Best OBD?

Right. Whatever an app shows you is bound to be a bit fuzzy, if only because it is using OBD-II queries to get the numbers and it's not getting them all from a single instant.

But for judging whether an app seems to be doing the right math, it's important to see how close its output comes to reflecting the right ratios, and that calls for an independent source of what the right ratios are.

For example, you can see the gen 4 Prime MG2 reduction ratio at 32:08 in Prof. Kelly's P610 Deep Dive:

Easiest is just to look them up in the New Car Features manuals, but my TIS subscription isn't paid up all the time.

 

I have all the mainline Prius gear ratios in a spreadsheet, but my values don't directly match what Prof Kelly is saying there.

For the MG2 reduction, my notes say:

G3: 58/22
G4 (HEV and PHEV) and G5 1.8: 65/17
G5 2.0 (HEV and PHEV): 53/16

And I've gone through the complete drivetrain maths based on those ratios, and it all makes sense it terms of max speed and rpms, so I don't think they can be squiffy.

He's saying 53/17 there, but the 53-tooth is the counter-driven gear leading to the wheels. From the point of view of the nomograph for the PSD, and for comparison with the G3, I think it makes more sense to view the reduction as 65/17 on the way to the PSD (so just ignore the counter-gear in the middle), then there's a 53/65 from the PSD to the countergear on the way to the wheels.

The fact that MG2 is transmitting power via the counter-gear isn't an important functional change compared to earlier generations - you need to keep looking at the ratio between it and the PSD ring. (Which was 1:1 in G2 and earlier).

(G5 has 49/53 as the ring to counter-gear ratio, so presumably there's a 49/16 between MG2 and the counter-gear).

 

The speed of receiving new data in the application depends on the speed of the OBD adapter and the speed of data exchange with the phone. In the file of any Hybrid Reporter report, you can view extended data in the form of a data array. I have included some of the most significant ones in the text file. The update rate is about 65-70 frames per minute. You can count once per second.

Date
Time
rps
speed_obd
gps_speed
hv_v
hv_a
soc
ice_temp
ice_rpm
ice_pwr
brk_reg_trq
brk_mcyl_trq
trip_nbs
trip_ev_nbs
trip_mov_nbs
trip_dist
trip_ev_dist
hsi
mg2_rpm
ign
ltft
stft
tripfuel
fuelflowh
dcl
ccl
bsfc
ice_load
inverter_temp
battery_temp
mg_temp
inhaling_temp
ambient_temp
room_temp
mg2_torque
mg1_rpm
mg1_torque
mgr_rpm
mgr_torque
glideindex
accelerator
positivekwh
negativekwh

The data can be converted into tables in Word or Excel.

 

I mostly just like to know what the MG2 reduction ratio is because there is no direct OBD reading of the PSD ring RPM, but there is a reading of the MG2 RPM.

You can also get the ring RPM from the final drive ratio, indicated vehicle speed, and published tire revs per mile, but that's a longer calculation with wider uncertainties (especially w.r.t. the tires).

Anyway, having two ways to calculate the ring RPM is always handy for making sure I didn't fat-finger the math either way.

 

Sure - but just be careful about thinking Prof Kelly's 53/17 or 3.118 is the right ratio. It probably isn't for the maths you're going to do.

 

I don't have a car of that gen, so luckily I haven't yet used that 53:17 in any math I've done for anything. Just jotted it down one day as I have a file where I try to keep tabs on such things and I was watching the P610 video and thought that was the ratio (and didn't have my TIS subscription paid up to go look in the manual). I'll put a note in that file to recheck it, thanks.

 

Me, I bought a X431 Elite Launch for Toyota and I am very satisfied.

It allows you to do everything, is bidirectional and to the free update for life, see the descriptions:

It is available elsewhere you only have to do a little research.