Innovate Motorsports OT-2 - Manual (Page 25)

A. The problem is that there is no standardized way to obtain MPG from the OBD-II port. Also, the
available information varies between makes and models. Other concerns are the precision and
the update rate of the data.
Take the example of many older Honda vehicles. Information available includes MAP, IAT, RPM,
and VSS. So, in theory, fuel consumption is somewhat knowable. But, if you look up the
equations you will find that there are other factors, like the displacement of the engine and its
“VE”, which varies with load and RPM. Even if we put in good estimates for these values, there
are other factors. MAP is reported with fairly low precision. Also, the older ECU is very slow. It
may only be possible to take the four readings once a second or so. This means that we are
taking snapshots of MPG every second or so, without knowing what happens in between.
What the Economy Meter does is try to give a good indication of relative fuel consumption with
the information a given vehicle provides. The purpose is not to replace your fuel gauge (the fill-up
log in the application is the best long term measure of GPM), but to give you a tool to improve the
economy of your driving. Variation in driving behavior can make a 35-40% difference in fuel
consumption!
5. Why does the Fill-up log report GPM instead of MPG?
A. MPG is not a linear scale. A good way to illustrate this is with a question. If you wanted to help
the environment, which would be better, trading in a 30 MPG vehicle for one that is 45 MPG, or
exchanging a 12 MPG vehicle for one that gets 19 MPG?
If we turn the terms over, it is still not a linear scale, but it is easier to relate to day-to-day life. A
good example of this is to turn on the ‘Mileage by 100’ option (press ‘i' on the fill-up summary
screen to find it). This simply shifts the decimal place on the results, but, suddenly, you can see ‘I
need x gallons to go 100 miles’ or ‘it will cost me x dollars to drive 100 miles’. Rather your goals
are saving money or reducing your carbon footprint, we believe that GPM, which is similar to the
European standard of liters per 100 kilometers, is generally more useful.
8 Software Developers Kit (SDK)
Information about the MTS data stream has always been available on request. In addition,
Innovate Motorsports has long provided some basic SDK tools to make accessing measurement
data from our hardware easier for third party applications.
What is different about the OT-2 SDK is that, in addition to documenting how to access the MTS
data stream, it also provides information on how to dynamically configure the OT-2 (basically
access and alter the features in LM Programmer). This allows software to dynamically pick which
channels are polled at what time, and perform (previously) LM Programmer only features, like
retrieving and clearing diagnostic trouble codes (DTCs).
In addition, the SDK offers an ‘expert mode’, where software can use the OT-2 to directly
communicate with the ECU(s) in the vehicle. This potentially gives access to make/model specific
information and features instead of just the ‘generic’ OBD-II information exposed via MTS.
Like our existing “MTS SDK”, the OT-2 SDK is freely available for download. In addition to
documentation, it includes sample applications for Windows, Mac (OS X), Linux, and iPhone.