Ford EcoBoost Speed Density Guide

 


Ford EcoBoost Speed Density Guide

Version 1.0

5/4/17


Introduction

Note: This guide covers CCF Speed Density for the Ford EcoBoost engines.

Overview

The CCF Speed Density feature is a powerful yet easy-to-use solution that brings simplified Speed Density tuning into the Ford engine control unit (ECU) and can be used to entirely replace the existing factory SD models. It is highly customizable and includes features such as real-time tuning to aid in a speedy and efficient tuning process.

Uses

CCF Speed Density (SD) has a number of potential uses that can improve the tuning capability for particular set-ups:

  • SD can eliminate the inaccuracies in aircharge estimation with heavily modified cars.

  • SD allows for the OEM speed density models to be ignored, eliminating the complexity of formulating orthogonal polynomial fits for quadratic equations.

Supported Vehicles List

The following vehicles designed for and sold in all regions unless otherwise noted are supported:

  • 2014-2017 Fiesta ST (USDM Only)

  • 2013-2017 Focus ST

  • 2016-2017 Focus RS

  • 2015-2017 Mustang EcoBoost

Glossary of Acronyms

    • ECT = Engine Coolant Temperature

    • ECU = Engine Control Unit
       
    • CAT = Charge Air Temperature

    • MCT = Manifold Charge Temperature

    • IC = Intercooler

    • MAP = Manifold Absolute Pressure

    • RPM = Revolutions Per Minute (referring to engine speed)

    • SD = Speed Density

    • VE = Volumetric Efficiency

    • WBO2 Sensor = Wideband Oxygen Sensor

Features

The following is a list of the key features of CCF Speed Density (SD):

  • SD works by calculating a new MAP sensor based aircharge to replace the factory modeled aircharge when SD is active. This keeps much of the existing factory logic in place, allowing for the safe and reliable operation of the factory ECU while reducing the learning curve associated with tuning SD.

  • Adding the SD functionality to your existing COBB maps is as simple as opening the map in the Accesstuner software with the SD ECU selected, saving the map, and reflashing the map to the car. From there, you simply start tuning with the Accesstuner software.

  • Tuning SD is achieved through manipulating a real-time tunable volumetric efficiency (VE) table. Because the VE table units represent actual VE, properly calibrated SD tunes can be used to compare VE across different cars with different mods, even if the SD aircharge is drastically different.

  • Several compensations have been added to allow for seamless operation and versatility.  While the calculation of the manifold charge temperature (MCT) pivot compensation is done automatically, a 3D compensation table is also available, and allows the tuner to tweak the SD charge temperature correction. This table can be tweaked according to manifold pressure, allowing for changes that may be needed based on the charge air temperature sensor placement. SD aircharge compensations for variable camshaft timing (VCT), engine coolant temp (ECT) versus charge air temperature (CAT), and barometric pressure are also available.

  • Additionally, an in-cylinder MCT compensation feature is available to aid in the estimation of MCT when the vehicle is stationary, or generating low amounts of airflow. This compensation allows for a blending ratio and time constant adjustment based on SD airflow to infuse a portion of ECT into the MCT final estimation.  This is an effective way to combat heat-soak from becoming influential to the aircharge calculation.

  • We have also included a few monitors to more quickly get the initial tune for the VE table up and running. This can be done when SD is disabled, where the VE table (and other SD elements) can still be tuned before enabling SD.  The (SD) Estimated VE (OEM) monitor uses the OEM speed density logic as an input into the CCF SD algorithms to create a estimation value. This monitor is dedicated, and will always report values from the OEM calibration.  The (SD) Estimated VE Corrected monitor includes a correction factor calculated by using the (SD) Total Fuel Trim monitor.  The corrected values are the "best suggestion" for what to populate into your VE table.  The input to the (SD) Estimated VE Corrected monitor is based upon the SD feature master switch.  When SD is disabled the OEM value will be used, when SD is enabled, the VE table value will be used. 

Hardware Requirements

The following minimum hardware requirements must be met in order to use the SD feature:

  • MAP Sensor - The manifold absolute pressure (MAP) sensor installed in the car must be accurate, reliable, and capable of reading boost greater than the car can ever achieve. A typical car that would necessitate an SD tune would likely max out the factory MAP sensor and require an aftermarket MAP sensor to be installed. Any aftermarket MAP sensor must be properly scaled in the map (via "MAP Sensor Offset" and "MAP Sensor Scalar" tables) and its accuracy should be verified by an external boost gauge before tuning SD. Note: A MAP sensor related check engine light can cause a failsafe load calculation to come into play, potentially causing issues when SD mode is active (please see "Tuning SD – Initial Map Configuration" section for more details).

  • CAT Sensor - Vehicle must have a working, accurate and properly calibrated charge air temperature (CAT) sensor. The CAT sensor is crucial to the SD aircharge calculation. The SD aircharge calculation relies on a theoretical input of the cylinder charge temperature. The closer the CAT reading is to the actual cylinder charge temperature, the more accurate (and consistent) the SD aircharge calculation will be and the easier SD will be to tune. The factory CAT sensor can be located in the charge pipe, or the intake manifold depending on application. Keep in mind that an aftermarket CAT or TMAP sensor may require a different calibration than the factory IAT sensor.

  • Other Sensors - Any sensor or component necessary for the operation of the factory ECU must be working, installed, and properly calibrated.

  • Wideband Oxygen Sensor - A properly functioning and installed wideband o2 (wbo2) sensor is necessary to tune SD. Thankfully, the EcoBoost comes with one pre-installed for you.

  • Mechanical Issues - Any mechanical problem with the car needs to be addressed before attempting to tune SD.

Warnings

OFF-ROAD USE ONLY

Some or all of the features and modifications discussed in this guide may not be legal to use outside of off-road racing applications. Always consult local, state and federal laws to determine what is legal for your particular situation.

