Things you can do, but shouldn't

[kolmstead]

Smidge, I couldn't agree more. I was hoping that carrying the idea of power braking to its extreme would start people thinking about what they're doing to the car. And as I said earlier, it's going to be pretty obvious to Nissan what was going on. Hmm... telematics says you did five seconds of 80 kW input, at zero RPM, brakes on. And you say that you don't know why the motor quit working?

-Karl

 

[gascant]

Smidge, I couldn't agree more. I was hoping that carrying the idea of power braking to its extreme would start people thinking about what they're doing to the car. And as I said earlier, it's going to be pretty obvious to Nissan what was going on. Hmm... telematics says you did five seconds of 80 kW input, at zero RPM, brakes on. And you say that you don't know why the motor quit working?

-Karl

uhhhh...I got a cramp in my left leg??

 

[Herm]

Is the anti-freeze solution in the car's heater common with the motor/inverter coolant? If so, we've just solved the problem of slow heatup for folks in cold climates. A second or two of power braking will have that coolant plenty hot.

-Karl

The coolant is not shared.. usually there is not much heat available from waste and when its most needed, a cold morning, then you will waste power trying to heat up a big chunk of iron, copper and silicon.

 

[TomT]

This almost sounds like a software bug or oversight to me as there is no practical reason to allow such behavior. In light of all the Toyota PR about them NOT having a brake override for the throttle and it contributing to the accelerator and floor mat runaway issues, you would think that Nissan would want to specifically prohibit such a situation in all of their vehicles.

You can power brake the car. I was a little surprised at this one as it would be trivial for the car to not apply power if you are on the brake. But you can pretty much apply full power while also on the brake. When I was doing testing, I didn't want to regen at all and with a little two foot driving and watching the power meter, you can keep the ball on the zero.

 

[turbo2ltr]

This almost sounds like a software bug or oversight to me as there is no practical reason to allow such behavior. In light of all the Toyota PR about them NOT having a brake override for the throttle and it contributing to the accelerator and floor mat runaway issues, you would think that Nissan would want to specifically prohibit such a situation in all of their vehicles.

You can power brake the car. I was a little surprised at this one as it would be trivial for the car to not apply power if you are on the brake. But you can pretty much apply full power while also on the brake. When I was doing testing, I didn't want to regen at all and with a little two foot driving and watching the power meter, you can keep the ball on the zero.

Then how many complaints will the get from two footed drivers that say the car didn't accelerate and they got into an accident?

I think the practical reason for it is that every other car does the same thing.

 

[kolmstead]

Top speed in reverse is 25 mph. I checked this morning. At least until Turbo figures out how to get around the governor.

-Karl

 

[smkettner]

Top speed in reverse is 25 mph. I checked this morning. At least until Turbo figures out how to get around the governor.

-Karl

So can you crank the wheel, spin the front around and jam it into drive for a fast getaway manuver?

 

[TomT]

Actually, most automatic transmission cars have brake override. Toyota was one of the very few manufacturers that did not. This was what was partially responsible for the negative PR they received. All current Toyota vehicles do have this now, by the way. What I don't know because I have never tested it or seen it written anywhere is whether or not brake override is always active or just kicks in above a certain speed...

This almost sounds like a software bug or oversight to me as there is no practical reason to allow such behavior. In light of all the Toyota PR about them NOT having a brake override for the throttle and it contributing to the accelerator and floor mat runaway issues, you would think that Nissan would want to specifically prohibit such a situation in all of their vehicles.

You can power brake the car. I was a little surprised at this one as it would be trivial for the car to not apply power if you are on the brake. But you can pretty much apply full power while also on the brake. When I was doing testing, I didn't want to regen at all and with a little two foot driving and watching the power meter, you can keep the ball on the zero.

Then how many complaints will the get from two footed drivers that say the car didn't accelerate and they got into an accident?

I think the practical reason for it is that every other car does the same thing.

 

[GeekEV]

So can you crank the wheel, spin the front around and jam it into drive for a fast getaway manuver?

Ya know, this thread got me thinking about doing a J-Turn in the LEAF just the other day. My guess is no. In a normal car, this can be done because the motor only turns in one direction and reverse is nothing more than a gear change. My understanding on the LEAF is that the gearing is fixed (no transmission). Which means that switching from forward to reverse would actually have to slow down and reverse the spin of the electric motor. If the computer even let you try such a thing (which I believe someone tried by accident, and it doesn't) the end result would almost certainly turn the motor into shrapnel...

