Performance injectors

"Thanks for reading our fuel injector article."

Your car might be performing just fine with stock parts, but, if you’re looking for greater horsepower, torque, and fuel efficiency, consider performance injectors.

These injectors can help your engine perform at maximum capacity and boost your fuel economy.

Performance injectors work by delivering more fuel into the combustion chamber, greatly increasing your vehicle’s power and performance (as long as it's matched with enough air).

Whilst it's true that more fuel does not mean more power, you'll find a tuned car often tends to run lean as the fuelling fails to keep up and you'll be losing power. So a performance injector rated to deliver more fuel will prevent this shortfall and restore that lost power to you.

How Fuel Injectors Work

Fuel injectors are responsible for delivering fuel to the engine. This is achieved by using a fuel pressure regulator, which draws gasoline in.

The fuel injectors then spray a fine mist of gasoline into the combustion chamber. In older cars, this was done using a carburetor system, which was not as fuel efficient and was harmful to the environment.

There are two types of fuel injection systems: mechanical and electronic. Most cars these days utilize an electronic fuel injection system. This is because electronic fuel injection systems are easier to reprogram to match the vehicle’s specific fuel needs.

Stock fuel injectors can deliver the right amount of fuel to a stock engine.

However, for engines outfitted with an aftermarket turbo or supercharger, stock fuel injectors will decrease performance as they won't be able to keep up.

Even though a turbo or supercharger will allow more air to flow into the combustion chamber, stock injectors won’t be able to deliver enough fuel to the engine.

But, before you rush to buy a new set of performance fuel injectors, you should take some time to plan your purchase based on your car’s modifications.

Stoichiometric Fuel Ratios

For Gasolene fuel you need 14.7 parts air to 1 part fuel, with slight deviation depending on the conditions and workload on the engine.

A diesel engine is lower at typically 14.5 parts air to 1 part diesel fuel effectively running lean,  primarily due to the unique way diesel engines burn fuel. (The range on diesel fuel combustion is much wider ranging from 40:1 to 3:1 depending on load and condition)

The stoichiometric point is when all oxygen is used and all fuel is burnt in the combustion process. Some of the oxygen remains unreacted with additional oxygen (over stoichiometric combustion).

Similarly, if the combustion is partial owing to a lack of oxygen, the fuel will stay unreacted. (Unreacted fuel may also remain owing to sluggish combustion or inadequate mixing of fuel and oxygen; this is unrelated to stoichiometry but a good injector design will improve the atomization and mixing of fuel.)

The stoichiometry of various hydrocarbon fuels varies due to differences in carbon, hydrogen, and other components and is carefully monitored and managed by your cars ECU.

What to Consider Before Purchasing

In cars fully outfitted with stock parts, fuel injectors only flow at around 80% capacity.

This capacity is fine for daily drivers with no modifications. For cars with aftermarket parts installed, the fuel injectors can perform at maximum capacity, depending on the extra parts added.

When it comes to turbo cars, you’ll need to upgrade your fuel system with performance injectors and a performance fuel pump.

Otherwise, the injectors won’t be able to flow enough fuel to the engine to make your car run the way you want it to.

You should also match your performance fuel injector to your specific engine. Before you purchase your performance fuel injectors, you should know how much NOS you want to add to your car. Fuel injectors that flow too much fuel into the engine can hinder performance almost as much as those that flow too little.

Consider using a fuel injector calculator to help you figure out the exact fuel injectors you’ll need for your vehicle.

We think this one is common sense, but you’ll need to match your fuel injector to the type of fuel your car uses as well.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58 psi of fuel pressure at idle.

4 Cylinder turbocharged engines

  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp
  • 58 PSI 682cc/min 400hp
  • 58 PSI 1022cc/min 600hp

5 Cylinder turbocharged engines

  • 58 PSI 273cc/min 200hp
  • 58 PSI 409cc/min 300hp
  • 58 PSI 545cc/min 400hp
  • 58 PSI 818cc/min 600hp

4 Cylinder NA (naturally aspirated) engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp
  • 58 PSI 568cc/min 400hp
  • 58 PSI 853cc/min 600hp

4 Cylinder supercharged engines

  • 58 PSI 312cc/min 200hp
  • 58 PSI 468cc/min 300hp
  • 58 PSI 625cc/min 400hp
  • 58 PSI 937cc/min 600hp

If you get a diesel performance injector for an engine that runs on unleaded, you’re going to run into trouble. Performance fuel injectors aren’t cheap, and you won’t want to waste time and money getting the wrong ones.

The spray pattern is just as important as the flow rates, and even more so with the arrival or direct injection engines. The VW group switched to a 5 hole design which allows for better combustion and makes more power over the previous design when comparing like flow rates.

Make sure your engine can handle the extra power. A daily driver with no other modifications probably doesn’t need performance fuel injectors, as we mentioned earlier they merely remove a restriction in your engine.

Some stock engines may not be able to handle the extra power performance injectors can give to a car. Other aftermarket parts may be needed for the engine, depending on the kind of engine and the car itself.

Modifications and Aftermarket Parts to Install

You won’t get the maximum performance you want if you install the performance fuel injectors by themselves.

Other aftermarket parts and modifications are needed to ensure you get the best performance out of your new fuel system.