READ ALL DOCUMENTATION BEFORE TUNING

CCF SD for Ford has been designed with the purpose of coming up with the best implementation for the unique attributes of the Ford ECU, while allowing for an easy and simplified conversion from the OEM SD models. CCF SD is not like other SD systems that you may be familiar with, including even COBB implementations for other platforms. As such, it is critical that you read through this guide and understand how CCF SD for EcoBoost works before attempting to tune. If you have any questions, we are always willing to help.

SD IS NOT FOR INEXPERIENCED FORD TUNERS

There are many unique qualities to Ford ECU logic that can make it challenging for someone new to the platform. If you are new to Ford tuning, it is recommended that you first become proficient at tuning OEM stock turbo set-ups before tackling SD tunes. OEM tuning can be much more forgiving to mistakes than SD tuning.

MANIFOLD PRESSURE SENSOR CHECK ENGINE LIGHT ERRATIC LOAD CALCULATION

Any diagnostic trouble code (DTC) related to the manifold pressure sensor will cause the Ford ECU to revert to the OEM tables (as a failsafe). This can result in an erroneous load calculation if the OEM calibrations settings were not altered. If this occurs when the vehicle is accelerating, a lean condition and incorrect timing can result. It will also likely cause the engine to eventually stall. If there is the possibility that any of the MAP sensor related DTCs (P0068, P0107, or P0108) could be triggered, it is critical that those DTCs are disabled in the tune. The installation of an aftermarket MAP sensor (required for SD if the factory MAP sensor is not sufficient) will make it more likely for these DTCs to be triggered, even though there may be nothing wrong with the sensor itself. Please see "Tuning SD – Initial Map Configuration" section for more details.

ENGINE HARDWARE CHANGES MAY REQUIRE A RE-TUNE FOR SD

It is important to understand that after the SD tune is complete for a given car, any further changes to engine hardware that impacts airflow efficiency in or out of the engine can potentially require tweaking or re-tuning of the VE table to avoid fueling/timing issues (due to incorrectly calculated SD load). Additionally, mechanical issues, such as intake/exhaust leaks, and issues related to the aging of the motor, such as combustion deposits and loss of compression, can also impact actual VE. It is highly recommended that a permanent wideband o2 sensor and gauge is installed in the vehicle and that the driver understands how to read the gauge and determine what is normal for their tune.

POTENTIAL RISKS FOR SD WITH A HEAT SOAKED CAT SENSOR

Any SD calculation, including CCF SD, requires an input for cylinder charge temperature, which is critical to the determination of accurate aircharge via SD. The estimation of cylinder change temperature is accomplished for CCF SD via the CAT sensor input. Generally, when the CAT sensor is in the recommended location (post-IC), the vehicle is moving and the driver is on the throttle, the CAT input can be a fairly reliable representation of actual cylinder charge temp. However, when the vehicle is sitting still (or at low speeds) and the driver is off the throttle (or low throttle), or the vehicle has been sitting with the engine off and a hot engine bay for a period of time, there is the potential for the CAT sensor to become heat soaked. That is, the sensor now reads higher than the actual intake air temp. When SD is active, this would cause the calculated SD aircharge (as well as load) to be lower than it should be, causing the car to run lean (and with generally more timing advance). This effect may subside after the vehicle gets moving and throttle (as well as MAP) increases, but it will generally not be an instantaneous improvement. Knowing this, we have implemented the In-Cylinder MCT Compensation feature so these conditions can be accommodated.  Please make sure to take advantage of this feature to avoid heat soak based issues.

SD Installation Steps

Before tuning with SD, you'll first need to update your Accesstuner software and Accessport firmware to versions compatible with the SD feature as follows. Always make sure to periodically check for future updates.

  • If your current Accesstuner version has the auto updater feature, you can update the software to the SD version via the internet ("Help" -> "Check for Updates"). If your version does not have auto-updater, you will need to download or submit a request for a new version.

  • Update your Accessport firmware to the latest version via the Accessport Manager software.
  • Now that your software and firmware is updated, you will need to reflash an SD-capable map to the car you will be tuning.

  • Run the Accesstuner software and select a vehicle listed by the "V3 Only" compatibility filter.

 

  1. You may now either open your existing map or simply use the default stock mapping in Accesstuner. Make any initial changes to this map that you wish to start from for SD (see "Tuning SD – Initial Map Configuration" later in this document).

  2. Save your map. This map will now have the SD feature.

  3. Reflash the new SD map to the car via the Accessport or.

  4. The car is now ready to be tuned via SD.

SD Basics

What is Speed Density?

The Ford ECU, as well as any engine management solution, needs to determine the mass of air entering the engine in order to determine the correct amount of fuel to inject for a given desired fueling target. With the Ford ECU, it is represented in terms of cylinder airmass (lbm/event), which, along with engine speed (RPM), is used to determine load (%). For the Ford ECU, load is not only used to determine the proper injector pulse width, but also the desired fueling/timing targets. The modern factory EcoBoost determines aircharge via the manifold absolute pressure (MAP) sensor and pre-calibrated computer modeling.

CCF Speed Density, on the other hand, attempts to estimate aircharge via MAP and other inputs. The basis for this calculation is given by the ideal gas law. The ideal gas law is a relationship in physics between various inputs that allows for an estimation of the mass of an ideal gas. In our case, the ideal gas is the air entering the combustion chamber of the motor. The variables involved in the calculation (for CCF SD) include manifold absolute pressure (from the MAP sensor), cylinder charge temperature (i.e. approximated by our CAT sensor input), volumetric efficiency (from our VE calibration table), engine speed (RPM), and engine displacement (tunable parameter). From this, an estimation of aircharge can be made (see "SD Math" section for a detailed explanation of the math involved).

What is Volumetric Efficiency?

Simply put, it is the amount of air inducted into the engine relative to the engine's displacement. An engine is essentially an air pump and volumetric efficiency (VE) defines how efficient that process is. A volumetric efficiency of 100% would indicate that the amount of air inducted is the same as the engine displacement (at standard conditions) for a given engine cycle. If all engines always operated at 100% VE, there would be no need to account for VE in determining the SD aircharge. But, this is far from the case.

