Exclusive interview with Gregg Peterson of Lotus Engineering
30 August 2011
Briefly describe your background in the automotive sector and your role at Lotus Engineering
I am a Senior Technology Specialist for Lotus Engineering. My responsibilities include technology transfer to Lotus, including integrating low mass materials into vehicle design, as well as program management. I led the Lotus mass reduction opportunities study published in 2010 by ICCT that projected near 40% vehicle mass reduction at minimal cost for an identical size vehicle. I am part of a team currently designing a low mass body structure to verify the structural performance and crashworthiness; this project includes ARB, EPA, NHTSA and DOE participation. My automotive background includes over 30 years of OEM and Tier 1 engineering experience including plastics technologies, ferrous and non-ferrous body design, chassis design and development, electronic control systems, powertrain, aerodynamics, thermal systems, and interiors.
Lightweighting has always been a driver in motorsport, but why is it now so important in production vehicles?
The U.S. government is mandating significantly higher fuel economy requirements for future vehicles. Reducing the mass of a vehicle is a known means of improving fuel economy and, directionally, decreasing emissions. Various industry studies, including those published by the U.S. Environmental Protection Agency and the Aluminum Association, have projected fuel economy improvements of 6% to 8% by reducing vehicle mass by 10%. These figures are for vehicles with powertrains adjusted to provide equivalent acceleration. Reducing vehicle mass by 30% could increase fuel economy from 28 MPG to 35 MPG with no loss of performance or utility.
There are other benefits as well. Lightweighting can positively impact vehicle handling. For example, lowering the center of gravity by reducing the roof mass contributes to improved vehicle response. BMW uses a low mass roof on some performance models to reduce the center of gravity. Additionally, lightweighting allows the engineering team to adjust the center of gravity relative to the wheelbase by reducing the front and rear masses extending past the wheels. The combination of lowering the center of gravity and placing the CG closer to the wheelbase centerline contributes to improved cornering capability and higher ultimate limits. This translates into increased driver control.
What do you consider in the balance between lightweighting and performance?
The cost vs. customer benefit is the key criteria for any lightweighting decision. Performance can mean many things, including increased fuel economy, lower GHG emissions, reduced braking distances, impact energy management, improved cornering or quicker acceleration.
As an example, hybrids offer much improved city fuel economy vs. conventional powertrains but what is the payback period for the owner to recoup the added expense for two powertrains and a premium battery pack?
Six pounds of gasoline has about the same energy as a quarter ton Li-Ion battery pack. Does it make sense to increase vehicle weight by 600 - 700 pounds and double the vehicle cost to increase fuel economy?
I think it may be possible to offer consumers a vehicle that provides hybrid like fuel economy with the simplicity and cost advantage of a conventional ICE powertrain. Low mass is key to achieving this objective. The Progressive Automotive X prize winner, Edison2, a sub 800 lb. four passenger vehicle powered solely by a small gasoline engine, achieved well over 100 MPG on the Urban efficiency test and averaged 100 MPG at 80 MPH.
The Edison2 demonstrates the potential of a lightweight, aerodynamically efficient gas powered passenger car to achieve outstanding fuel economy without the cost and mass disadvantages of a hybrid powertrain. The dynamic advantages mentioned in the previous response also apply.
An additional advantage is that performance gains relative to a baseline vehicle are achieved much more readily on a low mass car than on a heavy vehicle. Small horsepower increases result in substantially reduced weight/power ratios which translate into quicker acceleration. Small increases in tire width can substantially reduce braking distances and increase lateral acceleration. In every aspect, lightweighting improves vehicle performance; the performance advantage could be increased fuel efficiency, reduced emissions, improved control in an emergency lane change or it could be quicker lap times at a road course.
What are the alternative materials to carbon fiber composites? What advantages do they have?
Carbon fiber composites have demonstrated excellent performance in extreme applications such as Formula 1 body structures and the wings and fuselages of aircraft. F1 drivers walk away after hitting barriers at speeds well in excess of 150 MPH in 640 kg machines with limited front crush zones. The carbon fiber wing on the Boeing 787 was flexed upward by about 25 feet without fracturing in its development testing.
The alternative materials for carbon fiber are any materials that are less expensive that can provide equivalent structural performance. Magnesium, aluminum are steel are competitive materials. Their primary advantage is cost; their obvious disadvantage is increased density.
What role do you see carbon fibre composites playing in the future of the automotive sector?
I see carbon fiber playing an increasing role in the automotive arena. The CF industry is working hard to reduce cycle times, a key element in the cost equation. Some of the innovative forming processes are starting to capture the attention of the automotive engineers. The development work done by the CF industry and applied to projects such as the 787 and numerous light aircraft is helping to make the technology a consideration for automotive applications. As examples, the McLaren MP4-12C supercar incorporates a carbon fiber monocoque structure, the Lexus LFA uses a carbon fiber reinforced polymer body, the 2011 Corvette ZO6 Carbon Limited Edition uses a variety of CF components and the Mustang GT500 KR has a carbon fiber hood is carbon.
The use of carbon fiber is also expanding beyond limited production high performance vehicles; BMW will use be using a carbon fiber body for the 2013 i3 EV to help reduce the battery pack size and cost. The development done for the i3 body could contribute to the introduction of carbon fiber components on higher volume vehicles.
The real key for the automotive world is that the MP4-12C body structure is formed in four hours; the 1992 McLaren F1 tub required 3,000 hours to construct. This is a major achievement; part of this is due to the use of non-cosmetic CF material. This bodes well for future price reductions and creating the potential for cost effective OEM applications.
The need for the automotive industry to reduce mass significantly in a relatively short time frame may accelerate the implementation of CF components into more mainstream vehicles.
A key concern, particularly in Europe, is recyclability. Thermosets may need to be replaced by thermoplastics to be viable for volume automotive applications.
Finally, we are pleased to have you on board for this interesting programme, what are you hoping to gain from your participation?
My hope is that this conference will promote ongoing dialogue and constructive partnerships to help push the envelope for designing and engineering lightweight, safe and cost effective vehicles that are required in the very near future.
Hear more from Gregg at this year's Global Outlook for Carbon Fiber, 4-6 October, Hotel Monaco Seattle, US.
>> Book your place here
>> View the 2011 agenda