Uh.. REALLY? I stated that many times, thats obvious.
Do you have anything backing up the claim the front motor is geared any different than the rear? I'll stand by.
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Uh.. REALLY? I stated that many times, thats obvious.
Do you have anything backing up the claim the front motor is geared any different than the rear? I'll stand by.
breser
AutoPilot Nostradamus
You won't. It's still a quick car. When people start talking about the higher speed performance being less impressive on the P85D they're usually comparing it to another Model S. The only limitation ends up being the Tesla still doesn't have the top speed of some cars, but unless you're going to drag strips this isn't a concern.
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Nobody knows for sure. Maybe someone in Massachusetts could figure it out form the service manual. But there's been discussion of trying to gain access to the wiring to try and figure out gearing based on the energy usage/frequencies of the motors in other threads. Short of those ideas you're probably looking at someone taking apart the car, which I just don't see happening. I'm sure we'll know for sure once someone wrecks one and a tear down happens.
I have no proof, as I stated at the beginning. However, there is nothing at all preventing Tesla, and there are a number of things suggesting it is the case, starting with this video from the Model X reveal:
Tesla Model X demonstration - YouTube
From about the one minute mark, the Tesla employee talks about the benefits of different gearing.
There's also this patent, with the image in TEG's post #18:
Dual drive techincal questions - Page 2
Which is very clearly showing two different gear ratios. Again, no proof it's on the P85D - but there's no mechanical barrier to it, and lots of reasons to gear differently.
If you are understanding that there's no connection between the two systems, I guess I'm having trouble understanding why you're thinking there'd be a problem running with two different gearings.
As a thought experiment, try this: I have two identical cars, which are connected together by a tow hitch. The front car is driving in second gear at high RPMs and partial throttle, the rear car is in third at low RPMs and wide open throttle, and each is contributing the same amount of power to the combination. Is there a problem with this? If not, how is it different in your mind from a P85D?
Walter
I think 'Geared' is not the right term here. I was told at the Model X release in Hawthorne that the motors were each designed to be more efficient at a particular speed (RPM) and power requirement, thus working better together.
Interesting analogy, Walter.
In this situation, how would these two independent vehicles connected via tow hitch be able to accelerate faster being tied together? Ultimately, the motor powerful vehicle would outpower the lesser one- therefore, making the power of the lesser vehicle almost pointless other than initial torque from a stop, working in conjunction. If they were geared differently, it wouldn't matter as one vehicle has a 221 HP motor and the other a 470 HP motor. Unless both motors are 470 HP, I don't see the benefit of different gearing in this situation.
I guess we can go back and forth all we want, the fact of the matter is the P85D is really not that much quicker feeling that a P85 from a roll at 40MPH+.. if the gearing was actually different, than almost a 300HP difference would be felt and it simply isn't. The only benefit of the second motor is a crazy amount of torque from a stand still, yet the combined horsepower of both motors never exceeds the horsepower of the rear motor as shown on this dyno graph- the torque is there, but HP isn't. I truly do not think all 691 HP is working at the same time and the only benefit is torque. Not a big deal, but I think its a bit of a marketing hype and the launch feeling you get is just torque, not horsepower.
deonb
Active Member
Imagine putting a tow bar at the back of a Nissan Leaf and have it tow a Model S (in 'Drive', not 'Neutral').
Same principle.
Ok, imagine the Leaf flooring it and also the Model S floored. How does the Leaf's tiny motor even have an impact unless from a standstill because of more torque? Ultimately when moving, the Leaf being in front in no way would benefit the Model S as its overpowering and pushing the less powered motor in front of it. The Leaf could just shift to neutral after the initial launch and then go into Neutral and let the more powerful Model S push it- less resistance and would likely be faster.
