Saturday, November 28, 2015

Map your car fuel consumption

Torque Log Analyzer can be used on non-Hybrid cars also.
Here's a sample, using the RPM & Fuel Distribution chart, to map fuel consumption.
You'll need to collect RPM, FuelFlow (cc/min), and OBD Speed PIDs, which are standard PIDs, available for every car model.

As fuel consumption, at a given speed, is affected by many factor, (temperature, acceleration, slope), one single trip won't give consistent results, so collect multiple trips.
Best trips are:
1) trips on the same road, in both directions (to even out elevation differences), with similar weather conditions.
2) trips with long stretches of constant speed
3) different speeds on the same trip
4) same PIDs on all the trips, in the same order.
5) record mileage reported by the on-board computer for each trip, in L/100km.

Open the first csv log file
Select File / Import and choose the second log file
Select "Append rows to current sheet" as the import action
Repeat for all the log files.

Start Torque Log Analyzer
Select Additional Analytics / RPM & Fuel distribution
Select Option / Car: non-Hybrid
Select Option / Flow Correction Factor and set it to the value explained at this link

Click Analyze

Here is the result for a Fiat Panda 4x4 1.3Mj 75cv:

Friday, November 27, 2015

Flow Correction Factor

You may have noticed that the mileage reported by Torque is different from the consumption measured at the fuel station with the full-to-full method.
The Flow correction factor is applied to the Fuel Flow reported by Torque, to get results consistent with the one measured at the fuel station.

You can compute the flow correction factor following these steps:
1) Fill up fuel tank
2) Reset trip mileage and odometer.
3) Drive until a new fill up is required
4) At the new fill up write down trip distance and mileage (let's call them tdist and tmil) and the litres needed to fill up the tank. (l)

Note: mileage here is intended measured in litres/100Km

Calculate the effective mileage:
emil = (l / tdist) * 100

and then the offset from reported:

off = emil / tmil

For example, for a Fiat Panda 1.3Mj 75cv 4x4 Diesel car, I run 511 km with 27.58 litres, while the trip mileage indicator was 5.0l/100km

The effective mileage is (27.58 / 511) * 100 = 5.39 l/100km
While the offset is 5.39 / 5.0 = 1.078

So, every time the car is reporting a given mileage, the effective consumption is really 1.078 times the indicated value.

To calculate the Flow Correction Factor, you'll need a trip log on which you also recorded the mileage as indicated by the on-board computer of the car.
Now, load up a trip in Torque Log Analyzer and run an analysis with the Force Mileage option set to the mileage reported by the car from that trip (4.8 L/100km in this example)

After the Analyze run is completed, switch to the Calc sheet and get the CDB Correction value:

Repeating the procedure with several different trips and averaging the results, will give more precision.
For the example car (Panda) this resulted in 0.82120