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Pulse Split Exhaust Manifolds

Understanding Pulse Split Exhaust Manifolds

Understanding Pulse Split Exhaust Manifolds

 

1. What Is an Exhaust Turbo Manifold?

An exhaust manifold collects exhaust gases from the engine’s cylinders and directs them toward the turbocharger. In a turbocharged engine, the design of this manifold is crucial for both performance and turbocharger fitment.

There are two main types of exhaust manifolds:

  • OEM (Original Equipment Manufacturer) manifolds – designed for stock turbo setups and optimized for packaging and cost.

  • Aftermarket performance manifolds – designed to improve flow, equalize exhaust pulses, and fit larger or differently flanged turbochargers.

 

2. Why Use an Aftermarket Manifold?

The most common reason to use an aftermarket turbo manifold is fitment.
When upgrading to a larger or different-style turbocharger, your stock manifold may no longer fit because:

  • The flange type (connection point) is different.

  • The position of the turbo changes (for example, top-mount vs. bottom-mount).

  • The flow capacity of the OEM manifold becomes insufficient for your power target.

Even if the stock manifold flows decently, it often won’t physically accommodate a performance turbocharger.
That’s when an aftermarket manifold is required.

 

3. Equal-Length vs. Unequal-Length Runners

High-performance manifolds often use equal-length runners — meaning each exhaust pipe from the engine’s cylinders to the turbo is the same length.
This design helps:

  • Synchronize exhaust pulses reaching the turbine.

  • Improve scavenging (clearing exhaust gases from the cylinders).

  • Enhance turbo spool response and efficiency.

However, depending on the engine layout and available space, unequal-length manifolds can also work well — especially when packaging constraints or desired sound characteristics are a factor.

 

4. What Is a Pulse Split (Twin-Scroll) Manifold?

A pulse split or twin-scroll manifold divides the exhaust flow into two separate groups of cylinders based on their firing order.
Each group feeds a separate scroll in a twin-scroll turbocharger.

Purpose:

  • To prevent exhaust pulse interference between cylinders that fire close together.

  • To maintain higher exhaust gas energy as it enters the turbo.

  • To improve turbine efficiency and reduce turbo lag.

How It Works:

In a typical 4-cylinder engine (with firing order 1-3-4-2), cylinders are paired so that each scroll receives exhaust pulses evenly spaced in time:

  • Scroll A: Cylinders 1 & 4

  • Scroll B: Cylinders 2 & 3

This means that each scroll gets a strong, distinct pulse — allowing the turbine to spin more efficiently without pressure drop between pulses.

 

5. Benefits of a Pulse Split Manifold

 Faster Turbo Response – Reduced pulse interference means the turbo spools earlier.
 Better Low-End Torque – Improved scavenging at low RPM enhances drivability.
 Higher Top-End Efficiency – Exhaust energy is used more effectively.
 Consistent Flow Distribution – Equal-length design ensures smooth gas flow.

 

6. When Should You Upgrade to a Pulse Split Manifold?

You should consider a pulse split manifold if:

  • You are using a twin-scroll turbocharger.

  • Your power target exceeds what the OEM manifold can handle.

  • You want to optimize spool and reduce lag without sacrificing top-end power.

  • Your turbo’s flange pattern (like T4 twin-scroll) requires it.