Weber IDF Air Jet 150

OVERVIEW

Precision tuning is the heartbeat of any high-performance air-cooled Volkswagen engine, and the Weber IDF Air Jet 150 is a critical component in achieving that perfect air-fuel stoichiometry. When you are running a dual Weber IDF or EMPI HPMX setup, the air corrector jet plays a pivotal role in the main metering circuit. As your engine climbs into the higher RPM range, the air jet works in conjunction with the emulsion tube to "lean out" the mixture, preventing the engine from running overly rich as the venturi vacuum increases. A size 150 air jet is a staple in the tuner''s toolbox, offering a specific flow rate that helps smooth out the transition from the idle circuit to the main circuit, ensuring your Beetle, Ghia, or Bus pulls hard all the way to the redline without stumbling or loading up on fuel.

Crafted from high-quality brass to exacting tolerances, this EMPI-sourced Weber IDF Air Jet 150 is designed for longevity and repeatable performance. In the world of air-cooled performance, "close enough" is never good enough. Whether you are building a 1776cc street sleeper or a 2332cc stroker monster, the ability to fine-tune your high-speed circuit is what separates a mediocre build from a trophy winner. These jets are sold individually, allowing you to purchase exactly what you need for your dual-carburetor synchronization. By choosing genuine-spec components like the 77401.150, you are ensuring that your carburetor''s calibration remains consistent across all cylinders, protecting your investment and maximizing every ounce of horsepower your flat-four can produce.

FITMENT

This Air Jet 150 is designed for use with the following carburetor models and air-cooled Volkswagen applications:

• Carburetor Compatibility: Weber IDF Series (40, 44, and 48 IDF), EMPI HPMX Series.
• Volkswagen Type 1: Beetle and Super Beetle (All years equipped with IDF/HPMX conversions).
• Volkswagen Type 2: Bus, Transporter, and Kombi (1950-1979).
• Volkswagen Type 3: Fastback, Squareback, and Notchback.
• Volkswagen Karmann Ghia: All years (Convertible and Coupe).
• Porsche 914: 4-cylinder models equipped with IDF carburetor conversions.
• Custom Applications: Any engine utilizing Weber IDF or EMPI HPMX carburetors, including sand rails, buggies, and trikes.

SPECS

• Jet Size: 150 (.150mm orifice calibration).
• Material: Precision-machined solid brass for corrosion resistance.
• Thread Pitch: Standard Weber air corrector threading.
• Circuit Type: Main circuit air correction.
• Manufacturer: EMPI.
• Part Number: 77401.150.
• Quantity: Sold individually (Each).
• Function: Regulates air bleed into the emulsion tube at high engine speeds.

PRO TIPS

1. Understand the Inverse Relationship

It is vital to remember that air corrector jets work inversely compared to main fuel jets. While a larger main jet makes the mixture richer, a larger air jet (like moving from a 150 to a 160) actually makes the mixture leaner at high RPMs. If your engine is "blubbering" or blowing black smoke at the top of third or fourth gear, increasing the size of your air jet can help lean out that high-end mixture. Conversely, if you feel the engine "surging" or getting too hot at high speeds, you might need to go down in air jet size to richen the mixture up. Always use a wideband O2 sensor for the most accurate tuning results.

2. Never Clean Jets with Metal Wires

The calibration of a Weber air jet is incredibly precise, measured in hundredths of a millimeter. One of the most common mistakes we see in the shop is a customer trying to clear a clogged jet using a piece of safety wire or a steel needle. Because the jet is made of soft brass, the steel wire will inevitably gouge the orifice, effectively changing a 150 jet into a 155 or 160 without you knowing it. This leads to tuning nightmares where the two carburetors never seem to sync. Always use pressurized aerosol carburetor cleaner and compressed air to clear obstructions.

3. The Emulsion Tube Connection

The air jet does not work alone; it sits directly on top of the emulsion tube. When you change your air jet size, you are changing how much air is being mixed with the fuel inside that tube before it enters the venturi. If you find that a 150 air jet isn''t giving you the transition you want, you may need to look at your emulsion tube series (such as F11 or F7). A Pro tip is to keep a logbook of your jetting changes, recording the air temperature and how the car feels. This systematic approach is how the pros dial in a VW engine to run perfectly in any climate.