Types of tyres

To suit the demands of each circuit, Firestone have had to develop a plethora of different tyre constructions and compounds, giving the engineers lots of tyres to try and figure out.

There are essentially five types of tyres, based on their construction:

• Street course tyres
• Road course tyres
• Indy 500 tyres
• Superspeedway tyres
• Short oval tyres

Then there are two compounds, the primary (black) harder compound and the alternate (red) softer compound. On ovals, teams are only allowed to use the primary compound, however, due to the forces generated on ovals, each corner of the car requires a slightly different tyre compound or construction. On street/road courses teams can choose from the primary and alternate compounds as well as one wet tyre.

‘Firestone does tweak the tyres each year as well,’ highlights David Faustino, Lead Race Engineer at Team Penske. ‘Typically they are trying to tweak the balance between the primary and alternate tyre to get some crossover degradation. But it’s enough of a change which means going into a race weekend, it’s not always obvious how the tyres are going to behave relative to last year.’

Full course yellows

The biggest variable that is outside of the teams’ control is yellow flags and full course yellows. Unlike other series, if a full course yellow comes out during a race, the pit lane closes. A pace car is then released which picks up the race leader and the other cars bunch up behind. Once the pack is formed, the pit lane opens, giving cars the opportunity to pit before the race goes green.

If a car passes the Pit Commitment Line after a yellow, the driver cannot complete a full pitstop (but can repair damage or refuel for two seconds), and has to drive through the pitlane, ending up at the back of the pack. They can then complete a full pitstop when the pit lane opens again.

The strategic difference between ovals and road/street courses

‘A lot of our strategy comes down to how IndyCar handles full course yellows,’ explains Eric Cowdin, Race Engineer at Chip Ganassi Racing. ‘On road and street courses you want to pit towards the front of the pit window, because if a yellow comes out and you haven’t pitted, you have to wait until the pitlane opens again, by which time the pack has completely bunched up.’

‘Typically, cars that have completed a pit cycle before a full course yellow will have a track position advantage,’ highlights Faustino. ‘This is because the leaders will then pit under yellow and will cycle to the back of the cars that have stayed out, assuming they have enough fuel to complete the same number of stops overall. With the point structure in IndyCar you usually see the field split 50/50, so in a 26 car field, if you are the leader and haven’t pitted before a yellow, you could end up 13^th, which is a substantial hit,’ Faustino continues. ‘So usually cars will stop early and take the risk of having to fuel save for the rest of the race, in the hope that they will get lucky with a yellow where they can then conserve fuel.’

However, on ovals it’s a different story. Pitstops are initially dictated by fuel consumption and a normal pitstop can put a driver two or three laps down compared to the rest of the field. Therefore, by pitting under a full course yellow on an oval, once the pack has bunched up, a driver can complete a pitstop and re-join the track on the same lap – without going several laps down. So, if a yellow falls during a driver’s fuel window, then it is effectively a ‘free’ pitstop.

‘The strategy for ovals is the opposite to road courses. You want to run as long as you dare to try and catch that yellow,’ says Cowdin. ‘But then you also have to consider fuel and tyre degradation. There’s no point staying out 10 laps longer on older tyres if your rival is going considerably faster than you on a new set, because when you do pit, you will come out several places behind them.’

> To read the full article on IndyCar race strategy, check out the October 2022 issue

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How to set up a car for the Indy 500

The science behind wind tunnel models

On the 17^th of March, Pat Symonds received a phone call asking if F1 could get involved in the VentilatorChallengeUK. This is an initiative, led by Catapult, that brings together engineering companies from the motorsport, aerospace, automotive and medical sectors to rapidly manufacture ventilators. At the time, F1 was in its voluntary shutdown, waiting for races to be confirmed and the season to start.

‘The teams were essentially sitting in idle and it would have been a tragedy if we had such an incredibly competent group sitting there doing nothing,’ says Pat Symonds, F1’s Chief Technical Officer. ‘So I made a few phone calls and five days later, we convened a meeting at Red Bull Advanced Technologies in Milton Keynes. We had representatives from all UK F1 teams as well as some people from Olympus medical. We also had the COVID lead from the Association of anaesthetists, the national clinical lead for innovation for NHS in England and we had members of the military because a device that we worked on a lot had roots in military operations.’

