NOTE: THESE PROCEDURES AND TUNING IN GENERAL CAN RESULT IN SEVERE DAMAGE TO YOUR ENGINE IF IT IS NOT PROPERLY DONE. I ASSUME NO RESPONSIBILITY OR LIABILITY FOR ANY DAMAGE THAT MAY RESULT BY PERFORMING ANY OF THE SUGGESTIONS OR PROCEDURES. I ALSO ASSUME NO RESPONSIBILITY OR LIABILITY FOR ANY FALSE OR MIS-INFORMATION IN THE FOLLOWING WORK.
THE USER HAS BEEN WARNED!
The following posts will be taking us through the process of tuning the TS111/TS116 and Scout engines found on our Indian Motorcycles. I will be presenting general knowledge as well that can be applied to Victory as well as Polaris ATV's.
Introduction:
There is a lot of mystery that surrounds today’s Electronic Fuel Systems and the interplay between it and the other electronic modules that are installed on our Indian motorcycles. This document focuses on the Electronic Fuel System from Bosch and implemented on the Indian brand motorcycles.
In researching this topic, it became painfully obvious that there is a lack of an easy to understand resource that explains the in’s and out’s of fuel injection systems designed for motorcycles as well as a tuning guide to achieve a DIY’er custom tune for your motorcycle. It is in this spirit that I wrote this document.
This blog is not intended as an exhaustive study of tuning or the tools used to perform the tune, but as a aid to those wishing to go further with their knowledge of our fuel injection system. There is an inherent risk whenever you start modifying the parameters that the ECU uses to determine the operations of the engine. The user must exercise extreme care whenever modifying the ECU tables.
Use this information at your own risk! I take no responsibility or assume any liability for the correctness of this information or your use of this information.
When Polaris introduced the TS111 engine in 2014 and then the Scout in 2015, the fuel system was controlled by the Bosch ME-17 Electronic Control Module (ECM). This is a very capable, powerful ECM used on many vehicles worldwide. It is tried and proven to be very reliable. This was a very good choice on Polaris engineering’s part. The Indian fuel injection system and sensors are an engineered system with components from Bosch.
Just like a carburetor, the fuel injection system supplies a metered fuel and air mixture to the engine and reacts to various loads and conditions to maintain good operation parameters for the engine. The main difference between the two systems is the carburetor only has a few metering circuits that can be adjusted so optimal engine performance cannot be obtained under all operating conditions. The fuel injection system has many metering circuits with each one able to be adjusted to ensure an optimal Air Fuel Ratio (AFR) can be delivered under all operating conditions.
A major limitation of the carbureted system is the way one adjusts the AFR. The fuel metering is achieved through mixture screws and jets. For instance, an S&S Super E carburetor has 3 fuel metering circuits: Idle, Intermediate, and Main. The Idle circuit is adjusted by the Idle Mixture Screw. The Intermediate circuit is controlled by the Intermediate Jet, and the Main circuit is controlled by the Main Jet. These circuits are physically adjusted and in the case of the jets, changed out.
On the other hand, the Fuel Injected System’s fuel circuits are controlled through tables located in the ECM’s memory and operates the fuel injector(s) to ensure proper fuel/air mixture for a given load and RPM. The values in the tables control how the ECM interprets the fuel requirements of the engine through sensor inputs. The ECM then controls the fuel injector’s duty cycle, known as the Injector Pulse Width, to deliver a precise amount of fuel for the requested AFR based on these tables. To change these circuits, all that is required is a computer program that will allow the user to access the values contained in the Target AFR table, and then load the new values into the ECM.
Another major difference between a carbureted engine and fuel-injected engine is the spark timing. In a carbureted engine spark points or electronic ignition, both of which are timed from Top Dead Center (TDC) referenced to one of the cylinder’s piston, controls timing. Though there are some very good electronic ignition modules available, they still fall short on the adjustability found on a modern electronic fuel-injected system.
