2015 Toyota Prius Will Be Lighter, More Slippery

Frontal area is basically the frontal area of a vehicle that is first subject to air as you are moving forward. Think of it like Punching through a wall. The face of your fist meets most of the resistance wheras the sides of your fist only minimal resistance. A car can be streamlined but still have a large frontal area which increases total drag. To be truly aerodynamic a vehicle much have a low Cd and a frontal area with low square footage. This is why it is believed, by some that the GenIII is worse aerodynamically than the GenII because it has a slightly larger frontal area despite the lower Cd. So many things to consider huh?

Automotive aerodynamics - Wikipedia, the free encyclopedia


Automobile drag coefficient - Wikipedia, the free encyclopedia

 

Frontal Area is height x width. The key for drag is coeficient of drag(cd) x frontal area (A) or cd x H x W of the car. Lowering the car will lower both the Frontal Area and center of gravity, but may change the coefficient of drag. Sports cars will have a smaller frontal area than the prius, but higher coefficient of drag.

In a redesign decreasing frontal area is easier, but the ev1 had a cd of .19, the prius could drop a little from its 0.25, but not much. Active grill shutters can both lower drag and help warm up the engine faster.

You can lower the car. A side wind sees body Height x Length. Lowering the car won't affect the force of the wind, but it will be pushing a car with a lower center of gravity.

No one knows what the next generation batteries are going to be. The time table for the next prius is faster than testing would need to be to get one of these new batteries out there. I would not assume progress faster than 7%/year.

I have not seen panasonic announce progress like envia. This would be much less expensive than the nimh packs we expect in the next generation prius. If the greatest tech is in Envia's design, most of that was licensed from argone national labs. Panasonic can pay to license it if they get behind.
New Li-Ion Batteries Promise Less Cost, More Range | Autopia | Wired.com
Lower cost and weight are promised in the future, which is one reason the gen IV prius phv is rumored to have a bigger pack.

 

I want Toyota to play around with the ICE and computer systems on the next PHEV version. Maybe as a Prius PHEV Special Edition.

1. Use a 1.0L engine as weight saving.
2. Let the ICE be air cooled instead of water cooled for weight saving. Allowing the AC airflow be redirected to the airbox if above certain temperature. Like a Dakar rally car.
3. Saving the weight and space from ICE and cooling system to add 5 more kW of battery.
4. In the computer side, if 50% of battery SOC is seen, start the ICE on constant RPM regardless of car power requirement until 60% SOC is reached. And allow max power depending on the ICE temperature once below 35% SOC. I really want this feature as it allows "slow drain" of the battery. And good MPG for the ICE being in constant rpm.
5. Use a super cap like the Toyota hybrid race cars to protect the battery.
6. Allow the battery to drain a little more than the current PHEV Prius.

 

Not going to happen. It would need to be a turbo to have enough power, and marketing a 3cyl is tough. Compared to a 1..8L you shave less than 100lbs.

Even porsche went water cooled with years ago in the 911. Its simply much easier to hit efficiency and emissions goals,things and new prius will need.

If you are going big battery phev, then you might want to go down to the smaller ice for size. But I would expect the same ice in the liftback as the phv. I don't think 1L is toyota's plan though. A bigger battery seems to be planned for the phv though

Then you want lithium for bigger soc and higher power, which will also save weight. I'm sure the toyota engineers did the best they could with programing in our gen III. We simply don't have enough perameters to program it from the outside. The gen IV liftback is rumored to be nimh though, I hope that rumor is wrong.

The current ice has a fairly broad efficient range, but it could do a minimum efficient power to charge the battery when less is called for. This only makes sense in the phv model with a bigger battery pack. It would keep the ice off, if less than this efficient power was called for, but SOC was above a certain level.

The bms protects the battery. If super cap prices drop, a super cap can be used to capture more braking energy.

The phv soc is determined by that cars battery chemistry. The gen IV likely will have an improved batter which may have improved soc or capacity or both.

