Source: Chevy Bolt drag coefficient worse than Volt, Prius, Leaf | LeftLaneNews The electric MPV's blunt shape was a "disaster for aero," the project's lead designer, Stuart Norris, told Automotive News in a recent interview. The company's South Korean design studio eventually achieved a claimed drag coefficient of 0.32, only slightly better than the Subaru Forester. The figure is significantly higher than claimed specs for the Toyota Prius (Cd 0.24), Tesla Model S (Cd 0.24) and Tesla Model X (Cd 0.24), among others. Reducing drag coefficient and frontal area is particularly important for the first wave of mass-market EVs, allowing automakers to minimize battery costs and maximize driving range. The Tesla Model 3 is expected to be the Bolt's closest rival in terms of range an price. The Model 3 benefits from its sleek sedan shape, expected to widen the gap with a Cd of just 0.21. A company executive recently confirmed that its 215-mile range target with a smaller battery than the Bolt's 60-kWh pack. If accurate, this is not good. Bob Wilson
That is what I understand and the drag power curves are consistent with that value. One of my 'to do' tasks is to see if I can make an after-body form to reduce aerodynamic drag. I may also look at 'skirts'. Bob Wilson
That's the compromise of basing the Bolt off the Trax. GM could have gone with the Sonic/Aveo sedan to reduce the frontal area and get a tapered tail, but it wouldn't have the versatility of a hatchback, the battery would intrude more into the cabin and cargo areas, and the rear passengers would likely lose head room. Stepping up a size class to the Cruze platform would increase weight and cost. The Spark EV has a Cd of 0.326, and that is after aero tweaking the ICE model. Chevrolet Pressroom - United States - Spark EV The Trax has a reported one of 0.35. Without going to the extremes of the i3, like the huge and narrow wheels, a 0.32 Cd is likely the best possible wheel keeping the car normal looking. I like the i3 styling, but it is a love it or hate it of styling design, and carbon fiber aside, costs BMW more by not sharing a platform with other models.
Mind you, there's nothing stopping them from doing a liftback variant of the Sonic sedan specifically for this. After all, the Volt is essentially a liftback PHEV version of the Cruze sedan... The nasty thing about a high Cd on the Bolt is that it's worsened by the large frontal area of the tall form factor, and then EPA range is combined, not highway - so where range matters most, it'll underperform compared to more aerodynamic BEVs.
The rumors coming out around 2014 was that is was going to be a Sonic EV. Which could simply be due to the fact that the US didn't get the Trax until last year. I believe GM went with the Trax platform because the extra height gave them the space for the battery. I think they would have to raise the floor on the Sonic for it, and then you risk people feeling crowded by the ceiling. The Cruze wheelbase is about a half foot longer than the Sonic's and Trax's. That is a fair amount extra of length for getting an effective kammback without cutting out too much headroom in the rear.
The Bolt has a drag coefficient of 0.32, according to Norris. That’s an awful figure for an electric car, but in an attempt to improve air flow, several design elements and “tricks” were employed. Bolt Interior Those are described by Automotive News as follows: ” Norris’ design team incorporated a spoiler and sharply creased winglike canards along the tail edge of the car. Other tricks were underbody paneling, air dams and active grille shutters that close at certain speeds to streamline airflow. Designers even adjusted the radius of the A-pillar, modified the mirrors and fine-tuned tire coverage. “No fewer than six full-sized iterations of the Bolt underwent wind-tunnel testing.”
