Initial Calibration Setup
The first step in the setup is to pick a base map from Holley’s collection; there are several stored within the EFI software that comes with the system. It’s pretty simple, you just pick the combination that is closest to what you run. As Holley notes, these are the most basic fields, but they tell us one place you can’t guess with regard to setup is the fuel injector selection along with the fuel pressure values. When a signal is delivered from the ECU, the fuel injector opens and sprays pressurized fuel into the intake runner. The duration that the injector is open (pulse width) is proportional to the amount of fuel delivered. If you’re not accurate with the injector sizing and fuel pressure values, then your basic tune will be out of whack. Simple as that. Additionally, the basic setup will also mandate some simple questions about the sensors you’re using allowing with several ignition related questions.
As noted in the first part of this series, the Holley system has fabulous “learning” capability. With Holley’s Dominator, the engine will start and run off of the base calibrations we discussed above. Holley tells us that “learning” is when the ECU figures out the difference between the base calibration and your combination. With the Holley software, you can also disable (or even slow down the rate of learning) if you wish. But for most of us out there, setting the “learning gain” to 100% is the easiest and quickest way to obtain a great running EFI combination.
Closed Versus Open Loop
Electronic fuel injection setups can be “open loop” or “closed loop”. These two terms refer to the EFI system’s capability to measure feedback and modify what it is doing based upon that feedback.
Open Loop means there is no feedback of information back to the ECU. It simply means there is no sensing or measuring of the exhaust gas to see how the engine is running. The fuel injected is determined by the RPM and throttle position, derived from fuel injector pulse width numbers stored in the fuel maps, and is trimmed for environmental conditions due to air temperature, air pressure and engine temperature.
On the other hand, Closed Loop means there is feedback to the ECU. It means there is sensing or measuring of the exhaust gas to determine how the engine is running. This sensing is handled by a probe that generates a specific amount of voltage based upon the gas that surrounds it. These probes are referred to as Oxygen sensors, O2 sensors, Exhaust Gas sensors along with other names.
Holley notes that EFI setups with Closed Loop capabilities are much preferred. The reason is they can compensate for weather and elevation changes. A good example is the air you might have at the drag strip first thing in the morning versus the air you’ll encounter in heat of the day. With an open loop system, you’ll have to compensate manually for the change in conditions. With a closed loop system, the ECU does the work for you.
The Startup Enrichment section found in the Holley ECU software contains the cranking fuel, after-start hold off, after-start enrichment, and after start decay rate adjustments. With these adjustments (actually in chart form in the software), you can setup the way the engine starts and runs at any given temperature. Think of it as an automatic choke for your racecar. It also means you don’t have to change the starting procedure from the first thing when you roll it off the trailer to when you’re hot lapping the thing in the afternoon. Basically, the Holley Dominator allows your racecar to start just as easily as your daily driver.
Holley Engineers spent a huge amount of time setting up the idle parameters and adjustment capabilities with the Dominator software. If you click the icon found at the top of the software screen that looks like a tachometer, you’ll find a series of adjustments required to maintain a proper idle. Holley notes that changes to this section will determine the method in which the computer changes the idle fuel map, spark timing, and IAC operation composition.
There is a set of parameters with the software called “Acceleration Enrichment (AE) vs. Throttle Position Sensor (TPS) Rate of Change.” You can think of these as the accelerator pump shot and shooter size part of the tune up. Enrichment is measured in pounds per hour added to the base map based upon the TPS (throttle position sensor) rate of change. Other adjustments include AE vs. MAP kPa % of change, AE TPS vs. Coolant Temp, MAP AE Time vs. Coolant Temp, AE Correction vs. TPS, and MAP AE vs. Coolant Temp. Essentially, this series of adjustments accommodate everything from the engine load, to any temperature, and to any air you’ll encounter, and the ECU will compensate for it.
Holley points out that the base fuel table determines how much fuel in pounds per hour (lbs/hr) the injector will discharge at a given Manifold Absolute Pressure (MAP) kPa (kPa is “kilopascal” or a metric pressure amount determined by an EFI sensor) or Throttle Position Sensor (TPS) reading at a particular RPM. This information is determined by way of the learning cycle in the ECU or by way of the base calibration steps depending on where you’re at in the tuning process. The numbers in the base map work in conjunction with the target air fuel ratio on a separate graph. This is extremely useful when it comes to tuning out and bugs you may encounter during a dyno pull or while driving. As Holley notes, it is unlikely the engine will experience each field in the base map during the learn process — there’s a chance the ECU will encounter some peaks and valleys. Holley EFI actually includes a smoothing feature that takes a highlighted area (for example peaks and valleys) and levels out the highs and lows. This view will also warn you if you have requested more fuel than your fuel system can supply so you don’t run into tuning trouble. In the end though, the learning feature automatically tunes the base fuel table, or you can tune it manually.
Programmable Input/Outputs & Pin Mapping
Holley’s Dominator ECU is equipped with 47 programmable input and 36 output “pins”. These inputs can be configured for 12V, Ground, Digital Speed, IPU Speed, 5V, 20V, and Thermistor types. The outputs can be configured as +12V, Ground, or +12V and Ground Pulse Width Modulated (PWM) types. Holley notes that these pins can be configured to sense transbrake engagement, to turn on a low oil pressure light or to even create of a comprehensive data acquisition system. By the way, several of the pins are already configured as fuel pump triggers, electric fan controls, A/C override and IAC (Idle Air Control) kick.
When it comes to setting up the Ignition on the Holley Dominator, the first step is to fill out the “Ignition Parameters” section. Here the ignition type is designated. The menu also allows you to input the firing order, input the knock sensor parameters (if they’re used); the parameters for cranking timing, along with rev limiters. When it comes to rev limiters, the Dominator EFI system is equipped with three of the, each with four cutout options. There’s a primary rev limiter along with two limiters that can be setup based upon a programmable input signal (for example, a burnout limiter, or a launch limiter). The four limiting types include Fuel Only, which performs a “hard cut” of fuel flow when the RPM limit is reached. Holley states that the “Hard Cut” happens when fuel flow is stopped to all cylinders until the main low RPM setting is met. There’s a Spark Only limiter option where a “Hard Cut” of ignition to all cylinders only when the high RPM is hit and continues until the low RPM setting is met. The Fuel and Spark format is where a “hard cut” of ignition and fuel flow occurs when the high RPM limit is hit. The Soft type uses “soft cut” of ignition from individual cylinders as needed to bring the engine back to the low RPM limit. Holley notes that should the high RPM limit be reached despite the soft cut, a hard cut will be implemented (think of it as a fail safe for the rev limit). Similar to the base fuel map, the spark map can be viewed and adjusted in a table or a graph form. And like the fuel map you can make adjustments as you wish to the main table.
In the next issue, we’ll take a closer look at some of the ways the Dominator can be setup, along with a look at some of the things it can control. You might be surprised at the capabilities.