Mercedes Mullins
Fuel injectors are a critical component of an engine, and choosing the right size and type is essential for optimal performance. While bigger is not always better, sizing an injector larger can offer benefits, such as accommodating future power boosts. Injectors are rated to deliver a specific amount of fuel at a rated pressure, and this is typically measured in pounds per hour (lb/hr) or cubic centimeters per minute (cc/min). The CC rating of an injector indicates the amount of fuel it can flow, for example, a 190cc injector will flow 190cc worth of fuel. When considering different CC fuel injectors, factors such as horsepower goals, fuel type, nozzle size, and plug type must be taken into account to ensure proper performance and tuning.
Can you use different cc fuel injectors?
| Characteristics | Values |
|---|---|
| Fuel injector sizing | Critical for engine performance; bigger is not always better |
| Fuel injector selection | Consider horsepower goal, fuel type, and plug type |
| Fuel injector body style | OEM fuel injector is a good reference point; direct swap or adapter options available |
| Fuel injector flow rate | A 175cc injector will flow 175cc of fuel, and a 190cc injector will flow 190cc of fuel |
| Fuel injector nozzle | Affects pulse width and tuning ease; larger nozzles on small cc injectors reduce pulse width |
| Fuel injector dimensions | 34mm, 48mm, and 60mm are common sizes; Bosch ev14 compact is a popular 34mm motorsport injector |
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What You'll Learn
Injector sizing: bigger isn't always better
When it comes to fuel injectors, bigger isn't always better. While it can be challenging to determine the size and flow rate of your fuel injector, choosing the right size injector is critical. There are several factors to consider when selecting a fuel injector, including your horsepower goal, fuel type (such as gasoline, ethanol, race gases, or fuel additives), and plug type.
The size of a fuel injector is typically rated in pounds of fuel per hour (lb/hr) or cubic centimeters per minute (cc/min). For example, a Holley injector rated at 42 lb/hr can deliver 42 pounds of fuel per hour. However, this rating may not be as useful as understanding how much power can be generated with a specific injector size.
While larger injectors can provide benefits in certain situations, such as boosted engines or future power upgrades, there are also disadvantages to consider. For instance, a large nozzle on a small injector can lead to tuning issues, as it will result in a low pulse width, making it challenging for the tuner to tune the vehicle.
Additionally, the fuel injector must work against higher pressures in the intake manifold of a boosted engine, which can reduce fuel pressure in the fuel rail. As a result, fuel pressure regulators are often necessary to compensate for this pressure differential. Therefore, it's essential to carefully consider your specific engine and performance goals when selecting a fuel injector size to ensure optimal performance and avoid potential issues.
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Injector flow rate: CCs of fuel delivered
Fuel injectors are rated to deliver a specific amount of fuel at a rated pressure. For example, a Holley injector is rated at 42 pounds of fuel per hour (lbs/hr) or 42 lb/hr. They can also be rated in cubic centimeters per minute (cc/min).
The size of a fuel injector matters. While bigger is not always better when it comes to fueling your engine, sizing the injector larger than you might think offers other advantages. For boosted engines with the injector located in the intake manifold, the injectors are forced to open against much higher pressures than with a normally aspirated engine. Therefore, the larger injector offers enough additional fuel flow to offset the minor power increase.
The flow rate of a fuel injector is the amount of fuel it can deliver per unit of time. This is usually measured in cubic centimeters per minute (cc/min) or pounds of fuel per hour (lbs/hr). To calculate the flow rate of a fuel injector, you can use the following formula:
> If you turn the injector on for exactly 1 second (at your reference fuel pressure and reference voltage), how many CCs flow. Multiply that number by 60 to get the theoretical flow rate of the injectors.
It's important to note that the delay required for the injector to open and close will affect the flow rate. A typical delay may be 1mS, so the longer your pulse width, the less this influences the total flow. Additionally, the delay will change with voltage and differential fuel pressure.
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Nozzle size: how fast the body empties
The nozzle size of a fuel injector determines how fast the injector's body empties. The nozzle is the last part of the injector, and its size dictates how fast a certain amount of fuel can be delivered.
The size and flow rate of a fuel injector are determined by factors such as horsepower goal, fuel type, and plug type. Modern fuel injectors come in three main sizes: 34mm, 48mm, and 60mm. The size of the injector and its nozzle will impact the performance of the vehicle. For example, a larger nozzle size will generally make more power, as it can deliver more fuel.
