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Caleb Newman, head of Performance Design, argues that the most effective intake manifold is defined by its synergy with the engine’s cam and heads, as demonstrated by his Carbon XR manifold providing 50 horsepower and 50 foot-pounds of torque on a stock LS7. Newman’s argument challenges the idea of a ‘perfect’ universal part by highlighting the trade-offs between material choice, port geometry, and specific RPM targets. The intake manifold development process suits high-performance engine builders looking for specific power bands, while daily commuters should skip the technical details.
Who should act on intake manifold development and who should skip it
Readers who should act on intake manifold development
- LS engine owners should evaluate their manifold choice based on the specific head and camshaft configuration they intend to run.
- Drag racers should consider modular runner systems to tune their power band for specific high-RPM targets.
- Performance engineers should prioritize material science and flow dynamics when selecting components for high-output applications.
Readers who should skip intake manifold development
- Daily commuters should skip these technical details and look for general maintenance guides for stock engines.
- Aerodynamics enthusiasts should skip this topic and look for external body kit or wing reviews instead.
What to do next about the intake manifold development
- Select a runner length that matches your target RPM range to tune the power band for your specific engine configuration.
- Choose between a raised or tangential bell mouth based on your fuel delivery system, opting for tangential only if using a carburetor.
- Verify engine head port geometry (LS3 vs. LT) to ensure your manifold design avoids manufacturing undercuts or draft issues.
Packaging serves as the single biggest constraint in designing an intake manifold
Packaging serves as the single biggest constraint in designing an intake manifold. Engineers must fit the manifold and its runners within the available space of the engine bay while maintaining optimal flow.
Flow restriction occurs when the bell mouth is too small or poorly shaped to accommodate the required volume. Proper design requires balancing the size of the plenum and the length of the runners with the physical dimensions of the vehicle.
What is a bell mouth?
A bell mouth is the opening of an intake runner designed to optimize airflow into the cylinder. It acts like a funnel, ensuring that air enters the runner with minimal turbulence and maximum velocity.
Bell mouths provide the single biggest impact on flow development into the runner
Bell mouths provide the single biggest impact on flow development into the runner. Raised bell mouths offer more surface area to pull air from the plenum, while tangential entrances are used to pull air from the side.
What is a tangential entrance?
A tangential entrance is a runner entry designed to pull air from the side rather than head-on. This design is commonly used in carbureted systems to handle ‘wet’ fuel and is often easier to manufacture than a large, raised opening.
Raised bell mouths are generally superior for fuel-injected systems because the larger surface area increases volumetric flow. Tangential entrances are often preferred for manufacturing simplicity and for handling ‘wet’ fuel in carbureted systems to prevent fuel from puddling.
Nylon and carbon fiber are the primary material choices for high-performance manifolds
Nylon and carbon fiber are the primary material choices for high-performance manifolds because they insulate from engine bay temperatures. Unlike metal manifolds, which suffer from heat soak, these materials prevent heat from decreasing the density of the incoming air.
What is heat soak?
Heat soak is the absorption of engine bay heat into the intake manifold. This occurs most frequently with heavy metal castings and can decrease the density of the air entering the engine, ultimately reducing power.
Nylon is a common industry standard, with 95 plus percent of worldwide intake manifolds made of 3% glass-filled nylon. Carbon fiber serves as a premium weight-saving alternative that provides exceptional heat resistance for high-pressure applications.
Modularity and the Path to Optimal Tuning
Modular runners allow owners to tune the engine’s power band for specific RPM ranges without replacing the entire manifold. This system provides a cost-effective way to achieve a perfect match for a specific cam or displacement.
Interchangeable bells and runners allow for precise wave tuning, which is the process of adjusting runner lengths and volume to utilize pressure waves for specific RPM ranges. This modularity ensures that the manifold can adapt to different power goals, from low-end torque to high-RPM drag racing.
LS platform development was an industry milestone featuring the LS7 port design
LS platform development was a milestone for the industry, with the LS7 providing an amazing port design that remains a benchmark for many engineers. While the LS3 was a production goal, it left room in the aftermarket for specialized designs like the Carbon XR.
LT engine development provides a ‘perfect canvas’ for designers because of the transition to Direct Injection (DI). Direct Injection removes the need for fuel injectors in the flow path, allowing engineers to create straighter runners with fewer ‘dents’ or ‘pockets’ in the intake path.
The Myth of the ‘Perfect’ Manifold
No one perfect intake manifold exists because performance depends on the interaction between the camshaft, cylinder heads, and the exhaust system. A manifold must be chosen based on how it interacts with these other components to create a synergistic system.
Single plane manifolds can outperform many other designs if they are designed with tall, straight runners. However, these designs are often difficult to package in a vehicle compared to other styles like cross ram manifolds.
Carbon XR is a specific cross ram style manifold that offers a high-performance alternative to standard designs. While Holley offers the Hi-Ram as a competing cast aluminum option, the Carbon XR focuses on the benefits of carbon fiber construction.
LS engine owners gain the ability to choose manifolds that complement their specific head and cam configurations. Users seeking a ‘one-size-all’ part may lose out on the power gains that come from a synergized system where every component is matched to a specific goal.
Choosing a metal manifold for a high-horsepower application results in reduced power due to heat soak. Guessing wrong on the bell mouth type can lead to either inefficient flow or poor fuel handling in carbureted applications.
A truck owner selects a carbon manifold for an LS7 engine
Marcus owns a truck with an LS7 engine and wants to increase power while avoiding the heat-soak issues common with heavy metal castings. He chooses a Performance Design carbon-based manifold because it provides the necessary insulation to keep intake air cool.
Marcus selects a modular runner length that matches his specific target torque curve. By choosing this configuration, he achieves a 50 horsepower and 50 foot-pounds of torque gain while keeping the engine bay temperatures from affecting his intake air.
If Marcus were running a carbureted setup instead of fuel injection, he would have been forced to choose a manifold with a tangential entrance rather than a raised bell mouth.
Performance Design has not announced the carbon fiber manifold price or installation time
- Performance Design has not announced the official price for the carbon fiber manifold.
- Performance Design has not stated the estimated installation time for the modular runner system.
Frequently Asked Questions
What is the main difference between a raised and tangential bell mouth?
A raised bell mouth provides more surface area and volumetric flow for fuel-injected systems. A tangential entrance is better for handling ‘wet’ fuel in carbureted systems and is often easier to manufacture.
Why shouldn’t I use a heavy metal manifold with long runners?
Metal manifolds are heavy and prone to heat soak, which can negatively impact performance in high-output applications. Using a metal manifold with 6 and 1/2-in runners can result in a significant loss of torque and packaging issues.
How does Direct Injection (DI) change manifold design?
Direct Injection allows for straighter, more direct runners because the injectors are located in the head. This removes the need for ‘dents’ or ‘pockets’ in the manifold flow path that are required for port fuel injection.
Does one specific manifold work best for all engines?
No specific manifold works best for all engines because intake performance is an interactive system. The manifold must be matched to the specific camshaft, cylinder heads, and exhaust system to achieve optimal results.
Source: The Science of Intake Manifold Development with Caleb Newman of Performance Design (Summit Racing).