This has probably already been hashed out ad nauseum already, but
I'm *way* behind on CMPG in general so I'll stick a couple of
cents onto this one. There are several points at which that
"forward lurch" or whatever you want to call it can be felt.
The obvious one is down around 7 mph when the transition from
regen to hydraulic happens -- everyone knows about that one, and
there are many complaints about "grabby brakes" out on the other
forums for which I offer a very simple explanation at
Another one happens as you're coming off a highway and dropping
down through 42 mph. For some reason the ICE burns a little bit
of fuel as it transitions to shutdown -- possibly to reduce fuel
pressure in the rail after the pump is turned off, or something.
That adds a tiny bit of somewhat bumpy torque to the drivetrain
for a few strokes, and then the thing finally shuts down. It
often feels like a gentle "forward surge".
The 10-15 mph thing might be explainable by the fact that before
the ICE is fully up to temp, there's a path change in the coolant
loops which causes it to run a little more even if you're already
in stage 4 and not running the A/C. Eventually it shuts down
again once the ECU decides that it's sufficiently warmed up *that*
part of the system too, and that could happen just about any time.
Any shutdown has a chance of creating a little torque against
the drivetrain, since the ICE is never disengaged and is in fact
rather closely coupled to the wheels, which a driver's "butt-
dyno" can easily misinterpret.
Then of course there's the regen-loss problem, where bumps
make the hybrid ECU go "ohMYgod that was a huge current
spike into the battery" and just gives up. I still don't
know exactly how to recover from that one, since there's
not a lot of leeway to fool around during most decelerations.
Instrumentation would *so* help some of these folks...
The guy who runs the "hybrid tech training" things I'm starting
to pitch in on thinks the Prius is *clunky*, and that the FEH is
so much smoother. I haven't driven the FEH yet, so I wouldn't
know, but I've certainly gotten used to all the little prius
quirks and don't fault Toyota at all for not 100% compensating
for every little torque blip.