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Traction on hard acceleration
- Thread starter mattack4000
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- Driving Dynamics Model 3
Daniel in SD
(supervised)
My guess would be that the Model 3 does not generate enough torque to the wheels to spin the wheels. This is because it has a flat torque curve almost all the way to 60 mph and a single speed transmission. RWD ice vehicles with similar 0-60 times can spin the wheels because they have faster acceleration (more torque to the wheels) in 1st gear. While the ICE vehicle would beat the Model 3 off the line the Model 3 would catch up after the ICE vehicle shifted into second gear. Obviously this is in drag race type conditions. The ICE vehicle would have to rev the engine and feather the clutch (or load the torque converter in an auto) to achieve "magazine" 0-60 times. All the Tesla driver has to do is push the accelerator to the floor.
silentsnow31802
Member
I have not got my Model 3 to get wheel spin from a dead stop. The amount of power it can pull down that low seems limited. However when I am traveling 20-30mph I can get the traction light to come on. It reminds me the difference between a S85 and a P85.
I’ve noticed that launch is noticeably weaker in our 3LR than in our 85D ... but that, once going, both seem to have wickedly similar acceleration. My untutored guess is that traction control has been set to be very conservative on launches ... no wheel spin ... unlike S85 loaners I’ve had.
Daniel in SD
(supervised)
You can see from instrumented testing that the Model 3 has about 0.6G constant acceleration from 0-45 and then begins to taper off. That's not quite enough to spin the wheels on a good road surface in a RWD car.
Tesla Model 3 accelerates from 0-60 mph in 4.6 secs – faster than Tesla advertises
I can't find a similar plot for a competitive car but a BMW 340i also goes 0-60 in 4.8s but goes 0-30 in 1.8s (vs. 2.2s in the 3) and can do a wicked burnout
Maybe Tesla should bring back their 2 speed transmission? haha
Tesla Model 3 accelerates from 0-60 mph in 4.6 secs – faster than Tesla advertises
I can't find a similar plot for a competitive car but a BMW 340i also goes 0-60 in 4.8s but goes 0-30 in 1.8s (vs. 2.2s in the 3) and can do a wicked burnout
Maybe Tesla should bring back their 2 speed transmission? haha
omgwtfbyobbq
Active Member
In another thread there was speculation that the videos of model 3 burnouts from after the fuse for traction control was pulled. The 3's more than capable of putting enough power down to spin the wheels, but I think Tesla tries to maximize traction/minimize tire wear from the factory, as opposed to minimizing 0-60 times.
Petra
Member
Wheel spin is wasted energy (slows you down). Carefully controlling initial torque onset to not exceed maximum traction should provide the quickest 0-60 times.
As for the burnouts, pull the fuse for the stability control and I'd expect a transformation similar to that of the original RWD S85--tame with the system on and a tire melting machine with it disabled.
Daniel in SD
(supervised)
How do you explain the acceleration chart above? It looks like it is constant torque up to 45mph. I suppose it's possible that the stock tires are so bad that they limit acceleration to 0.6G. Has anyone put stickier summer tires on and measured acceleration? Other cars with similar 0-60 times are much faster from 0-30.
Obviously this all sort of silly. The Model 3 is quick. It's funny to hear people here say it doesn't feel that fast because they're all used to the acceleration of the Model S
Obviously this all sort of silly. The Model 3 is quick. It's funny to hear people here say it doesn't feel that fast because they're all used to the acceleration of the Model S
Daniel in SD
(supervised)
They do limit the power but I think it's a limitation of the motor controller maximum current and not the traction control. It's true that putting down 258hp at low speeds would easily spin the tires but it can't do that. All the Tesla power curves I've seen show constant torque at low speeds (linearly increasing horsepower) and constant horsepower at high speed.
Looking forward to see how fast they make the dual motor. If they keep the same rear motor and controller it's going to be a rocket! still won't do a burnout though
Looking forward to see how fast they make the dual motor. If they keep the same rear motor and controller it's going to be a rocket! still won't do a burnout though
Daniel in SD
(supervised)
Your RAV4 is front wheel drive. If they made the Model 3 FWD it could probably spin the tires all the way to 45mph. When you accelerate the weight transfers from the front wheels to the rear wheels. Probably even more dramatically in a softly sprung CUV.
insaneoctane
Well-Known Member
If there is no chirp or wheelspin, it is simply by Tesla design. More than enough torque to do the job, but Tesla chooses the "profile" on how that gets to the ground and they appear to be quite conservative. Probably for the greater good, but I still wish a TC-off was offered.
insaneoctane
Well-Known Member
Yes, but look at the 5-60 time for the BMW vs Model 3. I think it proves that the 0-30 in 1.8s is a result of a "clutch dump" type launch....