If the front motor of the P85D is geared different, its geared very low and likely has no effect after 50MPH. It might be there just to give that initial torque boost off the line, which would make sense as it isn't much faster than a standard P85 after that speed. The 470HP rear motor in the D vs the 417HP in the P85 is likely responsible for that slight performance boost and higher speed limiter, and maybe its gearing is a little different than the standard P motor as well. Could be that the P85D rear motor is taller geared and front motor is lower geared. Either way, a single 691HP with a transfer case/differential AWD setup w/ 2 speed gearbox would destroy the current P85D drivetrain config, in my opinion.
Full torque is immediate, runs level up to about 5000 RPM, then begins to taper off. I think 5000 RPM occurs at about 50 MPH. Starting at that speed and trying to accelerate is trying to start at the car's weakest point. The ICE car/driver downshifts to get back into a more powerful point on it's curve, so you get acceleration. Try leaving the ICE car in high gear to do this acceleration-- that will simulate what the Tesla is going through.
Is the car actually slower, or does it just not "feel" as fast? I have no data.
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
I agree. The front motor contributes at launch and much of the effect here has to do with putting grip and torque on 4 wheels instead of two. When rolling along and acclerating grip isn't really so much of an issue and as your analogy shows the front motor is just bein "pushed" by the larger rear motor. The benefit otherwise, of course, is for range i.e. to torque sleep the rear motor and let the front motor drive the car at a steady highway speed - as it's smaller it operates at higher load and thus is more efficient.
deonb
Active Member
Up to the point where the Leaf would have had enough power to accelerate the train of 2 vehicles by itself, adding that motor to the equation will be a net positive.
I'm not disputing that there is a point where it would be better to cut out the front motor (otherwise the front motor goes into regen, which is worse than neutral). Just explaining that there is nothing that prevents the front motor to be differently geared than the rear motor.
There's no point in providing the same kind of power to the front wheels that the rear wheels are getting.
Why? The weight transfer on hard acceleration. The P85 can break the rear wheels loose at any time under ~40 mph if not leashed by traction control I'm told - and the P85D uses the same motor on the same gearing at the rear.
Under hard acceleration, the front wheels would slip at maybe half that level of torque. So instead, you give that motor taller gearing to give it more efficiency as speeds rise - with the result that all the wheels are absorbing as much torque as they can, but you also get an extended performance speed range.
Actually, I believe that what you're seeing over 50 mph has more to do with the limitations on battery power output than anything to do with the motors or gearing - so far none of the videos or reports I've seen have shown it even reaching 480 kW, let alone the 515 that the oft-quoted 691 hp corresponds to.
Complete nonsense (much like everything else you've said so far in this thread). During torque sleep the rear motor goes to sleep; just the front is powered. So the gearing at the front cannot be shorter since at a 90mph cruise the P85D is basically a front wheel drive car. See first question on Driving Range for the Model S Family | Tesla Motors UK
This is also the reason why the D model cars have a higher top speed - their front motor is longer geared so it can still be used to propel the car at higher speeds.
Cars with two different "engines" with radically different power output characteristics working together to make something faster and more economical than it would be if either operated alone is really common. It's what happens in every single hybrid on the road today.
excuse me, "non sense". Wow, such a great welcoming attitude here. I'm still trying to dig up hard information that the front motor powers the car when cruising and is taller geared... Because if it was taller geared than the rear motor that wouldn't help its case on the launch. Heck you can even hear the gear whine on launch of the front motor which sounds like it's geared low and not tall.. Like some roots style super chargers or even short gears like a reverse gear in a normal transmission.
i admit I'm speculating but you speak as if it is fact- do you have a link to something that backs your claim?
It seems like there's still a failure to communicate here - you're thinking for some reason that the ratio of gearing is somehow relevant to the motor's ability to provide torque to the wheels. (The gearing of the individual motor matters - the ratio between the two, not at all.)
The best way to look at the acceleration is at the wheels themselves. The P85 can deliver ~4,300 foot pounds to the rear wheels after 9.73:1 gearing, which multiplied by the ~28" nominal wheel diameter gives ~3700 lbs of accelerative force.
