Today‘s IndyCar is 11 years old and counting. Its spec Dallara chassis has had various safety upgrades, most notably the ‘Aeroscreen’ now surrounding the cockpit, while its aero package was updated to the current IR18 specification for 2018. However, fundamentally it is the car that was introduced for the 2012 season to accept the new 2.2 litre V6 turbos fielded by Honda and Chevrolet.
Start of the 2022 Indianapolis 500 (Photo: John Cote)
As things stand, the IR18 will continue in service for the foreseeable future, whereas the powertrain will be revised for 2024, with the introduction of all-new 2.4 litre V6 turbos married to a hybrid unit. At the time of writing, details of the hybrid unit had not been revealed, but it was known to be a device connected to the transmission rather than the engine, and offering short applications of up to 100 bhp/75 kW.
Meanwhile, the new 2.4 litre engines from Honda and Chevrolet had first run on track in a joint test at the Indianapolis Motor Speedway (IMS) in late March 2022. At the May 2022 Indianapolis 500, RET caught up with key players involved in the preparation for this new era of IndyCar racing, including Darren Sansum, IndyCar’s managing director of engine development. We spoke to him on the morning of the 500-mile race.
Alexander Rossi’s Honda-powered car at the 2022 Indianapolis 500 (Photo: Travis Hinkle)
Development of the current 2.2 litre IndyCar engines is restricted via a homologation process. When it comes to the engine updates permitted from 2021 to 2022, Sansum noted, “What you can do on an annual basis hasn’t changed for the past three or four seasons.”
When asked about the more significant updates permitted for 2014 and 2016, he remarked, “That was because of the way the current regulations have been stretched – it was originally designed to be a 6-year formula.”
Darren Sansum is IndyCar’s managing director of engine development (Photo: Anne Proffit)
Sansum confirmed that there weren’t any regulatory changes affecting engine performance at the IMS from last year to this year. In particular, “We ran the same boost levels this year as last year. So we’re 1300 millibar [plenum pressure] for practice and the race, and 1500 millibar for Fast Friday and Qualifying.”
Asked immediately ahead of the race who he thought has the upper hand this year – Honda or Chevrolet – Sansum was non-committal. “I would say that if you look at the result of Qualifying, it goes by team and not by engine manufacturer,” he said. “So who’s got the upper hand now [ahead of the race]? Probably Chip Ganassi Racing [pole-sitter Scott Dixon in the #9, second-fastest qualifier Alex Palou in the #10, fifth-fastest Marcus Ericsson in the #8, sixth-fastest Tony Kanaan in the #1 and 12th-fastest, rookie Jimmie Johnson in the #48].
“Obviously there are Chevys that will be strong in race trim. I’m sure the Penske cars will be strong in race trim; other Chevys too. But in my mind the Ganassi team goes in as the favourite. Not as my personal favourite but the favourite to lead the race.” In the event, Ericsson won by the narrowest of margins over Chevrolet-powered Arrow McLaren driver Patricio O’Ward.
2023
Originally the plan was to introduce the 2.4 litre engine and associated hybrid unit for 2023, but the global pandemic postponed the new technology until 2024. Meanwhile, Sansum confirmed that there are moves afoot to ‘freeze’ some elements of the current engines rather than allow the normal annual re-homologation process. “There’s a discussion now [including the engine manufacturers],” he said. “We’re potentially looking at reducing the amount of things they can change for 2023, but that’s not agreed yet.”
What will be different in 2023 is the use of a ‘renewable’ fuel, supplied to all competitors by Shell instead of the current E85. This, reports its supplier, “consists of a blend of second-generation ethanol derived from sugarcane waste and other biofuels to create a fuel that is 100% composed of feedstocks categorised as ‘renewable’ under the applicable regulatory frameworks”.
