More Volt Specifics Revealed in Development Drive.
Wayne Gerdes - CleanMPG
- May 6, 2010
The Volt is just months from launch and the details are getting better all the time
Larry Nitz, General Motors electric and hybrid powertrain engineering executive director, provided an update Tuesday on the Chevrolet Volt, during a development drive on the West Coast.
A fleet of Volts has driven extensively in California from San Francisco to Lake Tahoe to Death Valley, Big Bear and Los Angeles to test the electric vehicle with extended range capability in a range of driving scenarios, all types of terrains and in a variety of altitudes. During the update, Nitz discussed the Volt's three driving modes - Normal, Sport and Mountain - as well as its two climatic modes - Eco and Comfort. He also addressed the teams' assessment of the three T's that most impact range and fuel efficiency - technique, terrain and temperature.
Teams are out testing in a number of different locations around the country as we tighten up the calibration.
I have thoroughly enjoyed my time in the Volt…
I hardly even notice it is an EV.
Full tractive effort with a full pack... pure electrical so it is an electric car…
We are meeting our targets…
As we bring on high accessory loads, we are meeting our goals for EV distances.
3T's - Technique, Terrain and Temperature will determine if you get a pure electric drive.
Even when the engine is on, most people will not notice.
The cluster will change but the character of the car is predominantly electric and it feels that way.
The Volt is a pleasure to drive but the public is remarkably aware of the vehicle. People notice it. We have 10 Volts in this ride. Pulling in to any location to swap cars or move between the cars. It is an event in whatever parking lot.
Q1. Meeting all your targets? What is keeping you up at night and keeping on the road to test it out?
A1: This is a complicated vehicle and a lot of diagnostics. Some regulated and some our own. Getting all of those systems to interact together seamlessly. Having the car actually drive well is sometimes the easy part. We spend a lot of time in the lab and a lot of time on the road. We have to submit our documentation to both CARB and the EPA regarding how the Volt works and operates. The customer should not see that. Just the great drive quality.
Q2: Calibration and calibrating the engagement of the combustion engine when it comes on. You have seen every altitude and every kind of load. What calibration iteration is needed for smoothing of the transition to the engine?
A2: The Volt is a car that may be your only transportation. We drive around LA, commuter routes and what many customers will want to do is drive out on vacation. We do test specific areas that we think will be challenging and normal. Because we have 10 vehicles on the trip, we can set them up in different ways and compare them in real time.
The engine engagements, engine starting, transition from pure EV to engine on, its good enough and most people will not know it is happening. The engine can go on and off during this extended range operation. We want it to be quiet and do not want a large delta between engine on or engine off. The acoustical noise is very good. We set it up to be different then a lot of other hybrids on the road.
We are going to make it feel like an EV even when the car is running in charge sustaining mode under normal conditions.
Q3: Where would you classify the current calibration of the Volt today?
A3: We have different levels internally. We are officially at 99% but not quite done. A lot of attributes the way the vehicle drives will not change from this point. We do not what to find fault where there is no fault.
Q4: What have you done to reduce engine NVH under hard acceleration or heavy load?
A4: The engine is a downsized engine. This engine makes about 55 kW of power peak but the drive system is 110 kW. Even under WOT or full power conditions, we are pulling from the battery to make full power. As you pull the battery down with more aggressive driving like going up a mountain grade, we have to make sure it drives smoothly without high engine speed as much as we can avoid it. When climbing you will need a higher average power and higher average RPM's will be needed. We have worked on acoustical feature and mountain mode. When you have a substantially downsized motor, we keep a modest reserve in the battery for normal drives. Mortmain passes may call for more than the 55 kW engine. Mountain mode basically a simple function that sets a larger reserve capacity from the battery. (Higher SoC allowed)
We ran up to Big Bear which is about 6,500'. Some cars in mountain mode and some in standard mode and compared acoustics... You have a bigger reserve to pull from. If you are in CS mode, it will elevate the engine power level to recharge the battery to a higher set point SoC.
Q5: Focusing on terrain issue. Is this driving represent on a longer range driving?
A5: Now that we are at the top of the mountain with a full charge. I want to brake the vehicle and have it slow down and I cannot put any more energy into the battery. If the battery is in CS level, I can fill the battery up. But if it were full, I have to dissipate power and we test that. We are at the point where the overall driving is what we are after. Not one particular aspect...
I was in a Super LA gridlock traffic. Stopped and then 60 and then stopped again. While driving in this, EV range is coming down and down and down. If I were in an EV, I would not be comfortable.
This is not focusing specifically on terrain but as part of the mix. We also focus on technique and temperature. Temperature, Terrain and Technique.
Q6: Will Mountain Mode be standard?
A6: Yes. MPG in CS mode is off-limits for today's discussion.
Q7: How do you get people to plan ahead which is something I do not do. Second Question but how much range varies with the Terrain, temperature and terrain? 20 to 30, 30 to 40 miles?
A7: We want our customers to be thrilled with and not bothered with. Given that these grades are substantial. There are circumstances when the vehicle’s performance will be degraded. The whole nature of the Volt is an interactive experience. Looking at a mode of operation with a mountain ahead, we think that most people will be able to click it into mountain mode before they get to the big grade. For people that are more a combination of technique and terrain, they will know how to do it.
There are few grades in the country like Denver to Eisenhower Pass where the vehicles needs to be higher than 55 kW so we want to offer that feature. Not that it will not be able to go up a grade but it will slow down a little bit. Mountain mode will be very helpful for customers that will want to combine technique with terrain.
Regarding range variation. It will vary quite a bit in any electrified vehicles. We have made it very efficient and we have tried to make it interactive with customers. We Eco mode. Our climate control has two auto modes. Eco and comfort modes. Comfort is 99% drivable that wants to be very comfortable. Eco mode is comfortable for me. ECO will be reduced by a lesser extent.
We have a full electric heating and cooling.
You can set it up to heat the seats which is far more efficient than heating the cabin. I was in Eco Comfort at 74 degrees and I was feeling the Love with the heated seats. Range will vary with the 3T's.
When its Midwestern cold in the winter. It takes more energy to heat the vehicle and the passengers in the vehicle then to drive down the road. This is a problem with electric cars. A huge problem with a car that doesn't have a an engine. Even in the cold Midwestern winters, the engine comes on and it can make heat in CS mode and you will not be overly concerned with range.
Q8: Mountain mode... You are still in EV, flip the switch, your EV range will be reduced because you will start the generator with battery SoC at a higher level?
A8: Yes. If I am going up a hill, I want that engine to come on sooner. maybe sometime in the future, we'll have more customer knowledge base... Maybe I do not want mountain mode because I want to be empty when I get home or to the top.
Q9: Knowing what you know today, would you do anything differently?
A9: Not at all. We have everyone in the company aligned to the technology.
Q10: Figures an Autoweek guy would ask this question
What is Sport Mode like?
A10: Distance you have to push the accelerator and mapping of torque response of the electric drive out of the pedal. You can map the pedal in a number of different ways. We like to map it for a balance for both standard performance and efficiency. Normal mode is default and you will have to select Sport.
Q11: What are the modes again?
A11: Normal, Sport and Mountain Driving Modes. The climate control has two comfort modes, Comfort and Eco.
“From the heart of the engineers working on this, we will deliver on the Volt”