Building a Cold Air Intake for the ST

Overview

A cold air intake can be fabricated fairly easily for ST Celicas. This comprehensive guide shows you how to build a custom cold air intake system using readily available parts.

⚠️ Difficulty Level: Intermediate
🕒 Time Required: 2-4 hours
💰 Cost Range: $80-120

Required Parts

Three 2.5" hose couplings (rubber or silicone)
One 180° mandrel bent aluminum pipe, 2.5" diameter
Six 2.5" hose clamps
Air intake filter with 2.5" inlet (K&N recommended)
AEM intake bypass valve (optional but recommended)

💡 Part Sources:
• Hose couplings: Lowes, Home Depot, or online
• Aluminum pipe: JC Whitney (~$30)
• Clamps: AutoZone, Advance Auto Parts ($0.78 each)
• Filter: K&N ($30-40) or budget option ($10)

Step 1: Remove Stock Intake System

Remove your old intake box and the black resonator box on the driver's side fender. Loosen all clamps and unscrew the bolts inside the box under the filter, then remove the bolts holding the intake box together. For the fender resonator box, remove the three 10mm bolts and pull firmly to remove it.

Step 2: Cut and Prepare Pipes

Cut the U-shaped mandrel bent pipe into three pieces:

Cut in half at the middle of the curve
Cut one half again to create a short curved piece
Cut 18" off the other half to create a long curved piece

You'll end up with four pieces total but only need three: short curved pipe, long curved pipe, and small straight pipe.

Step 3: Install IAT Sensor

Drill a hole in one of the pipes for the intake air temperature (IAT) sensor. Make the hole the same diameter as the sensor. If it's loose, wrap a few pieces of masking tape around the sensor for a snug fit.

Step 4: Assemble the Intake System

Install IAT sensor in the prepared pipe
Connect small curved pipe to intake manifold using hose coupling
Connect small straight pipe to curved pipe
Connect long curved pipe from fender to straight pipe
Attach intake filter to end of long curved pipe
Tighten all clamps securely

💡 Pro Tip: Jack up the car and work from underneath for easier access when connecting the fender section.

Step 5: Final Steps and Testing

Reinstall the splash guard to protect the filter from road debris and water. Consider installing an AEM intake bypass valve (~$30) for hydrolock protection. Double-check all connections, start the engine, and check for air leaks.