We don't have exact specs for the front motor, but if we assume it was a Nissan Leaf motor instead (as used above,) then it would have 173 ft-lbs in the front motor on 8:1 gearing, giving ~1400 foot pounds at the front wheels, and ~1200 lbs of accelerative force.
So a car using both motors would be pushed forward with ~4900 lbs, while one using only the rear motor would have ~75% of the acceleration, and one using only the front motor ~25%.
What if the front motor was a Spark EV, instead? 403 ft-lbs and 3.23:1 overall gearing - about 1300 foot pounds at the wheels, maybe 1100 pounds of accelerative force.
Notice how the ratio between the gearing changed massively - but the difference in acceleration is minimal, because both sets provide about the same torque at the wheels - and neither has any problem working with a shorter gearing on the rear motor - and the ratio of gearing didn't matter.
It all adds together, and it makes the AWD car substantially faster than if it wasn't using the front motor, despite the front motor's taller gearing (and the actual gearing is most likely a lot taller than the Leaf's - possibly somewhere close to the Spark's)
Walter
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Haven't we already seen that clip on youtube of a rolling drag between a p85 and p85d. It is a clear win from 35mph rolling start.
The rear has an extra 50bhp but the advantage is much greater than 50bhp so the front motor on the D must be assisting significantly. I have no idea on the gearing, but it is certainly in play.
The P85+ also spanked an aston martin rapid from the 30mph rolling start and the aston had the jump.
So its certainly quick rolling, it just doesnt feel as brutal.
The rear has an extra 50bhp but the advantage is much greater than 50bhp so the front motor on the D must be assisting significantly. I have no idea on the gearing, but it is certainly in play.
The P85+ also spanked an aston martin rapid from the 30mph rolling start and the aston had the jump.
So its certainly quick rolling, it just doesnt feel as brutal.
AMPd
Well-Known Member
P85D is definitely faster from a roll as well
Tesla Model S P85D (691HP) vs P85 (415HP) 35 MPH Roll Race - YouTube
William13
Active Member
Personally I think the op premise is incorrect. I believe that the Model S passes other cars quicker/safer due to its instantaneous response versus the 0.3 second lag when flooring other cars while they think, spool up, and downshift. I believe this then gives the illusion of faster passing with ICE vehicles rather than any significant time difference in the real world off a track.
BTW he later states that he was not quite serious in his complaint.
BTW he later states that he was not quite serious in his complaint.
That is correct, I was mocking those who complain about range by making my own complaint about acceleration. Personally, I find both to be at least adequate, at a minimum. But I do think that when you're at high speeds (much higher than 30...I'm really talking about 60+), it just feels relatively gutless compared to other high performance cars that can downshift at speed. There's no doubt in my seat of the pants that my P85D doesn't feel as stout as other cars I've driven when I'm jumping on it above 60 mph.
This is the equivalent of a "problems of the 1%" issue...I drive fast and I am that guy who will take up the challenge from the Aventador on an open road. So yeah, I'd like something like a second gear to kickdown into.
But really, it was just me wondering out loud and poking a bit of fun at people who seem to think that range is a serious issue.
If you want high speed acceleration isn't the obvious solution different gearing?
What if you lost a half second on the 0-60 - making it *only* 3.7 seconds, but gained a bunch of mid and high range acceleration by shifting the torque curve up?
If the P85D was a track car ( other problems about cooling solved ) I would totally want that. On the track you will accelerate from 30-60, 60-90, 60-120 infinitely more than 0-30. I would sacrifice the off the line for the mid and high range in a hearbeat.
The 1/4 mile time might actually be better.
What if you lost a half second on the 0-60 - making it *only* 3.7 seconds, but gained a bunch of mid and high range acceleration by shifting the torque curve up?
If the P85D was a track car ( other problems about cooling solved ) I would totally want that. On the track you will accelerate from 30-60, 60-90, 60-120 infinitely more than 0-30. I would sacrifice the off the line for the mid and high range in a hearbeat.
The 1/4 mile time might actually be better.