The F1 teams, along with their associated technology arms, supported the development of the Penlon ESO2 and the Smiths ParaPAC300 ventilator, helping to scale up production. The likes of Mercedes HPP designed and manufactured a brand new continuous positive airway pressure (CPAP) breathing aid while Ferrari developed a new ventilator in five weeks.

‘To provide some context, Penlon and Smiths ordinarily have combined capacity for between 50 and 60 ventilators per week,’ explains Dick Elsy, CEO of High Value Manufacturing Catapult. ‘However, thanks to the scale and resources of the wider consortium, we are targeting production of at least 1,500 units a week of the Penlon and Smiths models combined within a matter of weeks.’

Scaling up of production is not a skill you would expect to find in F1’s repertoire, considering that each racecar is effectively a one-off bespoke prototype, made up of thousands of specialist parts. ‘F1 is not high production, and in the end these companies [Smith’s and Penlon] worked with the likes of Airbus and Ford to achieve the high production rates required,’ highlights Symonds. ‘But what we were able to do was very rapidly bring them up to 21st century manufacturing. For example, the Smith’s device was still on 2D drawings, so one of the first things we did was reverse engineer it, so that it could be made on modern machines.’

UCL-Ventura

The new CPAP breathing aid developed by Mercedes HPP in conjunction with University College London (UCL) and clinicians at the University College London Hospital (UCLH) is called the UCL-Ventura. Currently used by the NHS, this device works by pushing an air-oxygen mix into the mouth and nose at a continuous rate. This not only keeps both airways open but also increases the amount of oxygen entering the patient’s lungs. These devices are so effective at helping patients breathe more easily that reports from Italy and China suggest that around 50% of patients that were given CPAP did not need to use a ventilator and therefore were kept out of intensive care. Whereas ventilators require the patient to be heavily sedated as a connection tube has to be placed in the patient’s trachea (windpipe) to deliver breaths directly to the lungs.

Mercedes HPP disassembled an off-patent device, reverse-engineered its design and improved its manufacturability to suit higher production runs. It took only 100 hours from the initial meeting to the production of the first device and by mid-April the Brixworth team had produced 10,000 units – proving that motorsport is also capable of high volume manufacturing.

‘You cannot give something to an F1 engineer and say, here’s a good product just go and make it,’ smiles Symonds. ‘They will always try to make it better.’ Unsurprisingly, Mercedes HPP went a step further and developed a second version. With a concern over the amount of oxygen available in hospitals, HPP utilised it’s CFD expertise to reduce the oxygen consumption of this device by 70% compared to the first design.

The UCL-Ventura has now received MHRA regulatory approval and all the details required to make the device are available for manufacturers to download for free at a research licensing website developed by UCL Business.

This highlights another new ethos that F1 teams had to adopt; sharing IP. Although in 2022, the new regulations will make this the norm for certain components. By allowing the design of the CPAP device to be open sourced, thousands of licenses were issued to over 105 different countries; helping to fight coronavirus on a global scale.

Blue Sky

Another device that F1 teams worked on, together with Olympus and the Ministry of Defence, was the Blue Sky portable ventilator. Red Bull Advanced Technologies worked with Renault F1 and took this device from a prototype, which included miniature servos from a model aircraft, to a fully developed product, ready for certification.

‘There was a lot of software to write, as well as a lot of electronics and mechatronics work to complete,’ says Symonds. ‘Normally, this would probably have taken two years to get into production, but we said well, we haven’t got that amount of time. We estimated that we could do it in around four weeks and that’s essentially where we got to.’

Despite the monumental effort to turn around this device in such a short timescale, sadly the UK government cancelled the order for the Blue Sky ventilators – four days before the device was due to go through certification.

‘It was decided by the Cabinet Office that they probably didn’t need the more sophisticated ventilators in the levels that they thought they would. To be honest, this was good news because it meant that things were not as bad as anticipated. But for us, I have to say it was a little bit of a disappointment,’ reveals Symonds. ‘So we then made sure all the documentation was completed, along with the bill of materials. We’ve left it in a state where the government has taken ownership of it and if at any point it needs picking up again, it really wouldn’t be very difficult to get the whole thing working again.’

One of the parallels between the motorsport industry and the medical sector is regulation. Consequently, the certification process of medical devices was not too dissimilar to the homologation process a racecar part.