Numerous factors impact how VE varies with conditions for a given engine. As far as engine hardware, this can include, but not limited to, the entire intake tract (from air filter to turbo to intercooler to throttle body), all exhaust components, intake manifold design, cylinder head design, intake/exhaust valve design, compression ratio, camshaft timing and lift (including variable camshaft timing via tuning), and so on.

Mechanical/aging issues, depending on their severity, can also potentially impact VE. Examples would include combustion deposits, intake/exhaust leaks, and loss of engine compression.

Among engine operating inputs, VE is most likely to change according to manifold absolute pressure (MAP) and engine speed (RPM). This is why the VE table uses MAP and RPM axes (as is typical with most SD solutions).

Volumetric Efficiency Table

The VE table is the primary means by which an SD tune is accomplished for a given car. Once tuned, changes to engine hardware and/or mechanical/aging issues that arise (as described in the section above) may require re-tuning of the VE table. What areas of the table that need to re-tuned or tweaked is going to depend on the change itself and how it impacts actual VE across a range of MAP and RPM.

Tuning the VE table is simply determining the actual VE so that the SD aircharge is as close to the actual aircharge as possible. This can be accomplished by comparing the ECU's fueling target with actual fueling (via wideband o2 sensor). All things being equal, increasing VE in the VE table will result in an increase in SD aircharge (for the MAP/RPM area impacted). This will result in an increase in load and fueling will become richer. On the other hand, decreasing VE in the VE table will result in a decrease in SD aircharge. This would have the opposite effect with load decreasing and fueling becoming leaner. Keep in mind that because load is also used as an input to ignition timing, cam timing (VCT), and several other tables, the change in load will also impact the desired targets for these tables.

Generally speaking, the peak VE for a given column of the VE table will generally occur at the RPM of the motor's peak torque and VE will progressively drop on either side of that RPM point. Also, VE generally tends to increase as MAP increases. Keep in mind that these are not hard and fast rules. You may find that the VE tune necessary for a given car does not follow these guidelines completely.

SD Activation

CCF SD is optional!

To use the system simply turn it on in the calibration using the Master Switch (Speed Density).

Disabled – A value of 0 in this table will use all of the OEM tables found in the Speed Density Tables section of the software. This results in cylinder airmass being determined exactly as the factory ECU logic dictates. That is, cylinder airmass is determined based on MAP sensor input and the OEM models. In this mode, the (SD) Estimated Airflow, and (SD) Estimated VE (OEM) will still be calculated even though it is not used. This will allow you to compare the OEM model to the CCF implementation. In addition, you can also tune the SD tables in this state. The (SD) Estimated VE (OEM) monitor (which is always available) will estimate VE based on the OEM models, which you can use as reference to get an initial tune of the VE table started. To re-instate when SD is disabled, you can make changes to the VE table while still running the OEM speed density models.

Enabled – A value of 1 in this table will enable CCF SD. That is, the cylinder airmass normally determined by the OEM tables found in the Speed Density Tables section of the software will always be replaced by the SD airmass calculation determined by your SD tune. Even though the (SD) Estimated VE (OEM) will not be used by the ECU, you can still monitor/log this value to compare against the final VE of your calibratoin.

Tuning SD – Mechanical Configuration

Before jumping in and starting tuning, make sure the car meets the minimum hardware requirements outlined in the "Hardware Requirements" section found earlier in this document. Failure to do so can result in an inconsistent tune as well as potential engine damage.

Tuning SD – Getting Started

  • Installing SD – Make sure an SD map has been reflashed to the car's ECU and you have the latest SD-capable software and firmware updates as outlined in the "SD Installation" section earlier in this document.

  • Opening Map – Run the Accesstuner software and select the ECU of the car you are tuning. Open the SD map you reflashed to the vehicle.

Tuning SD – Initial Map Configuration

Airflow and Load Limits

Because most of the factory logic is retained for CCF SD, factory limits that cap airflow and load are still applied. While not critical that these limits are raised for your tune, be aware that throttle closures will occur if they are hit. This is true regardless of whether CCF SD is enabled or not.

Manifold Pressure Sensor Diagnostic Trouble Codes

If a check engine light is set related to the manifold absolute pressure (MAP) sensor, the ECU will switch to the OEM speed density tables.

One or more of the MAP sensor diagnostic trouble codes (DTCs) can even be set when there is no actual failure of the MAP sensor. This can occur in the following circumstances:

  • High level of boost (i.e. MAP voltage) is seen by the factory or aftermarket MAP sensor that exceeds the factory DTC limits.

  • Lower level of MAP voltage due to aftermarket MAP sensor's expanded relative range.

The following are the MAP sensor related DTCs in question:

  • P0068 - Manifold Absolute Pressure Circuit Range/Performance Problem

  • P0107 - Manifold Absolute Pressure Circuit Low Input

  • P0108 - Manifold Absolute Pressure Circuit High Input

It is critical that if the possibility exists that any of these DTCs may be set, they should be disabled for the SD feature to continue working properly. This can be accomplished by unchecking these DTCs in the "Edit" -> "Advanced Parameters" menu, saving the map, and then reflashing the map to the ECU.

For the P0107 and P0108 codes, the DTC voltage limits can be configured in the Accesstuner software via the MAP Sensor Voltage (Max) table (found in the Sensor Calibrations -> MAP Sensor group). 

Conservative Fuel and Timing Maps

It is important to consider using conservative fuel and timing maps during the initial SD tuning phase. When starting your tune, the VE table will not be perfect until you've had a chance to dial it in. While you are tuning the table, any error from actual VE will not only result in the incorrect fueling, but also the incorrect load values. If the VE for a given cell in your table is less than actual VE, this will result in load that is less than actual load. Because the timing tables use load as an input, the timing advance will generally be higher than intended in this case. This issue would also impact the cam timing (VCT) tables as well as any other table that uses load as an input. If the VE for a given cell in your VE table is greater than actual VE, the opposite will occur, where load will be greater than actual. This is why you generally want to bias your VE values to a higher estimation of VE when starting out, rather than a lower one.