On the fuel-injected engine, spark timing is control by the ECM and is based on several interacting timing tables. The spark is timed to the crankshaft, indexed to TDC of the front cylinder. Through a very detailed ignition table, the ECM matches the current engine load and RPM to provide the optimal spark timing to meet the engine’s spark timing requirements. This results in a better firing event, which reduces emissions, provides better fuel economy, and a smoother running engine.
The modern fuel injection systems also have Knock Sensor(s) so that any spark detonation that may occur, the ECM will sense this condition and timing will be removed from the final timing to help stop and prevent further spark detonation. Our Indian engines have one Knock Sensor mounted to the front cylinder head and the ECM uses it to determine if spark detonation is occurring in the front or rear cylinder.
There are three types of Fuel Injection Systems commonly implemented: MAF, Speed-Density, and Alpha-N. None of these engine management schemes are 100% accurate and therefore engine control engineers select and implement the one that is best suited for the application and/or manufacturing. This discussion will focus on the Speed-Density method since this is the system implemented on our Indian motorcycle.
In a Speed-Density system, the air flow through the engine must be estimated before the correct fuel delivery can be calculated. How well the airflow is modeled will determine how accurate the fuel delivery will match the user’s requested AFR. The system determines the spark timing required by the engine for proper combustion of the fuel delivery. The importance for correct timing cannot be over emphasized.
The electronic modules used on our bikes that form the basis for our fuel injection system are interconnected and function as one system. These are:
VCM: Vehicle Control Module
- Provides the “catch-all” for all the switches and control outputs needed for a fully functional motorcycle…..Turn signals, Windshield control, Horn, Flashers, Radio functions, Lights, Brake Lights, etc.
- Functions as the middleman between the ETC and the ECM for cruise control.
ECM: Engine Control Module
ETC: Electronic Throttle Control (Fly-By-Wire)
ABS Module: Anti-Lock Brakes System
Fuel Pump: Provides the necessary fuel pressure and volume requested by the fuel injection system.
CANBus: Not a module, but the communication network between the Speedometer, Tachometer, Data Display, ECM, VCM, and ABS Modules. CAN stands for “Controller Area Network” and was developed to meet ever-increasing EPA requirements.
Defining the modules and sensors:
ETC is the Electronic Throttle Control (Fly-By-Wire throttle). The ETC is located on the air box and is part of the throttle body. The ETC takes the place of a conventional, cable-operated throttle body. It is responsible for responding to throttle commands by opening the butterfly air valve in the throttle body and providing throttle blade angle data to the ECM. It provides the data necessary for the ECM to calculate the rate-of-change of the throttle command and blade angle. It also provides a sanity check against the MAP sensor data.
ECM is the Engine Control Module, which is the brain of the Fuel Injection System. The ECU is the heart of the fuel and timing control of the engine. It receives measurements performed by sensors located on the engine and calculates what the actual engine demand is. It then compares the engine demand to a calibration “table”, which is loaded into the ECU to determine the correct fuel delivery required to meet the engine demand.
- The ECU determines the fuel requirement by calculating the amount of air entering into the engine. To perform this calculation, it uses the engine’s displacement, RPM, temperature of the intake air and its pressure, head temperature, and the position and rate of change of the throttle (blade angle) and the VE table. All these parameters are measured except for the VE table, which must be modeled based on actual engine performance. The spark timing is determined by RPM, load, knock sensor output, rate of change of the throttle (blade angle), and the timing table. The timing table is developed for maximum cylinder pressure per operating condition.
Fuel Injectors are the fuel valves that the ECM controls to deliver precise amount of fuel at the proper time. On the Indian, the Fuel Injectors are located in the intake manifold. This is considered a sequential port injecting system due to location and the two injectors are fired sequentially based on the cylinders intake valve operation.