‘We didn’t know about all the certifications that you have to go through for medical devices, but we’re quick learners. In Formula One, we work to pages and pages of regulations that get ever more complex and part of the skill of an F1 engineer is to find their way around those regulations. So this sort of experience is nothing new to us. It’s part of what we do,’ explains Symonds. ‘Some of the requirements for certification were challenging and there were many things that we wouldn’t have thought of because it was a new branch of engineering for us, so we learned many things from this collaboration. I think that if it were to occur again, we would do an even better job and I think we did a good job this time round.’

There are lots of aspects of high level motorsport that the medical sector could learn from. However, Symonds believes that the most important is the efficiency with which a race team operates.

‘One of the ways a Formula One team works so well, whether that is the pitstop team, the engineering team, etc is that we are very disciplined,’ highlights Symonds. ‘Everything is pre briefed, everyone knows what their job is and they do their job, they don’t try and do someone else’s job. You get to a point where, if you’ve worked together and had continuity within your team, you know what everyone is going to do and you know it will get done,’ continues Symonds. ‘From some of the medical professionals I have spoken to, I was horrified to hear that a lot of them meet for the first time in the resus area. I just do not understand how you can be effective like that. When I’m on the pit wall, and I’ve got my team around me, I know what they’re going to do, all I have to do is just conduct that orchestra. If there’s someone new, and I don’t know how they’re going to react, I cannot get the best from my team. So, I think there’s an awful lot that we can pass on [to the NHS] in the way of doing things.’

Furthermore, the competitive culture of racing means that teams are continuously analysing their performance, regardless of whether it is good or bad. ‘Learning from your mistakes is essential. You must have the time and the honesty to go through your mistakes,’ says Symonds. ‘For example, in my last year at Williams at Canada, it was a one stop race, so we only completed two pit stops. Yet the pit stop report from that race was 16 pages long, because everything was analysed. They were really good pitstops too. So it’s that sort of culture that I believe we can pass on to help the NHS in future.’

The Ferrari SF1000 arrived at pre-season testing with a tightly packaged rear end, redesigned suspension and modifications to the internal combustion architecture, along with many aero tweaks. Yet the cars were not as competitive as Ferrari had hoped for, with a disparity in the correlation between track performance and factory simulations.

‘The car in winter testing was not performing as let me say the design we did at home so there was a mis-correlation from design to track,’ reveals Mattia Binotto, Team Principal at Ferrari. ‘We started really trying to understand it as soon as we have been back at the factory, so during the shutdown period that was not possible. I think we realized that from the aero point of view mainly there were some miss-correlations. Eventually I think we pushed our project on trying to seek a lot of downforce.’

Another problem was the robustness of the aerodynamic design, which is something the team will look to improve as part of the Ferrari SF1000 upgrade. ‘I think whatever we developed was too fragile in terms of aero robustness when being back on track and what we are trying to do now is to have a step back and try to understand and reassess the problem and then moving forwards later on,’ says Binotto.

The upgrade package includes several aero tweaks to the front wing and underfloor. Leclerc ran the new front wing during FP1 at the Styrian grand prix (left) where the profile of the inboard section of the top main element has been tweaked slightly (highlighted in blue). Meanwhile, the endplate tunnel exhibits a more curved profile (highlighted in pink).

Zooming in on the front wing endplate, the below shows a nice comparison between the new (top) and old (bottom) front wing. The endplate tunnel is slightly narrower with a much more curved profile (highlighted in blue),compared to the flatter profile of the old design.

The rear floor has also seen some changes, with the addition of nine angled slots just in front of the rear tyre (highlighted in blue). This was seen on Leclerc’s car during FP1 (left) but Vettel completed some runs with the older version run in Austria (right).

It will be interesting to see if Ferrari continue with these upgraded parts and whether they will evolve throughout the rest of the season.

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The Engineering secrets behind sim racing

IndyCar’s 3D printed Aeroscreen

The art of manipulating performance

The aim of any racing game is to simulate the feeling that you are driving a real car by stimulating sensory cues that trick the brain. This can be particularly challenging with racing games as they rely only on visual and audio cues, unless you invest in steering wheels and pedalboxes that provide feedback. Whereas, advanced driver in the loop simulators can exploit full motion platforms to simulate longitudinal, vertical and lateral accelerations; providing realistic feedback to the muscles and therefore creating a more immersive experience.