Fuel Injector Scale and Latency

Tuning for new injectors for CCF SD is no different than the factory process. As such, you will need to make sure your fuel injector settings are tuned correctly prior to tuning with SD. If you are changing injectors at the same time as changing over to SD, you'll need to at least make sure that you have reasonable starting values for the new injectors.

Engine Displacement

CCF SD uses engine displacement as one of the inputs to the SD airmass calculation. As such, this requires that you input the correct displacement of the motor you are tuning via the Engine Displacement (Standardized Air Charge) table in the COBB Custom FeaturesSpeed Density group. This should be the closest value (in liters) to the car's actual engine displacement for a single cylinder. The default value varies by application but is derived from the OEM calibration settings.  Also note, changing values in this table will also show a change to the Standardized Air Charge (in the OEM Speed Density Tables group) as it's a converted representation of the same table. The final displacement will show when viewing the Engine Displacement realtime table, and can be modified to fine tune displacement as needed (remember to populate the final version divided by the number of cylinders).

VE Table Axis Scaling

The default values for the MAP axis of the VE table is in 2.23 psia steps up to a maximum of 44.7 psia and the default values for the RPM axis is in 400 RPM steps up a max of 8000 RPM. You need to make sure that the maximum values are enough for the max MAP and RPM that the motor will likely see. When either RPM or MAP exceeds their corresponding max axis values, the ECU will continue to use the VE values in the last row (or column). If you need to make a change, simply re-scale the axis values in realtime and reflash those changes to the ECU when finished. Keep in mind that the MAP axis is in units of manifold absolute pressure, not relative pressure. If you wish to determine the corresponding relative pressure values (for reference) simply subtract your barometric pressure from MAP. The barometric pressure can be read via the Barometric Pressure monitor. If you are at/near sea level (barometric pressure around 14.7 psi) and you wish to quickly determine the relative pressure in your head, simply subtract 15 psi from the MAP axis value you are looking at (for example, 30 psia – 15 psi = 15 psig). This will give you a quick approximation when you wish to think in terms of relative pressure.

Reflash Changes

Make sure you save this map with the initial changes and reflash to the car before continuing with the tune.

Tuning SD – Starting Values for the VE Table

The default values for the VE table are set to 100% across the entire table. This is not meant to be a starting point to run the vehicle in SD tune. Instead, you'll want to consider coming up with initial values in the VE table that are reasonable enough to run the car in SD. The following gives suggestions on how to proceed with various scenarios.

Using the OEM model as a reference

If the car runs well enough with the OEM tables, you can use the (SD) Estimated VE (OEM) monitor to aid in determining starting values for your VE table. If there are issues with the accuracy of the OEM calibration settings, or problems with the CAT sensor, MAP sensor, and/or engine displacement inputs, this will impact the accuracy of the (SD) Estimated VE (OEM) monitor.

The idea here is that you will be tuning your starting VE table while entirely using the OEM tables. That is, if the car you are tuning runs well using the OEM tables, you can get a decent initial set-up for the VE table before actually running the car with CCF SD enabled. In addition to the (SD) Estimated VE (OEM), you can also view/log the (SD) VE Base monitor, which is the current VE table look-up. This is VE based on the VE table that would be used in the SD airmass calculation if CCF SD was enabled. By comparing the(SD) Estimated VE (OEM) and (SD) VE Base, you can tweak the VE table appropriately. Keep in mind that the (SD) Estimated VE (OEM) monitor is not a substitution for actually tuning the VE table with CCF SD enabled based on actual fueling.

There are a handful of methods you can use to take advantage of the (SD) Estimated VE (OEM) monitor in order to come up your starting VE tune using the OEM tables. You may find some or all of these are useful, depending on what tools you have available and the time you have to spend with the vehicle:

  • Data logging – One way to come up with reasonable initial VE values for specific MAP and RPM areas of the VE table is via data logging. You'll need to at least log the (SD) Estimated VE (OEM), Manifold Absolute Pressure, Engine Speed, and Accelerator Pedal Position monitors. Logging Accelerator Pedal Position will allow you to filter out the inaccurate (SD) Estimated VE (OEM) values when throttle is rapidly changing (ex. during tip-in and tip-out). With data logging, the more data points you have for a given MAP/RPM range, the more accurate your estimation of VE will be as it will allow you to throw out more extreme values. But, you should keep your starting VE values towards the higher side to reduce the chances of a VE error in the starting map resulting in a lean condition when you start to tune when CCF SD is enabled. Keep in mind that if the CAT sensor becomes heat soaked, which may occur with extended idling and stop and go driving, the (SD) Estimated VE (OEM) monitor will overestimate VE compared to actual. You may want to also log Charge Air Temperature, (SD) MCT Final, and Vehicle Speed so you can see if there's any relationship between a higher (SD) Estimated VE (OEM) and the conditions that may result in a heat soaked CAT sensor. As you accumulate data, modify the VE table appropriately and then add the (SD) VE Base monitor for additional logging. You can then compare your table VE to estimated VE so you can tweak VE further.

  • Steady-state tuning on dyno – If you are tuning on a load-bearing dyno, you can also hold cells of the VE table and come up with an initial VE for a given cell based on the estimated VE monitor. This would be accomplished by enabling live tracing on the table and taking advantage of real-time tuning. As you view the (SD) Estimated VE (OEM) monitor, it will show a range of values as the inputs to this calculation rapidly change. Try to use the highest reasonable value shown. It is not realistic to attempt to do this for every cell of the table just for an initial VE pre-tune. But, you could focus on, for example, the RPM row that is likely to be closest to peak torque and, therefore, where VE is likely to be highest (for a given MAP column).

  • Filling in the blanks – Depending on the time available for the tune, it may not be feasible to try to estimate the majority of the cells in the VE table using the methods described above. Instead, you can focus on more narrow portions of the map representing low, mid and high MAP areas and then "fill in the blanks" between these areas. Generally speaking, as MAP increases, VE also increases. Also, as it relates to RPM, VE will tend to follow the torque curve of the motor, generally peaking at the same RPM as the peak torque of the motor. These are not hard and fast rules, but they are sufficient enough to allow you to interpolate between the areas of the map you have worked on for the starting VE tune. Keep in mind that the WOT area of the VE table (i.e. high MAP) is going to be the most crucial area of your pre-tune. This is because load errors at high MAP have the most potential to cause engine damage. You do not want your first WOT pull in SD mode to result in an overly lean condition with more timing advance than anticipated. This is also a reason to go with more conservative fuel and timing maps until you get the VE table dialed-in after switching to SD mode.

