Calculators. Drew Technologies DashDAQ XL, DashDAQ Series II

Tap [Save]. Make sure the speed gauge is set (section 0) and tap [save] once more.

At the performance menu, tap on [User Tests]. This screen appears:

Tap on [User Test 1].

Tap [Start] to start User 1’s test.

Follow the on-screen instructions. The results will be posted on-screen at the end of the run. Example of a results screen:

CALCULATORS

DashDAQ can calculate values for horsepower, fuel economy, or even subtract two signals. The calculators can be selected in the USB

Update Tool and can be installed using the Driver Manager.

INSTALLING A CALCULATOR DRIVER

Here’s an example of how to install the Fuel Economy calculator:

1. From the Main Menu tap [Setup] >> [Devices] >> [Manager]

2. In the Device Manager select the next blank, available row then tap [Add Device]. Figure 24 shows the Device Manager with row “E” selected because it is the next available row.

3. Now tap on the driver you would like to install and tap “Install.”

4. You will now be prompted to select which port the driver will use. See figure 24.

Figure 24: Selecting the next unused row

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Figure 25: Configure the driver and assign it to a port

SETTING THE PARAMETERS FOR ANY CALCULATOR DRIVER

Some calculators have some tunable parameters like: vehicle weight, fuel density, or engine displacement. Others may require you to choose a signal for Vehicle Speed or Engine RPM. All of these decisions are ultimately your decision. You might specify Engine RPM from

GenericOBD2 connector but use a Vehicle Speed from a GPS for higher accuracy. Choose the setup that works best for your vehicle.

Figure 26: Parameters available for the Economy Calculator

To adjust parameters for a driver:

• From the main menu tap on [Setup] >> [Devices] >> [Parameters]

• Use [<] or [>] buttons to the Navigate to the “d-Economy Calculator” option

• Select a row by tapping

• Tap [Change]. Enter the number or text. Tap [Save] to confirm

DYNO CALCULATOR

DashDAQ can estimate instantaneous horsepower based on energy required to overcome inertia and accelerate (or decelerate!) the vehicle’s mass. It looks at the change in kinetic energy ignoring air-resistance, rolling-resistance, and all forms of friction. During acceleration this represents the engine’s power to move the vehicle forward. At cruising speed the numbers will show near-zero because (ignoring air resistance) no power is needed to maintain speed. During deceleration the numbers will be negative representing the force exerted by the brakes, resisting the forward-motion of the vehicle.

Make sure that the “Dyno Calculator” was selected when reflashing the firmware (section 0) and install the driver on an available port

(section 0).

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Figure 27: Parameters for dyno calculator

Only three parameters are required for the calculation:

• Input Speed Signal: Choose Vehicle Speed from GenericOBD2

• Input RPM Signal: Choose Engine RPM from GenericOBD2

• Input Vehicle Weight (lbs): Enter the vehicle weight in pounds

The other parameters can usually be ignored, but you can try tuning the values for increased accuracy:

• Input Acceleration Filter Time:

• Input Accel Calc Type:

• Input Speed Filter Constant:

The driver generates two measurements that may be assigned to any gauge (section 0) and can be data logged just like any other signal

(section 0):

• Calculated Horsepower:

• Calculated Torque:

If you’ve assigned either statistic to a gauge but you’re not seeing values, double-check that you’ve assigned signals for both the Input

Speed Signal and Input RPM Signal parameters. Also try assigning the input signals to a gauge to verify that DashDAQ is actually able to get a reading.

FUEL ECONOMY CALCULATOR

DashDAQ can calculate instantaneous fuel economy and display the results by distance (miles per gallon) or by time (gallons per hour).

Make sure that the “Statistics Calculator” was selected when reflashing the firmware (section 0) and install the driver on an available port (section 0).

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Figure 28: Parameters for Economy Calculator

This calculator uses airflow to find the amount of fuel entering the motor. Vehicles with a Mass Airflow Sensor can measure airflow directly. In this case you’d only need to configure four parameters:

• Air Fuel Ratio: 14.7 for gasoline

• Fuel Density: 720 for gasoline

• Speed Signal: Vehicle Speed from GenericOBD2

• Mass Air Flow Signal: Air Flow Rate from MAF from GenericOBD2

If the vehicle does not have a Mass Airflow sensor, this driver provides a way to estimate MAF based on Manifold Absolute Pressure and a few other variables. In this case you’d additionally need to set:

• Mass Air Flow Signal: Calculated Mass Airflow from Economy Calculator

• Intake Air Temperature: Intake Air Temperature from GenericOBD2

• Manifold Pressure: Manifold Absolute Pressure from GenericOBD2

• Engine Displacement: Based on the motor, in liters. For example, 2.7 for some Dodge Chargers

• Volumetric Efficiency: Based on the motor. For example, enter 0.67 for 67% efficiency.

