ACO Engine Rules
The Automobile Club de l’Ouest has released its technical regulations for the 2004 Le Mans Prototype classes (so we didn’t have to wait until Sebring); as expected, they differ from the FIA regulations in some aspects - most importantly, the engine regulations.

For the smaller 750kg class - or in ACO-speak, LMP2 - a distinction is made between "free" (i.e. purpose-built) and "homologated" engines, which must be homologated in "LM"-GT and compliant with the "LM"-GT technical rules. The regulations for purpose-built engines in this class follow those currently in place for LMP675, i.e. 3400cc 8 cyl. N/A, or 2000cc (up to) 6 cyl. single turbocharged. FIA SR2 regs. are therefore different ‘here’ – up to 3000cc N/A production-based racing engines only.

Homologated engines are limited to 4000cc, as opposed to 4200cc in FIA SR2 (the first person to explain why this difference of 200cc is necessary will win a prize); turbocharged engines are not allowed (they are for the FIA’s homolgated SR2 units). Also, the ACO "homologated" engines explicitly must not be stressed - this rule doesn't exist in the FIA rulebook.

An addition has been made to the LMP1 (900kg) prototype engines: turbocharged Diesel engines with a maximum size of 5500cc are now allowed. Diesel engine manufacturers will take note of article 5.5.3: "the engine must not produce visible exhaust emissions under race conditions".

Annex 1 to these regulations has a prefix which states that air restrictor sizes and turbo boost limits "are made out to balance the performance of the LMP1 on the one hand and of the LMP2 on the other hand".

The chassis regulations are indeed identical to those of the FIA.

Is it just us? We’re still confused regarding weights and restrictors for current 675 cars next year. Presumably that will be sorted out at / by Sebring, and we’ll simply see them racing against the 900s – just as they are this year (and were at the end of last year)! We suspect that this will be how the situation will be resolved.