While tinkering with my new S1, I decided to have a look around the intake system to see how everything fits together.
I started by making a short video of the stock scooter starting up and revving in place, to compare volume after any changes.
The airbox is pretty well-sized and sucks in air from the hole at the bottom.
Removing the screws around the sides of the box allows you to separate the two halves.
On the right-hand side of the picture, you can see the rubber hose that takes in air that has passed through the filter and runs to the throttle. The left-hand section of the box includes the filter and the air intake.
The filter is a neat-looking panel that wouldn't add to much restriction to the airflow, being about half the size of the one in a 100hp small car.
What isn't so neat-looking is this funny rubber snorkel stuck over the intake hole, which diverts the airflow straight into the opposite wall of the airbox to the filter.
The crinkly stuff on the bottom of the snorkel is a tar-like glue that only weakly holds it in place, and it easily slides out without having to undo any screws or clips.
This thing is surprisingly heavy, being made of a dense rubber with four thin channels letting air through. It certainly looks like a good sound-deadening measure, but not such a good thing for moving air.
With the restrictor removed and the airbox reassembled, the engine takes on a more "growly" sound, as you can hear in the vid below.
On the road, takeoff felt about the same, but once moving it seemed to build speed more easily (e.g. 60-80 felt a lot quicker)
Unfortunately, I couldn't think of a way to work a stopwatch with both hands full, so I'll restrict my performance verdict to saying it felt a bit better, and sounded a lot cooler when leaving the lights. I'll be checking fuel consumption over the next week to see if that improves, as the scooter seemed to be using less throttle to maintain a constant speed.
If anyone else wants to try this and can find a way of directly measuring power or acceleration, I'd like to hear the results.