From Sonic Retro
In Sonic Adventure 2, the Jet Engine is an upgrade to Doctor Eggman's walking mech. It enables the mech to hover short distances after jumping. It is necessary to complete the level it is located in: Lost Colony.
To get the upgrade, proceed past the first Point Marker, and you will come into a room that is in complete darkness. Navigate through it until you find a way to the upper level. The Jet Engine will be there waiting.
|Character upgrades in Sonic Adventure 2
|Light Shoes | Ancient Light | Bounce Bracelet | Flame Ring | Mystic Melody | Magic Gloves
|Booster | Bazooka | Laser Blaster | Mystic Melody
|Shovel Claw | Air Necklace | Hammer Gloves | Sunglasses | Mystic Melody
|Air Shoes | Ancient Light | Mystic Melody | Flame Ring
|Jet Engine | Large Cannon | Protective Armor | Laser Blaster | Mystic Melody
|Pick Nails | Iron Boots | Mystic Melody | Treasure Scope