However, the most important cues are visual and audio and so the key to achieving a realistic simulation is to accurately model the virtual world. In racing games that virtual world consists of three main areas: 1) the racecar 2) competitors and 3) the surrounding environment.

To emulate the dynamic behaviour of a racecar, vehicle models are used. These consist of a network of modules which include a system of engineering equations. When linked together, these equations effectively simulate the behaviour of a certain component according to the inputs at that particular timestep.

The vehicle models used in modern racing games are now more advanced than ever. Detailed aeromaps, hybrid deployment strategies and full damper curves now underpin the majority of vehicle models found in the latest gaming titles.

‘We model all elements of the Formula 1 power unit and drivetrain,’ reveals Lee Mather, F1 game franchise director at Codemasters. ‘We model the behaviour of the MGU-H and MGU-K, adhering to the F1 technical regulations covering harvesting and deployment levels. We also model the internal combustion engine, along with multiple fuel modes. These work as they would in real life. Running more power generates more heat and wear on the power unit for example. This extends as far as when running in dirty air, where cooling becomes an issue,’ Mather continues. ‘Player controlled DRS is available when the rules allow its activation. It works by reducing drag and downforce to the rear wing as it does on a real Formula 1 car.’

So how do these companies actually go about developing these advanced vehicle models? ‘There are two parts to developing a car model,’ highlights Chris Lerch, Vehicle Dynamics engineer at iRacing. ‘There’s the artwork side and then there’s the physics side. The artwork is every bit as complicated and involved as the physics. A lot of the fundamentals need to be put in place in the artwork before we can really get a meaningful start on the physics.’

To replicate the visual appearance of the car, gaming platforms use CAD data which has either been provided by the manufacturers or captured themselves by handheld 3D scanners. ‘The teams provide us with CAD data and any livery and brand guidelines that go with them,’ says Mather. ‘We can’t use the CAD as-is since the geometry we get from the teams is incredibly dense and complex, so our team of highly skilled artists resurface over the CAD while adhering to our tighter polygon budgets. To scan classic cars such as the new Schumacher classics for F1 2020 as well as the ’09 Brawn and ’03 Williams, we’ve recently adopted the use of handheld 3D scanners.’

Photographs are also an essential tool to building a visually representative model. Codemasters use hundreds of photographs taken at F1 preseason testing to help its artists replicate every livery detail in accordance with the brand and livery guidelines they have received from each team. These images can also be used to track the constantly evolving aerodynamic packages in F1.

‘As aero development happens at a fast rate, we often see new aero that hasn’t been accounted for in the CAD, so artists carefully camera match the photos to the models and fill in the gaps,’ highlights Mather. ‘The models are then submitted to the F1 teams who have final sign off. The whole process usually takes three to three and a half months depending on the quality of reference.’

To develop the physics side of a model, detailed vehicle data needs to be collected to then parameterise the model. This data can be sourced from official timing data, regulations or the manufacturers themselves.

‘To create authentic handling we first research, or are supplied with, each vehicle’s specifications, and then investigate whether it had any distinct characteristics through first-hand experience from the professional drivers or contacts we work with,’ explains Ross Gowing, DiRT Rally Game Director at Codemasters. ‘After that we enter the phase of creating the handling model and data for the vehicle, and then a period of testing and validation before it goes into a development build of the game.’

Typically, racing games modify an existing vehicle model, updating all the parameters to the values of the new car, rather than building a new car model from scratch. ‘Essentially the vehicle dynamicist steps through each of the vehicles systems and updates them accordingly,’ explains Lerch. ‘As we do that we’ll want to recompile the model and check that there aren’t any errors. Typically, that’s not a terribly lengthy process and normally takes a couple of weeks. After that we then focus on the tyre development which is extraordinarily time consuming. That alone can take a month to develop because tyre models are always evolving and we try to keep our products as up to date as possible.’

Another challenge that racing games such as F1 face, is modelling the different performance potential of each car and driver, so that the player can feel the difference between a Mercedes and a Williams, for example. This is particularly difficult when there is no real data available. ‘We differentiate the F1 cars in all of the ways that they differ in the real world such as wheelbase, width, ride heights, weight distribution etc,’ says Mather. ‘Real data isn’t something any F1 team is open to sharing with anyone, however we do receive great insight in to these sorts of areas and we do as much research as possible to help us understand how a car achieves its lap time. Hitting a specific lap target is one thing, but how you do that is equally important. For the power unit for example, we have different power/torque curves, friction, fuel efficiency and ERS which are all configurable by one of the vehicle handling designers.’

