Help calm my nerves with this issue

I travel on a steep downhill grade to go to "town" about 30 miles away and have never experienced a slow down (actually have to gear down) with the exception of areas on this grade that appear to continue downward physically but actually are leveling off and have a slight incline. In these areas the car will slow down after going rapidly downhill for a while. Hopefully that is what you are experiencing but if not, ouch! Get that vehicle into the dealership.

 

Every Prius will slow down downhill if you don't touch the gas pedal at all. Reason is simple. Your battery is recharging and that is what slows the car down. My solution to this problem is simple. Just be very gentle when pressing gas pedal and try to find the sweet spot where the car is using only gravity to go coast. In my case this works very well and car usually speeds up.
If your car slows down going downhill in neutral than you should definitely check your E brake. Sometimes emergency brake stays engaged but not completely. Play with it several times and take it out for a spin.
Hope that fixes your problem.

 

That's that regen thing. You'll have to keep your foot on the gas pedal enough to keep it out of regen and not into the accelleration part of the graph. You should see the mpgs go up, or you could watch your energy management screen to see it.

 

Correct me if I'm wrong, but I think you have to hold the shifter in the neutal position for several seconds before it goes into neutral. At least that is true on my regular Gen II Prius, might be different with the floor shifter in the "c".

 

Its different lol

In the C it is like a normal car shifter. Once you shift, your shifted.

Unless your shifty then your never shifted, your always shifting.

 

What Revan said. You shift into neutral and you are in neutral immediately, at least the display says so and the car behaves so. I do the neutral shift trick every day, there are two places on my drive where if the lights are correct, I can go a good two miles without losing speed.

 

I never reach highway speeds in my Vancouver commute, but I did get some highway experience on a recent road trip to Seattle. Remember everyone, the Prius C is less aerodynamic at highway speeds than the liftback. Wind and rolling resistance is non-negligible. I experienced just as the OP that in the 60-70 MPH range, a gentle downhill does not impart enough energy to counteract resistance when it's in neutral-equivalent (Eco screen, no blue or green showing). There were some much more significant declines though along the route, and yes, at a certain grade it does start to accelerate downhill. If you used to drive a more aerodynamic car, the grade required to accelerate downhill may have been gentler. Also if you used to drive a *heavier* car, the same might be true - if two vehicles are facing the same force of wind resistance at the same velocity, the heavier one will lose a smaller percentage of its kinetic energy.

My usual commute I'm mostly at 40-60 km/h speeds (yes, different unit) when I'm moving at all. There is one part of my commute where it's a gentle downhill, then gradually gets steeper. Even at 60 km/h, you do need a bit more than a gentle downhill to accelerate in neutral-equivalent. It's nothing to panic about, just simple physics.

 

Check your tire pressure, I''m using 41psi and getting way better mileage, car slides like a piece of ice on the floor.

 

That's why I value that MFD INFO screen on the Gen II. It really does assist in figuring out pedal pressure, hills, regen, warp stealth etc. The INFO display, while better than the III, in my wifes HyCam is a great aid in learning the feel of the car as you drive. If I could just get her to listen, look and figure it out. Ms. LeadFoot! I can now just by feel know what mode I am in, and what I need to do to max the MPG!

 

yes it is reasonable for the car to slow down. I think it is designed so that "foot off the gas" is a signal to the computer that you want to reduce speed. You have to remember that on a Hybrid car the gas pedal is really a computer input device and is NOT directly connected to the engine.

So this is a "bonus". On the Prius you have some extra margin of control that is lacking on most cars. The gas pedal angle is calibrated differently so that the "don't change speed" (or "zero acceleration") position is slightly forward. The computer does not care if you are on a hill, when you take your foot off the gas the computer will slow the car and try and re-generate some power and re-charge the battery. That is just how it works.

If you want to continue at 65 MPH keep the foot on the gas and trust the computer to control the engine and motors based on the grade of the road. If the hill is steep enough the computer will completely shut off the gas engine but on most freeway type hills you need engine power to maintain 65MPH evengoing down hill.

