Understanding Monster Tuned Stage X Calibrations

Posted by Timothy Pownall on

If you are reading this, you're probably asking yourself "what the heck is OEM+ Stage X ?".

I've had lot of questions regarding our different approach to tuning, so I wanted to take the time to write this article to explain the benefits of OEM+ over the competition.

Let's start with the basic pros/cons:


  • No revisions needed
  • Fast tune delivery
  • Change parts at any time with out tune changes
  • Maximum performance in all conditions


  • None


So now that we got that out of the way let's explain how it works with out giving away too many secrets. 

Modern day PCM's in most vehicles are extraordinarily complex and much different from the PCM of the old days.  More and more vehicles are moving towards Speed Density airflow calculation as opposed to MAF (air density calculation performed usually near the intake with a MAF sensor.

MAF based cars are very finicky and simply put a bent air filter can be enough to throw off fuel trims drastically.  Speed Density is significantly more forgiving.  You will typically have sensors that measure the following:

Manifold Pressure (Pressure)
Intake air temp (IAT)
Post intercooler air density (pressure/temperature)

Some other cars like the VW measure charge air temperature before and after the intercooler by having temperature on the manifold sensor. 

These sensors infer air density calculations based on pressure and temperature.  In addition most Speed Density vehicles infer barometric pressure from IAT (intake air temp) so it's important to keep the IAT near stock level (closed air box) for an accurate  barometric pressure reading as this will impact load calculations in the tune. 

Now you are asking "Okay so what does this have to do with your calibrations?"  

Well not any vehicle can have an OEM+ Stage X type calibration.  To achieve what we do, we need the PCM to have the available tables and controls so that we can control air/spark/fuel in all conditions (5000+ feet above sea level) or 110 degree Texas heat.  There is a science to calibrating an engine so that it can perform optimally in all conditions and we adjust engine load and spark targets based on conditions to prevent knock,  but keep the engine performing right under the knock threshold in all conditions for maximum power.

Let's use the Focus ST as an example here.  When you put your foot on the gas pedal you are making an APP request (Accelerator pedal position).  This is called (Driver demand torque request).  Your pedal position performs a lookup against the torque tables and based on pedal position the vehicle will make a targeted torque request.  This torque request if exceeding a given threshold will need to pass through combustion stability checks (some tuners bypass these) and then it will perform a lookup against the torque to load conversion tables.  Based on Speed density calculations (baro pressure/air temp) the car will make a decision on it's targeted load. This will then be cross referenced against the LSPI load tables to have a final load desired based on torque controls. 

Factory method is to change LSPI tables (High/Medium/Low) based on LSPI factor that is modified by knock.  Our method re writes the strategy for these tables to keep the vehicle under the knock threshold so that there is no knock at wide open throttle operation.

In addition the Focus ST has a PID controller for it's boost control system.

What is a PID controller?  https://en.wikipedia.org/wiki/PID_controller

This is essentially a constant correction model to ensure that the wastegate model is corrected to reach desired engine load.  We utilize the factory PID controller for boost control with some proprietary tweaks to increase boost response and ensure smooth transition to wide open throttle with no throttle closures.  Utilizing the factory PID controller allows us to make the tunes adaptive in a sense of boost control and why our tunes are not compatible with aftermarket wastegate actuators as the wastegate response and base tables would need to be drastically altered to be compatible with an aftermarket wastegate actuator. 

How about spark control?

We spent a great time in R&D developing an optimal spark curve that will help keep the vehicle close to peak cylinder pressure (pump gas) or at peak cylinder pressure (ethanol) to ensure maximum performance on a given fuel.   

We also went about using some tables that are not used by OEM (blank) to our advantage in gaining advanced spark control based on temperature.  By default the spark curve already has compensations based on temperature, but we took this a step further by capping the spark ceiling based on temperature to help further prevent knock events at WOT operation.


There is a great deal of time and effort into our OEM+ maps.  Essentially our promise with these maps that they will maintain the smoothness of the factory tune with all the power the stock turbo/fuel is capable of and nothing being left on the table power wise.   There is a lot of engineering and logic in our calibrations to adjust to power mods (within the requirements of the tune defined on the product page) and vehicle conditions to ensure a level of performance and safety other tuners just cannot provide. 

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