Chassis CAN Logging To ASCII Text Plus Graphing

[P85DEE]

Mike,
I love the overlays..... One graph says everything I need to know about the L upgrade. On average with an XYZ mile battery, these are typical results. Adding Bill's P90DL data to the overlay list will answer the 90 v. 85 question just as quickly.

As for roll out, I did an integration of wheel speed earlier in this thread to estimate when my MS had covered one foot of ground. The time to do so is in that post. I'll see if I can find it (along with the supporting logic for generating the number).
update
Link to roll out comment #2563
Looks like I found my car used 0.21 seconds to traverse the first one foot.

apache,
I look at things as having several ways to collect data. The wireless/hardwareless approach has its appeal. I was a little more interested in high resolution data as close to the source as possible which is why I looked into the chassis CAN logging.

We are on MS number 5 and I've been surprised to see that all of them have been either spot on or dithering on GPS speed at 60 mph. My experience with OEM speedometers in the past has had most all of them being over optimistic in their reporting (thus presumably over optimistic in the car's efficiency which is what I was investigating when I checked my spedos). When compared to the VBox, CAN wheel speed has the benefit of an order of magnitude higher report rate and will be more repeatable even if there is an absolute inaccuracy. The repeatability allows for very accurate back to back tests even if there is an accuracy issue that would prevent perfect 0-60 (and like) measurements.

Basically, the logger is but one more option for those looking to understand their cars.

On a different note, I've heard the argument on the HP thread about the larger spec motors being able to generate more low end torque even though overall power is battery limited. By the looks of all the graphs, Tesla is torque limiting both motors (those flat initial lines) prior to battery limiting kicking in (the torque knees). There may be bigger motors in MS but it would not appear as though Tesla is making using of the extra torque available at lower rpm from over spec'd motors. This can also explain why times are not improved on sticky prepped drag strips. The launch is not traction control limited but simply torque capped by the electronics.

If this is true, then we've probably seen our best 60ft times.

 

[sorka]

So P85DL gets 435 kW at 70% SOC. P90DL gets circa 460 kW at 90+%. I wouldn't be surprised if the P85DL is equivalent to the P90DL performance wise.

My P85DL gets 453KW at 89% after supercharging but without using max battery. Haven't seen higher yet. Pete90D's made 456 from his REST log but I think I saw AWDTesla claim 468KW at one point.

 

[smac]

Fantastic graphs Mike!

Very interesting how the car is effectively putting out identical torque figures up until 1 second in, and that the current ramp ups (from inference of the power figure) overlay exactly right up until the point the you hit the old 1300A current cap. I am surprised quite how close they are.

It so close it I'm thinking the car isn't traction limited (despite the rhetoric) but software coded to perform in such a predictable way. My guess is to protect the gearbox / drive shafts. I wonder what they are rated for? 450Nm on the rear, 250Nm on the front ?

My car exhibits very similar behaviour. It first caps torque, then caps current. (albeit stretched over the time axis and compressed on the vertical axis .... You guys are already at 60 mph before mine has got to the point I'm current limited )

 

[sorka]

There's no question that the software limits power at lower RPMs to limit torque so that you don't hit the traction limits. That's why going from 19" to 21" wheels with a wider contact patch and much stickier rubber makes no difference. The real stress on the motor, diff, and shafts are all peak torque.

The drop in power after sustained output is simply the battery's chemical reaction running out in the short term causing the voltage drop. Can't wait to see this compared to the 90.

Mike, I'm not sure I'm reading the graph right. Insane is showing about 390KW and Ludicrous 420KW. Was the battery cold for both of these?

 

[MikeBur]

You'll see rollout estimated as a 0.3 second difference according to at least one source.

So subtract approximately 0.3 for rollout.

How We Test Cars and Trucks

thanks, thats easy enough

- - - Updated - - -

There's not question that the software limits power at lower RPMs to limit torque so that you don't hit the traction limits. That's why going from 19" to 21" wheels with a wider contact patch and much stickier rubber makes no difference. The real stress on the motor, diff, and shafts are all peak torque.

The drop in power after sustained output is simply the battery's chemical reaction running out in the short term causing the voltage drop. Can't wait to see this compared to the 90.

Mike, I'm not sure I'm reading the graph right. Insane is showing about 390KW and Ludicrous 420KW. Was the battery cold for both of these?

