Actually did a little test on this. Boosting without using any coolant in MSPR grants you ~452 meters before overboost explosion (don't ask how I calculated that, it's really complicated). You'd have to find some kind of coolant in order to extend your boost for a few more seconds.
Take a mudplugger to SnowGod Canyon, stick to the high side of the avalanche mountain, and simply hold down X. Be sure to start this without any boost heat to begin with, and be wary of the tight corner you will exit into.