>>28466606>diesels had a 50% displacement advantage for years before Audi raced the R10.Not in the ACO rules. Diesels had no real set tech regs prior to the 2006 rule changes when they went from LMP900/LMP675 to LMP1/LMP2. All it said before that was that alternate fuels were subject to ACO discretion which was why nobody ever bothered with it. The ACO only started to have actual regulations for diesels when they published the 2006 rules which coincided with the Audi R10.
Among these changes, the displacement discrepancy was only about +38% in favor of diesels and only applied to FI engines. There was no discrepancy for NA engines as both diesel and petrol engines were both limited to 6000cc. They didn't bother changing the NA displacement limit because the R10 wasn't NA.
Source: http://www.mulsannescorner.com/2006LMP12.pdf
When you examine the rules, it's pretty blatant that it was tailor made for the Audi diesel program and rendered petrol engines non-viable.