Engine Safeties - McLaren

M-Engineering Custom Engine Safeties are custom code compiled to run alongside the OEM strategy to close the throttle in the event of a part failure or unknown condition resulting in critical engine or transmission data being outside of calibratable boundaries.

We currently support seven (7) different engine safeties which have alerted dozens of end users and shops to potential issues well before the issue has had a chance to result in damage or further part failure.

When an engine safety is tripped boost control is cut and the throttle is closed. For the 3.8L cars that means the wastegate duty cycle is set to 0.0% and for the 4.0L cars, with electric wastegates, the wastegates are set to a fully open position. This safety condition will persist for as long as the pedal is held at full throttle. The safety will clear after 10 seconds of light pedal allowing for normal operation but will trip again under full throttle if the same conditions persist. When an engine safety is triggered it will still allow for enough power to navigate traffic and doesn’t result in a no power situation, just limited power.

We have designed custom engine monitors to alert the driver of which engine safety was tripped. There are three different monitors in association with engine safeties that the end user can see in M-Tuner while monitoring data. These are:

This monitor will tell you if an engine safety is active. If this value is 1 an engine safety has been tripped and boost and throttle control has been limited. For information on which engine safety may have been tripped consult the Engine Safety Source Monitors

This value will give you a value which corresponds to which engine safety is currently being tripped. It will be active as long as the safety is active and will revert to 0 when the safety is cleared. Below is a list of what each engine safety is and their corresponding number.

0 = No safety is active
1 = Overboost Safety (Delayed)
2 = Overboost Safety (Immediate)
3 = Differential Fuel Pressure (Delayed)
4 = Differential Fuel Pressure (Immediate)
5 = Knock (Single Cylinder)
6 = Knock (Multi Cylinder)
7 = Short Term Fuel Trims (Delayed)
8 = Short Term Fuel Trims (Immediate)
9 = Lambda (Delayed)
10 = Clutch Slip
11 = Misfire Safety

This value will give you a value which corresponds to which engine safety had been tripped. It will store the last safety that was tripped. If you are out driving and trip an engine safety when you aren’t logging you can reference this value to see which safety you tripped most recently. Below is a list of what each engine safety is and their corresponding number.

0 = No safety is active
1 = Overboost Safety (Delayed)
2 = Overboost Safety (Immediate)
3 = Differential Fuel Pressure (Delayed)
4 = Differential Fuel Pressure (Immediate)
5 = Knock (Single Cylinder)
6 = Knock (Multi Cylinder)
7 = Short Term Fuel Trims (Delayed)
8 = Short Term Fuel Trims (Immediate)
9 = Lambda (Delayed)
10 = Clutch Slip
11 = Misfire Safety

The following list contains the engine safeties, enumerations that are set, and a brief description of each:

(click on topic for an expanded description)

Overboost will keep tabs on your boost pressure and trigger a safety if boost is out of range. A timed boost cut is calibratable per map slot with a global immediate boost cut being setup for complete failure of the boost control system.

Overboost (Delayed) (1)- This will trigger if boost pressure is over a calibratable limit for a set amount of time. Typically triggered by a slight overboost. The delay timer is typically set at 500ms.
Overboost (Immediate) (2) - This will be triggered most times by a complete mechanical failure of the boost control system resulting in a very quick spike in boost pressure. The moment boost pressure is greater than or equal to the threshold boost pressure set in the calibration the safety will trip. This safety reacts as quickly as the sensor supplies the data to the ECU, roughly ~10ms.

Differential fuel pressure is the delta between the fuel pressure in the fuel rail and the air pressure in the manifold. For instance, if you were running 200kPa of boost pressure and 600kPa of fuel pressure, your differential fuel pressure would be 400kPa. Differential fuel pressure is vital to a properly running engine. If fuel pressure is too low the fuel injected into the manifold will not atomize correctly resulting in less than ideal combustion. If it gets too low it will result in lean conditions and possible engine damage as well. Typically differential fuel pressure safeties will be triggered by an aging or failing fuel pump, kinked fuel lines, or if the pump is pushed past its limits. Keep in mind the fuel pressure sensor is located on bank1 and infers the fuel pressure for bank2.

Differential Fuel Pressure (Delayed) (3)- This will trigger if differential fuel pressure falls below a calibratable limit for a set amount of time. This value is typically set at 300kPa with a 1000ms timer.
Differential Fuel Pressure (Immediate) (4) - This will be triggered most times by a complete mechanical failure of the fuel pump resulting in a loss of fuel pressure. The moment differential fuel pressure is less than or equal to the threshold pressure set in the calibration the safety will trip. This is typically set at 250kPa. This safety reacts as quickly as the sensor supplies the data to the ECU, roughly ~10ms.