Gen 4 Staff Manual (In Japanese) =/ Specs/Design/Other Info

"In addition, a fixed gear second gearset is implemented: the drive motor (MG2) is linked to the front wheel transaxle by means of a second planetary gearset, thereby making it possible to increase the power density of the MG2. This allows for a motor with less torque but higher power (and higher maximum rotary speed)"

This sounds exactly like the 3rd-gen HSD, not the 4th-gen. The 4th gen has one planetary gearset that is at the heart of the HSD. The 3rd gen has one planetary gearset at the heart of the HSD, and another to connect/reduce the MG2 to the final drive... exactly as described for the RX400h here.

And you can see in this video:

The engine front-and center (marked THS II + E-Four) is the RX400h engine. You can see that the engine crankshaft/MG1/MG2 are all coaxial. Close-up detail is seen at the 1:13 mark.

 

See what your saying editing previous post. Wasn't considering the actual coaxial production.

Looking at block diagram pg 19 of ref. If you change from ring1 (Ice/mg1) to carrier2 (mg2/output) and instead connect ring1 to ring2 via the counter gear and allow ring2 to rotate then Ice/mg1 and mg2 are parallel and the second gear set can also functions as a reduction gear. Anyway parallel, easier seen in the Ford diagram, gets us away from the mg1 over speed problem and having to friction spin the Ice to prevent it No? Wonder how many % friction that's worth. Higher EV speed as a result too?

 

Does this manual show fuel tank capacity for new Prius?

 

38L for Eco, 45L for models above

 

The Gen4 Staff Manual says the JP E grade has 38 liters and the other JP grade has 43 liters.

Ken@Japan

 

The Gen4 Staff Manual says the Cd value is 0.24.

Ken@Japan

 

Thanks! So the gains due aero are marginal!

 

Really? What the change in frontal area?

 

The Gen4 Staff Manual says the JC08 fuel economy numbers are...
E grade: 40.0 km/L IW=1310kg and below
S grade: 37.0 km/L IW=above 1310kg (2WD) 35.0 km/L (4WD)
A grade: 37.0 km/L IW=above 1310kg (2WD) 35.0 km/L (4WD)

The Gen3 actual JC08 fuel economy numbers are...
L grade: 32.6 km/L IW=1310kg and below
S grade: 30.4 km/L IW=above 1310kg
G grade: 30.4 km/L IW=above 1310kg
(note: IW stands for inertia weight of chassis dynamo load on fuel economy testing.)

The Gen3 Prius EPA unadjusted fuel economy number is 71 mpg ( 30.2 km/L).
source: http://www3.epa.gov/fueleconomy/fetrends/1975-2014/420r14023a.pdf#page=17

Ken@Japan

 

0.48% reduction in frontal area, marginal?

 

The Gen4 Staff Manual says the body size is...

length: 4540mm +60mm vs Gen3
width: 1760mm +15mm
height: 1470mm -20mm
wheel base: 2700mm no change

Ken@Japan

 

So on JC08 Gen4 is 21.7% better than Gen3? Since JC08 is centered around city cycle, we can expect similar showings on EPA city. Even if highway rating will go up by modest 5% (4% engine efficiency and 2% due to aerodrag) we can expect close to 14% overall rating improvement.

62 city/ 50 hwy

57MPG combined??

 

Total drag = (Cd) x (Frontal Area of Car)

Anyone want to calculate the percent decrease in drag?

 

Jay wants..

my back of the napkin calculations show 4% reduction in Cd and 0.5% reduction in frontal area, so 4.5%?

Keep in mind that EPA is still testing at 55MPH (or rather use in approximation formula), and at that speed less then 60% of drag is generated by aero. 40% tires, and they include A/C and acceleration/deceleration into account. The later hasn't change b/c the weight stayed the same

 

You have missed ...
20% less friction on the transaxle
20% less loss on the PCU

Ken@Japan

 

My (trivial I know) beef: there's one engine in there. There's not, for example, an internal and an external combustion engine. And I'm not sure what's the alternative to a "combustion" engine. In short: a fluffed-up, three word description, purely so we can turn it into an esoteric, pretentious acronym, of something that used to be just fine with one word: engine. Terse, succinct, what's not to like.

Oy, ranting.

(Oh crap, managed to quote myself.)

 

I calculate a 7% decrease in total drag with the Gen 4 Prius with the Cd of 0.24 in the Japanese staff manual:

Gen 3: 0.25 x 6.2 sq. ft = 1.55
Gen 4: 0.24 x 6.0 sq. ft = 1.44

 

I've used the "conservative" numbers.

I agree with you if 57MPG confirmed most of the gains come from these, not from engine and aerodrag. And that should have the biggest impact on city cycle.

 

I do not see frontal area change by that much -0.2sq ft.

 

Will have to double check the frontal area number, but that was the guess:

Aerodynamics/Drag Coefficient | PriusChat