. Upgrade your driving experience today! Order the Speedconverter for Rongmao ECU and enjoy more speed and performance!

🔎 Possible reasons why your scooter doesn't go above 50 km/h

1. Mechanical limitation in the vario

• Vario bushing / ring too long → prevents the front pulleys from closing fully, so the belt does not climb up.

• Wear or incorrect belt size (too short/narrow) → belt runs lower. Yours requires a 669-18-30 , at least 17,5 mm wide when new.

• Seized or overly heavy rollers → engine revs too low to shift up.

2. Exhaust and intake Euro5 restrictions

• Euro5 exhausts often have narrow bends, small passages and sometimes additional catalyst restriction.

• The air intake/airbox can choke → at higher speeds not enough air, the engine runs “dead”.

• Euro5 Scooters with high mileage may have a clogged catalytic converter.

3. ECU-limitations despite 'unlimited'

• many Rongmao ECU's still have one speed cut around 7.500–8.000 rpm, even with the speed limiter removed.

4. Overall adjustment not suitable

• Rollers too heavy → scooter won't enter the powerband.

• Rollers too light → high revs but no real top speed.

• Incorrect counter-spring → shifts up too early or too late.

5. Power deficit 50cc engine

• A completely original 50cc GY6 with Euro5-injection has only ±3–3,5 hp.

6. Other possible inhibiting factors

• Brake/disc rubbing or tire pressure too low → sounds simple, but can make a difference of 5 km/h.

✅ What you can do to find the cause

1. Marker test : draw a line with a marker on the variator, ride at full throttle → you can see how high the belt comes.

2. Measure variator bushing length : >20 mm = possible limiter.

3. Measure belt : width <17 mm? → replace.

4. Swapping rollers : try lighter (e.g. 5,0g) to see if it spins faster.

5. Check exhaust: original Euro5? Then that is often the biggest throttling tap.

More information about tuning scooters: Everything about tuning your scooter

adapters

There are 2 different adapters available, depending on the scooter model you have. During the ordering process, please indicate which adapter you need in the comments field when filling in the address details. If in doubt, we will send both adapters with you, so that you always have the right one.

Installation Euro5 scooter La Souris Sourini:

A short editing video La Souris City is down here.