The renewable ethanol will be sourced from Raizen, a Brazilian joint venture created in 2011 by Shell and Cosan. “Raizen is one of the largest sugarcane ethanol producers in the world and owner of the first commercial second-generation ethanol plant.” To that Shell adds that this fuel will make IndyCar “the first US-based racing series to use 100% renewable fuel, and will enable at least 60% greenhouse gas emissions reduction compared to fossil-based gasoline”.
The current E85 it replaces is 105 RON/99 AKI [= RON+MON/2]. Sansum says, “From the specification sheet it looks very similar from an octane rating perspective.” Is it a faster or a slower burning fuel? “The manufacturers have not shared that information, but both of them have told us that the performance is very similar. So that would suggest the burn rate is similar.”
2024
The new-generation 2.4 litre V6 turbos are being produced to design and development – that is, homologation – constraints fundamentally unchanged from the current ones, apart from the 200 cc displacement increase. Asked about the key differences aside from that and from the marriage to a hybrid system, Sansum noted a restriction of bore size.
The current regulations allow a maximum bore size of 95 mm, which if exploited is combined with a stroke of 51.7 mm for 2199 cc. “The new regulations specify what the bore size is: 96.5 mm [which combines with a stroke of 54.6 mm for 2396 cc],” said Sansum. “Under the current regulations in 2012 you could have homologated any bore up to the maximum permitted [with corresponding stroke]. But now there is a set bore size, so that’s a change.”
Sansum added that despite the bore increase (of 1.5 mm or more), the new engines must still fit within the 460 mm available between identically specified chassis and transmission mounting points. The crankshaft axis again has to be 100 mm above the base of sump, while the engine must still interface with Dallara IR18 coolers and associated plumbing. Aside from the accommodation of the hybrid unit it will be a straight swap.
“The box you put the engine in is the same size, so it’s actually quite a challenge to get the additional bore and stroke in,” Sansum added. “The crank becomes quite a design challenge because of the extra stroke and the extra size of the cylinder bank.” He also noted that the minimum weight of the engine has been increased from 112.5 kg to 118 kg.
As with the current engines, compression ratio continues to be a free development area. Fuel mileage is a crucial consideration in IndyCar racing; the timing of fuel stops is often a key factor in winning the Indy 500, for example. In this respect it is worth noting that since 2012, Formula One has demonstrated the potential of pre-chamber combustion technology in making the contemporary IC race engine more fuel-efficient (RET 97 September/October 2016). Sansum told us that the regulations for 2024 – echoing the current ones – do not specifically outlaw it.
The 2024 regulations do continue to ban pneumatic valve return springs though. In many other respects they follow the current rules in terms of permitted technology and homologation updates. However, Sansum noted, “There are now some regulations that are frameworking how we would apply additive manufacturing to parts.”
So far as the turbos go, those will continue to be a spec part supplied by BorgWarner. “It is actually the same centre section as we run right now,” Sansum said. “But it’s a different compressor wheel and compressor housing.”
2.4 litre performance
The engine mileage requirement will remain the same, at 2500 miles. The 2.4 litre engines will again run to a maximum of 12,000 rpm. At Indy, 1.3 bar will continue to be the maximum permitted plenum pressure on race day, so given the additional displacement we can expect top-end power to increase pro rata from about 600 bhp to about 650 bhp.
However, the road course plenum pressure will up from the current 1.5 bar to 1.6 bar. Sansum told us that this change, together with the larger displacement “will add approximately 100 bhp”. The higher road course plenum pressure is the same as is currently used under push-to-pass conditions. Sansum confirmed, “Using the 2.4 litre engine the push-to-pass [option] will be provided by the hybrid system.”
We asked, how will the shape of the 2.4 litre power curve compare to that of the current engine? “I don’t know that it will be that different. There are options on firing order and bank angle for both manufacturers, and they may choose to do something different to what they do now, so that may change their power curve.”
