RCEXL Ignition Systems: A Complete Guide to Choosing the Right CDI for Your Petrol Engine
If you’re running a petrol/gas engine in your RC model, the ignition system is one of those components you never think about — until it lets you down. A weak spark, a fried module, or the wrong plug cap fitment can ground a model on flying day. That’s why so many UK modellers standardise on RCEXL ignition systems for their single and twin cylinder engines.
Prices start from £53.45, with the exact price depending on which single or twin configuration you need.
Here’s what you need to know before you buy, and how to pick the right one from our range.
What Does an RCEXL Ignition System Do?
An RCEXL ignition (CDI, or Capacitor Discharge Ignition) generates the spark that fires the fuel-air mixture in a petrol/gas engine, in the same way a car’s ignition coil does — just scaled down and built to survive the vibration, heat and G-forces of an RC airframe.
RCEXL units are a popular choice because they:
- Run reliably across a wide 6V–14.4V input range, so they’re compatible with 5-cell NiMH packs, 2S LiPo, and 3S LiPo batteries without extra regulation
- Are available for both single and twin cylinder engines
- Come in multiple cap angles (Straight, 90°, and 120°) to suit different cowl and engine layouts
- Fit a wide range of popular engine plug types
Choosing the Right Model: Plug Type Matters Most
The single biggest decision when ordering an RCEXL ignition is matching the plug/cap type to your engine. Get this wrong and it simply won’t fit. Our range covers four common cap fitments:
| Plug Type | Fits |
|---|---|
| ME-8 1/4-32 | Common on many popular single and twin petrol engines |
| CM-6 – 10MM | 10mm cap fitment, found across several popular engine ranges |
| BMR6F – 14MM | 14mm cap fitment |
| BMR6A – 14MM | 14mm cap fitment, alternate spec |
If you’re not sure which cap your engine uses, check your engine’s manual or the existing ignition module fitted — it’s far easier to match an existing part than to guess.
Cap Degree: Straight, 90°, or 120°?
Once you know your plug type, the next choice is the angle of the cap itself. This is purely about physical clearance inside your cowl:
- Straight — where you have room for the lead to run directly off the plug
- 90° — the most common choice, ideal for tight cowls where the lead needs to turn sharply away from the cylinder head
- 120° — a shallower angle, useful for certain engine and cowl geometries where a full 90° bend won’t clear
If you’re replacing an existing ignition, matching the old cap angle is usually the safest bet.
Single vs Twin: Match It to Your Engine
We stock both:
- Single ignition systems (model numbers 1121–1128) — for single cylinder petrol/gas engines
- Twin ignition systems, Version 2 (model numbers 1221–1228) — for twin cylinder engines, firing both cylinders from one unit
Each is available across the same range of plug types and cap angles listed above, so once you know your engine’s fitment, choosing between single and twin is simply a matter of matching your cylinder count.
Quick Fitment Reference
| Model | Configuration | Plug Type | Cap Angle |
|---|---|---|---|
| 1121 | Single | ME-8 1/4-32 | 90° |
| 1122 | Single | ME-8 1/4-32 | 120° |
| 1123 | Single | ME-8 1/4-32 | Straight |
| 1124 | Single | CM-6–10MM | 90° |
| 1125 | Single | CM-6–10MM | 120° |
| 1126 | Single | CM-6–10MM | Straight |
| 1127 | Single | BMR6F-14MM | 90° |
| 1128 | Single | BMR6A-14MM | 90° |
| 1221 | Twin | ME-8 1/4-32 | 90° |
| 1222 | Twin | ME-8 1/4-32 | 120° |
| 1223 | Twin | ME-8 1/4-32 | Straight |
| 1224 | Twin | CM-6–10MM | 90° |
| 1225 | Twin | CM-6–10MM | 120° |
| 1226 | Twin | CM-6–10MM | Straight |
| 1227 | Twin | BMR6F-14MM | 90° |
| 1228 | Twin | BMR6A-14MM | 90° |
Why Buy From Carbon RC Parts?
We stock the full RCEXL ignition line-up as standard, single and twin, across every cap type and angle, so you can order the exact spec your engine needs rather than settling for whatever happens to be in stock elsewhere. Selected models are held in UK stock for faster dispatch.
Prices start from £53.45 (Aug 2026), varying by single/twin configuration, plug type, and cap angle — see the reference table above for the full line-up.
While you’re fitting a new ignition, it’s also worth checking your kill switch — our RCEXL RXE2207 Big Power TOC Switch with Futaba plug is a popular pairing and a sensible thing to replace at the same time if your current one is showing its age.
Browse the full RCEXL Ignition Systems range →
Not sure which model fits your engine? Get in touch and we’ll help you find the right part before you order.