I always assumed 'Test'
But in the context of the race S-car for 'spare' would have made more sense.
Spare cars were always known as 'T' cars as predominantly it was the 'test' car which was pressed into service if the there was an issue with the proposed race car.
Race cars would normally have lower mileage parts to the spec. confirmed by the test car during testing and practice.
There were also 'Q' cars at races like Le Mans. Built with a 'sprint' spec engine which would have a life much shorter than a 24hr sec engine.
Far fetched? That's exactly why 'party mode' is being banned from this weekend as the use of high boost pressures and advanced timing considerably reduces the engine life.
Qualy spec cars are not new in F1. Back in the early eighties I remember seeing Piquet's Brabham pitting just prior to the end of qualifying at Monaco to 'adjust' the engine. A mechanic whisked away the engine cover whilst some spanners were rattled in the engine bay.
Seconds later, four burly members of the crew wrestled 'an' engine cover back on the car before the driver completed a out lap prior to the car being weighed at the end of the session.....
I also noted that the fire bottle was a plastic blow moulded replica which probably weighed about 5 ounces rather than the regulation 5kgs......