The relationship between injector and nozzle size is important to consider. A larger injector with a smaller nozzle may not deliver the desired power increase, as the smaller nozzle may not be able to keep up with the fuel flow. For instance, a 190cc injector with a stock nozzle will deliver more fuel at low RPMs, as there is more time available to leave the injector pulsed. At higher RPMs, a larger nozzle would be required to realise the available fuel in the larger injector body.
Additionally, the atomization of fuel is important for performance. A smaller nozzle can improve atomization, leading to better fuel mileage, less smoke, and lower exhaust gas temperatures. This is particularly beneficial for trucks used for towing or daily driving, as a smaller nozzle can provide a noticeable difference in power while still maintaining a clean and cool operation.
In summary, the nozzle size of a fuel injector plays a crucial role in determining how fast the injector's body empties, and the right size will depend on the specific vehicle and performance goals.
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Injector body style: O-ring to O-ring measurement
Fuel injectors come in different sizes and flow rates, and choosing the right one for your engine is critical. There are a few ways to determine the right fuel injector for your needs. One way is to look directly at your OEM fuel injector, as there may be a direct swap or adapter option available. If you're using an aftermarket intake, it may have come with a fuel rail kit, or you can reuse your OEM rails. The manufacturer should be able to provide guidance on the injector body style you need.
Another way to determine the right fuel injector is to estimate your horsepower goal and multiply it by the Brake Specific Fuel Consumption (BSFC). For example, let's say you have a horsepower goal of 500. Using this equation, you would calculate 500 x BSFC = injector size needed.
When it comes to injector body style and O-ring measurements, there are a few things to keep in mind. Firstly, modern fuel injectors typically fall into one of three main sizes: 34mm, 48mm, or 60mm. While there is no industry standard, Snake Eater measures from the inside O-ring to the inside O-ring. The 34mm style is often found in cutting-edge fuel injectors, while the 48mm size is also known as the EV14 medium or mid-length and is commonly used in GM race-based engines. The 60mm size is popular because it's easier to raise the fuel rail with a small shim and longer hardware than to fabricate custom mounts for a shorter injector.
It's important to note that O-rings come in different sizes, and using the correct size is crucial to prevent fuel leaks. Some common O-ring sizes for fuel injectors include 7mm and 8mm, and they can usually be purchased at auto stores or online. Additionally, some fuel injectors may use larger O-rings on the bottom than on the top, so it's important to verify the correct sizes for your specific injector.
If you're using an older injector with a newer intake, you may need to use adapters or pigtail connectors to ensure compatibility. It's also worth noting that some manufacturers use different O-ring sizes, so it's always a good idea to check with the manufacturer or a fuel injector specialist if you're unsure about the correct O-ring size or injector body style for your specific application.
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Fuel type: gasoline, ethanol, race gasses, etc
Fuel type is a key consideration when choosing a fuel injector. The most common fuel types are gasoline, ethanol, and race gases.
When sizing your injector for gasoline, a simple rule of thumb is 1cc/min flow for each horsepower. For example, if you want to make 1000 crank horsepower on 93 octane gasoline, using a fuel pressure of 43 psi, you will need a 1000cc injector.
For ethanol-based fuels, the same rule of thumb can be used, but it is important to remember to add 30% since ethanol requires more fuel to generate the same power. For instance, if you are running a standard Chevy truck engine and adding a turbo that will run on around 7 lbs of boost and ethanol-based fuel, you will need 404 lbs/hr of fuel flow or 50.5 lbs for each of the 8 fuel injectors. This is because ethanol has been associated with injector problems, especially in older engines built before 2001, due to the dissolving of rubber and plastic parts in the fuel distribution system. These dissolved components can show up as a black sticky resin in fuel injectors and other engine areas, causing potential issues.
Race gases and fuel additives such as MTBE or Oxygenators are also options, but it is important to consult a specialist to ensure the correct injector is used and adapted to fit your specific needs.
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Frequently asked questions
The manufacturer should be able to provide guidance on the body style injector you need. You can also look directly at your OEM fuel injector, as there may be a direct swap or adapter option available.
Sizing a fuel injector larger than you need can be beneficial if you decide to boost the power at some point, as the larger injector can provide enough additional fuel flow to offset the minor power increase.
Nozzle size determines how fast the body will empty. A large nozzle on a small CC injector will have a low pulse width, so injector builders will often put smaller nozzles on smaller injectors to keep the pulse width up.
Most modern injectors fall into one of three sizes: 34mm, 48mm, or 60mm. Cutting-edge fuel injectors are typically only available in the 34mm style.
Bigger is not always better when it comes to fueling your engine. It is critical to find the proper size fuel injectors for your engine. Remember that every injector has a maximum operating pressure.