Daniel in SD
(supervised)
There is no doubt that Tesla could design a vehicle that puts more torque to the wheels than a Model 3. After all they make the P100D. The profile they have chosen, as shown in the measured acceleration data, is a flat torque curve. Gas engines produce zero torque at zero RPM so naturally some slip is necessary (either clutch or torque converter). The BMW produces very little torque without slip at 5mph. However with the turbo spooled up a BMW 340i in first gear puts more torque to the wheels than a Model 3 and therefore has faster acceleration in first gear.
Not accounting for drivetrain loss or tire size:
BMW 340i 1st gear 4.11:1 * final drive ratio 3.23:1 * 332 lb-ft = 4407 lb-ft
Model 3 drive ratio 9:1 * 307 lb-ft = 2763 lb-ft
The Model 3 doesn't have to shift and once in second gear the BMW's torque drops to 2478 lb-ft. Of course the multispeed transmission in the BMW has more loss than the single speed in the Model 3.
I'm also hoping that there is a way to turn of traction control and stability control. I'd like to autocross the Model 3 at least once to see how it does.
Not accounting for drivetrain loss or tire size:
BMW 340i 1st gear 4.11:1 * final drive ratio 3.23:1 * 332 lb-ft = 4407 lb-ft
Model 3 drive ratio 9:1 * 307 lb-ft = 2763 lb-ft
The Model 3 doesn't have to shift and once in second gear the BMW's torque drops to 2478 lb-ft. Of course the multispeed transmission in the BMW has more loss than the single speed in the Model 3.
I'm also hoping that there is a way to turn of traction control and stability control. I'd like to autocross the Model 3 at least once to see how it does.
insaneoctane
Well-Known Member
I don't question your math. It proves that the BMW can out accelerate the Model 3, below, say 100 MPH, only during a brief window. Specifically, 1) within a limited RPM range of the engine (not too low and not too high) AND 2) Only in first gear. This is the compromise of ICE. And to have this wonderfully engineered monstrosity of combustion capable of matching the 0 to 60 time of the Tesla (if you are willing to launch the BMW just right and are skilled enough to do so) what MPG must you settle for? I know that the Model 3 gets 130 MPGe.... I just love my cake and eating it too
I don't question your math. It proves that the BMW can out accelerate the Model 3, below, say 100 MPH, only during a brief window. Specifically, 1) within a limited RPM range of the engine (not too low and not too high) AND 2) Only in first gear. This is the compromise of ICE. And to have this wonderfully engineered monstrosity of combustion capable of matching the 0 to 60 time of the Tesla (if you are willing to launch the BMW just right and are skilled enough to do so) what MPG must you settle for? I know that the Model 3 gets 130 MPGe.... I just love my cake and eating it too
Better put that cake down fat boy
Assuming the figures that Daniel quotes are right, namely 307 ft-lbs and 9:1 gear ratio, and the 258 rated horsepower as per the EPA document then we can do some simple maths and figure out at what speed the Model 3 hits it 258hp limit.
I'm converting to SI units, because I don't work in ft, lbs or slugs.
307ft-lbs = 416N.m
258hp = 192 kW
Power = Torque. Omega ( in rad/s)
192000 = 416 . Omega
Omega =192000 Watts / 416 N.m = 461 rad/s
461rad/s * 60/2*pi = 4402 motor rpm
4402 / 9 ( gear ratio) = 489 wheel rpm
a Model 3 19" tire has 764 rotations per mile according to tiresize.com
so 489/764 = 0.64 miles/minute.. x 60 = 38.4mph. So anytime the model 3 is doing more than 38mph, it is at its 258hp limit, and torque is dropping accordingly.
the BMW 340i makes more than 258 hp from 4200rpm all the way to redline (7000rpm). It redlines first gear at 41mph, so lets look at where in second gear it gets to 4200rpm.
4200 engine rpm / 7.48 = 561 wheel rpm which on a 225/45/R18 tire equates to 43.3mph. (7.48 = 2nd gear ratio * diff ratio)
So actually, at no point above ~45mph is the Tesla putting more power to the ground than the BMW (except for while the BMW changes gear) .... and given that the BMW is lighter than the Model 3 LR its clear to see who will win that race.
