Fuel Pressure For Blow-Through Carb: How Much Is Enough?

The fuel pressure required for a blow-through carburetor depends on a few factors, including the desired horsepower, boost pressure, and regulator type. Blow-through carburetors, often used with superchargers and turbochargers, operate with boosted pressure, accelerating the induction process and increasing fuel flow. To calculate the required fuel pressure, you need to consider the base fuel pressure, boost pressure, line losses, and regulator type. For example, a blow-through engine with a bypass regulator, a boost pressure of 20 psi, and a base fuel pressure of 7 psi would require a fuel pressure of 32 psi. Additionally, the fuel pump should be able to provide sufficient fuel flow to meet the horsepower requirements. It's important to consult the owner's manual or seek expert advice to ensure the correct fuel pressure and avoid issues such as dry fuel bowls or fouled spark plugs.

The Aeromotive A1000 pump can handle 1200 HP for a carbureted, supercharged application

The Aeromotive A1000 pump is a popular choice for those seeking high performance from their carbureted, supercharged engines. This pump is designed to support a significant power output of up to 1200 HP in such applications, making it an ideal option for those seeking substantial horsepower from their vehicles.

The A1000's ability to handle 1200 HP in a carbureted, supercharged setup is a testament to its performance capabilities. This pump is well-suited for forced induction engines, which typically require more fuel compared to naturally aspirated engines with similar power levels. The A1000's specifications highlight its capacity to meet the fuel demands of high-performance applications.

The A1000's return-style design is a key feature that contributes to its effectiveness. This design provides a dynamic fuel delivery system, ensuring that the engine receives a consistent and adequate fuel supply. The base fuel pressure of the A1000 can be adjusted within a range of 3-15 PSI, allowing for customization to match the specific requirements of the engine.

Additionally, the A1000 is a versatile pump that can be used with Aeromotive's A1000 and Eliminator Fuel Pumps, as well as similar EFI pumps in carbureted applications. This adaptability makes it a convenient choice for those looking to convert from fuel injection to carburetion while still using the stock, in-tank pump.

It's important to note that the A1000 pump is designed for high-performance applications and may be louder than other fuel pumps due to its performance capabilities. However, with proper installation and configuration, the A1000 can be a reliable and powerful addition to your engine setup.

Overall, the Aeromotive A1000 pump is a robust and dependable option for those seeking to achieve 1200 HP in a carbureted, supercharged application. Its performance, adjustability, and compatibility make it a popular choice for enthusiasts and professionals alike.

A pump that flows 600 lbs/hr at 32 psi is needed for a 1000 Hp turbocharged engine

Selecting the right fuel pump for your vehicle is crucial to ensure optimal engine performance and reliability. When it comes to determining the amount of fuel pressure for a blow-through carburettor, there are several factors to consider, including target horsepower, base fuel pressure, boost pressure, and fuel type.

In the given scenario, we are dealing with a turbocharged engine targeting 1000 horsepower. To estimate the required fuel flow, we need to calculate the brake-specific fuel consumption (BSFC). The BSFC measures the amount of fuel needed per horsepower per hour, and it varies depending on the type of fuel. For a turbocharged engine, the BSFC typically falls between 0.55 and 0.60 lbs/hp-hr.

Using the BSFC value of 0.60 lbs/hp-hr for a turbocharged engine and the target horsepower of 1000, we can calculate the fuel flow requirement as follows:

Fuel flow = Target horsepower x BSFC

Fuel flow = 1000 hp x 0.60 lbs/hp-hr

Fuel flow = 600 lbs/hr

Now that we have determined the required fuel flow, we can turn our attention to fuel pressure. The fuel pressure needed depends on the regulator type used in the system. If a bypass or return-style regulator is employed, the fuel pressure can be calculated as:

P = Base fuel pressure + Boost pressure + Line losses

Assuming a base fuel pressure of 7 psi, a boost pressure of 20 psi, and line losses of around 5 psi, the fuel pressure required would be:

P = 7 psi + 20 psi + 5 psi = 32 psi

Therefore, for a 1000 hp turbocharged engine with a bypass regulator, a pump that delivers 600 lbs/hr of fuel flow at 32 psi is necessary. It is worth noting that this estimate assumes certain standard conditions and that adjustments may be required based on specific engine configurations and operating conditions.

Additionally, it is important to consider the electrical system's capabilities when selecting a fuel pump. Some pumps may require higher voltages, such as 13.5V, to achieve the desired flow rate, which may not be feasible if multiple electrical accessories are in use. As a result, it is generally recommended to err on the side of caution and choose a pump that can deliver the required flow rate at a lower voltage.

A bypass or return-style regulator does not need extra pressure

A bypass or return-style regulator is designed to bleed off excess pressure in a return line back to the fuel tank. This means that the regulator sends excess pressure back to the tank, providing a reliable operating pressure to the fuel rail or carb. This is controlled by a bypass valve that is spring-actuated. As fuel flows through the regulator, pressure increases in the system, forcing the spring to open the bypass valve and allow excess pressure to bleed off.