The gas pedal is NOT a throttle. It is an acceleration command input device. It is calibrated such that "foot off" commands a slight negative acceleration and slightly depressed commands zero. Acceleration here is TOTAL of kinetic and gravity. Yes going up or down a hill at a constant speed is "acceleration". Remember that gravity is 9.8 meters per second squared.

As I look at how my new Prius C was designed and how it works. I can see that Toyota let the engineers have their way with this car

 

Cars going downhill are converting potenial energy to kinetic, some of which will be dissipated by aerodynamic drag, some by the car's moving parts, and some, possibly, by regeneration. If there is something defective that is slowingthe care by dissipating significantly more energy than it should it will be getting hot! If nothing is hot, probably the hill isn't steep enough.

Richard

 

So I'm reading it is OK to put the C in neutral while moving??????

 

I don't think it is ok. Maybe briefly but not for long and not on a regular basis. If it was ok then this would be a towable car, and its not, according to Toyota.
dan

 

I don't suggest doing it on a regular basis but you can do it. In fact you should practice all of the basic methods of shutting your car down in the event your throttle is stuck wide open. Putting the car in neutral is one of them.

The only danger to the car is putting it in neutral below 42mph and allowing the car to speed up above 42mph (46mph in other versions). The battery will not charge in neutral so that is also something to consider.

 

Wait a second... If I am approaching a downhill slope, why is it not safe to slip the car into neutral and let it coast a ways? Not a hill, mind you, I'm just talking about an ever so slight slope that would keep your speed steady or only increase it by a few miles. When you're ready to brake, brake. I ask because there are two stretches of road I drive on regularly, and if the traffic and lights allow, I do this very thing. Does not seem to have harmed the car thus far.

 

It all depends on at what speed you shift to neutral and what speed you plan to reach while still in neutral.

Regenerative braking | PriusChat

 

The concern is exceeding the threshold speed at which the ICE always automatically comes on - even if not consuming any fuel - to prevent overspeed of MG1. Try visiting Toyota Prius - Power Split Device and playing with the sliders. Leave the ICE at 0 RPM and pull the MG2 silder up until the connecting line turns red because MG1 has already hit its RPM limit. In the real world, in D, the ICE will start at that point. If you pull the ICE slider up to 1000 rpm you'll see suddenly MG1 has a lot more breathing space without exceeding its limit. In N, it appears to be that the ICE cannot start if it was not already started, hence the concern about not entering N below this speed threshold and then - through the force of gravity - speed increasing above this threshold.

The relationship/limits are slightly different in different Prii. For what it's worth, in my c this forced entry of the ICE occurs at a point between 76 and 77 km/h (47.2 and 47.8 mph) as indiciated on the dash.

I can't tell you anything from personal experience as I refuse to use N - I glide by backing off the pedal and then depressing it slightly to make the HSI indicate no blue or green bar. It's partly a personal choice, it's partly that driving in Neutral is illegal in Australia (and a new driver doing it on a driving test will be failed, regardless of how well they did everything else). It's considered not having proper control of a vehicle here. For me it's that I want normal pedal response at all times and I like being ready to fine tune my speed with movements of my foot, as the road and traffic require.

Not saying Neutral is wrong, but I choose not to use it. I have it in the back of my mind if the mythical "unintended accelleration" ever comes up.

 

that tool seems to be for the GEN 2 system. I think the GEN 3 motors are built to go up to 12,000 rpm.

 

It's illegal in many US states also, although I don't know how they would catch you doing it. But I agree with you on the control issue - one concern would be what if an emergency arises while you're coasting and you suddenly need to accelerate? The instinct would be to immediately step on the accelerator, but if you're in Neutral you'd first have to think about putting the car back into Drive.

 

I believe it is, but it's far and away the best demonstration of the concept available. The c is meant to have an enhanced version of the Gen II system, but it seems it draws many likenesses from both worlds... then does some things its own way!