What the RPM limiter does
When engine speed reaches the limit you set, the Elite stops firing injectors or spark plugs to hold the engine there. That keeps valves off pistons, rods in one piece and a missed shift from turning into a rebuild. In ESP it's set up in two places: the RPM Limiter tab, which decides how the limit is enforced, and the RPM Limiter table, which decides where.
Choice 1: what gets cut
| Cut Method | What happens | Our take |
|---|---|---|
| Injection | Injector outputs are switched off to hold RPM | Quiet and gentle on the exhaust. The cylinders run lean momentarily as fuel is removed, so it's best kept to brief events |
| Ignition | Spark outputs are switched off to hold RPM | Fast and precise, and the fuel mixture stays intact. Unburned fuel reaches the exhaust, so expect pops and heat, especially on turbo cars |
Which one is right depends on the engine and exhaust. Ignition cut is popular for its precision. If the exhaust or catalytic converter can't tolerate unburned fuel, injection cut is the kinder option. Whichever you choose, check how the engine behaves on the limiter in your logs.
Choice 2: how hard it cuts
Hard Cut
Below the End RPM, everything fires normally. At or above it, every selected output switches off. RPM drops, the outputs come back, RPM rises again, and you get the familiar bouncing limiter.
With hard cut you also get Hysteresis. This is how far RPM must fall below the End RPM before firing resumes. A small value makes a quick, buzzy limiter. A larger value gives a slower, choppier one that drops further off the limit each time.
Soft Cut
Instead of cutting everything, the Elite switches off individual cylinders in a random pattern, just enough to keep RPM at or under the End RPM. It feels smoother, and the engine holds right at the limit instead of bouncing off it. Hysteresis doesn't apply in soft cut.
Choice 3: where the limit sits
The End RPM in the RPM Limiter table is the speed at which all cylinders are cut. It doesn't have to be a single number: you can map it in 3D with an 8x8 table. That lets you, for example:
- Hold a lower limit until the engine is warm by using coolant temperature on an axis.
- Allow a higher limit in upper gears and keep first gear tamer.
- Drop the limit when a switch or fault condition is active.
If you need a second, independent limit, such as a pit or valet limit, use the auxiliary RPM limiter rather than making the main table complicated.
Settings summary
| Setting | What it does | Our advice |
|---|---|---|
| Cut Method | Injection or Ignition | Pick based on the engine and exhaust, then confirm in logs |
| Cut Type | Hard or Soft | Soft cut for a smoother, more controlled limiter |
| Hysteresis | RPM drop needed before firing resumes (hard cut only) | Keep it small. A large value makes the limiter harsh |
| End RPM table | The limit itself, mappable up to 8x8 | Set it below the lowest safe limit of your valvetrain and bottom end |
Why is my engine limiting? Reading the channels
The RPM limiter is only one of many features that can cut fuel or spark. When the car stutters and you don't know why, these channels tell you who's responsible:
- RPM Limiting Function: which feature is enforcing an RPM limit right now.
- RPM Limiting Method: how it's doing it, or None.
- RPM Limiter Active: 1 (Active) while any RPM limit is being enforced.
- Cut Percentage Function, Cut Percentage Method and Cut Percentage: the same idea for features that remove a percentage of firing events instead of holding an RPM. Cut percentage normally sits at 0%.
- Engine Limiting Function, Engine Limiting Method and Engine Limiter Active: summary channels. They report the RPM limit if one is active, otherwise any cut percentage, otherwise None.
Engine Limiting Function is the one to put on your dash or log screen. It can name the main or aux limiter, launch control, flat shift, rolling anti-lag, traction control, torque reduction, overboost cut, decel cut, engine protection, limp mode, the immobilizer, kill switch, speed limiter, turbo timer, flood clear, anti-flood, transbrake, driveshaft RPM control and various error states such as DTC, map version, ETC or injection system errors. Our engine limiting channel states article goes through them.
Troubleshooting
| Symptom | Usually |
|---|---|
| Engine cuts out well below the limit | Another function is limiting. Check Engine Limiting Function |
| Violent bouncing on the limiter | Hard cut with too much hysteresis. Reduce it or try soft cut |
| Big bangs and flames on the limiter | Ignition cut sending fuel into a hot exhaust |
| Limit changes unexpectedly | The End RPM table is mapped against a channel you forgot about |
FAQ
What RPM should I set my limiter at?
Below whatever part of the engine gives up first, usually valve springs or the bottom end. If you don't know that number, ask your engine builder before you pick one.
Is soft cut safer than hard cut?
Both protect the engine. Soft cut is smoother and easier on the driveline, while hard cut is simpler and more obvious to the driver.
Related Elite functions: decel cut and boost control.
