If in 2019 you had suggested that new V12s would be arriving on the market in 2023, most listeners would have scoffed. But as it turns out, for those lucky enough to have sampled the rarefied air at the top of the hypercar market, emotion and soul are qualities that even the most gut-wrenchingly rapid EV cannot deliver. This is exactly what Jens Sverdrup, chairman and CCO of Danish manufacturer Zenvo, had customers saying to him when the company’s latest masterpiece, the Aurora, was being planned. “Early on the feedback was, ‘Whatever you do, don’t go electric,’” he recalls.
To date, Zenvo’s cars have featured V8s, but for the Aurora the company wanted to up the ante with its own powertrain. “We started with a questionnaire, asking customers what they would want from a new hypercar in 2023 – electric, V6, V8? The answer was 100% a V12,” reveals Sverdrup.
There was also a strong desire in the company to see the ICE era out in style. “Selfishly, speaking for myself and quite a lot of the guys on the team, we always dreamed of a V12 as something we would like to do as petrolheads,” he admits. “It’s the ultimate emotional powertrain, with no real advantages beyond being smooth and sounding fantastic.”
A helping hand
There is a big difference between wanting a V12 and having the ability to develop one, and for a small manufacturer like Zenvo, external help was always going to be necessary. Enter Mahle Powertrain, the UK-based engine-development arm of component supplier Mahle, with all the capabilities in-house to build such an engine from scratch. The company has an extensive history of working with OEMs on engine development projects, most of which are kept tightly behind closed doors. But with Zenvo, it has been permitted to talk openly about its work. Zenvo’s brief to Mahle had a few key demands.
First, the engine would need a 90° bank angle and hot vee. This was a result of its styling direction with the Aurora. “We already had sort of a concept early on, before we decided on engines,” says Sverdrup. “We really wanted to work heavily on the design language using negative space and we wanted to send the airstream through the car as opposed to over it. There would be no sidepods in which to stash intercoolers or other ancillaries. That led us down the path of doing a 90° V12.”
There were also commercial considerations, not least a desire to offset the considerable cost of developing an engine from scratch. “We wanted to justify the investment, so wanted to see if we could work with modularity,” says Sverdrup. That led to a base design of a block that we can get more engines out of. We can also have a 90° V6 and V8.”
Notably, though the V12 will be kept exclusive to Zenvo, the company plans to make the V6 and V8 versions available to other manufacturers. Given how many other niche manufacturers in Europe and the USA rely on engines from major OEMs – which may or may not be available by the end of the decade – there is unlikely to be a shortage of customer demand.
Bespoke expertise
The relationship between Mahle Powertrain and Zenvo began in 2020 with a project calibrating Zenvo’s TSR model to meet European emissions regulations and achieve homologation. “From that point onward there was always talk of this new vehicle they wanted to do,” recalls John Hollingworth, sales and marketing director at Mahle Powertrain, who has worked as the linchpin between the two outfits.
“The choice of a V12 was dictated to us quite early on, and Jens also had some performance figures of where he thought the hypercar market was. He didn’t want it to be a screaming race engine, so it would rev to around 9-9,500rpm. It was then up to us to go away and decide on what the engine would need to be.”
The layout settled on was a 6.6-liter, 90° turbocharged V12 with a 96.5mm bore and 75.2mm stroke, which would be augmented with a hybrid system. Most of the engine architecture is quite conventional – for example, chain-driven dual overhead cams (chosen for their NVH advantages over a gear drive) and valves actuated by finger followers.
Quad approach
V12s are nothing new to Mahle Powertrain, which has worked on the development of various examples for other customers. However, the approach to forced induction with quad exhaust-driven turbochargers is something new. “The turbo discussion was a contentious one in our business for a few months,” reveals Hollingworth. “Initially it was always going to be a twin-turbo engine. But then there was a curveball thrown in that Zenvo might want to do a non-hybrid version. Then it was suggested that spooling up four smaller turbos would give better transient response.”
Quad turbos clearly had their advantages, but came with added complexity over the known quantity of a twin-turbo setup. “We decided in the end that having quad turbos was a more technologically advanced solution and we could rise to the challenge, so we stuck our neck out.” The response from Zenvo was certainly positive. “As soon as we mentioned quad turbos to Jens, he said, ‘Yes, we’re going in that direction.’”
Packaging four turbochargers into the engine vee is no mean feat and presents some interesting cooling challenges. “We have to make sure we can run cooling air in through the vee, for the components there, and ensure there is enough space under the turbos and for other pipework,” outlines Hollingworth.
