Recently, I have noticed a non catastrophic, although damaging, amount of detonation in S3 engines using the required VP MS98 fuel at the 2008 Supernationals. We (customers and SRS) haven't experienced that problem here using VP C12 or Tracktek 111 fuel. So it seems that the spec Hondas are tuned so well now that they will detonate if octane levels are lowered to the MS98 level.

On the dyno and the track VP MS98 fuel (96 motor octane) and VP C12 or Tracktek 111 (106-108 motor octane rating) fuel perform virtually the same in the SRS S3 spec Hondas we are familiar with. However, in long races especially with long straight-aways the C12 type octane level prevents detonation. Summarizing, increasing the octane level does not gain a performance advantage in the S3 spec Hondas, but prevents engine damage from detonation.

Fortunately the spec Honda classes have rules that tightly limit compression, port timing and other power enhancing modifications. That will save the class from costs spiraling out of control. Assuming that some improved new pipe is not homologated, I think most top tuners have achieved power level from the spec Hondas that requires fuel with a higher octane rating than VP MS98.

As long as the standard fuel is rated at less than 100 motor octane, I think most racers will elect to suffer the non catastrophic, although damaging, amount of detonation that will occur rather than retard the timing and go slower. So preventing the engine damage from detonation by increasing the octane level of the fuel will keep the current performance level, but reduce the spec Hondas' top end maintenance cost without changing the engine rules.

For more detailed information about SRS Shifter Kart engine recommendations, call us at 903-769-4140.