TMAP is the Temperature and Manifold Absolute Pressure sensor. The TMAP in conjunction with engine RPM are the primary sensors used to determine air flow by using the speed-density method. The ECM calculates the air flow of the current engine demand so the correct fuel can be injected to achieve the desired AFR. The accuracy of this calculation is vital to obtaining the proper AFR. To know how much fuel to deliver into the combustion chamber, the ECM implements complex equations based partly on the Ideal Gas Law. Because a Speed Density Fuel System does not measure this mass of air directly, it uses a table that is a model of the engine’s air throughput; this table is called the “Volume Efficiency” or VE table. We will model the VE table by taking measurements of the AFR at the exhaust ports, at various RPM and loads, and apply corrections to the VE table until the correct AFR is produced.
- The accuracy of the modeled VE table will determine how accurate the ECM calculates the fuel to achieve the requested AFR. The VE table(s) is what makes the Speed-Density fuel injection system viable. It is this table that manufactures’ and tuners spend time manipulating based on measured data from dynameters and wideband O2 sensors. Our Indian ECM contains 1 VE table that affects both cylinders. For final individual cylinder AFR correction, our ECM using Injector Pulse Width Compensation (IPW Comp) tables for the front and rear cylinders.
Barometer Sensor is located within the ECM and is used to determine the altitude the bike is operating at. The altitude is used to correct the calculations that determine the air mass density entering the engine.
CHT is the Cylinder Head Temperature. This lets the ECM know when the engine has reach operating temperature. It is used in the Speed-Density calculations to help determine the mass of the air ingested during the engine’s intake event. It is also used for the engine protection so when the ECM determines the engine has reached a high level, it will richen the mixture in an attempt to cool the engine. If this does not address the heating adequately, the protection system goes into a limp mode. This mode radically cuts the power of the engine.
CPS is the Crank Position Sensor and is used to let the ECM know exactly what rotation angle the crank is at any instant in time. It is indexed for TDC for the front cylinder. This is critical for spark and dwell timing.
- When the TS111 engine is first started, the CPS signal provides TDC index and rotational reference to the ECU. The ECU provides a spark signal to each spark plug until the engine starts. Once started, the ECU determines which cylinder is the front one based on the behavior of the CPS signal during compression stroke and the TDC timing index. The ECU then only provides spark to the cylinder that is undergoing its compression stroke.
Wheel Speed Sensors They are used to provide feedback to the ABS Module as well as provide the vehicle road speed to the Speedometer and ECM.
Knock Sensor is used to detect engine detonation occurring. Once detected, the ECM backs spark timing back to reduce/eliminate the detonation.
- Our engines have one knock sensor, which is mounted to the front cylinder head. This knock sensor is sensitive enough to detect spark detonation occurring in both front and rear cylinders. The ECU sets a load threshold before it is active as well as a measurement window that looks for spark detonation after the spark event and stops looking at a predetermined crankshaft rotation.
Ignition Coil provides the energy necessary to ignite the fuel/air mixture in the combustion chamber via the spark plugs.
Oxygen Sensors are used to determine the stoic state of the exhaust (14.7:1 AFR or Lambda 1). The O2 sensors used on the Indian are narrowband O2 sensors and basically operate as a switch, being either on or off. The sensor outputs three conditions to indicate a Rich condition (< .1Vdc), Stoic condition (=.5Vdc), or Lean condition (>.9Vdc).
- When the ECM is the closed loop operating condition, it uses the output of the O2 sensors to maintain a 14.7:1 AFR. To achieve this 14.7:1 AFR, the ECM will cause the O2 sensors to switch on, off, on, off…..rapidly by enriching or leaning the fuel delivery so that the O2’s switch changes state (on/off). When switching from a lean to rich or rich to lean condition the midpoint voltage of the o2 sensors represents the stoic state. So the ECM will try to maintain an average of the midpoint voltage to maintain a stoic condition. When viewed with an oscilloscope, the output of the narrow band sensor is constantly switching on/off/on/off showing that the ECM is trying to maintain this average value representing stoic condition of 14.7:1 AFR by taken the AFR rich to lean to rich rapidly. This switching between rich and lean is very important for the proper operation of the catalytic converter.