It's an electronic throttle, so there's no way to check the cable position. But if you were only getting 75% throttle, you'd probably feel that, no? Any chance you've driven other MINIs to compare? My point is, trust your butt. Don't believe everything the computer tells you.
I'd be willing to guess that the ECU dumbs down some of the information it gives to the OBD to make it compatible with the standard system, or maybe there's something lost in translation between the OBD and the Garmin.
If you want to verify, pop the intake tube off the throttle body and rev it in neutral. See what happens. (Although now that I think about it the engine might get confused - somebody else chime in here.)
but a couple of points... On a drive by wire system, there are a couple things to look at.
Driver demand is the gas pedal position. And while there is no cable, there are two signals that are proportional to pedal position. This is done so that they can be checked against each other, and they better match or you'll get one of those "signal plausibility errors", thow a code and go into limp mode. Same thing for throttle body position (for the cars with throttle bodies). For the variable valve lift stuff like in the Prince Cooper engine, it's something else as well.
I'm just guessing here, but if this really is the case, I'm guessing that the full allowable voltage range isn't used by the system, even when at WOT. What I guess is being reported is % of max voltage range of the sensor input.
Another thing to keep in mind is that these scaling numbers are nice, but don't really matter. For example, I was logging what the ECU thought my injector duty cycle was in milliseconds, and I found that it was open for about 115% of a cam revolution! How's that for going to 11! The scaling factors are nice to have correct, but I don't think that's what is really used inside the ECU. Probably something more mundane like some number of oscillator counts for time. Or bits thrown out of a couple of bytes or whatever.
assume that WOT is WOT. Log throttle body position, and see what % you get at maximum. Define this as all the way open. Scale the data to that when you're doing analysis.
The hard stuff is to actuall monitor the position voltages directly with Analog-digital converters. Then compare this to the % throttle reported.
If you have an extra throttle body lying around, take it apart and look at the voltages based on butterfly position.
I've always wondered if, on the 1st gen cars at least, if the TPS reading was degrees, not %... the readings I get seem perfectly rational IF that is the case.
that none of this is really first principles design stuff. Yes, there are preferred units for reporting data out of the OBD port, but the manufacturers all know how they're reporting and how to interpret, and really don't care what any one else wants.