JR Hildebrand’s Chevrolet-powered car at the 2022 Indianapolis 500 (Photo: Walt Kuhn)
When the 2.4 litre engines from both manufacturers debuted at the IMS in late March 2022, how did that go? “It went very smoothly,” replied Sansum. “Both manufacturers ran over 600 miles across the three-and-a-half days.”
Hybrid
At the time of our interview [on the morning of the 2022 Indy 500] Sansum said, “Both Honda and Chevy have now taken delivery of a hybrid system. So they’re going through the initial fire-up phase of that hybrid system with an engine attached.”
And track testing will be when? “Although the 2.4 litre engine itself has been on the track, to be combined with the hybrid system, a lot of integration is involved in doing that. And there have been some delays with parts supply.
“We are aiming for the first track test of the 2.4 litre with the hybrid system at the end of June. We have the [IMS] track booked and we’re pushing very hard for it, but we understand that there is a lot of work to be done. So that end of June target is not 100% yet.”
What do you believe are the implications of the use of a hybrid system? Sansum replied, “I think the main advantage is that it provides a push to pass and one that provides a bigger boost than we have right now from our [boost-level] push-to-pass system. From a competition perspective, we’re still working out the most effective way to frame the use of the hybrid system in order to get the best advantage from that perspective.”
When they do the engine testing with the hybrid will they need to use the full transmission on the dyno? “No. There is an adapter plate that adapts the whole transmission onto the back of the hybrid.”
How much track testing do you expect to allow them ahead of the 2024 season? “As of now, we have four tests scheduled for this year And we’re still discussing how much testing we’ll do next year. But we will hope to get to multiple team testing before the end of next season.”
THE CURRENT INDYCAR ENGINE
By regulation, the current 2.2 litre IndyCar V6 turbos are conventional race engines having four valves per cylinder operated by double overhead camshafts through finger cam followers and with pneumatic valve return systems banned.
Twin rather than single turbos were specified from 2014, and these and the associated wastegates are spec items. By contrast, the plenum and the exhaust system are engine-specific but must fit within the tight Dallara IR18 envelope. No charge cooling is permitted. Another spec item is the ECU, and IndyCar prohibits the use of anti-lag systems, traction and launch control. However, calibration is open.
Both current engines exploit a combination of port and direct injection with a 300 bar limit on fuel pressure. There is one port injector and one direct injector per cylinder with at any given time the split between them defined by the ECU’s calibration. That split can differ from cylinder to cylinder as the engine accelerates through speed and load points, and sometimes one injector is shut off completely.
It is a subtle control strategy, and in RET 80 (August 2014) we reported HPD’s then IndyCar technical chief Mark Crawford saying, “The fuel system is probably one of the most important parts of IndyCar engine development. In order to develop it, you need a stable fuel specification. It needs to be very consistent. IndyCar has been good at supplying such [spec] fuel.”
Each year’s engine specification has to be homologated in many respects. IndyCar controls engine hardware development by allowing freedom of certain items while allowing some others to be re-homologated annually and freezing others, albeit in some cases with an occasional dispensation for re-homologation.
Open items include the piston, rings, bearings, valves and valve springs – all within certain material limitations. For example, steel pistons and titanium rods are outlawed. In fact there is a blanket ban on magnesium-based alloys, MMCs, inter-metallic materials and alloys containing more than 3% by weight of beryllium, iridium or rhenium.
Coatings are open for specific items. The rules do not allow DLC on piston skirts, camshafts, the ID of the liners, the crankshaft or the con rods. All coatings and surface treatments are subject to approval by IndyCar.
Con rods are an example of items that can be re-homologated on an annual basis, whereas the crankshaft and the block remain as homologated for 2012. Everything above the block was permitted to be re-homologated for 2014, and the top end was further allowed to be redesigned for 2016.
Since 2012 the maximum permitted engine speed has been 12,000 rpm. The maximum permitted plenum pressure is specified by IndyCar according to application. Since 2012 it has been 1.3 bar for the Indy 500 race, with initially 1.4 bar allowed for ‘Fast Friday’ and Qualifying. Of late, the latter figure has been 1.5 bar.