Agree on software limits here. Note I'm on SottoZerros on non-staggered 21s. Purposely held off a couple of weeks before swapping back to staggered perf tires so could do fairer before/after. Not sure staggered tires helping acceleration now... Of course, more tests when they get swapped over

in terms of power, I'm reading peak power from that data stream. If you look towards the start of the power curve, you can see these higher numbers. Battery temp is listed on top right of each source graph (47.1C for insane, 46.8C for Ludicrous), both were Max Battery "Ready!" . What are you seeing / expecting?

Also, first time I've ever saw Max Battery indicator listing "cooling..." as a status.

 

[MarcG]

Mike, thanks again for putting all this effort in logging, graphing, and sharing it all with us!

Would you by chance have done any highway-speed acceleration tests and logged them before the upgrade?
I'm curious to know the difference in acceleration from, say, 50 or 60mph using your methodology - and would love to see overlaid graphs!

This would be a great follow-up to my completely unscientific measurements when the first person on here (yo mama) got his upgrade -- we compared our cars and I shot some video footage:

 

[MikeBur]

As for roll out, I did an integration of wheel speed earlier in this thread to estimate when my MS had covered one foot of ground. The time to do so is in that post. I'll see if I can find it (along with the supporting logic for generating the number).
update
Link to roll out comment #2563
Looks like I found my car used 0.21 seconds to traverse the first one foot.

Thanks. Looks like we have the MotorTrend way "subtract 0.3" or the proper way

 

[sorka]

in terms of power, I'm reading peak power from that data stream. If you look towards the start of the power curve, you can see these higher numbers. Battery temp is listed on top right of each source graph (47.1C for insane, 46.8C for Ludicrous), both were Max Battery "Ready!" . What are you seeing / expecting?

I didn't see power on the graph so I took the product of amps * volts to get the power. Am I missing something?

 

[MikeBur]

Mike, thanks again for putting all this effort in logging, graphing, and sharing it all with us!

Would you by chance have done any highway-speed acceleration tests and logged them before the upgrade?
I'm curious to know the difference in acceleration from, say, 50 or 60mph using your methodology - and would love to see overlaid graphs!

This would be a great follow-up to my completely unscientific measurements when the first person on here (yo mama) got his upgrade -- we compared our cars and I shot some video footage:

I do, though aligning the data is a little harder, as I want to reduce as many variables as possible. I thought I did .
I was dealing with house guests last night and that took more cycles than anticipated, reducing my ability to post #2 and #3. If you look further up thread you'll see some pre data, as well as link to google drive with source excel files for insane. I'll try to get rest done today - promise I'm not trying to be a tease ;-)

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I didn't see power on the graph so I took the product of amps * volts to get the power. Am I missing something?

Separate graphs are Amps and V, yes. Combined graph I already converted to kW - thereby reducing number of data series. I'll post source data later - off PC and traveling at the moment

it it sounds like you're expecting more power. What are you seeing?

 

[sorka]

With this detailed logging and millisecond by millisecond voltage readings, it will be interesting to see over time how much the voltage drops under a 1500 load as the battery ages. After 35 MPH, the fuse is maxed out and the power you get is now at the mercy of whatever voltage you have. In a car like the S85, the fuse limit is never even close to reached until you drop below 30% which leaves tons of headroom for them to raise the current as the voltage drops. On an S85, as the SOC drops, it can still produce the same peak power because the current limit is raised until it drops to about 30% and then stops rising so the power starts falling after that. On the PD cars, this occurs at 90% or higher so as the battery ages, the peak power it produces will fall off. Hopefully the voltage drop will be minimal and not something like 65 volts (302 down to 235) at 100K miles otherwise we'll be looking at a huge power drop even if the range is not significantly decreased.

 

[MikeBur]

My P85DL gets 453KW at 89% after supercharging but without using max battery. Haven't seen higher yet. Pete90D's made 456 from his REST log but I think I saw AWDTesla claim 468KW at one point.

Didnt see this, presuming this is what you're referring to for your power? Did you measure this using CAN data, REST data, or ? perhaps battery temperature is allowed higher than the temp I've seen whilst driving?

 

[sorka]

I do, though aligning the data is a little harder, as I want to reduce as many variables as possible. I thought I did .
I was dealing with house guests last night and that took more cycles than anticipated, reducing my ability to post #2 and #3. If you look further up thread you'll see some pre data, as well as link to google drive with source excel files for insane. I'll try to get rest done today - promise I'm not trying to be a tease ;-)

- - - Updated - - -



Separate graphs are Amps and V, yes. Combined graph I already converted to kW - thereby reducing number of data series. I'll post source data later - off PC and traveling at the moment

it it sounds like you're expecting more power. What are you seeing?