For gaming platforms such as iRacing and Assetto Corsa where players can pick to race the same car but from different teams, the performance differentiators between teams are not modelled. ‘If you jump into a Porsche 991 RSR, everybody has the same Porsche 991 RSR,’ says Lerch. ‘You can change the setup and the driver but everyone starts from the same place. So although the RSR competes against the BMW M8, and the Ford GT, where each of those cars are different, the car you’re racing is the same model as everyone else who has selected that car.’

However, when it comes to racing against the AI, which is an option in Assetto Corsa Competizione, the performance of different drivers has to be modelled. ‘In these situations we have talent files inside the AI which gives each driver different characteristics,’ says Aristotelis Vasilakos, head of vehicle handling and R&D at Kunos Simulazioni, the company behind the Assetto Corsa software. ‘This differentiates a little bit the performance of the drivers when racing against the AI.’

It’s fair to say that modern racing games now incorporate more engineering than ever before. What’s even more impressive is that these racing games also have to be capable of accurately modelling extreme situations, which would be highly unlikely to happen in real life.

‘This is a big difference between racing Esports and reality,’ highlights Vasilakos. ‘In reality all drivers start from under the limit and slowly work their way up to the optimum lap. Whereas in sim racing because you’re not worried about damaging the car or your own life, you start above the limit and drivers have the opportunity to try everything which helps them gain extra performance pretty much everywhere throughout the lap. This is one of the reasons why in sim racing you see drivers achieving faster lap times then they could in real life.’

Check out the July 2020 issue as we discover the technical secrets behind racing games and advanced simulators (out 5th June)

How do exhausts work?

The journey of the exhaust gases begins once combustion has occurred. Then, during the exhaust stroke as the piston moves back up the cylinder, the exhaust valve opens and the burnt gases are expelled from the combustion chamber. The gases then travel into a set of primaries or headers, with one primary per cylinder (red, purple, blue). The three primaries coming from each bank of the engine then join together in a three-to-one primary collector (orange) and then a secondary pipe (yellow). The two secondaries (one from each side of the engine) then go into the turbocharger.

Depending on the engine manufacturer, the primaries, collector and secondaries can either be all one piece and integrated into the turbocharger, or separate pieces. A tailpipe (blue) from the turbocharger then carries the exhaust gases from the turbo out the rear of the car. While there is also a wastegate which controls the speed of the turbo and consists of either one or two wastegate pipes (red) that come off the secondaries and bypass the turbine housing, exiting at the rear of the car.

Despite the concept of an exhaust system appearing relatively simple, there is an entire science behind parameters such as pipe length, diameter and layout which can be manipulated to tune the torque and power band of the engine.

Packaging

The more compact you can get the exhaust system, the tighter you can make the bodywork, which gives an aerodynamic benefit. But with exhaust gasses reaching temperatures of 1,000degC and pipes that are within a millimetre of bodywork, new insulation strategies and thermal coatings have had to be developed. Overall, an effective exhaust design is one which strikes the perfect balance between exploiting engine and turbo performance within the smallest package possible, without damaging the surrounding components.

At the beginning of the turbo-hybrid era, in 2014, teams initially positioned the compressor at the front of the engine block and the turbo at the rear. Some manufacturers opted for a compact manifold and short primaries, with a longer secondary pipe going from the collector to the turbo. However, the optimal design in terms of packaging was to have long primary pipes which consequently not only decreased the size of the sidepods, but also meant that the ‘coke bottle’ shape of the rear of the car could be emphasised; improving aerodynamics. To ensure that these longer pipes were as tight as possible to the engine, they often had to be of unequal length, which for turbocharged engines is less of an issue.

‘In the early turbo days teams went for more conventional manifolds with equal length primaries,’ highlights Nick Henry, Engineering Director at SST technology who manufactures F1 exhausts. ‘But the traditional benefits of equal length systems aren’t as great with turbochargers because the turbo helps to draw the exhaust gases out, rather than relying on the pistons to push the exhaust gases out. So, the aerodynamic advantages of being able to package the exhaust system tighter outweigh the benefits of equal primary lengths for these hybrid powertrains.’

