Do you know how much lighter the regular rotors are (inside the 18" Aeros used on all other variants of the 3)? I've been wondering how much faster the P3D- would be than the P3D+ as a result of lighter rotors and wheels.
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5% increase in power
- Thread starter Carotene
- Start date
Theoretically it should be faster in a straight line due to less rotational inertia overall.
In going to slap on my lightweight 18" road trip wheels and do a run. I'm also trying to source some carbon ceramic rotors to further decrease rotational inertia, unsprung weight, and overall mass.
diamond.g
Active Member
Knightshade
Well-Known Member
It does not by default, though you can tell it to (and it does list it for 1/4 mile runs)
SleeperService
Member
Installed 2019.8.4 this morning. Might be a day or two before I can take the data, but I'll update as soon as I can!
So I have updated my LR RWD this morning to 2019.8.4. These are my somehow-scientific measurements on 0 to 60 times:
0-60 mph Before Update: 5.3s (data points: 5.3, 5.3, 5.2, 5.3, 5.3)
0-60 mph after Update: 5.0s (data points: 5.0, 5.1, 5.0, 5.0, 5.0)
Effectively a ~5% decrease in 0 to 60 times.
Methodology: 5 videos of screen while flooring it, then editing videos from frame where power bar starts to turn black until speed turns from 59 to 60, then measuring length of each video. Probably not as accurate as reading from the computer directly, but the consistent methodology shows that indeed we see a 5% improvement.
0-60 mph Before Update: 5.3s (data points: 5.3, 5.3, 5.2, 5.3, 5.3)
0-60 mph after Update: 5.0s (data points: 5.0, 5.1, 5.0, 5.0, 5.0)
Effectively a ~5% decrease in 0 to 60 times.
Methodology: 5 videos of screen while flooring it, then editing videos from frame where power bar starts to turn black until speed turns from 59 to 60, then measuring length of each video. Probably not as accurate as reading from the computer directly, but the consistent methodology shows that indeed we see a 5% improvement.
StealthP3D
Well-Known Member
Some things that can affect acceleration and 0-60 mph times:
The circumference of the drive wheels. I measured my 235/45/18 Pirelli Sottoszero II's as having 2% less circumference than my 235/45/18 Michelin MXM4 Primacy's. The smaller diameter provides more torque to the road and gets the motor(s) into peak powerband 2% sooner. Since the power curve rises sharply from 0 rpm, these two factors will make a big difference in 0-60 mph times. An additional factor is the tread is the heaviest part of a tire and it is also the furthest from the axis of rotation. So a smaller diameter tire will have less rotational inertia to accelerate. Also, as the same tires wear down they will be faster for the same three reasons above.
Extra weight. Take all items out of the car before making a measurement. You can leave your clothes on in case you get pulled over.
I need to remove the bottom aero fairings and clean out the dirt from last winter. I think I have about 60 lbs. of road sand and gravel under there from driving to a ski area that uses tons of sand/gravel every month. It mixes in with the snow and slush which helps transport it to the under fairings. When the snow/slush melts the sand/gravel is left behind.
Turn off the heater and air conditioner. The peak power limit includes all current from the high voltage system. Also, if the 12V battery is on a charge cycle it will limit the peak power to the motor(s). I don't know how you can control this except to install a voltage monitor and do the run when the voltage is at the native battery voltage of around 13V instead of 14.8-15.3V. These electrical considerations are small effects (except for the heater) but every little bit helps if you are using accurate instruments to measure acceleration.
Tire pressure. I suspect (but don't know for a fact) that a lower pressure than is otherwise ideal for cornering traction will yield slightly faster times due to the effectively smaller diameter with which to deliver torque to the road. This assumes the higher torque overcomes the slightly higher rolling resistance. I suspect it would on a 0-60 mph run. However, tire pressure that is too low will not have enough traction for optimum acceleration and could compromise the integrity of the wheel/tire.
By far, of all the factors listed above, the factor with the most impact will be the circumference of your tread (actual tire diameter). Smaller is better.
The circumference of the drive wheels. I measured my 235/45/18 Pirelli Sottoszero II's as having 2% less circumference than my 235/45/18 Michelin MXM4 Primacy's. The smaller diameter provides more torque to the road and gets the motor(s) into peak powerband 2% sooner. Since the power curve rises sharply from 0 rpm, these two factors will make a big difference in 0-60 mph times. An additional factor is the tread is the heaviest part of a tire and it is also the furthest from the axis of rotation. So a smaller diameter tire will have less rotational inertia to accelerate. Also, as the same tires wear down they will be faster for the same three reasons above.
Extra weight. Take all items out of the car before making a measurement. You can leave your clothes on in case you get pulled over.
I need to remove the bottom aero fairings and clean out the dirt from last winter. I think I have about 60 lbs. of road sand and gravel under there from driving to a ski area that uses tons of sand/gravel every month. It mixes in with the snow and slush which helps transport it to the under fairings. When the snow/slush melts the sand/gravel is left behind. Turn off the heater and air conditioner. The peak power limit includes all current from the high voltage system. Also, if the 12V battery is on a charge cycle it will limit the peak power to the motor(s). I don't know how you can control this except to install a voltage monitor and do the run when the voltage is at the native battery voltage of around 13V instead of 14.8-15.3V. These electrical considerations are small effects (except for the heater) but every little bit helps if you are using accurate instruments to measure acceleration.
