Power Train Test Upgrades
20 October 2016
Ilmor Engineering is one of those companies that largely chooses to fly underneath the radar. Its customers include some of the biggest names in motorsport and beyond, ranging from NASCAR teams to aircraft manufactures. And yet you could quite easily drive past the company’s Northamptonshire headquarters in the UK without even noticing it.
Across the road sits the factory where Mercedes makes its all—conquering Formula 1 engines. That too was part of the Ilmor empire until the German brand completed its purchase of the group in 2005. The rights to the name and the non-F1 side of the business were promptly sold back to its original owners and since then the two have gone on as separate entities.
Ilmor has diversified over the years into OEM automotive, marine and defence but motorsport remains the backbone of the business. These days it’s perhaps best known for developing and manufacturing the Chevrolet IndyCar engines but the company also works with Roush Yates Racing Engines on the Ford NASCAR program, not to mention Renault on its F1 units. Add to that a number of GT and World Rally Championship projects and it’s obvious Ilmor is doing a lot behind the scenes.
The unremarkable–looking industrial unit that forms its UK base is home to 85 staff and array of test facilities. There’s a bank of seven dynamometers, including an in-house designed F1 dyno capable of more than 20,000rpm – due to be retired shortly for a new Apicom FR500BRV eddy current unit. Alongside it sit three Schenck D700 water brakes, two Apicom FR1000S eddy current dynos and an AVL Elin EBG P22 transient AC dyno run in tandem with an Apicom FR500BRVS eddy current brake.
Each cell is fed with its own stream of inlet air, with independent control of temperature, pressure and humidity. This largely to provide fixed environmental conditions, rather than full climatic testing but one of the cells does have a neat trick in the form of a large compressor that mimics the effect of a turbocharger or supercharger. This provides up to 8 bar of boost, allowing engines to run in a forced induction mode without the associated hardware.
“At any one time we’re typically using four of those dynos for internal use and hiring out the remainder” says Ian Whiteside, chief engineer of advanced projects at Ilmor. “They’re fed by a 42,000-liter tank above ground or one of five 9,000-liter subterranean tanks, which can be loaded with anything from aviation fuel to methanol”.
The company is currently in the process of switching over its dynamometer control systems to the REO-dEC platform. There’s also a Horiba MEXA 7170D emissions measurement system and a total of four AVL IndiSet analysis machines for high-speed data acquisition.
At the high-performance end of the spectrum, the biggest challenge is actually getting cylinder pressure transducers to survive, explains Whiteside: “On our Formula 1 and IndyCar work we’re really pushing the capability of the sensors. Even using the highest quality 300 bar sensors from AVL and Kistler, their lifespan ranges from a few hours down to a single knock event. They tend to have a bit of concussion after that!”
Less brutal, but no less important, is Ilmor’s off-engine rig. This is another in-house designed device developed for testing engines or components in a motored state. It is powered by a 46kW electric motor, which provides enough torque for large-capacity road engines and even th4e big NASCAR V8s.
Some of the most interesting work carried out on this rig revolved around valvetrain development. Whiteside explains. Just down the corridor, the company has a single-valve rig, which enables valve and spring motion to be examined in even greater details – something that is particularly critical in NASCAR engines, which rev to higher than 9,000rpm with pushrod actuation and mechanical springs.
“It’s interesting, because the valve doesn’t always move in the way you think it’s going to move”, says Whiteside. “NASCAR valvetrains are designed to allow lofting – where the follower parts company with the camshaft to achieve higher lift. Getting it to come off is quite simple but getting it to go back down is a bit trickier! On the single-valve rig it’s also quite difficult to get the right lubrication on the rockers and the push rods during the test, so we could only run that for a few seconds at a time”.
A number of techniques are used for capturing the details of this valve motion. One option is to bounce a laser beam off the face of the valve, explains Whiteside, while another is to cut a series of serrations onto the valve to be picked up by an eddy current sensor embedded in the valve guide. High-speed video is another method, often used in conjunction with a tracking system that picks up the motion of coloured dots placed on the components.
Further down the facility lies the injector flow rig, which is routinely used for characterizing the injectors on the firm’s IndyCar engines. Quite unusually, it features a rate tube, which can capture will be open 12:00-15:00he injector flow on a crank angle basis, as opposed to averaging it out over a longer time period.
“With this rig, we can look at how the mass flow changes as the injector opens and closes. That’s really useful for comparing the repeatability of injectors, but it’s also good for looking at the performance as the injector ages”, notes Whiteside.
TIME AND MONEY
Although the airflow rig is still used for correlation purposes, most of the development work has been carried out in CFD since the company underwent a major overhaul of its simulation capabilities in 2015. It now has a new 32-core computing cluster, running the converge CFD code from Convergent Science.
Developed with in-cylinder combustion modelling firmly in mind, this package contains a variety of different features designed to improve the speed to accuracy balance of the CFD simulations. It’s Ilmor Engineering’s first foray into the world of in-cylinder simulation and, according to Whiteside, the results have been impressive.
“One of the first major projects we did using Converge was the revised IndyCar cylinder head for the start of this season”, he reveals. “We saved six to eight weeks in terms of development time – a reduction of around 50% - and arguably got to a better solution as a result of using simulation. By screening the designs in the virtual world, we also saw a 75% reduction in our prototype build costs”.
Embracing an increasingly digital age is one of the things that keeps Ilmor at the cutting edge of engine development and means there’s surely a lot more come from this company.
Taken from Automotive Testing Technology International September 2016