Once you have a reasonable starting VE table, you may want to consider bumping up the values in the entire table just to make sure your pre-tune is more likely to overestimate VE than to underestimate it.

Starting from scratch

If the OEM tables are not properly calibrated and the vehicle configuration drastically varies from stock, then there is not a means to directly estimate VE for a given car. Over time, however, you will see specific patterns in the VE table for cars you've tuned (for a given set of mods) and setting up a reasonable starting VE table for similar vehicles will not be difficult. If you have no frame of reference, however, you can start with some general guidelines. The default values in the VE table will be 100% for all cells. This will be generally too high in the lift-throttle, idle, and cruise areas (i.e. much too rich). Generally speaking, you may see more like 50%-60% in lift-throttle/idle areas and 60%-80% in cruise areas. Moderate boost may be in the 80%-90% range. Higher boost may be in the 90% to over 100% range. To stay on the conservative side of things with your starting VE table, you want to bias your estimate towards higher values rather than lower. This will reduce the chance of a lean condition when the table VE is less than actual VE. This is especially critical at higher boost where a lean condition (and greater timing advance) due to lower than actual load would be more of a problem.

Tuning SD – The Tables

"Volumetric Efficiency" Table

The Volumetric Efficiency table is the primary means by which the SD tune is accomplished. Once you have your starting values configured for this table (as described in the previous section), you can get to the actual tune. You'll need to make sure the SD master switch is enabled and that the car is at operating temperature. As you hit the MAP/RPM area corresponding to a given cell, if your wideband o2 (wbo2) sensor reads richer than what the ECU is targeting, you reduce VE for that cell. If your wbo2 sensor reads leaner than what the ECU is targeting, you increase VE for that cell. You continue this process until you've dialed in as much of the VE table as you can.

The final ECU fueling target can be determined via the Commanded EQ Ratio monitor. This may be different at times than your primary open loop fueling map due to additional fueling compensations that come into play, such as post-start/warm-up enrichment, long-term fuel trims, and others. Also, in closed loop, the ECU is not always targeting 1.0 lambda (i.e. 14.7:1 AFR gas). The Commanded EQ Ratio will account for all these changes as it is the final fueling target used to ultimately determine injector pulse width.

You should be aware of when the closed to open loop fueling transition occurs for your tune. When the transition to open loop happens, you may see a lean or rich spike when the short-term fuel trims are no longer applied if that area of VE table needs work. You can determine the closed/open loop status via the Closed Loop Status monitor.

If the car has a functional and accurate front o2 sensor, you can also tune VE in closed loop via the short and long-term fuel trims. For ease, we recommend using the (SD) Total Fuel Trim monitor and try to get this value as close to zero as feasible by manipulating VE. If the value is positive, the ECU is adding fuel because of a lean condition and you will need to increase VE. If the value is negative, the ECU is removing fuel because of a rich condition and you will need to decrease VE.

You may be tempted to simply manipulate the VE table to hit the fueling target you desire for a given MAP/RPM area regardless of the Commanded EQ Ratio. While this is certainly possible, it does have a few downsides. First, tuning this way would result in VE values that are not representative of actual. That is, you could not easily compare them to other tunes. It can be quite useful to compare VE tables across tunes as it gives you an idea of VE changes with different mods (and cam timing). It can also help you use those values as a starting point for new tunes for cars with similar mods. Second, making changes to fueling after completing the tune is a little easier if the VE table represents actual VE. You would simply modify the Desired Lambda (Power Demand) table to your new desired fuel targets.

When you've dialed in the VE tune, use the Accesstuner graphing to help to smooth the table. Generally speaking, actual VE should not drastically change with small changes in RPM and MAP and, therefore, you should not see drastic changes in VE between cells in the VE table. Smoothing the table will result in a more consistent load calculation and therefore, more consistent fueling and timing.

In addition, you will also need to estimate the areas of the VE table you were not able to hit when tuning. The values should be reasonable given the adjacent cells that were directly tuned. Also, keep in mind when estimating VE, that VE will generally increase with an increase in MAP and for RPM, it will generally follow the torque curve of the motor (with the peak VE occurring at the RPM in which peak torque occurs and decreasing on both sides of that peak).

"VE Compensation (MCT Pivot)"



Like the VE table, the VE Compensation (MCT Pivot) table is another critical component of the SD aircharge calculation. In order for our SD aircharge to be accurate, we not only need to know MAP, RPM, VE, and engine displacement, but we also need to know the temperature of the cylinder charge. Without this input and its corresponding correction, any given cell in our VE table would only be valid at the charge temperature in which it was tuned. Without this correction, if the cylinder charge temp dropped from our tuned charge temp, we would go lean and if it went up, we would go rich.

We have no means of directly measuring cylinder charge temperature so we have to rely on measuring charge air temperature at some point as a means of estimating the in-cylinder temperature. Generally, the closer to the combustion chamber we measure the charge temperature, the closer we'll be to in-cylinder temperature. Having the ability to tweak the charge temperature correction is an important component to the SD tune.

Normally, if applying the ideal gas law to estimate engine aircharge, the non-linear correction factor for charge temperature would be wrapped up in the ideal gas law equation. However, in order to allow the ability to tune this correction, it has to be externalized. For CCF SD, this is accomplished by first calculating SD aircharge at a specific reference temperature of 100 degrees Fahrenheit. Then the VE Compensation (MCT Pivot) is applied (along with the other SD compensations) to determine the final SD aircharge. As you can gather from the default values in the table, the 100 deg. F column has no correction (1.0 multiplier). The default values for the rest of the columns are scaled with the ideal gas law and our reference pivot temperature in mind. As such, this allows for a tunable charge temp correction.