Tire pressure. I suspect (but don't know for a fact) that a lower pressure than is otherwise ideal for cornering traction will yield slightly faster times due to the effectively smaller diameter with which to deliver torque to the road. This assumes the higher torque overcomes the slightly higher rolling resistance. I suspect it would on a 0-60 mph run. However, tire pressure that is too low will not have enough traction for optimum acceleration and could compromise the integrity of the wheel/tire.
By far, of all the factors listed above, the factor with the most impact will be the circumference of your tread (actual tire diameter). Smaller is better.
SleeperService
Member
I updated from 2019.5.15 to 2019.8.4 this morning and ran one instrumented (accelerometer in my phone...) 0-65mph test on my way home today. Updated the spreadsheet. There were a couple differences from my recorded run on 2019.5.15: I was at 50% SOC this afternoon vs. 90% last time, but my battery was more warmed up (just got off the interstate vs just pulled out of the garage/charger). I was pleasantly surprised, to say the least...
Accelerometer DAQ
Accelerometer DAQ
MagnusMako
Member
How accurate is this accelerometer built into your phone and does it factor in slope? Help me understand what is going on in your spreadsheet. You have over 9,000 entries.
SleeperService
Member
Precision (repeatability) is more important for a comparison like this than absolute accuracy, that said, while I don't know the specifications for the phone's accelerometer, it appears to provide very repeatable data. It was collecting at 400 hz, hence the large number of data points. It does not have a built in correction for slope, so you'll just have to take my word for it that I wasn't going downhill! I basically just zeroed out the gravity vector from the g-force vector, then found its magnitude and converted to feet per second squared then did the first and second integrals to find the speed and distance traveled respectively. Everything else is just unit conversions.
TLDR: Math. Good for comparison.
SleeperService
Member
I don't like how Google Sheets charts things, here's an Excel graph showing the accelerometer data comparison between 2019.5.15 and 2019.8.4. Pretty significant difference at 90 SOC, same stretch of road (~3 feet of elevation gain over ~1/4 mile), same temperature (38F), same amount of time out of the garage/off the charger (~3 minutes). I did have it in track mode for both runs. OEM 18" MXM4s, Aero caps on. No modifications. Makes a pretty massive difference 0-100 mph...almost half a second (0.481 s).
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MagnusMako
Member
Gotcha. My concern about slope is that even with the naked eye, it can be easy to mistake a flat strip of road for one that has greater than a 1% grade. I've managed several runs under 4s (rollout) just with slightly more than 1%. One was a 3.98 like yours, at -1.17% grade but the road looked super flat to me. If you can do a validated 3.9 with a Dragy without rollout - I'd be in awe. Examples of my runs just barely out of slope validation...
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SleeperService
Member
Well, I've got a P3D-, so I do under 3.5 all day, everyday.
I've checked the slope of my stretch of road using GIS (Geographic Information System) information, plus I've walked it quite often. I'm pretty confident in the ~0-2 feet of rise over ~1/4 mile on my stretch of road. Again, great for comparison on one car between different configurations (software, modifications, whatever), but probably not as universally applicable as something like a VBOX. I don't feel the need to buy a Draggy or a VBOX, it'd just be a single use toy that wouldn't add much value to my life. Plus, this kind of data acquisition and analysis is more FUN for me!
MagnusMako
Member
Understandable. I was just looking at of the lines highlighted green from the sheet and the 60 time listed as 3.9 so I wasn't thinking it was a P3D.
SleeperService
Member
Ah, I see the confusion. That's the "clock time" after I hit "start recording" on my phone. Column H is the actual "from 0 mph" time. The green row is the "start" from 0.8 kph (which is when the Draggys and VBOXs of the world trigger a start). The yellow row is the the 1 ft rollout start time, the orange row is 60 mph, and the red row is 100 mph. I made these for me, and I thought people might find them interesting..so they aren't particularly "clean" to just look at and read. If you scroll over to column R, you can see the calculated times. Again, wasn't really DESIGNED for public consumption, just thought I'd share because I thought it's neat data.
AlanSubie4Life
Efficiency Obsessed Member
Ah, I see the confusion. That's the "clock time" after I hit "start recording" on my phone. Column H is the actual "from 0 mph" time. The green row is the "start" from 0.8 kph (which is when the Draggys and VBOXs of the world trigger a start). The yellow row is the the 1 ft rollout start time, the orange row is 60 mph, and the red row is 100 mph. I made these for me, and I thought people might find them interesting..so they aren't particularly "clean" to just look at and read. If you scroll over to column R, you can see the calculated times. Again, wasn't really DESIGNED for public consumption, just thought I'd share because I thought it's neat data.
Have you redone your camera method with the new software (I don’t have it yet)? I’m kind of surprised that your accelerometer data shows higher acceleration basically all the way from 5mph on, since that was not expected. And I thought the dyno plots for the P3D (for what they are worth) also showed differences only above 40mph or so.
Just thought maybe a second time with the camera analysis (which seemed very accurate) might be good to see whether it shows the same acceleration increase.
SleeperService
Member
I have not re-done the camera method, no. I did do the accelerometer method at 50% SOC (in that spreadsheet) that also showed the higher acceleration from 5-40 mph (but dropped faster after that due to the SOC). It seems "real." The dynograph I saw only had the torque curve for the "after update" condition and didn't show it for the "before update" condition.
Edited: Mislabeled graph, 50% SOC testing WAS done on 2019.8.4 NOT 2019.5.15
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AlanSubie4Life
Efficiency Obsessed Member
Interesting. I guess I have to poke around for the dyno data I saw; I thought it was comparative.
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