Initially 1.55 bar was permitted for road courses but during the 2012 season that was reduced to 1.5 bar with then 1.6 bar available for short ‘push-to-pass’ bursts. For 2016, push-to-pass was increased to 1.65 bar.
The engine mileage requirement was initially 1850 miles, which was increased in annual steps through to the current 2500 mile requirement. In the past we have noted that typically the loss of performance over that distance is less than 1%.
However, given the mileage requirement, the amount of detonation the engine can withstand becomes the limiting factor as to how hard it can be run though its life. As such, detonation is constantly monitored and the calibration tuned accordingly.
Interestingly, in RET 80 (August 2014), discussing the specific requirements of the IMS with Crawford, he remarked, “I think if you went back 15 or 20 years you would say, ‘It is a 500-mile race, it is the longest race we run’, so you would probably have thrown durability in there [as a requirement]. Nowadays, having to engineer an engine that is good for 2500 miles, and being able to put a new one in for [usually qualifying and] the race, none of us are worried about durability.
“By regulation, we have five times the durability we need for the Indy 500 race. So it really does come down to outright power – how much power you can make, and how well you can get it down to the track.”
In 2019, Crawford added, “The loading estimates we started the project with in 2012 are much lower than where we’re operating right now. The original plan was for that engine to be redesigned after 4 or 5 years, and we anticipated the loading regime would change but that it would be good for that timespan. But in 8 years it’s gone well beyond that.
“Nowadays, we have to pay very close attention to the piston, rods, bearings and so on. We’re constantly improving the materials, the lubrication and the strength of all the components to take the increased loading.”
Given 1.3 bar maximum power was initially (in 2012) in the region of 550 bhp, but within a couple of seasons the manufacturers had obtained 575 bhp. The rise continued somewhat more slowly to 600 bhp, after which the gains became marginal. Today's engines make in the region of 600 bhp at 1.3 bar, rising to around 700 bhp at 1.5 bar.
That suggests a pro rata gain with increasing plenum pressure, whereas in fact it is somewhat less than theoretical owing to the lack of charge cooling. Higher pressure increases charge temperature, so the charge is less dense and the engine is more prone to detonation.
HONDA
The Honda perspective on IndyCar powertrain evolution was provided by Wayne Gross, manager, trackside support and large project leader for the current 2.2 litre V6 turbo at Honda Performance Development, which designs and develops the marque’s IndyCar engines. We met him at the IMS after Qualifying and the Monday practice that followed that weekend.
Discussing HPD’s engine modifications from last year to this, Gross remarked, “Within the homologation regulations there are a few areas that are open to work on, including some hardware items, and we can constantly keep working on calibration. So we keep pushing in those areas we are open to explore. We work with IndyCar within the regulations and push forward where we can.
Wayne Gross, manager, trackside support and large project leader for the current 2.2 litre V6 turbo at Honda Performance Development (Photo: Anne Proffit)
“The base engine control software is fixed, but we can constantly change calibration items. IndyCar controls certain parameters, and then we have parameters we can modify and optimise. So we’ve got a full group back at HPD and then people here at the track who are always pushing those parameters, to optimise performance for all our teams for every track, every event, every condition.”
In terms of the regulations governing 2022 engine performance, Gross noted, “It is pretty well a carryover from last year. [The regulations] have been pretty well stable and mature for a number of years now.”
In terms of performance increase from Indy in 2021 to Indy in 2022, Gross remarked, “Due to the stability of the rules and regulations, our engine performance is pretty well optimised, and we’ve really been at that peak for a couple seasons. There are little things here and there but what we’ve done most is to try to help our teams optimise the full vehicle package.
“So full vehicle simulation, aero simulation, vehicle dynamics studies, gearing studies, all that stuff to extract the full performance from the whole car, not just from the engine itself. We have all the great men and women back at HPD in Santa Clarita helping and we’ve got a group here in Indianapolis that does a lot of work with our driver-in-the loop simulator.
