Cruisin' in Neutral - Actually a blast!

[slcasner]

If you are engaging ABS - the brakes are plenty strong. Since all cars can easily engage ABS with a good stab of the pedal let's assume that the brake hardware is sufficient for now.

Right. When I was driving on the track at Laguna Seca, I found that I needed to stomp on the brakes pretty hard in order to brake as late as seemed appropriate, but when I did so I could tell the ABS was engaging. That means there is enough friction between the pads and the rotors. Maybe there is just not as much power assist as people are expecting. Time for some leg exercises!

 

[Doug_G]

When I did the race school, we had trouble with the accident avoidance maneuver, but not in the way you'd think.

The Roadster kept stopping way too quickly. We had to get it going pretty fast before we could get the ABS to trigger. And that was on deliberately wet pavement.

So I think the brakes work pretty well.

 

[mpt]

I don't see how this could possibly be any more wear and tear than flooring the pedal from a standstill.

I think that the thunk from the transmission when you take out the slack could be damaging at full power. It's aways going to be the maximum amount of lash (I think that's the proper term?) as well from the proceeding drag.

 

[zack]

I spent an hour discussing these sorts of details with Eric Bendler (from Tesla service in Chicago) today. He said that when the "transmission" is in neutral, no electric fields are being induced in the rotor and when you switch the drive back on it simply starts up the magnetic fields again. There's no real "shock" to the system... rather, the computer calculates a frequency, voltage and current to apply to the motor to put it into regen mode if your foot is off the throttle, or to accelerate if your foot is on the throttle pushing it past the point where it would have been had you been coasting in drive at that exact speed (if that makes sense). He's going to go back and consult with the engineers, but he's about 100% sure that you can't hurt the car by taking it in and out of neutral no matter what you're doing with the throttle at the time. In other words, it seems that the "thunk" is a calculated one that doesn't exceed what the transmission can handle, and represents the most instantaneous and most powerful action the motor/transmission can take safely at that moment depending on the speed of the car and the position of the throttle.

 

[bonnie]

I spent an hour discussing these sorts of details with Eric Bendler (from Tesla service in Chicago) today. He said that when the "transmission" is in neutral, no electric fields are being induced in the rotor and when you switch the drive back on it simply starts up the magnetic fields again. There's no real "shock" to the system... rather, the computer calculates a frequency, voltage and current to apply to the motor to put it into regen mode if your foot is off the throttle, or to accelerate if your foot is on the throttle pushing it past the point where it would have been had you been coasting in drive at that exact speed (if that makes sense). He's going to go back and consult with the engineers, but he's about 100% sure that you can't hurt the car by taking it in and out of neutral no matter what you're doing with the throttle at the time. In other words, it seems that the "thunk" is a calculated one that doesn't exceed what the transmission can handle, and represents the most instantaneous and most powerful action the motor/transmission can take safely at that moment depending on the speed of the car and the position of the throttle.

That's been my worry, while reading this thread. Thanks, Zack. I'll wait to hear confirmation before trying.

 

[vfx]

...

I agree that it would be nice to be able to turn regen on and off (better yet: dial in a level for when your foot is off the pedal). But that really just makes it easier to get top efficiency;....

I want regen on demand. I image a steering wheel stalk (car have so many these days, why not?) that is a regen adjustment lever. Push up for less regen and down for more. Push in to turn it off quickly and push it again to go back to last setting.

 

[bonnie]

That's been my worry, while reading this thread. Thanks, Zack. I'll wait to hear confirmation before trying.

I lied. Not intentionally. I tried it on the long drive back winding back through my neighborhood (which ends with stopping at my mailbox). Fun!

 

[S-2000 Roadster]

I want regen on demand. I image a steering wheel stalk (car have so many these days, why not?) that is a regen adjustment lever. Push up for less regen and down for more. Push in to turn it off quickly and push it again to go back to last setting.

You already do have regen on demand: just use your foot. It's incredibly simple to get less regen with the stock system. I found it very easy to transition from compression braking skills learned on ICE vehicles to the regen braking skills necessary to completely control the Tesla Roadster. The only thing you can't do is get more regen than the maximum the computer allows when you completely release the pedal.

 

[S-2000 Roadster]

Getting OT for this thread, but there could be a lot of reasons for "sub-par" braking performance. But a couple notes:

1. If you are engaging ABS - the brakes are plenty strong. Since all cars can easily engage ABS with a good stab of the pedal let's assume that the brake hardware is sufficient for now.
2. Now that you've got the tires nearly locked up - what you really need are stickier tires. As others have already mentioned, the Roadster is a lot heavier than the Elise, but the tires are the same width. Wider tires ought to reduce braking distances significantly. The Auto-X / track guys seem to like 195 width tires in the front
3. The other problem with "weak" brakes could be brake fade - but I didn't hear anyone complain of that so I'll assume the stock brake equipment is sufficient. Perhaps after stickier tires you'll find that brake fade is an issue - looks like there are big-brake-kits for the Elise that might fit.

I tend to agree: The stock equipment should be more than sufficient.

