Any engineers here care to speculate on this? (or just regular non-engineers like myself) The generation 4 Prius by all accounts will have a reduced frontal cross-sectional area with a 20 mm decrease in height (1,470 mm) despite a 15 mm increase in width (1,760 mm). Also the rear end of the vehicle appears to have progressed towards a more boat-tail aerodynamic shape consistent with decreased drag turbulence. The increased engine thermal efficiency should buy at least a few mpgs. But guessing a few more mpgs will be squeezed out by this aerodynamic change alone. Should help highway mpgs.
Engine "over 40% efficiency" alone should kick highway rating from 48 to "over" 50 MPG. A little can be gained from "transmission" losses and the rest only from rolling resistance (weight) and aero drag. We will see when we get the final number.
Drag is established as cdA, the A went down 0.5%, the cd if it went down didn't move down much from the look of the car. My guess is we have moved from cdA = 6.2 square feet to 6 square feet, rolling resistance likely fell more, and the engine efficiency is rumored at 40% versus 38%. If epa highway is 60% drag, 40% rolling resistance and rolling resistance dropped 10% (could do with different tire materials and the weight reduction) we may get 53 mpg highway from 48 mpg. Epa 53 hwy/ 59 city would be 56 mpg combined, so I'm guessing 52 mpg hwy as they have been saying 10% and that would likely bring us to 55 mpg combined.
Well they certainly didn't change the back end to improve aesthetics, so hoping some significant cd gains there.
They did mention up to 18% improvement on NEDC. My bet: 58 city 55 highway with the most efficient model.
"Toyota says the car has a world-class coefficient of drag (Cd) so expect a 0.23 to 0.24 result helping the higher highway speed efficiency while lowering noise." Even More on the 2016 Fourth Generation Toyota Prius - CleanMPG Forums
My guess: Cd improves from 0.25 to 0.23. Apparently the underbody will be more slippery too with the new TGNA.
I agree based on profile as well as statements issued, it is more likely 0.23 or at worse 0.24. I assume there is some drop in frontal area too. Even if frontal area is same, lowered height will improve under-body airflow and reduce drag. Adding to the reduced drag, improved engine efficiency >40% (seem like 42% based on some statements) impacts highway mileage more than local. So my assumption would be more improvement in highway number compared to local. I am guessing high-way number to be more like 54, and local around 56 for non-Eco models. My guess is Eco models will have grill shutters, smaller tires, no spare, probably lithium battery providing better overall local and highway mileage(May be around 60 local and 56/57 highway.
Now that's were things start to get interesting ! Toyota said at reveal that it would have world's best cd value ! Since Mercedes has allready achieved 0.22 on one of their vehicles (I have to go and look which it was ) Toyota either lied about it ,didn't do their homework or the manual is simply wrong ! So cd on the new Prius should be at least 0.22 or even lower! !
It all depends on which version is tested ! They should have testet the CLA Blue Efficiency Edition which has Automatik grill shutters and so on . Automatic grill shutters aren't available in the US for the CLA 180 .
But the Model S and the new Sonata hybrid both have 0.24 cd, which leaves the gen4 as 'world's best among others'. Its smaller size and frontal area should mean the cda should be lower.
Yes it should be and I believe it will ! I somehow have the feeling not all the specs in that dammed manual are correct ! Would be foolish anyway giving away all the cars specs before they drop the bombshell at Tokyo Motor Show !
Gen III prius and tesla S both have cdA of 6.2 sq feet in the car and driver wind tunnel. If the prius fell to 0.24 then using its 0.995 frontal area compared to gen III, would get 5.9 sq feet around the 6 that I guessed from the shape. If rolling resistance fell proportionally then highway mpg would rise to 50 mpg from 48 mpg. Other improvements need to have come from the engine, electronics, and motors. My guess is 53 mpg highway, but we will have to wait for official numbers.
