Reigning World Endurance Champion Toyota is evaluating all aspects of its technical package for 2016 after admitting that it has been leapfrogged by rivals Audi and Porsche this season.
Ahead of this weekend's Le Mans 24 Hours, Toyota Motorsport GmbH technical director Pascal Vasselon has revealed that the retrieval systems, energy storage unit and normally-aspirated engine used in the latest TS040 HYBRID were all under review.
"We are examining what we do next year, because we need a plan," he told AUTOSPORT.
"We had an advantage last year and when we put our updated car on the track it was immediately 2.5 seconds faster [than last year's version], but it is not enough.
"The question was not if it would happen but when, because we know we have less resources, but we thought our advantage would last another year."
TMG is known to have been evaluating a move away from its super-capacitor energy storage system, and considered switching to batteries for this season.
Vasselon refused to rule out switching its internal combustion engine concept away from its current normally-aspirated V8.
"What we can say is that under normal conditions, a normally-aspirated engine is reasonably competitive," he said.
"But a turbo has a wider window and can react to all conditions, such as high altitude and hotter temperatures."
Vasselon conceded that the two Toyotas TS040s "will not be the fastest" cars at Le Mans this week.
He said the Japanese manufacturer would be "going for a strategy based on maximum reliability".
"We know that one second a lap is six and a half minutes over 24 hours, but last year the winning Audi spent 25 minutes in the pits," he explained.