Venting the Exhaust

Rob drills guide holes at the base of the cans

That's going to be extremely hot air being pushed out those Hayabusa pipes when they start venting nitro methane exhaust, so Rob is drilling holes to draw in cooler external air.

The actual exhaust pipe runs inside the cans to carry the hot gases from the engine. Just adding a dead air space between the pipe and the outside adds a layer of protection from the heat.

Each hole is three quarters of an inch in diameter

By opening vent holes, Rob is creating an active air exchange. As blazing hot exhaust rushes through the pipes, it will pull cooler air through the holes. That will lower the temperature of the exhaust, while creating extra force.

The area of the the holes is approximately equal to the area at the end of the can, making a vacuum that should make a dramatic effect.