What this all means is that there may be scenarios where your charge temperature reading may be notably different from the actual charge temperature. As such, the default ideal gas law based values in this table may need to be tweaked. As you can see, the table also has a MAP axis. This allows you to come up with different sets of corrections based on MAP. This is important because MAP is one of the primary factors which can impact necessary tweaks to the table. The default values for the MAP axis are mostly in vacuum, but these can be changed as needed.

"In-Cylinder MCT Compensation"



The other scenario in which the CAT reading may differ markedly from actual charge temperature is when the CAT sensor becomes heat-soaked. What happens is that the sensor itself absorbs heat from the surrounding air and intake piping and reads a temperature higher than the actual temperature of the aircharge. Generally, this effect is progressively more pronounced at lower MAP/airflow and therefore you may be more likely to see it in conditions such as stop and go driving, extended idling, or a hot restart. Because the CAT reading is higher than the charge temperature, this would cause the aircharge calculation to be less than actual and you would end up going lean (as well as causing potentially more timing advance). When MAP/airflow does increase, the heat soak effect of the sensor does not instantaneously diminish, so the heat soaked reading may continue at higher MAP for a period of time. This may present a problem if, for example, the car is subject to high loads (such as wide open throttle) soon after heat-soak of the sensor sets in.  For these reasons, we have added a way to bias the charge air temperature with engine coolant temperature in a means to estimate the in-cylinder charge temperature.

To use this feature, simply set the Enable Switch (In-Cylinder MCT Compensation) to 1 and modify the Bias and Time Constant tables as needed.  The bias table chooses the percentage of Charge Air Temperature is used against Coolant Temperature for blending.  Additionally, we filter the blend of these two temperatures with an adjustable rolling average time constant.  Larger values in this table will take longer to blend, while lower values will blend faster.  Experimentation will determine the appropriate values for these tables, but the defaults can be useful for starting out.

Here is how the math for this works (note the filter is not shown here but is present):

Let's run an example, current Charge Air Temperature is 128 deg. F and Coolant Temperature is 205 deg. F, the Bias request is 80%. 

Keep in mind though that the heat soaked CAT reading can potentially occur even at colder temps. For example, the charge temperature may be 40 deg. F and the CAT reading is 60 deg. F. This would still be a heat soak scenario (although one which would be difficult to account for) even though the temperatures are relatively mild.  Be sure to adjust these tables accordingly to prevent this phenomenon from becoming an issue.

"VE Compensation (Base)" Table

It is typically not necessary to tune the VE Compensation (Base) table as far as the ideal gas law and our SD aircharge calculation is concerned. The default values are generated from an OEM equivalent table. However, you may find some circumstances where it may be useful to tweak this table for your SD tune. One example would be more extreme coolant temperature readings (on the high end). You may want to increase correction at this extreme as this may mean a more likely heat soak scenario for the CAT sensor (high ECT likely means higher radiant engine heat). As described in the previous section, a heat soaked CAT sensor (relative to actual charge temp) will result in a lean condition with SD.

"VE Compensation (Barometric Pressure)" Table

As you go up in altitude, the barometric pressure drops. The SD aircharge calculation for CCF SD accounts for this change because MAP is a part of the ideal gas law calculation and therefore, as barometric pressure decreases, MAP also decreases (all else equal) and SD aircharge will also decrease. However, exhaust gas backpressure also decreases as barometric pressure decreases, which can impact VE. As such, you may need to tune the VE Compensation (Barometric Pressure) table if the car is going to see notable changes in altitude. In addition to the barometric pressure axis, this table also has a MAP axis. This will allow you to tune the compensation against MAP where the effect of exhaust gas pressure on VE may vary.

Tuning SD – Post-Tune Recommendations

When you feel your SD tune is complete, there are several things you should consider in order to maximize the long-term reliability of the SD tune:

  • It is important that your reflashed map has the same Master Switch (Speed Density) table value as your real-time tune. For example, if you previously enabled SD via real-time and tune the car, but didn't save the map and reflash, the SD feature would be disabled upon the next key cycle. It is always important to reflash your final tune to make sure it is always part of the "base" map.

  • If the SD tune was completed on a dyno, it is important to drive the car under conditions that it is likely to see during normal operation and verify that the tune is safe and that there are no driveability concerns.

  • The owner/driver of the car needs to be instructed about the potential for a heat soaked CAT sensor and under what conditions this is likely to occur (extended idling, hot soaked re-start, etc). It is important that the owner/driver understands that putting the car immediately under heavy load when a heat soaked CAT sensor may be a possibility should be avoided when running SD. Instead, under these conditions, allow the car to get moving without getting heavily into boost for at least a few minutes before putting the car under heavy load.

  • The owner of the car also needs to understand that practically any engine mod that impacts aircharge in any way may require a re-tune or tweaking of the VE table for cars running SD. This is important as even seemingly minor mods might cause a significant enough change in VE that there could be fueling and load issues for SD.

Tuning SD – Additional Topics

Recommended Calibrations for Aftermarket TMAP Sensors

When an aftermarket TMAP sensor is installed, you may need to tune the CAT sensor calibration which will be different with an aftermarket sensor as compared to the factory CAT sensor. This is done via the CAT Sensor Calibration table in the Sensor Calibrations group.

The following shows the recommended CAT scaling for the Bosch 4-bar TMAP sensor . Keep in mind that both the axis values (top row) and data values (bottom row) may change in this case. Note: These calibrations are provided for your convenience only and do not represent an endorsement for or against any particular product. Manufacturer's specifications can change at any time. It is important that you verify the sensor calibration you are going to use before tuning SD.

 

Recommended Calibrations for Aftermarket MAP Sensors

When an aftermarket MAP/TMAP sensor is installed, you will need to set up the MAP sensor calibration appropriately. This is done via the MAP Sensor Scalar and MAP Sensor Offset tables in the Sensor Calibrations group. The Boost Pressure reading (via Accesstuner software or Accessport) should then be compared to an external boost gauge to verify accuracy before tuning SD. The recommended calibrations for some of the most popular aftermarket MAP/TMAP sensors are shown below (note: values are shown in psi). Note: These calibrations are provided for your convenience only and do not represent an endorsement for or against any particular product. Manufacturer's specifications can change at any time. It is important that you verify the sensor calibration you are going to use before tuning SD.

