More Balance Of Performance Adjustments

Post-Sebring, IMSA has released its latest bulletin, on April 7, following fairly hot on the heels of the most recent revision to the performance of certain cars (March 1).

In LMP1, both types of Lola receive a performance gain, the B06/10 with a reduction in its minimum weight, from 925 to 900 kg, the EX257 / B01/60 with an increase in restrictor size, to 43 mm (from 41.8). Absolute intake boost pressure is also increased for the two litre car, from 2500 to 2800 mB.

There was considerable discontent regarding the performance of the winning car at Sebring – although the R10s won’t be racing in the next three ALMS events.

In LMP2, all two litre turbocharged engines – in effect the AER inline fours – have their maximum boost pressure raised from 2500 to 2700 mB.

The Porsches were notably quicker than anything else in their (LMP2) class at Sebring.

The Courage Mazda benefits from a change in the equivalency formula (to calculate its restrictor size), which in simple terms means that the 1.25 figure in the relevant equation is changed to 1.3.

There are changes in GT1 too, for the Aston Martins and Saleens. GM’s Doug Fehan had anticipated that the (Konrad) Saleens would have been quicker than they were at Sebring – but their performance there has resulted in a reduction in weight (1125 to 1100 kg) and a 46.4 mm restrictor (that is, two sizes to the right, or larger – in effect, the restrictor applicable to a 1300 kg car, without the extra 0.3 mm for using air conditioning).

The Aston Martin DBR9s have their minimum weight reduced from 1125 to 1100 kg, and they’re given a ‘leg-up’ with two 31.8 mm restrictors. At Sebring the DBR9s had the option of 31.2 mm restrictors at 1125 kg or 31.8 at 1175 kg.

Tyres are part of the ‘equation’ when comparing Corvettes and their competitors: the DBR9s certainly set faster lap times than the C6.Rs in the cooler hours at Sebring.

Finally, in GT2, there are changes for the Porsches... but only slight ones. The 3.8 litre engines can now run with two 29.0 mm restrictors and the 3.6s two 29.2 mm restrictors - exactly as per the ACO restrictor / weight table.

"This takes them back to the spec. that is in the book before the "Le Mans" penalty," explains IMSA's Tim Mayer. For comparison, the 3.8 engines ran at Sebring with 28.7 mm restrictors.

Hopefully this is the end of the adjustments for some time - because they make the editor's head hurt.

"(But) can you imagine what it is like to come up with these numbers?" responds Tim Mayer. "We believe that these adjustments will take us to mid-July at least."


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