The recall had fixed this problem when the friction brakes are applied, but not for 100% regen mode. If you slowing down at regen and hit pothole, Prius still surges forward for a few feet. Does not happen when friction brakes are on. this is on early 2010 which was affected by recall.
As stated dozens of times in other threads, this issue is a fundamental result of combining two braking systems. With regenerative braking the Prius brakes with only the front wheels. Given the differential connecting the front wheels to the braking generator (MG2), as soon as one front tire loses traction regenerative braking is no longer effective. Loss of braking effort means a reduction in deceleration, which produces the sensation you describe as a surge. In physics this is called "jerk" and is the rate of change of acceleration over time. It is the third derivative of motion. The only way to prevent this "surge" is to have the Prius anticipate the loss of braking action, which is a physical impossibility. You can complain as much and as loudly as you want, but it can't be made to go away unless we move away from the current braking system. It can't be fixed with a software patch or modification of the hardware unless you are willing to give up on regeneration. Tom
Tom, IMHO it is not quite the case b/c the surge continues after the "slipping" wheel comes in contact. After running over wet manhole the effect maintained for at least 2-3 lengths.
That's because the braking transition is in progress. The initial loss of traction forces the transition, not the length of the loss. The software update reduced the time needed to transition to friction braking, but it still takes a finite amount of time. Only an anticipation system could eliminate the interval by initiating friction braking before the loss of traction. Even then it would probably be a little rough, as the friction from brakes varies with a number of environmental factors. Tom
Not sure that you have to anticipate to correct for it; you could just apply friction brakes as soon as you detect front wheel slip (which usually takes milliseconds). Either way this probably should be reported to Toyota.
This is how it is presently done. Friction brakes are applied as soon as slippage is detected. Unfortunately people are even better at detecting a change in acceleration and interpret it as a surge. Toyota is very aware of this issue, as it is inherent in the design. Tom
There is no surge, grasshopper. It's a -release- of braking for a fraction of a second as the car transitions to full hydraulic brakes. The problem is most people also release the brake pedal as they think that will help (subconsciously). If you press harder on the pedal you WILL stop. Quickly! But this is old, has been known since or even before the GII, and has been discussed ad-nausium. Get over it. Learn to drive your car.
And if you do ever have to "slam on the brakes" for any reason....quickly doesn't seem to do justice to how quickly the car actually stops. Holy cow, I almost ate the steering wheel the one time I had to do it (darn deer jumping across the road in front of me!). It took a few minutes for my pulse to steady back down that night.
Maybe the next feature should be "brake modes" where the driver can choose how hard & fast the friction brakes are applied. OP may want the "drop anchor & stop on a dime" mode.
If this is still causing you consternation, then sell the vehicle and buy something else. Several other manufacturers have or will have hybrids this year. The important thing is that you feel happy with your vehicle.
out of curiosity: why so much hostility?? why is it you feel necessary to diss on someone who pointed out an issue? it is not like someone told your bride is fat and has only one leg
As a newbie here, I, for one, appreciate these discussions, and do not appreciate attempts to quash them. A few days I thought I experienced something I perceived as a brief acceleration after hitting a bump... now I know what it was.
All the recall does is shorten the regen to friction transition time to the Gen II's level. It used to be too long, freaking out too many people. The Gen II's transition (as well as the Gen III post-recall) is short enough to be comfortable for the vast majority of the population. Nothing to report to Toyota.
It happens to me whenever I go over a bump. The regen does not recover until a full stop. I have complained endlessly to no avail. I'm waiting until I have an accident because of this, then Toyota will have their ass sued.
Considering that this happens only with regen braking, which operates only with light to moderate brake force, the occurrence of this dropout should stand as proof that you did not apply hard braking. How will proof that the driver failed to apply full braking force play out in a lawsuit?