In the real world, the Telsa will spank the BMW off the line in most cases , but then its all downhill for the Tesla.. and thats simply because the BMW will not make full power on a cold unspooled turbo, but by the time the BMW hits 4500rpm in 2nd (from a standing start) the turbo will be doing what its designed to do and starting reeling in the Tesla. If you have a good driver launching the BMW and the turbo & manifold are already hot, the Tesla is going to get spanked from go to whoa. Those few moments when the BMW is changing gear and putting no power to the ground are not going to make up for a 60hp and 150lb disadvantage the Tesla has.
insaneoctane
Well-Known Member
Who you callin' fat?Better put that cake down fat boy
Assuming the figures that Daniel quotes are right, namely 307 ft-lbs and 9:1 gear ratio, and the 258 rated horsepower as per the EPA document then we can do some simple maths and figure out at what speed the Model 3 hits it 258hp limit.
I'm converting to SI units, because I don't work in ft, lbs or slugs.
307ft-lbs = 416N.m
258hp = 192 kW
Power = Torque. Omega ( in rad/s)
192000 = 416 . Omega
Omega =192000 Watts / 416 N.m = 461 rad/s
461rad/s * 60/2*pi = 4402 motor rpm
4402 / 9 ( gear ratio) = 489 wheel rpm
a Model 3 19" tire has 764 rotations per mile according to tiresize.com
so 489/764 = 0.64 miles/minute.. x 60 = 38.4mph. So anytime the model 3 is doing more than 38mph, it is at its 258hp limit, and torque is dropping accordingly.
the BMW 340i makes more than 258 hp from 4200rpm all the way to redline (7000rpm). It redlines first gear at 41mph, so lets look at where in second gear it gets to 4200rpm.
4200 engine rpm / 7.48 = 561 wheel rpm which on a 225/45/R18 tire equates to 43.3mph. (7.48 = 2nd gear ratio * diff ratio)
So actually, at no point above ~45mph is the Tesla putting more power to the ground than the BMW (except for while the BMW changes gear) .... and given that the BMW is lighter than the Model 3 LR its clear to see who will win that race.
In the real world, the Telsa will spank the BMW off the line in most cases , but then its all downhill for the Tesla.. and thats simply because the BMW will not make full power on a cold unspooled turbo, but by the time the BMW hits 4500rpm in 2nd (from a standing start) the turbo will be doing what its designed to do and starting reeling in the Tesla. If you have a good driver launching the BMW and the turbo & manifold are already hot, the Tesla is going to get spanked from go to whoa. Those few moments when the BMW is changing gear and putting no power to the ground are not going to make up for a 60hp and 150lb disadvantage the Tesla has.
I still think my statements are valid. I will agree that once the cars are at speed (about 40MPH+) the BMWs HP advantage will likely translate to superior acceleration. But, the Tesla owns the BMW at most legal street speeds and off the line against a significant % of BMW drivers (because many aren't willing to do whatever it takes to ensure that the turbo is hot & spooling). As a matter of fact, even with a skilled, who-cares-about-this-tranny&clutch launch, the BMW only ties the Tesla to the quarter mile (both at 13.3 seconds). Now, if you factor in most drivers, it's best represented by using 5-60 data instead of 0-60 data, you have to add 1.1 seconds to that number for the BMW, which puts it at 14.4 seconds. That is a healthy lead for the Tesla just past 100 MPH. Again, the BMW has more power and certainly by 100 MPH it is gaining (illustrated by the 106 MPH trap speed). So, by my estimation, the Tesla will usually beat the BMW off the line all the way through the quarter mile at 100 MPH. With the turbo, I can't imagine many typical scenarios below 100 MPH where the BMW with both it's gears and turbo would be able to get that all going before the instant torque of the EV doesn't trump. It's not just having the RPM, but the RPM with full boost.
Without question, the BMW is a fast car with more horsepower. But it is an ICE with a turbo and therefore quite well matched by Tesla's EV. Your math shows how the BMW is theoretically faster and I concede those facts. Against just the right driver, the BMW wins. My cake comes from the opportunity to beat the BMW (or certainly match) against most drivers.
/IMO
Daniel in SD
(supervised)
FlyingKiwi, the Model 3 certainly has less drivetrain loss so it's makes up for it's HP disadvantage a bit there.
I agree that for all practical purposes the Model 3 is the quicker car. Not having to downshift is a huge advantage! Unless you like driving around at 45mph in 2nd gear
Maybe after selling flame throwers Elon can add a special burnout mode to the Model 3. My guess would be that the motor controller could probably be programmed to output more current for the time necessary to light up the tires.
I agree that for all practical purposes the Model 3 is the quicker car. Not having to downshift is a huge advantage! Unless you like driving around at 45mph in 2nd gear
Maybe after selling flame throwers Elon can add a special burnout mode to the Model 3. My guess would be that the motor controller could probably be programmed to output more current for the time necessary to light up the tires.
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