  1. Bosch 3.5 bar (Part # SNSR-03088) –> MULTIPLIER = 10.878 psi , OFFSET = 1.813 psi 

  2. Bosch 4 bar (Part # SNSR-03089) –> MULTIPLIER = 11.944 psi , OFFSET = 2.474 psi 
     
  3. Freescale 4 bar (Part # MPXH6400AC6T1) –> MULTIPLIER = 11.981 psi , OFFSET = 0.504 psi 

Forcing Open Loop Fueling

In some cases, you may find it more straightforward to temporarily force the ECU into full-time open loop fueling when tuning the VE table. This can be accomplished by the following procedure:

  • Change any of the 14.7 values in the Desired Lambda (Cold) table (found under the Fuel Tables -> Closed Loop group) to 14.65:1 AFR (or 0.997 lambda for non-standard units).

  • Uncheck the Enable A/F Learning checkbox in the toggles menu (Control + A). This will prevent any long term learning.



  • Save map and reflash map to car.

  • Verify that the ECU remains in open loop full-time by viewing or logging the Open Loop Status monitor in the Accesstuner software.

It is not recommended that you run full-time open loop operation after the tune is complete. This is because certain scenarios with SD that would result in fueling errors, such as a heat soaked CAT sensor or changes in VE due to mechanical/aging issues, can be partially mitigated by short-term fueling corrections (and potentially long-term fuel trims) when closed loop operation is active.

Long-Term Fuel Trims

You may find it necessary (or more optimal) to manipulate how the long-term fuel trims are determined when running SD. The long-term fuel trims are determined based on patterns of short-term correction. They are calculated and applied across several airflow ranges. These ranges are determined by the A/F Learning Breakpoints (LTFT) table (under the Fuel Tables -> A/F Learning group). The following is an example:

As you can see, there are six values to this table (though the ECU has 7 locations internally shown below in the real-time only A/F Learning Applied Trims (LTFT) table), though not always normalized.

The airflow ranges are determined from these values as follows (given the example):

Range 0: 0-<0.70 lbm/min

Range 1: 0.70-<1.80 lbm/min

Range 2: 1.80-<3.80 lbm/min

Range 3: 3.80-<10.50 lbm/min

Range 4: 10.50-<16.00 lbm/min

Range 5: 16.00+ lbm/min

Range 6: 16.00+ lbm/min

The individually defined ranges are responsible for holding accountability for discrepancies in fueling error.  Best practices for calibration are to keep these trims extremely low, in the ranges of +/- 3% for optimal operation.

Additionally, you can also modify the allowable limits for A/F Learning via the A/F Learning Limit (Lean/Rich) tables (also under the  Fuel Tables -> A/F Learning group):

You can view/log long-term fuel trims via the Long Term Fuel Trim monitor. This shows the currently applied long-term fuel trim. You can also view all 7 ranges via the  A/F Learning Applied Trims (LTFT) table by live connecting to the ECU.

Cam Timing (VCT) Tuning Changes and Effect on VE

Most tuning changes are not going to impact VE. For example, once you have your VE table dialed in, you can make changes to timing, fuel, and boost tuning without needing to revisit the VE table due to those changes. However, there is one exception. That is changes to cam timing (VCT). Cam timing changes can definitely impact VE and will likely require you to tweak the VE table as a result. When attempting to dial-in the VE table, large changes in cam timing with small changes in load/RPM will change actual VE and you may end up with feedback loop of sorts that makes it more difficult to tune.  For this reason we have added compensation tables to allow for changes made to cam timing to be accommodated for.

How to Monitor the Tune

In addition to the monitors already included for the EcoBoost, CCF SD adds new monitors specific to the feature. These will be useful in the tuning process as well as verifying/monitoring the tune once it is complete.


(SD) Estimated Airflow -> This monitor outputs airflow mass derived from the OEM aircharge (CCF SD off) or the VE table (CCF SD on).  This value is fed into the In-Cylinder MCT Bias Compensation feature when enabled and aid in the appropriate estimation of manifold charge temperature.

(SD) Estimated Load -> This monitor outputs load derived from the OEM aircharge (CCF SD off) or the VE table (CCF SD on). This is only used for general comparison purposes.

(SD) Estimated VE (OEM) -> This monitor outputs VE derived from the OEM aircharge at all times. This is used for general comparison purposes.

(SD) Estimated VE Corrected -> This monitor outputs VE derived from the OEM aircharge (CCF SD off) or the VE table (CCF SD on), which also includes a correction factor applied based on the (SD) Total Fuel Trim.  This is used to aid in rapid calibration by suggesting an appropriate VE value to use in the VE table.

(SD) MCT Final -> This monitor represents the final estimation of manifold charge temperature. This value begins as a copy of Charge Air Temperature, but can be blended with Coolant Temperature using the In-Cylinder MCT Bias Compensation feature.

(SD) Total Fuel Trim -> This monitor simply combines Short Term Fuel Trim and Long Term Fuel Trim for you to prevent the need to log both values. This is also used to create a correction factor for the creation of the (SD) Estimated VE Corrected monitor.

(SD) VE Base -> This is the commanded volumetric efficiency (%) as determined by your Volumetric Efficiency table. This value is always calculated, even when SD is disabled.

(SD) VE Compensation Baro -> This is the current lookup value from the VE Compensation (Barometric Pressure) table.

(SD) VE Compensation Base -> This is the current lookup value from the VE Compensation (Base) table.

(SD) VE Compensation Final -> This is the final multiplier created from combining all of the compensation values listed here.

(SD) VE Compensation MCT Pivot -> This is the current lookup value from the VE Compensation (MCT Pivot) table when the Enable Switch (MCT Pivot 3D) is enabled. When not enabled, this value is automatically calculated using the ideal gas law.

