---
title: Pulse Split Exhaust Manifolds
description: Understanding Pulse Split Exhaust Manifolds
---
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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.
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