Once configured this driver provides two signals that you may assign to any gauge (section 0):

• Fuel Economy vs Distance: Shows MPG or km/L depending on the Imperial/Metric setting

• Fuel Economy vs Time: Shows gallons/hour or L/hour depending on the Imperial/Metric setting

If you’ve assigned a statistic to a gauge but you’re not seeing values, double-check that you’ve assigned signals for each parameter. Also try assigning each input signal to a gauge to verify that the DashDAQ is actually able to get a reading.

Rescale Signal Calculator

DashDAQ can perform a multiplier/offset calculation. This can be used to rescale a signal, for example adjusting the vehicle speed to compensate for tire size. Alternately this could be used to compare two signals, for example subtracting manifold absolute pressure from atmospheric pressure to find turbocharger boost pressure.

The calculator implements a simple, linear scaling:

Output Signal = (Multiplier Signal) * Input Signal + Offset Signal

This provides the ultimate in flexibility because you can multiply two signals together, add/subtract two signals, multiply a signal by a constant value, etc.

Make sure that the “Rescale Signal Calculator” was selected when reflashing the firmware (section 0) and install the driver on an available port (section 0). This calculator can be installed several times; once for each signal that you wish to rescale. There are a few critical parameters:

• Input Signal: Signal to modify. Pick a signal for vehicle speed, voltage, or anything you want to rescale.

• Multiplier Signal: Either a vehicle signal or “Constant Multiplier” described below

• Multiplier Sign: Specify 1 to leave the multiplier unchanged, or -1 to make the multiplier negative

• Offset Signal: Either a vehicle signal or “Constant Offset” described below

• Offset Sign: Specify 1 to leave the offset unchanged (add), or -1 to make the offset negative (subtract)

The calculation is based on signals, so if you want to multiply/offset by a constant number you’ll need to create a signal with that constant number. Fortunately this driver has two parameters that can generate signals with a constant value:

• Constant Multiplier: Used to generate a signal called “Constant Multiplier”.

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• Constant Offset: Used to generate a signal called “Constant Offset”.

For example you could specify “3” as your Constant Multiplier value, pick Constant Multiplier as your Multiplier Signal, then your calculation will multiply the incoming signal by 3. Finally, to keep things straight there are a few parameters to help you identify the output signal:

• Name: Abbreviation to identify this signal. Used as a gauge label and displayed on the assign signals screen.

• Units: Physical units for the calculation. Any automatic Imperial/Metric occurs afterward. For example, if a calculation results in

°C the number could be automatically converted to °F before display.

• Precision: Number of decimal digits to display.

The calculated value will be available when you assign signals to a gauge (section 0).

EXAMPLE: DISPLAYING RPM AS 0-8 INSTEAD OF 0-8000

Some people prefer a tachometer that displays RPM x1000 because the gauge face has fewer unnecessary zeroes and looks less cluttered. This calculation looks like:

Adjusted Tachometer = Engine RPM / 1000

To perform this calculation on the DashDAQ, try setting:

• Input Signal: Engine RPM from GenericOBD2

• Multiplier Signal: Constant Multiplier from Rescale Signal

• Multiplier Sign: 1 (Positive)

• Constant Multiplier: 0.001. Represents the divide-by-1000

• Offset Signal: Constant Multiplier from Rescale Signal

• Constant Offset: 0 to add/subtract nothing

The calculated value will be available when you assign signals to a gauge (section 0).

EXAMPLE: CALCULATING BOOST

Many vehicles do not provide an enhanced signal for Turbo Boost but it’s pretty easy to calculate. We’ll assume that boost is the additional manifold pressure above normal barometric pressure (~14.7psi). For example, MAP=19.7psi minus BARO=14.7psi implies that the turbocharger is providing BOOST=5psi. This calculation looks like:

BOOST = MAP - BARO

To perform this calculation on the DashDAQ, try setting:

• Input Signal: Manifold Absolute Pressure from GenericOBD2

• Multiplier Signal: Constant Multiplier from Rescale Signal Calculator

• Multiplier Sign: 1 (Positive)

• Constant Multiplier: 1.0

• Offset Signal: Barometric Pressure from GenericOBD2

• Offset Sign: -1 (Subtract)

The calculated value will be available when you assign signals to a gauge (section 0).

EXAMPLE: ADJUSTING VEHICLE SPEED FOR TIRE SIZE

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