(SD) VE Compensation VCT -> This is the current lookup value blended between the VE Compensation (Exhaust) and VE Compensation (VCT Intake) tables.

SD Real-Time Tuning

Real-Time Tunable SD Tables

Most of the new tables added for the SD feature are real-time tunable. See the "Realtime Tables" group in the Accesstuner software for a complete listing of all real-time tables for a given ECU.

SD Math

This section describes the math behind the CCF SD calculations which are based on the ideal gas law. It is not necessary to understand this math in order to tune SD, but some may find it interesting.

Ideal Gas Law – Introduction

The ideal gas law is an equation that governs the relationship between the pressure, volume, amount and temperature of an "ideal" gas:

P = Pressure (inHg)

V = Volume (Liters)

N = Number of Moles (i.e. amount) (Mol)

R = Gas Constant (L*inHg)/(K*Mol)

T = Temperature (Kelvin)

MMA = Molar Mass (lb/mole)

PV = NRT

N = PV/RT

We want to solve for the amount of gas:

Our "ideal" gas is quite simply the air that is being ingested by the engine. For our purposes, we want to know the mass of air entering the engine. We can determine the mass of air by using a constant that dictates the mass (in lb) per mole of air (i.e. the molar mass of air, which we'll call MMA):

Because N = PV/RT, we can express this as:

Ideal Gas Law – Real-World Inputs

Given the above equation, we need input data for pressure (P), volume (V), and temperature (T). Given our engine scenario, these inputs would be determined as follows:

P = Pressure = Manifold absolute pressure (MAP) as determined by the MAP sensor. Units dependent on gas constant (R) used (see below)

V = Volume = Displacement of the engine (in liters).


T = Temperature = Cylinder charge temperature in Kelvin as estimated by the charge air temperature (CAT) sensor. Temperature in Kelvin can be determined as follows: CAT Celsius + 273.15

Let's rename the symbols used for these inputs so they are more appropriate for our engine example:

MAP = P

DISP = V

CAT = T

COMPS = All applicable speed density compensations (Base, Barometric Pressor, MCT Pivot, VCT).

VE = Volumetric Efficiency (from our table).

The constants R and MMA are determined as follows:

R = ideal gas constant. Using MAP units of inHg -> R = 2.455257605 (L*inhg)/(K*Mol)

MMA = Molar Mass of Air Constant = 0.063867917 lb/mole

Ideal Gas Law – Volumetric Efficiency

 


The above equation is only valid for our engine example if volumetric efficiency is always 100%, which is obviously not the case. We must therefore add VE and its compensations as correction factors.


Ideal Gas Law – Airflow Mass

To determine the air entering the cylinder per unit of time, we add RPM as an input. Because the crankshaft rotates 720 degrees (i.e. two revolutions) for a full stroke, the number of times air is entering the cylinders per event is included and used for our ultimate conversion into an estimated airflow mass in lb/min:



  Ideal Gas Law – SD Reference Calculations

The non-linear charge temp correction is inherent to the equation above in determining the estimated aircharge. However, it would be useful to be able to tweak the charge temp correction because our CAT sensor input may not always be exactly representative of actual charge temp. This is highly dependent on the placement of the CAT sensor for a given car.

To allow for tweaking of the charge temp correction, the ECU first calculates a reference SD aircharge using a constant for charge air temperature (100 deg. F). Then the MCT Pivot correction is applied to the reference value. The default values of the MCT Pivot table are set-up with the ideal gas law in mind given our reference temperature.

Consider the following example:

MAP = 50.289 inHg (native units of the ECU, which is the same as 24.7psia)

RPM = 3000

VE = 0.8 (i.e.80%)

DISP = 2.261 liters (default for a 2.3L application)

SARCHG = 0.001526150 (Standardized Air Charge default for a 2.3L application)

MMA = 0.063867917 (L*inHg)/(K*Mol)

MCT = 310.928 Kelvin constant (our reference temp of 100 F)

R = 2.455257605 (L*inhg)/(K*Mol) (using the inHg native ECU units for MAP)

First the ECU will calculate the estimated aircharge:


 


Followed by the estimated airflow:

Additionally, we can estimate load at this point with the given aircharge by dividing against the SARCHG.

SD Final Aircharge

We have calculated the SD reference aircharge, airflow, and load above. However, these calculations were only valid at our given reference temp of 100 degrees F. We must apply the MCT Pivot compensation which, with the default values in the tables, follows the ideal gas law the same as if we had originally plugged the current CAT value into the estimated mass airflow equation that was first described in this section. Let's assume that the current CAT is 122 degrees F. Looking at our MCT Pivot compensation table:

We see that the table calls for a multiplier of 0.96 (-4.00% correction at 122F MCT). From our reference example, we calculated a reference airflow of 11.42 lb/min. We apply the MCT Pivot correction from our table as follows:

If we were to plug in the CAT of 122F (50C) into the original equation given our current example:

MAP = 50.289 inHg (native units of the ECU, which is the same as 24.7psia)

RPM = 3000

VE = 0.8 (i.e.80%)

DISP = 2.261 liters (default for a 2.3L application)

SARCHG = 0.001526150 (Standardized Air Charge default for a 2.3L application)

MMA = 0.063867917 (L*inHg)/(K*Mol)

MCT = 323.15 Kelvin constant (our new temp of 122 F)

R = 2.455257605 (L*inhg)/(K*Mol) (using the inHg native ECU units for MAP)

So, lets do the math:



We can now realize more complete accuracy in the calculations with these compensations applied. Note that in these examples the other compensations were assumed to be 1.0.

Estimated VE Calculation

The SD ECU has the (SD) Estimated VE (OEM) monitor which allows you to determine an estimate of VE based on the OEM speed density model. The math for estimating VE is simply solving for VE in the estimated airmass equation given above. We are using the airmass as determined by the OEM tables as an input to our estimated VE calculation. Also note that displacement is being represented by all cylinders during this calculation.

Let's take the previous example and solve for VE given our previous estimated aircharge of 0.0018305647062397 lbm/event:


As you can see, we end up with the same VE calculation as used in the original example.