  1. Reprogram the ECU. The ECU is the engine control unit, or the car’s “computer.” If you’re going to be adding aftermarket parts that boost engine performance without reprogramming the ECU, your performance will suffer. This is because the ECU controls the engine and will still be operating according to stock specifications.
  2. Upgraded fuel pump. This is not necessary for all cars but is generally recommended. A high flow pump can provide maximum fuel flow to the engine for optimal horsepower and fuel efficiency.
  3. Adjustable fuel pressure regulator. Just like the upgraded fuel pump, adding an adjustable fuel pressure regulator isn’t necessary for every car. Still, you’ll need to make sure that your new injectors are running on the right fuel pressure. An adjustable regulator can also help boost your fuel efficiency.
  4. Fuel treatment. If you’ve upgraded your entire fuel system, you might as well upgrade your fuel. Boost your fuel economy with a fuel treatment or catalyst to get the most miles out of every tank.

Warning Signs to Watch For After Installing

If you’ve installed your new performance injectors and notice any of these signs, you may be experiencing a malfunction with your fuel system or injectors:

  • Engine stalls while driving
  • The car accelerates too slowly
  • Rough idling
  • Smoke coming from the engine
  • “Check Engine” indicator lights up
  • Odor in the fuel

Decrease in fuel efficiency

You’ll need to make sure you’ve installed all necessary aftermarket parts properly.

These signs could be an indication that you’re missing a part or that something isn’t working correctly.

Maintenance and Aftercare

Performance injectors don’t come cheap, so you’ll want to ensure you take care of them properly.

Specific maintenance instructions may vary depending on your vehicle and the modifications you’ve added to it. However, we’ve got some useful general tips for taking care of your new fuel system:

Change the fuel filters every 15,000 miles or once a year. Sometimes, the warning signs listed above may be caused by an old fuel filter.

Make sure you change your fuel filters – or take them to a mechanic to have them changed – approximately every 15,000 miles.

Clean your fuel injection system every 20,000 miles. This is standard for electronic fuel injection systems.

Dirty fuel injection systems can hinder performance. You’ll need a fuel injector cleaner kit. This is not generally required in new cars with less than 60,000 miles.

Keep a record of your car’s fuel economy. Knowing your mpg can help you visualize the extra power your vehicle is getting from the new injectors. Plus, it can also help you diagnose a problem if it decreases in the future.

Your performance fuel injection system may require cleaning more often. For the best advice, consult your automotive technician. Or, if you prefer to do it yourself, like many gearheads, do your homework and read up on your vehicle’s fuel injection system cleaning and maintenance recommendations.

If you’ve got a daily driver with stock parts, chances are you don’t need performance fuel injectors, but, if you’ve fitted your car with a turbo or supercharger, you’ll need to invest in a performance fuel injector system to get the most out of your modifications. The extra expense is well worth it in the long run.

Please Check out my YouTube channel, we're regularly adding new content...

PLEASE HELP: I NEED YOUR DONATIONS TO COVER THE COSTS OF RUNNING THIS SITE AND KEEP IT RUNNING. I do not charge you to access this website and it saves most TorqueCars readers $100's each year - but we are NON PROFIT and not even covering our costs. To keep us running PLEASE Donate here

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Feedback - What do You Think?

Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article, I really want to improve this article with your help and suggestions.

Please watch this video and subscribe to my YouTube channel.

5 Responses to “The Benefits of Performance Injectors vs. Stock Parts”

  1. TCJBOLDIE says:

    Higher flowing injectors when mapped correctly will not overfuel the motor as the EMS will be getting the airflow info from either the AFM or the MAP sensor.

    FYI my 4 cyl turbo car with 380 hp at the tyres had 800cc injectors that were at 87% duty cycle at WOT so your recommendations re injector sizes appear to be a bit low so it’s better/ safer to have them flowing less so they can accommodate any future power increase gained by increasing the boost pressure as more power requires more fuel.

  2. TorqueCars says:

    Thanks for your helpful comments and insights, what PSI is your fuel pump/rail running at? I based the calcs on a 58psi system.

  3. TCJBOLDIE says:

    I had a stock FPR

  4. EDWAR says:

    Which is better CPI or EFI? Why?

  5. TorqueCars says:

    CPI was a GM compromise which sprays fuel at the intake port rather than the throttle body. If sprayed sequentially you get good performance but early systems just sprayed fuel into all ports. CPI is a form of EFI (electronic fuel injection), EFI is more popular and has really taken off. Early EFI sprayed fuel into the intake manifold, later versions directed it at each cylinder. The only notable improvement in recent years has been direct cylinder injection allowing very high compression ratios and great fuel efficiency but the early versions have a carbon build up issue in the intake valves.

    Everything has it’s pros and cons and depends what you are trying to achieve, reliability, performance or economy, all have different answers when it comes to choosing a fuel system.

Member Benefits

Join our forum today and benefit from over 300,000 posts on tuning styling and friendly car banter.

You will also have full access to the modifed car gallery, project car updates and exclusive member only areas.

(All car owners of all ages and from all countries are welcome).

BMW 335i - 2021 COTY

We gave the BMW 335i our coveted car of the year award, read more about this awesome car and see why 335i Tuning Guide

Tips for N54 Tuning

Tips for N55 Tuning
Tips for B58 Tuning

Popular articles

Tuning Diesels
Remapping the ECU
Double Clutch
Induction Kits
Customize a car
Performance Chips
Modded Car insurance
Track day insurance cover
Diesel remaps
Calculate MPG
Cleaning a DPF
Tuning Stages

Turbo Faq

Turbos Explained

Engine Balancing

Engine Balancing – balancing pistons, rods and crank.

Alloy Wheels 2

Choosing Alloys.

Stretched Tyres

Stretched tires legal & safe?

Vehicle Checks

How to check a vehicle

Astra Sport Diesel

Tuning the 150bhp Diesel Astra Sport Hatch

MPG Calculator

MPG calculator UK miles per Gallon – calculate MPG