“Our trackside group is kind of scattered throughout the country, but overall it’s just an awesome team to be part of. And you know, we just keep pushing and keep finding little things that we can help our teams with.”
After Chevrolet won the first four races of this year, you really had to be scratching your heads, we suggested. “Yes, we were frustrated. Obviously it was not what we expect of ourselves. We hold ourselves to very high standards. The past couple of years have been mighty successful for us, so we don’t appreciate or expect that and we don't accept it.
“So we find ways to push on, and I think the win for [Colton] Herta in the rain here [on the IMS road course, 2022 race five] was awesome for the whole group. A weight off our shoulders. But that is racing, it’s why we do this.
Honda-powered Marcus Ericsson en route to victory in the 2022 Indianapolis 500 (Photo: Joe Skibinski)
“We’d had chances at earlier events but things had’’t gone our way. But the competitor makes a step and we come back with another step. And that’s what we do, we keep pushing.”
And Pole Day here was awesome? “Yes!” How much of a part did the engine play in Scott Dixon’s track record four-lap average of 234.046 mph?
“Qualifying at Indy is the ultimate dyno, it’s flat-out for four laps. And obviously the Chip Ganassi team did an awesome job themselves – five cars in the top 12, four in the top six, two on the front row. So a huge hats off to the whole Chip Ganassi organisation.
“From our side, we thought it would be tight. Again, Chevy pushes us and we push them. But I think for the quickest qualifying time ever on record for a four-lap average, that’s mighty impressive and we are happy to have Honda power push them there.”
What happens if it rains,, as is expected on Carb Day? “Luckily we got our race engines in yesterday [for the Monday practice]. So we’ve got some time on our race engines already. So that helps us out with preparation there and it means we have some data to look at if by some chance Carb Day doesn’t happen.”
Did everyone change engine after qualifying? “All our full-time entries got their race engine for yesterday [Monda’’s] running.” But part-timers are on a single engine programme for this 500? “Yes, it’s just two part-timers for us, we’ve got Marco Andretti and Tony Kanaan here.”
Observing that this was the 11th season of the 2.2 litre V6 turbos, Gross remarked, “It’s actually been incredibly impressive, the competition between Honda and Chevy going back from 2012, all the way up to now. There has never been a very stark advantage on either side. We [both] always come up with ways to find little bits and keep competing, and keep edging ourselves further [on]. And the amount we’ve gained since 2012, on both sides, has been mighty impressive.”
How much performance increase has there been since 2012 for a given level of boost? “I would say tens of horsepower over the years.”
2023
Will there be any modifications to your current 2.2 litre engine for 2023? “Our plan is to carry on as we have [been doing]. It’s just another year's extension for our current engine package, so we plan to do that for another year.”
So you are anticipating improvement in performance here at IMS for next year? “Whatever we can find! We'll keep pushing. That’s why we do this!”
At the time of our discussion with Gross the use of a renewable fuel in 2023 hadn't been disclosed, and talks between Honda, Chevrolet and IndyCar were continuing as to what extent – if any – engine development would be constricted for 2023 compared to the regular scope.
Pit stop for Honda runner Tony Kanaan during the 2022 Indianapolis 500 (Photo: Dana Garrett
2024
Of the new 2.4 litre, Gross remarked, “We’re obviously flat-out with that.” Asked when HPD started designing it, Gross replied, “It’s been in the works since the regulations started coming out, so for more than 3 years. We started out in 2019 on our single-cylinder research engine, then moved to V6 testing shortly after. The original plan was to race it in 2023, and obviously the extension to 2024 gives us another year to keep pushing it forward.”
What will be the key differences compared to the current engine? “The regulations are similar but obviously there is the 200 cc displacement increase. There are also likely boost level differences at certain tracks. But the big thing is the hybrid system coming online.”