 

ag or Dipper: What's a "super cap"?

 

A super capacitor. They cost more than batteries, but can handle more power, and being solid state instead of chemical should not degrade.

 

Thats a thought, do we maintain any sort of wishlist of nice things to have for Prius Gen4 ? I am talking about aspects of the car we would like to see improved. We can of course talk/suggest hybrid tech improvements but I'd leave those to toyota, after-all they ARE the experts. But there are all the other aspects such as reduced cabin/road noise and other internal rattles, better rear visibility, LEDs wherever possible (including headlights) as standard, 16-inch wheel option, NS4-like styling etc.

Let's also make sure Toyota US, Europe and Japan sees our feedback and wishlist - I am sure they'd be interested. What do you think?

 

Another wish list:
Gen4 should be plug-in by default with small capacity (like current PiP or even smaller), optional should be an upgrade to 8 kWh or 12 kWh. If they are changing body they should calculate space according to different sized battery packs.
It should have a clutch to disconnect ICE when EV driving at high speed. I really don't understand why the PiP battery pack is so limited when you could have 60 kW EV power. I know that you can not have 60 kW EV boost with ICE because of the MG1 feeding MG2 but with pure EV you could have that power today.

 

They need to size the car to the largest battery capacity they put into the car. Bigger batteries might mean different suspension components though to handle higher weight.

I would expect an uptick capacity and power. The clutch is only needed at high speeds, at lower speeds the power the battery can provide is limited by the battery pack. I would like a clutch so that the phv could be EV at all speeds, but 62 mph is not that bad if its mostly on battery. By the time the gen IV comes out, I expect an improved battery with higher power, but not the clutch.

 

There's a bit of irony in that here we are - getting ready to enter the 20-teens of this century - and yet production cars that you can buy, never surpassed the drag coefficiency delivered last century - the 1990's - GenI Insight. Ok, it was only a 2 seater. Being narrow, its frontal area was in the neighborhood of only 5sq feet. But it was aluminum. Due to it falling under old EPA foumulas, it was the only car to be EPA rated in the 70mpg's. Bottom line - to date - we haven't touched that kind of low drag in a production car you could buy. There's only so much you can do, without going to aluminum - and/or 3cyl ICE - an/or dropping passenger capacity to only 2 people - or jacking the price up to the level of the Tesla model S. Practicality always wins over specs.

 

Having 2 seats doesn't reduce drag, it reduces weight. The tesla S is more slippery than the insight, but the gen I insight had a much smaller frontal area. Being a 2+2 instead of a 5 seater lets you have similar dimensions. Aerodynamics can't make progress, they don't change with computers, only design choices. Active grill shutters, removing side mirrors, rear wheel fairings all can decrease it.

Again aluminum is about weight. You can drop drag a little more like aptera by using carbon fiber, as this can change shape, but the main advantage of cf is weight. Its fairly easy to get insight type numbers on drag, but hard to sell the cars.

 

Anyone know how to maintain a sticky thread in this forum? I am thinking we should have a list of features listed with a rank (or vote) alongside which represnts how many of us like that feature. Any feature with less than (say) 10 votes will get removed eventually. Perhaps voting buttons would be the best way forward, perhaps coupled with checking user's IP so that one individual doesn't do multiple votes by mistake.

 

How about a high-speed-deployable inflatable boat tail?

 

After looking at Hyundai Sonata Hybrid and Ford's C-Max Hybrid, the 4th gen Prius is going to needs to do atleast 60 mph in electric mode only and to do that the 4th Gen Prius is going to need to switch to a Li-ion Battery Pack.
No combined amount of weight savings or aerodynamics changes is going to get the next gen of Prius there except a HV Lithium-based battery pack.

 

There is one, in the Prius Gen III Main Forum:
Summary of proposed improvements for future versions of Prius | PriusChat
It does most of what you want except the rank by vote.