Hello, my name is John Kelly, and this is the WeberAuto YouTube channel. this is a second in
the series of videos on the evolution of the Toyota Prius hybrid transaxle as you can see
sitting behind me here I have a second generation Toyota Prius this model was available in the model
years 2004 through 2009 which was six model years which interestingly enough was the
same number of years the first-generation Prius was available from 1998 through 2003 however the
first-generation Prius was only available in the United States between the model years of 2001 and
2003 yet it was still a six year old model by time the end of the 2003 model year came around
the second generation Prius that we have here is greatly improved over the first generation
Prius this particular model here is a 2004 so it's the first model year of the second
generation Prius if we were to look at the back of this vehicle it has a badge that reads Hybrid
Synergy Drive and the Toyota hybrid synergy drive system was a concept that aimed for a
better balance between the power of the transaxle and the power of the engine and the switch over
there they made great improvements in the inverter converters assembly made changes in the battery
made significant changes in the transaxle that increased the power of the transaxle
the engine power is pretty much the same as it was before it's the same engine they've made
some small adjustments to the variable valve timing but other than that it was the same
engine so the majority of the changes that made the improvements in the second generation Prius
were due to the control of the transaxle and the transaxle in this car is the P112 hybrid
electric transaxle so let's go take a look at the major changes and the differences in the
P112 transaxle if you recall from the P111 transaxle video the MG1 rotor turns
the power split device Sun gear one of the three parts of our planetary gearset we've
got a Sun gear a planet carrier right here that turns the same speed as the engine and
then MG2 back here that drives the ring gear that turns the same speed are not the same
speed but it when it moves it makes the tires move alright so let's put our flywheel up inside
there we go and then our planet carrier
splines to the splines to the flywheel so as the flywheel and clutch rotate it
turns the planet carrier and then we've got the ring gear right here the ring gear that
MG2 drives make sure I've got the bearings in place there notice it slots right down
into the chain drive sprocket, it's got some splines down inside there that'll spline right
to the MG2 rotor so let's bring that rotor over here with its V configuration magnets
and there we go so just like the P111 transaxle in the first generation Prius we have an inline
axis hybrid drive system here both electric motors MG2 and MG1 are in line with the
centerline of the engine crankshaft MG2 also referred to as a traction motor is what moves
the vehicle down the road it's always going to rotate if the vehicle is moving and the vehicle
cannot move unless we rotate MG2 MG1 is both the starter motor notice if I rotate MG1 it causes
the flywheel here to rotate and it also when the engine is running notice the flywheel turns MG1
and makes it be a generator and it's got a 2.6 to 1 gear ratio there to cause that to rotate
faster than the engine we have as we mentioned before 50 kilowatts of power 68 horsepower 400
Newton meters of torque which is 295 foot-pounds of torque which is pretty impressive the forward
rotation of the vehicle is in this direction and it should take 4.11 three turns of MG2
to get one turn of our final drive gear here so let's try it out watch the stickers here
there's one two three four and just a tenth more 4.13 to get one rotation
of the final drive just like on the P111 the engine flywheel is not connected to MG2 the
engine does not make the vehicle move down the road MG1 does not make the vehicle move down
the road it's the combination of controlling the speed of MG1 and the engine that allows through
the planetary gearset the engine to contribute torque to help rotate the MG2 motor notice if I
hold MG1 still and turn the flywheel mg turned or MG2 also rotates if I let MG1 slip a little bit
it doesn't turn it as much so by controlling the rotational speed of MG1 with the engine running
we can control how much torque the engine delivers to MG2 to help power the vehicle down the road MG1
is a generator and when the high-voltage battery which on the second generation Prius is at 201.6
volts which is 72 volts lower they took out 10 of those flat-pack battery cells 7.2 volts
each and drop the voltage down to 201.6 volts when that battery voltage starts to get low which it's
bumped up to the 500 volts to help drive MG2 the engine can spin MG1 faster or slower depending on
to deliver to MG2 and also when he left over go back to the battery to help charge the 201.6 volt
battery so pretty much the exact same operation just a more powerful MG2 with a different gear ratio