Is there any difficulty in fitting the new engine with the hybrid system into the existing car (which at the time of writing was due to continue in service through 2024)? “It gets tight. It’s a slightly bigger engine and we have essentially the same volume to work in. And the hybrid will be packaged within the current envelope of the car.”
Are there any aspects of the current engine to be carried over to 2024? “No, it’s a whole new engine for us, and then there is the hybrid system, so a bunch of new exciting stuff.
“On the engine side, I think we’re pretty well prepared. It's a larger [displacement] engine but it’s still very similar architecture. We’ve had many years to hone and optimise that package. And it’s throwing all the intricacies in and new things with the hybrid system that we have to sort out.”
What scope is there for new technology within the 2024 regulations? “I think the biggest new technology we’re all excited about is the hybrid system. That’s obviously the way the automotive world is headed. And it’s very important for Honda to have that in a racecar. So we are fully supportive of that direction and it really pushes the envelope from a technology standpoint.
“And there’s some stuff contained within the hybrid package that is mighty impressive. So we’re very happy about it.”
Will you use pre-chamber combustion technology? “It is within the regulations.”
2.4 litre performance
What are the implications of the added 200 cc? “More power; it’s a good thing.” Anything else? “It means we push the engine harder and it’s more stress on engine components. But [coping with that] is what we are here to do.”
It would appear that the engine mileage requirement in 2024 will remain as now? “That has been an ongoing discussion within IndyCar. There’s obviously a financial reason to try and maintain the current mileage. Otherwise we get into spending the wars; we want to try and maintain some common sense there. None of our budgets are going up so we have to try and keep things in check.”
How much more power do you expect the IC engine to give over the current one? “You can assume it roughly scales with the displacement increase. So about 10% more [for a given level of plenum pressure].”
And where are you at now in terms of top-end power? “In Indy Qualifying and on a road course [at 1.5 bar] w’’re around 700 bhp; at Indy in race trim [1.3 bar] around 600 bhp.”
How will the shape of the 2024 power curve compare to today’s? “It will be a similar shape but higher up. We work with our teams to try and optimise it, to make the engine as usable as it can be.”
How did the initial 2.4 litre engine track test here at IMS go? “That went really well. It checked off the boxes we wanted to check off. Since it was the first time the 2.4 litre engine hit the track we had a number of things to go through and a lot of systems checks. So we had a work list, we worked through it and we got through everything we wanted to.
“In our minds it was a very successful test, because we had a new engine on track for the first time and we got through our systems and ran roughly 600 miles.” How many cars was that? “We had one car and Chevy had one. We had Scott Dixon with Ganassi.”
And what kind of report did he give you? “I think we set his expectations right. We had to let him know it’s a new package and there are gonna be some growing pains. We weren’t there to set lap times and optimise things. It was more of just getting the car on track and working through our systems.”
Hybrid
We asked Gross, what are the implications of the use of a hybrid system, including in terms of driveability, especially on road courses and including in terms of engine control technology, and durability? “I think there’s still a lot to learn and figure out. We have a lot of testing ahead of us to answer those questions.”
Has the engine been tested on the bench with a hybrid system? “Those tests are ongoing at different levels. There’s different components testing.”
Has that included running with the full transmission? “There are different levels of testing going on. It’s all new stuff so you want to test it at a small level and then slowly build up to the full level.”
How much track testing is to be permitted ahead of 2024 season? “I think as much as we need. Obviously we want to make sure we put a good package on track for IndyCar and our teams. That’s the end goal for all of us. IndyCar, us and Chevy, we’re all in this together. We all want the same end goal – a good product on track, that will provide good competition. So limiting testing seems like a silly thing to do at this point.”
CHEVROLET
To provide the Chevrolet viewpoint, Rob Buckner, GM’s IndyCar programme manager, was accompanied by representatives of Ilmor Engineering, which designs and develops its IndyCar engines. They were Mario Illien, company co-founder and technical director, Steve O’Connor, managing director of the UK headquarters of Ilmor Engineering, and Paul Ray president of Ilmor Engineering Inc, its US offshoot. This group met RET on race morning at the 2022 Indy 500.
