With manufacturing based in Brixworth, Northamptonshire, and maintenance offices in Plymouth, Michigan, the company supplies engines and consultancy to the IndyCar Series and MotoGP.

After the death of Paul Morgan in a vintage aeroplane crash in 2001, Mercedes increased its stake until it owned the entire company, and renamed it Mercedes-Benz High Performance Engines Ltd.

However, the business is now using its racing expertise to diversify into other areas such as OEM automotive, defence, marine and energy efficient engine applications.

There was some acrimony in their split from Cosworth, their former employer claiming that the Ilmor engine was little different from their planned modifications to the DFX.

The Ilmor 265-A, badged initially as the Ilmor-Chevrolet Indy V-8, debuted at the 1986 Indianapolis 500 with Team Penske driver Al Unser.

Emerson Fittipaldi drove a "Chevy-B" to 4th place in points, but both he and Mears dropped out of that year's Indy 500 due to crashes.

In 1991 Ilmor entered Formula 1 with a V10 engine as exclusive supplier to the ambitious Leyton House team (formerly March).

In order to protect their image, Mercedes took on an observational role in the project and the cars had "Concept by Mercedes-Benz" written in the engine cover.

After scoring 12 points in 1993, Mercedes entered officially in 1994 using an updated version of the 1993 engine, and now "Powered by Mercedes-Benz" was seen on the Sauber engine-cover.

Originally stock-block engines based on production units, fitted with two pushrod and rocker arm actuated valves per cylinder, were permitted to run at increased cubic capacity (3.43 litres vs 2.65 litres) and significantly greater turbo boost than the pure racing engines.

Ilmor realized that this provided scope for a completely new pure-bred racing engine – it would need to retain pushrods, but could be designed specifically for the requirements of the Indianapolis 500, and in strict secrecy schemed a completely new V8 engine which was approximately 200 bhp (150 kW) more powerful than the Cosworth XB and Ilmor 265D opposition.

Team Penske's cars were by far the fastest at the 1994 Indianapolis 500, and Al Unser Jr. won the race, with Emerson Fittipaldi also figuring strongly until an accident on lap 184.

Rahal-Hogan Racing joined Penske as major teams, as Bobby Rahal collected five podiums to finish third in the overall standings.

In 1996, Penske's Unser Jr. finished fourth, Rahal seventh and his teammate Bryan Herta eighth, with neither collecting wins.

In 1997, Unser Jr. had a poor season, whereas Penske teammate Paul Tracy claimed three wins but retired in the last five races to finish fifth in the standings.

PacWest drivers Maurício Gugelmin and Mark Blundell claimed four wins combined and finished fourth and sixth in the standings.

[10] Ilmor was heavily criticized when four of its NT1 engines failed during the 2019 World of Westgate 200 at Las Vegas Motor Speedway, effectively eliminating ThorSport Racing drivers Grant Enfinger and Johnny Sauter from the playoffs.

In 2001 Paul Morgan was killed while landing one of his vintage airplanes, a Hawker Sea Fury at Sywell Aerodrome, Northamptonshire.

From its start as an Indy Car engineering and trackside support group Ilmor, Inc.’s capabilities have grown to encompass design and analysis tools, engine and sub-systems test capabilities – including emissions compliance benches, precision manufacturing, electronics and wiring design and manufacture, and facilities for service and support.

the expanded facility (over 44,000 square feet) houses more than 100 people, and produces high performance products in multiple powertrain related arenas including auto racing, boat racing, high-performance road cars, high performance offshore powerboats and custom V-twin motorcycles.

Since 2004, Ilmor's high-performance marine division has enjoyed substantial growth, becoming a well-established supplier in the U.S. and European boat market.

The 700-horsepower, naturally aspirated marine engine was developed with significantly improved fuel efficiency and a light-weight package.

The success validated Ilmor's belief that its production based high-performance marine engine could race and win against any competition throughout the world.

[14] Former 500 cc race winner Garry McCoy was confirmed as the rider for the Michelin-shod bike in its 2006 appearances, scoring points both in the 2006 Portuguese Grand Prix at the Autódromo do Estoril and the 2006 Gran Premio de la Comunitat Valenciana,[15] becoming the first rider to score points on an 800cc MotoGP machine, though McCoy finished last on both occasions, four and seven laps down respectively.

On 18 December 2006, Ilmor Engineering confirmed via their website that Jeremy McWilliams and Andrew Pitt had been selected as riders for the 2007 season.

[17] On 30 April they announced that they would run a "slimmed-down" set-up focused purely on engine development, releasing all unnecessary personnel but keeping riders McWilliams and Pitt under contract.