This task is not only down to Mahle Powertrain, but also Zenvo’s engineers, with some of the cooling air from the roof-mounted snorkel being diverted to the vee in addition to feeding the charge coolers above the engine.
Jet power
Beyond the V12 and quad turbos, the other headline feature of Zenvo’s V12 is the application of Mahle’s Jet Ignition system, which uses an active prechamber. “It is the first production road application we’ve used it on,” says Hollingworth. “It allows us to run a full area map at lambda one, which we know will be vital for emissions legislation requirements going forward.”
This is an important asset for Zenvo, which wants to ensure the car is viable in the European and US markets. Mahle is aiming to hit the US emissions targets first as it believes they are the strictest, and if they can be met,
the European standards should be achievable.
“It’s one of the key things to get across about this engine,” notes Hollingworth. “It’s not a race engine that we are putting aftertreatment on to try to get it through emissions. We’ve considered emissions from day one.” The hybrid nature of the powertrain helps here, not only in being able to harness electric-only drive for elements of the WLTP cycle, but also for functions such as catalyst preheat. Hollingworth does point out, however, “If Zenvo does a non-hybrid version, the engine needs to be able to stand on its own.”
The use of the pre-chamber ignition system provides a faster burn and enables it to protect the components at high boost levels without having to resort to over-fueling. The implementation of an effective pre-chamber system is not simply a case of adding it to an existing chamber design, and considerable development has gone into the combustion chamber and piston. “That’s part of the secret that Mahle has been developing over the past 10 or so years,” notes Hollingworth.
Expanding on this, he adds, “I can’t go into specific details, but we have done a lot of different engines and trials with Jet Ignition, so we know what works and what doesn’t. There are specific designs around the chamber and particularly around the nozzle jet, the sizing of the jets and the holes around the jets. The operation of the system is also highly sensitive to combustion chamber temperature, which means getting cooling around the jet is important as well. It is all critical to getting the system to operate efficiently and correctly throughout
the complete rev range.”
A further string to Mahle’s bow regarding emissions regulations is an extensive back catalog of ECU development. “We’re going for a whole bespoke ECU that we’re going to develop in conjunction with Zenvo,” reveals. Hollingworth. “That will have full OBD2 capability and is likely to be a twin ECU concept, able to control each bank. That’s because a lot of processing power is going to be needed for this type of engine.”
Capabilities
Not only is Mahle Powertrain well able to design Zenvo’s V12, but it also has an impressive suite of on-site capabilities for development and testing. “Facilities-wise, we’ve got two four-wheel-drive chassis dynos, which include climatic capabilities. We can take vehicles down to -40°C and up to +60°C,” highlights Mahle’s John Hollingworth. “We also have a barometric chamber, which is unique in the UK. There are only three independent facilities in Europe with that capability, and we can simulate up to 5,000m in altitude.” The result, he quips, is that, “We can simulate any kind of road around the world without having to leave Northampton.” Of course, a full real-world vehicle testing program will also be conducted. However, the availability of such impressive on-site capabilities helps to keep costs down.
This is an important factor for Zenvo. Though it manufactures multimillion-dollar cars, there is a reason most hypercar manufacturers buy engines in: bespoke development is fearsomely expensive. The modular design of the engine should lend itself to income generation down the line, but costs still need to be controlled. Mahle has recognized this in its approach to the test and development program.“To be honest, we’ve had to look at a different approach to how we develop the engine, looking at what the use of the vehicle is going to be, and then working out exactly what the development program should be to validate an engine that will be used in such a way,” says Hollingworth.
“These cars aren’t going to be doing 200,000 miles over their lifetime, so you have to look at a pragmatic approach.” Here, Mahle’s experience allows it to rationalize in some areas, confident that it will not be sacrificing performance or longevity. “We’ve managed to cut down the development loops to the bare minimum and keep the cost of the actual development program down to something that makes it more palatable for a company like Zenvo.”
It is still relatively early days for Zenvo’s V12. Design work is nearly complete and the first dyno runs are planned for early 2024 – an impressive feat as the green light for the project was only given in early 2023. The final architecture of the hybrid system is also still under development, with the final configuration of motors, batteries and power electronics still to be confirmed.
Overall, the general sense one gets from both Zenvo and Mahle Powertrain is that this is a chance for one last great hurrah for the V12. Sverdrup is under no illusions that its engines are somehow furthering the world’s goals of sustainability, but they don’t need to. “Hypercars are not a solution, they are an art form, in the same way that a mechanical watch is an art form,” he expounds. “They have graduated to become an expression. And the engine is, of course, part of that. I think that’s what we all feel. So let’s just go out with a bang and make it the greatest ever.”