Rob Buckner is GM’s IndyCar programme manager (Photo: Anne Proffit)
Talking of improvements over the 2021 2.2 litre V6 twin turbo, O'Connor remarked, “We were pretty much changing all those components that we can [by regulation] on the engine. For example, for this year as usual we were permitted to change the con rods and the exhaust system. And then there are other components that we can change on a race-by-race or build-by-build basis. And changes of calibration, you could introduce at the next session.”
We asked if there had duly been a performance increase from 2021… then adding: ‘I see that smile Paul. Does that means yes, but we are not talking about it’?
“That means all we can say is that we have improved the engine, yes,” replied Ray. “The changes we made over the winter have helped with the race results of this year [winning four of the five races before the 500]. So we’ve definitely made worthwhile improvements.”
We asked, what have been the main areas of improvement of the engine since 2012? “I think we’ve changed most things on the engine,” replied O’Connor. “At various points along the journey since 2012 we’ve been allowed to re-homologate a lot of the engine. So cylinder heads, fuel system, plenum, exhaust system, camshaft profiles, pistons, valvetrain and so on.
“At the point where we’re allowed to update homologated parts, we typically look at all those components we’re free to update.”
We asked, what do you think are the pros and cons of your engine today versus Honda? “It seems really close,” replied Buckner. “It’s hard to say on an event-to-event basis. It seems like we’ve kind of congregated to a similar performance in a lot of areas. We’re always trying to find an advantage or address any weaknesses, but right now it seems like, especially on [IMS] race pace both engines are very, very competitive and close.”
2023
In respect of the coming of ‘renewable’ ethanol fuel for 2023 revealed just a couple of days before our meeting, O’Connor reported, “We’ve already used it in our engine test cells. Both us and Honda have tested with it, and have approved the fuel for use next year.”
Asked how it will affect the operation of the current engine, O’Connor replied, “In itself, I don’t think it will change how the engine runs. It’s obviously a great thing to do for the environment and the carbon footprint of IndyCar. But in terms of engine operation, the testing we’ve done has been really good and, no, no difference. Shell has supplied a really good fuel straight out of the box. So we’re very, very pleased and impressed.”
Mario Illien is company co-founder and technical director of Ilmor Engineering (Photo: Anne Proffit)
Compared to the existing E85, is the new fuel relatively fast or slow burning? “It is an ethanol as well so it doesn’t make any difference [in that respect],” replied Illien. “Ethanol is a relatively fast-burning fuel.”
Asked if there was a clear message at to what engine development is to be permitted for 2023, Buckner replied, “That is still to be determined; we’re not exactly sure what the 2023 regulations are going to look like.”
We pointed out that there isn’t a huge amount of time available before the annual December 15 homologation deadline. “Steve [O’Connor]’s group is really, really good. He doesn’t need much of a heads-up!” replied Buckner.
O’Connor added, “We are working on [potential] changes all of the time. We are constantly working on development items in the areas where we’re allowed to, so you never stop. It’s a constant churn of engine development, performance development, on-track performance development. So there’s no letting up in trying to improve the engine.
Steve O’Connor is managing director of the UK headquarters of Ilmor Engineering (Photo: Anne Proffit)
“The question on the table is: Will we have the same freedom for 2023 as we had for this year? Or will it be locked down, either partially or entirely so that we’re not allowed to do anything? This is an ongoing dialogue with IndyCar right now. If there is to be a lockdown it will be one that we [Chevrolet, Honda and IndyCar] all agree to.”
2024
Asked when design work started on the 2.4 engine, O’Connor replied, “A couple of years ago. So I think we started a bit behind Honda in that respect.” He added that it first ran on the dyno in November 2021.