that gives us more turns of the rotor MG2 rotor to one turn of the tires which gives us more torque
multiplication gives you more acceleration gives you more torque and a higher speed up to 10,000
rpm if we need to really generate some power we can crank the engine speed higher or lower
depending on the rotational speed of MG2 to get the power that we need to move the vehicle down
the road they really did a lot to make sure that you did not go into the turtle mode the
first generation Prius had a turtle mode where a dash light of a turtle would come on that would
indicate that you're out of battery power and that it was all the engine turning mg one could do to
generate power to run MG2 that rarely happened unless you liked those magazine articles I talked
about it the first of this video are driving up a super steep long mountain pass but that turtle
light was gone in the second generation Prius higher voltages higher power stronger magnets
stronger higher torque motors the overall height of this transaxle is the same as the P111so those
are equal but the weight has been dropped by looks like eight and a half pounds this and only
weighs 236 pounds versus the 244 and a half that the mg or I'm sorry that the P111Wade okay this
has been a review of the overall operation of the second generation Prius P112 transaxle the second
generation Prius has quite a following it was sold for six model years and has a pretty good
reputation of being a good reliable car battery life I've helped a couple of people that I know
change batteries in theirs they were around a hundred and sixty hundred and seventy thousand
miles and they were both 1011 years old that's here in Utah with our hot and cold climate I don't
know how they are holding up in other parts of the country or the world but it seems to be a really
good transaxle design and nice hybrid system but it gets even better in the next episode when we
take a look at the third generation Prius transaxle the p4 can we take it to a much
higher level of power and efficiency and I look forward to reviewing that transaction with you
also alright there's one more thing I need to show you that I forgot to show you in the P111video
and that's in regard to the shifter positions for these Prius transaxles all of the shifters for all
four generations of the Prius have a B position so there's Park there's reverse there's neutral, there's
drive so what happens in the drive position the D position on these transaxles is when you slow down
when you decelerate MG2 which if you recall drives the vehicle is a set of spinning magnets it eight
rows of spinning magnets inside of the stator assembly which is three coils of wire and that
induces current into these coils of wire which it physically slows down the rotor from spinning
because the first occurrence into the stator create counter electro-motive force that actually
creates a repelling magnetic field to the rotor to the rotation of the rotor so it's physically
slowed it down it makes it harder to turn in the be positioned the braking position both
the MG2 and the MG1 rotors go into regenerative braking so apparently in the drive position it's
just MG2 that does regenerative braking in the B position you've got two electric motors doing a
regenerative braking at the same time to help slow you down but of course MG1 is maybe half the size
or less than MG2 so it's not going to be a huge difference but it does make a difference when you
slow down or it can make a difference it really just depends on the state of charge of the high
voltage battery if the high voltage battery is already charged then there's not going to be a lot
of regenerative braking going on because there's no place to put that a lot extra electrical energy
but if the high voltage battery is in need of a charge then of course there's some place to
put it now if you're still going down a mountain pass and you have the regenerative braking going
on either on one or both motors in a D or the B positions then what happens instead is we use that
current to rotate the mg one rotor to spin the crankshaft of the engine so we dissipate that
electrical energy by cranking the engine the fuel system is disabled when that happens and so it
just cranks the engine won't start but it allows that electrical energy to be dissipated
you can't just spin a magnet inside of a coil of wire and not have the electrical power go
somewhere it is either has to go to the battery or be used some other way and so that's what
happens here in the B position two motors in B one motor in D by the way if you put it in neutral and
coast there is no regenerative braking that that takes place at that time it will not charge the
battery will not regenerate either I'm not sure electrically what happens because you're still
spinning a set of magnets inside of a coil of wire it's possible that the resistance has just turned
up really high in the controllers for the stator and it just creates extra heat instead of charging
the battery or cranking the engine over but neutral position does not give you any charging