For any motorsport engineering supplier tempted to carry its highly specialized expertise along the winding – often hazardous – road to series cars, the journey can be fraught with nasty surprises. But some peel off to travel an alternative route to ensure that its technology takes it to a different and influential destination that nevertheless will influence OEM high-volume development. Xtrac is one of them.
A significant player in the rarefied world of design and manufacture of transmission systems and driveline components for, states the company, “most of the world’s top-level professional race and rally teams,” it is increasingly connected to the emerging world of high-performance hybrids and electric vehicles (EVs) – on both the road and track.
Bridging the two, in particular via electrified racing and rallying, is now a significant part of Xtrac’s programs, said CEO Adrian Moore, interviewed by Automotive Engineering about the first electric-powered cars to compete in the 2021 to 2024 FIA World Rallycross Championship. “Xtrac’s presence is across the grid, from supplying every IndyCar since 2000, to our competition-ready Integrated Lightweight Electric Vehicle (ILEV) range of transmissions. These include the new P1316 e-axle for cars competing in the Championship from 2021.
“Xtrac has two divisions – Motorsport and High Performance Automotive – the latter also running our Formula E programs because the technology link between high-performance road EVs and Formula E is incredibly strong. Our unit manufacture is now high hundreds/low thousands per annum, but in production terms, we do not plan to become another volume Tier 1 supplier such as Graziano or Getrag,” Moore said, noting Xtrac’s gained EV experience, particularly in Formula E, will continue to be an important but indirect contribution to the development of mass-production vehicles.
“Formula E is about how you make a high performance racecar achieve a specific task and ensure that it does so with a limited and tightly controlled amount of energy and rate of energy delivery: its power," Moore explained. "It has a small operational envelope within equally tight FIA rules, in a highly optimized vehicle that must be as fast as possible over a race distance, balanced with utilizing its restricted amount of on-board battery energy. Transmissions may be single-speed or multi-speed, all with a balance between the key performance parameters of weight, efficiency – and cost.”
In essence, all of this is significant. With EV technology arguably still in its infancy compared to ICE drivetrains, Formula E is a combination of entertainment and technology demonstration on track – but also leading to implementation in road vehicles.
Road and track for hypercars
For Xtrac, those electrified road cars are typically in the ultra-high-performance and hypercar categories. But an OEM may choose Xtrac’s transmission systems for building a “halo” model and, in the process, better learn how to make lower-performance, high-volume vehicles, Moore said. “But hypercars, which can legally only be used to their maximum capability on very few public roads, will in the future be enjoyed only on tracks,” he believes. “However, they would invariably be driven (rather than trailered) to those tracks on public roads.” He is very confident that the hypercar market will continue to grow strongly.
Although Xtrac’s transmission and driveline technology will have a dotted line via global OEMs to high-volume models, Moore stressed that the company would always remain at the upper end of the market. “There, we are the integrator, joining the power source to the road wheels – and whether it is an ICE or an electric power source doesn’t matter to us,” he noted.
Moore added that Xtrac’s experience via its ILEV transmissions has provided extensive experience in achieving that integration within very tight package space. Its P1316 e-axle will be supplied to Austrian company Kreisel, which the FIA has selected as the supplier for the introduction of a battery-powered propulsion system into the World Rallycross Championship from 2021 onwards.
Of the P1316, Moore shared, “Our ability to deliver a competition-ready EV gearbox reflects our continuing investment in transmission technology. We have compelling technology to help make motorsport even more exciting, which also influences the crucial evolution of the next generation of road cars.”
Matching e-axles to 250 kW power, Kreisel has responsibility for motors, inverters and batteries. Each 4WD rally car using Xtrac's transmission technology incorporates both front and rear e-axles. With an overall ratio of 7.90:1, the P1316 is capable of being matched with motors of up to 250 kW at an output speed of 15,000 rpm.
Moore said the e-axle uses an internal eccentric rotor pump to handle lubrication, with pressure feed to “all critical areas.” It uses a semi-dry-sump oil pickup. The e-axle incorporates a multi-plate ramp-type limited-slip differential with adjustable pre-load as an option. The e-axle unit weighs in at around 21 kg (46.2 lb), depending on the specific application. Together with use for Rallycross cars, the P1316 can be used by touring cars or circuit racers.
Xtrac employees total 380 (of whom more than 80 are engineers) including some 40 trained via the company’s apprentice and undergraduate schemes. “For our apprentices and undergraduates to develop their skills, knowledge and experience to our global customer programs, we work very closely with key universities and Newbury College in the U.K.,” Moore said.
The company recently completed a 27,000-sq-ft extension to its U.K. factory (it also has facilities in the U.S. in Indiana and North Carolina) and installed two extra test rigs to support accelerated duty-cycle development capabilities. The 200-kW rigs are 3-axis and 4-axis respectively, the latter facilitating twin input drives for testing twin-motor ILEV transmissions.Continue reading »