Paul Ray is president of Ilmor Engineering Inc (Photo: Anne Proffit)
And, we asked, presumably of late you have suffered from the supply issues that have been dogging the rest of the racing industry? “Yes. Some of it is driven by availability of raw materials, some components that we buy in. But a lot of the parts that we put into the engine we make ourselves.
“Some aspects of our 2024 engine are now locked down because they’re less performance-sensitive than others. But right now, we haven’t frozen its specification, because we have another year of development and we want to be as competitive as possible.”
Asked if there are any aspects that will be carried over from the existing engine, O’Connor replied, “No, there aren’t any features or components that are being carried over on the mechanical side. I think we’ll probably continue with some of the sensors we use now. But because of the different capacity we will be re-engineering all components to suit that new capacity.”
Ray pointed out, “There is more boost in the new engine as well – it’s not just a capacity increase.”
In terms of the size and weight of the 2.4 litre engine, O’Connor said, “It is just under 10% larger by swept volume, so it is marginally larger. But lengthwise it has to be the same. Then the rules dictate it has to be heavier – we have a new minimum weight of 118 kg [versus 112.5 kg].”
O’Connor added that he doesn’t see any significant scope for the use of new materials in the 2.4 litre. Asked about the introduction of a pneumatic valve return system, he commented, “We would like to use one but the rules still do not allow it.” The rules do allow the integration of pre-chamber combustion technology though, and O’Connor confirmed that, as expected, this will be a characteristic of the new-generation Chevrolet engine.
2.4 litre performance
In respect of the initial 2.4 litre track test at IMS, Buckner said [with a smile] “We learned that at Indy in March, it can be a pretty miserable, cold and wet day! But the test did go really well.”
Asked how much power the 2.4 litre will give at 1.6 bar plenum pressure, O’Connor reported “about 100 horsepower more compared to the 2.2 litre”.
In terms of the shape of the power curve, Illien remarked, “It’s very similar really.” Will the use of the hybrid unit affect the shape of the power curve? “Not necessarily”, he replied. “Obviously the hybrid is a benefit in that it provides the potential to shape the curve a bit differently, but we don’t know how we can use the hybrid yet. That is still open [to discussion with IndyCar].”
In respect of the inherent driveability of the new engine, Illien added, “There shouldn’t be any difference really. The higher boost could have a small effect on driveability but the 200 cc increase, no.”
Chevrolet runner Juan Pablo Montoya on track during the 2022 Indianapolis 500 (Photo: Karl Zemlin)
Hybrid
O’Connor commented, “I think having the hybrid unit should give us more and different options on the driveability side compared to having the IC engine alone.” Illien added, “Obviously it depends on the freedom we are given with the hybrid system.
“Potentially it can shape your torque; you can make quite a few changes to improve driveability,” he added. “But we don’t know what those freedoms are yet. We don’t know what kind of software input we can have.”
We asked, what scope will there be to use the hybrid power boost at IMS and on other speedways? “We don't know”, replied Ray. “None of that has been determined yet.”
In terms of getting the hybrid system onto the track, O'Connor remarked, “We now have the hybrid unit and we expect to start bench testing it in the next couple of weeks.”
Bruckner added, “The target is a June test. That is what IndyCar and everyone is currently working towards. The March 2.4 litre test we did here [at IMS] was just engine with alternator, which we don’t intend to run on track again [without the hybrid unit].”
In respect of how much track testing will be permitted ahead of the 2024 season for the 2.4 litre engine with the hybrid unit, Ray said, “A great deal, because it has to work. It’s brand new technology. It’s a brand new system for us. A lot of application work has to be done. So we’ve already agreed to a lot of testing this year and next.”
It follows that in this respect you, Honda and IndyCar are all on the same page? “Yes, definitely. All the testing we’ll do together with Honda at the track. So we won’t be testing independently, we’ll be testing together. There's really good collaboration between the manufacturers and IndyCar.”