Engine Safeties - McLaren

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

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.

Knock is one of the most harmful conditions for an engine to encounter and can happen due to a myriad of reasons. The result of knock is isolated areas of extreme pressure inside of the combustion chamber which can damage pistons, rods, valves, plugs, and bearings if left to run rampant over time. Most commonly knock is caused by poor quality fuel with lower than advertised octane, high charge temperatures (dead low temp circuit cooling pump), wrong map slot (too aggressive of a map slot for the octane), or oil contamination. We monitor knock for every cylinder and the engine safety for knock can be triggered in two ways:

• Multi-Cylinder Knock Count (6) - This will trigger if three or more cylinders are above the calibratable knock threshold set for that map slot. The higher octane slot the lower the threshold will be. This is due to already increased cylinder pressures typically associated with higher octane fuels.

• Single Cylinder Knock Count (5) - This will trigger if a single cylinder has a stronger knock event than any other cylinder. Typically set slightly higher than multi cylinder but is set to trigger in the case that only one cylinder is knocking.

Short Term Fuel Trims (STFT) are a measurement of the percentage of fuel which is added or removed based off of o2 sensor feedback. If STFT is 20% this means that 20% more fuel is being added than the model commanded to reach the target lambda, or air/fuel ratio. Fuel trims tend to waver over normal driving conditions but is limited by +/-25%.

• Short Term Fuel Trims (Delayed) (7) - This will trigger if short term fuel trims are too high for too long. In a typical street car application this value is set at 24% with a 500ms timer while over a calibrated load threshold.

• Short Term Fuel Trims (Immediate) (8) - This will trigger immediately if short term fuel trims max out. This is typically only used in motorsport applications and rarely on street cars.

This safety will monitor the lambda sensor feedback and trigger a safety if lambda is too lean for too long while over a calibratable load threshold. If the lambda is too lean safety 9 will trigger. There are post cut and post shift inhibit timers built in as well as to not give a false positive during gear shifts or traction control events where cylinders are cut to reduce power.

Clutch Slip safety will monitor your engine speed and axle speed using associated gear ratios to ensure the clutch is not slipping. Clutch slip is not something encountered until you have some significant modifications to the vehicle. If clutch slip does occur an engine safety will be triggered. There are post shift inhibit timers set to not give false positives.

Engine Misfires are typically associated with the ignition system. Typically a coil and plug change will have the situation rectified quickly. For this safety we monitor engine roughness of each cylinder and trigger a safety if engine roughness for a particular cylinder is out of bounds when a cut is not demanded. If too many misfires happen is a short amount of time a safety will be set.