When autocross guys who aren't familiar with the Tesla see the rotors, they often say that they're incredibly large. I don't even think they're adjusting for the small size of the Roadster. Tesla even put larger hubs than the stock Elise - are you folks sure that the brake equipment is identical between the Elisa and Roadster, even though the hubs are different?

 

[vfx]

You already do have regen on demand: just use your foot. It's incredibly simple to get less regen with the stock system. I found it very easy to transition from compression braking skills learned on ICE vehicles to the regen braking skills necessary to completely control the Tesla Roadster. The only thing you can't do is get more regen than the maximum the computer allows when you completely release the pedal.

Not even close. There is no "on demand" neutral. Attaining neutral on mountain roads takes a skillset that is impossible and unnecessary if it can be on a steering stalk. And no "on demand" full regen (stops a 40 miles per hour car in 12 feet)

 

[S-2000 Roadster]

Not even close. There is no "on demand" neutral. Attaining neutral on mountain roads takes a skillset that is impossible and unnecessary if it can be on a steering stalk.

What's wrong with the Neutral button on the center console?
Besides, I don't have any problem dialing in Neutral with the pedal on Snoqualmie Pass (elev. 3000 ft to sea level in 40 mi)

And no "on demand" full regen (stops a 40 miles per hour car in 12 feet)

I have serious doubts that Tesla Motors is going to invite owners to use a steering stalk regen brake in an emergency situation requiring 40-to-0 mph in 12 ft. Good lord, you need to be on the mechanical brake for that and not trying to remember whether you're still on a Range Mode charge where regen is not completely functional.

 

[vfx]

What's wrong with the Neutral button on the center console?
Besides, I don't have any problem dialing in Neutral with the pedal on Snoqualmie Pass (elev. 3000 ft to sea level in 40 mi)

I have serious doubts that Tesla Motors is going to invite owners to use a steering stalk regen brake in an emergency situation requiring 40-to-0 mph in 12 ft. Good lord, you need to be on the mechanical brake for that and not trying to remember whether you're still on a Range Mode charge where regen is not completely functional.

First off i don't have the cost saving buttons they put on the later cars and 2nd, taking hands off the steering wheel is what I was trying to avoid.
If you had ever driven a EV with adjustable regen you might see the advantages. It makes the EV a better driver's car. The Model S will have some sort of adjustment. I am simply specing out my wish list.

 

[bonnie]

After now playing with Neutral ... adjustable regen is on my wish list, too.

 

[bolosky]

And no "on demand" full regen (stops a 40 miles per hour car in 12 feet)

Recall that because regen works through the drive train, you're only ever going to get regen on the rear wheels. Panic stops clearly need all the rubber they can get, so you'll need the friction brakes.

I also seem to remember hearing someone (possibly a Tesla engineer) saying that the current limit on regen was because with more the car behaved strangely with only the rears slowing.

 

[vfx]

Recall that because regen works through the drive train, you're only ever going to get regen on the rear wheels. Panic stops clearly need all the rubber they can get, so you'll need the friction brakes.....

Yeah,

I never said anything about using regen as braking in panic stops. I want the car to slow down at foot-lift an adjustable amount. How much? Strong regen is like going from driving on concrete to suddenly hitting sand. I threw out a number.

 

[Doug_G]

I tend to agree: The stock equipment should be more than sufficient.

When autocross guys who aren't familiar with the Tesla see the rotors, they often say that they're incredibly large. I don't even think they're adjusting for the small size of the Roadster. Tesla even put larger hubs than the stock Elise - are you folks sure that the brake equipment is identical between the Elisa and Roadster, even though the hubs are different?

Parked next to an Elise today. From what I recall I'm pretty sure the Roadster rotors are bigger.

 

[Doug_G]

I never said anything about using regen as braking in panic stops.

Actually it's pretty hard not to; the regen is providing some of the drag even when you're pouncing on the brakes. You'll realize that right away if you hit a big bump while braking, even if you're braking hard.

 

[zack]

Speaking of, if the TC is off when you hit said big bump, does the regen turn off like it does normally?

 

[S-2000 Roadster]

Recall that because regen works through the drive train, you're only ever going to get regen on the rear wheels. Panic stops clearly need all the rubber they can get, so you'll need the friction brakes.

I also seem to remember hearing someone (possibly a Tesla engineer) saying that the current limit on regen was because with more the car behaved strangely with only the rears slowing.

Good point. Also, keep in mind that severe braking shifts the weight of the car to the front wheels, lifting off on the rear wheels. Basically, the harder you stop, the less down force there is on the rear wheels. You really, really need the front wheels to contribute to the braking (and the Sport has wider tires, so that will help - those of us with standard Roadsters might want to fine tune the balance between rolling resistance and better braking friction).

 

[Doug_G]

Speaking of, if the TC is off when you hit said big bump, does the regen turn off like it does normally?

Nope. On dry but bumpy pavement TC can really get in the way, and you might want to consider switching it off. There's a rather bumpy intersection near my house where I'm often braking from 80 kph to make a turn. If the pavement is dry I often switch off the TC. Otherwise the bumps sometimes trigger TC and the car lurches forward. Tends to freak out my wife. And of course it's off for autocross.

On the other hand, on slippery roads the TC is essential. The Roadster has a lot of power and you could easily end up spinning.