 

[palmermd]

if you perform it correctly the direction change in the drive wheels will occur from the direction change in the car, regardless of power application. The complication comes from the creep power applied to the motor. Does it creep in reverse as well as forward?

 

[GeekEV]

Good point. I suppose if you time it just right you'd be ok. But given as I've never done one in any car, I'm sure not about to try it in my LEAF.

 

[akohekohe]

That's pretty scary, that you might be able to dump 80 kW into the motor windings with the car power braked. I hope the motor cooling system is really robust! ....
-Karl

Karl, your post came right after mine about using power braking for starting on a steep hill as opposed to what the Nissan manual is advocating, which is essentially using power braking with the parking brake. So are you saying that it is a bad idea to brake with the left foot to keep the car from rolling back while starting up a steep hill? I really was hoping to get some opinions about whether this approach would be better than Nissan's parking brake method for starting on a steep hill.

 

[Smidge204]

Karl, your post came right after mine about using power braking for starting on a steep hill as opposed to what the Nissan manual is advocating, which is essentially using power braking with the parking brake. So are you saying that it is a bad idea to brake with the left foot to keep the car from rolling back while starting up a steep hill? I really was hoping to get some opinions about whether this approach would be better than Nissan's parking brake method for starting on a steep hill.

Parking brake release is automatic, so as soon as the vehicle starts to move even the slightest bit the brake is off. A human driver trying to do that with the hydraulic brakes would be putting power to the motor with full brakes for longer than the fraction of a second the parking brake is engaged.
=Smidge=

 

[turbo2ltr]

Karl, your post came right after mine about using power braking for starting on a steep hill as opposed to what the Nissan manual is advocating, which is essentially using power braking with the parking brake. So are you saying that it is a bad idea to brake with the left foot to keep the car from rolling back while starting up a steep hill? I really was hoping to get some opinions about whether this approach would be better than Nissan's parking brake method for starting on a steep hill.

Parking brake release is automatic, so as soon as the vehicle starts to move even the slightest bit the brake is off. A human driver trying to do that with the hydraulic brakes would be putting power to the motor with full brakes for longer than the fraction of a second the parking brake is engaged.
=Smidge=

I don't know if you've actually tried it, but it actually takes a second or two to release the parking brake after hitting the throttle using nissan's method. It's nowhere near instantaneous. Two footed braking would be much quicker. And the amount of power we are talking about is far less than doing 55mph so speed of releasing the brake is of little concern.

I tested the parking brake while moving thing more. Left 2ft skid marks all over the parking lot.. It basically applies the brake while beeping at you then releases it as soon as it's fully applied. Kinda weird. Locks the rears up for a half second.

 

[DaveinOlyWA]

I tested the parking brake while moving thing more. Left 2ft skid marks all over the parking lot.. It basically applies the brake while beeping at you then releases it as soon as it's fully applied. Kinda weird. Locks the rears up for a half second.

kinda weird, or maybe built in safety feature that kicks it out when it sensing an overheating condition?

 

[turbo2ltr]

I tested the parking brake while moving thing more. Left 2ft skid marks all over the parking lot.. It basically applies the brake while beeping at you then releases it as soon as it's fully applied. Kinda weird. Locks the rears up for a half second.

kinda weird, or maybe built in safety feature that kicks it out when it sensing an overheating condition?

I think it's simply because locking up the rear wheels and leaving them locked while moving puts a slight damper on handling... lol.

 

[garygid]

turbo...,
Not lock and release as you wrote earlier, just lock and leave locked?

 

[TomT]

The parking brake is driven by a motor operated mechanism that pulls and releases the cable that actually applies the parking brakes and is far from instantaneous. Thus, I'd think it would be a rather poor device to use for starting on hills... Heel and toe on the pedals or two feet would be a far better solution. I honestly don't know what motivated Nissan to eliminate the time tested manual parking brake lever and replace it with this scheme... It appears to have been a (expensive) solution in search of a problem...

Parking brake release is automatic, so as soon as the vehicle starts to move even the slightest bit the brake is off. A human driver trying to do that with the hydraulic brakes would be putting power to the motor with full brakes for longer than the fraction of a second the parking brake is engaged.
=Smidge=

 

[DaveinOlyWA]

turbo...,
Not lock and release as you wrote earlier, just lock and leave locked?

i think he is saying he locks it, the car unlocks it

 

[turbo2ltr]

If you pull it while moving, it will apply it all the way, then release it automatically even if you hold it. It will not stay applied until you are stopped.