For your insane graph, I saw 300v * 1300 amps = 390KW but we should see on a warm battery(not max battery) 414KW at 90%. I guess I should have asked what your SOC was
For Ludicrous I saw 290ish * 1500 = 435KW. I guess i was eyeballing it at 280 volts earlier so 435KW is closer but on a warm battery I'd expect to see in the 450s.

- - - Updated - - -

Didnt see this, presuming this is what you're referring to for your power? Did you measure this using CAN data, REST data, or ? perhaps battery temperature is allowed higher than the temp I've seen whilst driving?

This was KW as reported by REST streaming.

 

[MarcG]

I do, though aligning the data is a little harder, as I want to reduce as many variables as possible. I thought I did .
I was dealing with house guests last night and that took more cycles than anticipated, reducing my ability to post #2 and #3. If you look further up thread you'll see some pre data, as well as link to google drive with source excel files for insane. I'll try to get rest done today - promise I'm not trying to be a tease ;-)

Awesome, thanks Mike! Looking forward to the new graphs.

 

[sorka]

Alight so I admit I'm not caught up on this thread. I'd like to get in on the action. I don't get to spend as much time tinkering as I used to as my job is very time consuming. What's my best route for logging CAN BUS data? Buying SavvyCAN? Lola, is what you built readily buildable?

Sorry if this was already covered and I didn't read it.:redface:

 

[smac]

Alight so I admit I'm not caught up on this thread. I'd like to get in on the action. I don't get to spend as much time tinkering as I used to as my job is very time consuming. What's my best route for logging CAN BUS data? Buying SavvyCAN? Lola, is what you built readily buildable?

Sorry if this was already covered and I didn't read it.:redface:

I went the SavvyCAN route, mainly due to time constraints, and it's pretty turnkey and tested. It works fine but needs some post processing to get to something graph friendly. (I'm doing some work on that, but I've other projects on.)

Note it won't work on VERY recent cars due to the change in diagnostics connector however (so anything after the X launch would need checking).

 

[llavalle]

I haven't seen any 85D data here so here's my contribution.

Note that speed (right axis) is in KPH, not MPH. 77kph to 159kph, 100% TPS, on a private road, which is also kind of narrow : this was a bit scary.

SOC was 88%, outside temp was pretty cold (-10C)
Max amp draw is 1164A
Max Power is 356kW

edit : woops, forgot to add : green is voltage, red is power and blue is speed.

kudos to wk057 for helping me with the stupid 15bit signed integer this morning!

Volts & kW

Same graph, with Current instead

 

[sorka]

I went the SavvyCAN route, mainly due to time constraints, and it's pretty turnkey and tested. It works fine but needs some post processing to get to something graph friendly. (I'm doing some work on that, but I've other projects on.)

Note it won't work on VERY recent cars due to the change in diagnostics connector however (so anything after the X launch would need checking).

SavvyCAN it is. I'll place my order now.

 

[lolachampcar]

Sorka,

Oh, I've been waiting to bait you into the fray Shoot me a PM with your address and I'll get a logger out to you unless you have your heart set on a SavvyCAN.

Alight so I admit I'm not caught up on this thread. I'd like to get in on the action. I don't get to spend as much time tinkering as I used to as my job is very time consuming. What's my best route for logging CAN BUS data? Buying SavvyCAN? Lola, is what you built readily buildable?

Sorry if this was already covered and I didn't read it.:redface:

smac,
Thanks for the heads up on the diagnostic connector. I saw you had posted that in another thread.

I've checked with our P90D participant to see if his is white (old) or blue (new). Regretfully, this probably excludes any Model X participation until we get the new connectors. Has there been any progress identifying/sourcing the new shell?

 

[sorka]

Sorka,

Oh, I've been waiting to bait you into the fray Shoot me a PM with your address and I'll get a logger out to you unless you have your heart set on a SavvyCAN.



smac,
Thanks for the heads up on the diagnostic connector. I saw you had posted that in another thread.

I've checked with our P90D participant to see if his is white (old) or blue (new). Regretfully, this probably excludes any Model X participation until we get the new connectors. Has there been any progress identifying/sourcing the new shell?

OK that is tempting. Hmm. Have you thought about producing this yourself and selling it to compete with what appears to be the only product currently available for sale?

 

[lolachampcar]

NOPE
I learned my lesson with the Fob. Been there, done that, not doing it again.

That said, I'm happy to loan you one. Use it for your testing or until you get a long term solution then send it back (or on to the next owner looking borrow one). I've got four out there now and bought ten cables for the project.