This type of regulator does not need extra pressure because the regulating orifice is on the return side of the system. This means that there will be pressure losses in the system from fuel lines and fittings, as well as acceleration losses. These losses need to be accounted for with more pressure at the pump.

A bypass regulator is beneficial as it provides constant effective fuel pressure to the outlet port. This enables fuel pressure to be set more accurately and remain constant regardless of load. The engine does not need to be running to adjust the fuel pressure. This style of regulator also results in longer pump life and quieter pump operation as the pump only needs to maintain the set pressure. The regulator keeps the entire system cooler as fuel is constantly circulated. This reduces the risk of vapor lock and can make more power.

However, there are some drawbacks to this style of regulator. The system requires extra plumbing, which adds expense, complexity, and weight. A return line is very sensitive to pressure drops, and large return lines must be used with limited bends and a direct return to unpressurized tanks or reservoirs.

A dead-head style regulator needs an additional pressure differential of 10-15 psi

When selecting a fuel pump for a blow-through setup, it's important to know the pressure your setup will need and how much horsepower you plan on making. If you're using a dead-head style regulator, you must have an additional pressure differential of 10-15 psi across the regulating orifice to be able to control fuel pressure. This is because, in a dead-head style regulator, the regulating orifice is on the return side of the system. This means that the pump will be working at full capacity and pressure against the regulator, which can reduce its lifespan.

A dead-head style regulator is normally open, meaning fuel will flow through the regulator and be restricted once the pressure reaches its pre-set limit. This is in contrast to a return style regulator, which is normally closed until the pressure limit is reached, opening the bypass outlet to return the excess volume back to the tank. This means that a dead-head regulator places an additional load on the fuel pump, as it operates at full capacity and pressure against the regulator. This can lead to a temporary drop in fuel pressure, especially in high-horsepower, carbureted drag cars.

A dead-head style regulator is a simpler option, as it does not require return plumbing. This makes it a less expensive option, with fewer components, connections, fittings, and lines. Dead-head style regulators are perfect for use with most low-pressure mechanical as well as some electric fuel pumps. However, they may not be suitable for street cars, as they tend to pull more amperage from the charging system and place maximum load on the fuel pump. Additionally, at low speeds, the fuel is heated by the pump working against the head pressure, which can cause vapor lock issues in hot weather.

Overall, while a dead-head style regulator may be a more cost-effective option due to its simplicity, it's important to consider the potential drawbacks, especially if you're planning on using it for a street car or high-horsepower application.

A fuel pump that generates sufficient fuel pressure and flow at full throttle is usually designed to have an additional 15% capacity

When selecting a carburetor for a blow-through application, it's important to ensure that the fuel pump can provide sufficient fuel pressure and flow, especially at full throttle. This is crucial to maintain optimal performance and prevent engine damage.

A fuel pump's capacity is influenced by factors such as the desired boost pressure, regulator type, and horsepower. To calculate the required fuel pressure, you need to consider the maximum boost you plan to run and the type of regulator used. If you're using a dead-head regulator, an additional pressure differential of 10-15 psi is necessary for effective fuel pressure control. On the other hand, a bypass or return-style regulator doesn't require this extra pressure. Additionally, fuel line bends, fittings, and acceleration losses can result in pressure losses of around 5 psi.

For example, let's consider a blow-through engine with a bypass regulator, a base fuel pressure of 7 psi, and a boost pressure of 20 psi. The formula for calculating the required fuel pressure (P) is:

> P = (base fuel pressure) + (boost pressure) + (line losses) + (10-15 psi if running a dead-head regulator)

Plugging in the values, we get:

> P = 7 psi + 20 psi + 5 psi = 32 psi

If we were using a dead-head regulator, we would need to add an extra 10-15 psi, resulting in a required pressure of 42-47 psi.

Now, let's discuss the fuel flow requirements. To determine this, we need to consider the target horsepower and the engine's Brake Specific Fuel Consumption (BSFC). The BSFC represents the amount of fuel, in pounds, needed to support 1 horsepower for 1 hour. For a turbocharged engine, the BSFC typically ranges from 0.55-0.6 (lbs/hr)/hp. By multiplying the target horsepower by the BSFC, we can calculate the required fuel flow.

For instance, if we aim for 1000 horsepower, we would calculate the fuel flow as follows:

> Fuel flow = Target horsepower x BSFC = 1000 hp x 0.6 (lbs/hr)/hp = 600 lbs/hr

To meet this fuel flow requirement, you would need a pump that can deliver 600 lbs/hr at the calculated fuel pressure. It's important to refer to fuel pump performance curves to ensure the selected pump can provide the required flow rate at the specific pressure.

In summary, when designing a fuel system for a blow-through carburetor, it is crucial to select a fuel pump that can deliver adequate fuel pressure and flow, especially at full throttle. By considering factors such as boost pressure, regulator type, and horsepower, you can calculate the required fuel pressure and flow rate. This ensures that your engine receives the necessary fuel supply for optimal performance without risking damage due to insufficient fuel delivery.

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