Tightly packaging the exhaust system is a challenging process, with many factors to consider. ‘When you are laying out the car the [first requirement is the] compressor output position [which] is defined by the power unit so there is a discussion there on engine architecture,’ highlights Jody Egginton, Technical Director at Alpha Tauri. ‘Then there is the S-bend which goes from the compressor to the tailpipe and you need to make sure that you’ve got a geometry that optimises performance so there’s a chunk of CFD work involved there. The geometry is never perfect, because the perfect geometry is straight which is impossible. Then you need to consider the tailpipe diameter which needs to be within the legality box as well as how that [flow] interacts with the rear wing pylon. Again you want a nice clear path but the aero guys want minimum blockage through the engine cover so you don’t want to have to move the flow around wishbones because aero is king, so you’re trying to find the best tailpipe position and how to best orientate the wastegates,’ Egginton continues.

‘It’s a mixture of suspension design, packaging and power unit performance but the overall view is aero and the best overall package. If you had a straight tailpipe which is good from a power unit performance perspective, but you have a ridiculous hole in the back of the engine cover and the flow around the rear wing pylons is horrible with flow separation, then you wouldn’t do that. It’s all about the global car performance.’

Packaging is without doubt the most difficult element of modern F1 exhaust design. ‘Our part of the problem is packaging the set of primaries and the entry to the turbine on the side of the engine and adjacent to the front of the gearbox. Then trying to get the exit air from the radiators upstream,’ says Rob Taylor, Chief Designer at Haas F1 Team. ‘We have lots of radiators and we’re constantly trying to find creative spaces to put them. Sometimes you wonder ‘why am I putting something that is meant to be cooling adjacent to something that is really hot?’ because that’s the only space you’ve got. One of our central coolers is adjacent to the tailpipe – why would you do that? Because you have to.’

Aerodynamics 

In addition to optimising the packaging for sleeker, narrower bodywork for aero gain, teams also utilise the energy of the exhaust flows to improve aerodynamic performance. The most renowned example of this was the blown diffusers of 2010 which was first showcased on the Red Bull Racing RB6. The regulations then changed in 2012 and the teams response led to the development of Coanda exhausts which exploited the ‘Coanda effect’.

Teams have also experimented with miniature rear wings or monkey seats which are positioned rearwards of the exhaust tailpipe and direct the exhaust flow to the underside of the rear wing. This has two main benefits; firstly by increasing the speed of the flow in this region, the pressure decreases leading to a larger pressure differential between the upper (high pressure) and lower (low pressure) surfaces of the rear wing; improving downforce. Secondly the high energy flow is less likely to separate so blowing it underneath the rear wing allows teams to run a more cambered wing that would otherwise stall.

‘A few years ago we had various winglets appearing adjacent to the exhaust outlet but with the FIA restrictions on flow rates and throttle positions this has largely declined,’ explains Taylor. ‘In the past it was about making more of a cascade between the diffuser, the intermediate wing and the main wing to make them all act together. The more you can do that, the more tolerant the wings are to onset flow, detachment and therefore stalling. If you look at the size of that little wing and the stalks they’re on they’re not producing a great deal of downforce in themselves, but they had a beneficial effect on the bigger elements because it meant you could put more camber into the wing above it as it wouldn’t detach as early.’

When the regulations changed the position of the exhaust tailpipe and this monkey seat, teams then started to point the exhaust tailpipe towards the rear wing by the maximum allowable angle of five degrees as specified by the regulations. This can be seen on the Renault RS18 from 2018 where a thermal barrier coating was also applied to the underside of the rear wing to protect the carbon fibre from the heat of the exhaust plume.

‘At the end of the day a tailpipe in a racecar sticks out the back, so it is a wetted surface and subject to aero flows so we are constantly trying to optimise it and minimise any deficit we get from its effect on the flow coming out of the back of the car or off the rear tyre jet,’ highlights Egginton. ‘If there’s a way that we can make the tailpipe and wastegate flows useful then we do it, but the amount of usefulness is reducing compared to years ago and everyone has probably found all the big gains now.’

Find out more on F1 Exhausts in our November 2019 issue: