# How to determine injector size for custom engine?

## How do I know what size injector to get?

Injector Math: How to Calculate Optimum Fuel Injector Size

1. Step 1: Determine Horsepower. …
2. Step 2: Determine Approximate BSFC (Brake-Specific Fuel Consumption) …
3. Engine Type BSFC Using Gasoline. …
4. Step 3: Determine Your Safe Duty Cycle. …
5. Step 4: Calculate Your Optimum Injector Size. …
6. Step 5: Fine-Tune the Flow.

## Can I run bigger injectors than I need?

Can’t change injectors without changing the ECU. The stock ECU is set to one injector size. If you put in a different size the duty cycle for that injector will put in more or less fuel than the OEM set injector. A 1000cc will net you plenty of flow for the power goals.

## What happens if your injectors are too big?

It’s easy to fall into the trap of thinking that bigger fuel injectors equal more power, but unless your engine is set up to deal with the extra fuel, you’ll be on a fast track to trouble. The excess fuel will flood the engine and it either won’t run at all, or will be running too rich.

## How do you size a fuel pump and injector?

Calculating Injector Size

Injectors are normally rated in cubic centimeters (cc’s) per minute. Take the calculated fuel pump size in liters and divide the number by 16.67. If you want this number in pounds per minute, divide the cc’s per minute by 10.5. Fitment and drive must also be considered.

## How much power can 650cc injectors handle?

So 650cc injector= 650hp if injector is running at 100% duty cycle. I would scale it down a bit to around 80-85% duty, so that would put you at around 520-550hp range. A single walbro can flow enough fuel to feed the car about 500-550hp, but I would advise against it.

## How many cc are 80lb injectors?

Fuel Injectors | Siemens Deka | 80 lb/hr | 875 cc/min | High Impedance | EV1 | 8 Cyl.

## How much power are 1000cc injectors good for?

The 1000cc Injectors can support 650+whp.

## Do bigger injectors increase HP?

Larger throttle body and injectors

A larger high-performance throttle body will deliver more horsepower. Depending on what type of engine you have, you can gain as much as 10-20 more horsepower and comparable torque.

## Do you need a tune for fuel injectors?

Fuel injectors directly affect the air/fuel ratio for the engine and new fuel injectors do require a new or updated tune.

## How many Lph do you need for 500hp?

Making the Choice

Fuel Pump Free Flow Carbureted Engine Fuel Injected Engine
40 gph/155 lph 450 hp 400 hp
50 gph/190 lph 600 hp 500 hp
67 gph/255 lph 750 hp 650 hp
90 gph/340 lph 1000 hp 850 hp

## How many LPH is a 1200 hp?

To estimate flow, simply multiply 1,200 horsepower x 0.9 BSFC = 1,080 pounds of projected fuel per hour.

## How much fuel pressure do you need for fuel injection?

Required fuel pressure can vary depending on your vehicle’s engine and fuel system. Carbureted engines may require as little as 28 kPa (4 PSI), while modern multipoint fuel injected high-performance engines can require as much as 414 kPa (60 PSI).

## How do I choose fuel injectors?

Fuel Injectors are sized by their flow rate. Flow rate is a measurement of how much fuel can be delivered over time. It is listed in pounds per hour (lbs./hr.) or cubic centimeters per minute (cc/min.). The right size injector can supply enough fuel under full load conditions at an 80% duty cycle.

## Should rpm increase fuel pressure?

Fuel pressure should depend upon engine vacuum; as vacuum drops with throttle advance FP should increase, as when you remove the vacuum line to the FPR. The FP delivers a constant volume of fuel and the FPR regulates the pressure. The FPR should hold constant pressure at constant vacuum level.

## What happens if fuel pressure is too low?

Decreased Fuel Pressure

Low fuel pressure can lead to engine misfires, low acceleration, rough idles, and engine stalls. If your check engine light is on and your car has been stalling out, you may have a fuel pump failure.

## How do I check my fuel pressure without a gauge?

There are two ways to check the fuel pressure on your vehicle without a gauge. You can use a diagnostic code reader or OBD II scanner, which will provide live data of fuel pressure. Alternatively, if you hear buzzing as you turn the keys ON but don’t see any other symptoms this means that your pump is working fine.

## What should fuel pressure be at idle?

When an engine is idling, it may be pulling 20 inHg of vacuum, which translates to roughly 10psi. The reference to the regulator will allow it to adjust and lower the pressure in the rail to 48psi, resulting in 58psi effective pressure, which is the same as the base pressure.