Find solution

The high-mount stoplight or combination light assembly, as Hyundai calls it, on the rear of the 2007 Sonata uses a 921 bulb, which is a key part of the Sonatas rear lighting system. The light is designed to be highly visible to drivers behind you when the Sonatas brakes are applied and helps to avoid rear-end collisions. Removal of the Sonatas taillight assembly is required to replace the stoplight.

Instructions

1

Open the trunk of your Sonata and lay on your back inside the trunk looking up at the bottom of the package tray, or rear deck, directly below where the light assembly sits. Locate the two gold-colored Phillips head screws that retain the light assembly.

2

Remove the two retaining screws using a long Phillips screwdriver then move to the inside of the car to access the light assembly on the top side of the rear deck, which is inside the passenger compartment. Lift the rear of the assembly slightly while pulling it forward to free it from the package tray. Turn the assembly over and locate the bulb socket on the underside.

3

Rotate the bulb socket counterclockwise to unlock it, then pull it out of the taillight housing. Grasp the bulb, pull it straight out of the socket and discard it. Push a new 921 bulb into the socket; make sure it seats completely.

4

Slide the bulb and socket into the taillight assembly then rotate the socket clockwise a quarter turn, locking it in place. Turn the taillight assembly over, slide the tabs on the bottom of the assembly in the holes in the package tray and slide the assembly forward until it sits flat on the tray.

5

Move to the trunk and reinstall the two Phillips head screws with the long screwdriver. Tighten the screws until they are snug. Do not over-tighten these screws or you will crack the taillight assembly.

6

Close the trunk and test the light; have someone step on the brake pedal or watch the light while you press the pedal. If the light functions properly, the repair is successful.

The design of an exhaust system affects the flow rate of gases expelled from an engines cylinder ports through piping leading outside. Exhaust flow determines engine power and fuel efficiency. Small piping decreases flow rates but increases gas velocity, which increases torque. There must be a balance between flow and velocity.

Piping Diameter

High flow exhaust systems increase top-end power. However, excessively large piping allows full flow but reduces exhaust velocity. A larger amount of combustion occurs when there is a strong exhaust velocity, causing increased torque. Balancing flow and velocity optimizes engine power, fuel efficiency and strain on the engine.

Piping Shape and Length

Bends in exhaust piping reduces flow rate and velocity. Race cars use open headers for their short length and lack of bends. Open headers expel gases directly into the air without routing it through a front pipe, catalytic converter and muffler. While street cars normally cannot use open headers because of noise and emission laws, the quicker exhaust gas releases outside, the less chance the engine loses power due to exhaust system causes.

Catalytic Converter and Muffler

A catalytic converter filters harmful chemicals out of exhaust gas. A muffler reduces exhaust sound. High flow aftermarket catalytic converters and mufflers increase flow and velocity by reducing internal restrictions.