40mm Venturi, for 45 Dcoe Weber Carburetors

Product Overview: Precision Tuning for Your Dual-Throat Powerhouse

When it comes to extracting every ounce of performance from your air-cooled VW, the carburetor is the heart of the operation, and the venturi is its pulse. This EMPI 40mm main venturi is specifically engineered for the legendary Weber 45 DCOE series and high-performance clones. In the world of side-draft carburetion, the venturi (or choke) is the most critical component for determining the airflow characteristics of your engine. By utilizing a 40mm venturi inside a 45mm carburetor body, you are creating a high-velocity environment that is perfectly suited for large displacement engines or high-RPM racing applications. These precision-machined components allow you to fine-tune the "signal" sent to the main circuit, ensuring that fuel atomization is crisp and consistent across the entire power band. Whether you are running a weekend-warrior street Bug or a dedicated drag rail, these venturis provide the mechanical adjustment needed to match your induction system to your specific camshaft profile and cylinder head flow.

Selecting the right venturi size is a balancing act between low-end throttle response and top-end breathing capacity. A 40mm venturi in a 45 DCOE is a robust choice for those seeking maximum CFM (Cubic Feet per Minute) without sacrificing the venturi effect required to pull fuel from the auxiliary venturi at lower speeds. These are manufactured to exacting tolerances by EMPI, a name synonymous with VW performance for decades, ensuring a perfect drop-in fit. The smooth internal taper is designed to minimize air turbulence and maximize laminar flow, which translates directly to smoother transitions from the idle circuit to the main jet. If you have recently upgraded your engine''s displacement or installed a more aggressive valvetrain, swapping your existing chokes for these 40mm units is often the missing link to unlocking the full potential of your 45 DCOE setup. Don''t settle for "close enough" when it comes to your air-fuel mixture; give your engine the precise airflow it craves.

Vehicle Fitment and Compatibility

This 40mm venturi is designed for universal application on air-cooled Volkswagen engines equipped with Weber 45 DCOE or EMPI 45 DCOE carburetors. Common fitments include:

• Volkswagen Type 1: Beetle, Bug, and Super Beetle (High-performance 1915cc to 2332cc+ builds).
• Volkswagen Type 2: Bus, Transporter, and Kombi (Performance-oriented 1700cc-2000cc upright or Type 4 conversions).
• Volkswagen Type 3: Fastback, Squareback, and Notchback (Dual side-draft configurations).
• Volkswagen Type 14: Karmann Ghia (Modified engines with side-draft induction).
• Volkswagen Type 181: Thing (Off-road performance builds).
• Custom Sand Rails & Dune Buggies: Ideal for high-displacement stroker engines.

Technical Specifications

Engineered for durability and performance, these specs ensure you are getting the highest quality tuning component for your Weber-style carburetors.

• Manufacturer: EMPI
• Part Number: 43-5617-0
• Internal Diameter (Bore): 40mm
• Compatible Carburetor Body: 45 DCOE (Side-draft)
• Material: High-grade Zinc Alloy Die-Cast for thermal stability.
• Finish: Precision machined internal taper for optimized airflow.
• Quantity: Sold Individually (Each).
• Compatibility: Fits original Weber, EMPI HPMX, and other DCOE clones.

Expert Pro Tips from the AppleTree Workshop

Tip #1: The 4mm Rule for Venturi Selection

In the world of professional tuning, a golden rule of thumb is to select a venturi size that is approximately 4mm to 5mm smaller than the carburetor butterfly size. Since you are using a 45mm DCOE, this 40mm venturi is the maximum size we typically recommend for street-performance applications. It provides the largest possible opening for top-end power while still maintaining enough air velocity to keep the main circuit active during mid-range cruising. If you find your car "stumbling" or feeling sluggish at low RPMs despite proper jetting, you might be over-venturied, but for high-revving 2275cc engines, this 40mm size is usually the sweet spot.

Tip #2: Recalibrating Your Main Jet Circuit

Remember that the venturi size dictates the vacuum signal that pulls fuel through your main jets. When you increase your venturi size (for example, moving from a 36mm to a 40mm), the air velocity decreases at lower RPMs, meaning you will almost certainly need to increase your main jet size to compensate for the weaker signal. A common starting point is to multiply your venturi size by 4 to find your main jet (e.g., 40mm x 4 = 160 Main Jet). Always perform a plug chop or use a wideband O2 sensor after swapping venturis to ensure your air-fuel ratio remains in the safe zone.

Tip #3: Ensure Proper Seating and Alignment

When installing new venturis into your 45 DCOE, cleanliness is paramount. Even a tiny speck of debris can prevent the venturi from seating fully against the carburetor body, which can lead to air leaks or a "rattling" venturi. Before sliding the new 40mm choke into place, inspect the bore for any burrs or old fuel deposits. We recommend a light coating of thin assembly oil or carburetor cleaner to help it slide in smoothly. Once installed, ensure the locking screw or retaining mechanism is tightened to spec so the venturi cannot rotate, as any movement will disrupt the alignment with the auxiliary venturi and ruin your engine''s synchronization.