1980: three-year-old season

Detroit did not race as a two-year-old, beginning her racing career with a five-length win in a maiden race over 2100 metres at Saint-Cloud Racecourse in May 1980. She was then moved up in class for the Group Three Prix de Fille de l'Air over the same course and distance on 21 June. Ridden by Alain Lequeux, she started the 2.1/1 favourite and won by two and a half lengths from Gold River. On 19 July, the filly started the 1.4/1 favourite for the Group Three Prix Chloé over 1800 m at Evry Racecourse and won by one and a half lengths from Licara. Detroit's next race was the Prix de la Nonette over 2000 m at Deauville Racecourse on 31 August. She started the 9/10 favourite and won by two lengths from India Song with the Prix de Malleret winner Luth de Saron in third place.^[4]

Pat Eddery took over from Lequeux for Detroit's next race, the Group One Prix Vermeille over 2400 m at Longchamp Racecourse on 14 September. She started the 11/4 favourite against a strong field which included Aryenne (Poule d'Essai des Pouliches), Mrs Penny (Prix de Diane), Cairn Rouge (Irish 1,000 Guineas) and Gold River. Detroit was unable to obtain a clear run until the closing stages, but then produced a strong late run to finish third, beaten half a length and three quarters of a length by Mrs Penny and the Irish-trained outsider Little Bonny. Many observers, including Timeform, considered Detroit to have been a very unlucky loser. On 5 October, Detroit was one of twenty horses to contest Europe's most prestigious weight-for-age race, the Prix de l'Arc de Triomphe over 2400 m at Longchamp. Ridden by Eddery, she started the 6.7/1 fourth choice in the betting behind the British four-year-old Ela-Mana-Mou, the French colt Le Marmot and the 1979 Arc winner Three Troikas. Unusually, the race was run on firm ground and the presence of several pacemakers ensured that the early pace was very fast. Eddery retrained the filly in the early stages before moving to the outside to make her challenge in the straight. Detroit made rapid progress, overtaking Ela-Mana-Mou and Three Troikas inside the last 200 m and holding the late run of Argument to win by half a length.^[4] The winning time of 2:28.0 was a new record for the race.^[5]

1981: four-year-old season

Detroit's form in the early part of 1981 was disappointing. She finished fourth of the six runners behind Argument in the Prix d'Harcourt and fifth of nine behind the same horse in the Prix Ganay on 3 May. Detroit was off the course for sixteen weeks before returning to win a minor race over 2200 m at Clairefontaine in August. She then followed up by winning the Prix Ridgway at Deauville, beating Ruscelli by one and a half lengths. According to Timeform, she looked to be in much better condition than in spring, but wore bandages on her legs, suggesting injury problems. In September, Detroit started odds-on favourite for the Prix Foy over 2400 m at Longchamp. In a slowly run race, she accelerated clear of her three opponents early in the straight and was eased down in the closing stages to win by two lengths from Lancastrian, with Gold River in third place. On 4 October, Detroit started the 7/2 second favourite in her attempt to win a second Prix de l'Arc de Triomphe and was ridden by Freddy Head, who had opted to ride her in preference to Gold River. Detroit was well-placed in the early stages but dropped away in the straight and finished twentieth of the twenty-four runners behind Gold River. On her only subsequent appearance, Detroit finished fifth behind April Run in the Turf Classic at Aqueduct Race Track.^[6]