Or: even the best engines are subject to the whims of a little squirt!
You’re doing your daily commute in the car. You have it serviced at all the regular intervals that you have been told are necessary to keep it in tip top running order, yet somehow it doesn’t run like it did on the day you drove it out of the showroom. Maybe it’s got a bit of a stutter, or the engine hesitates at odd times, or perhaps the fuel economy isn’t what it was. Maybe you’ve just had one of your regular services and it still feels a bit off. But there are no warning lights, so everything must be fine, right?
Even with all the best modern technology under the hood for economical fuel, engine and power management, there is still wear and tear that is not programmed to be identified by the 30 or more onboard computers that do their best to keep things running smoothly by constantly compensating for wear and tear - and other things that you might not have thought of.
One such factor is fuel injector spray patterns. Perhaps this isn’t something you have considered before, but it’s important for the performance and longevity of your vehicle, so read on to find out more.
Let us spray
Whereas engines used to have carburetors and fuel was atomized into the air intake system at an air to fuel ratio of around 14:1, modern gasoline-powered engines utilize fuel injection. Fuel injection systems are far more advanced and have evolved over the years to achieve better fuel economy and more power, while meeting ever more stringent emission standards. Early injectors were mounted in the throttle body in the carburetor. As injection system design advanced, it was found to be more efficient to move the fuel injectors closer to the intake valves in the intake manifold. Eventually, they were mounted in the cylinder head, injecting atomized fuel directly into the combustion chamber at ratios ranging form 14.7:1 to as high as 65:1 depending on the design and power requirements of the engine. Back in the day, carburetors had to be re-built every couple of years or so. Despite advances in technology and the expectations of modern vehicle owners, this is also a necessity for injection systems. In order to maintain optimum performance, injector systems should be stripped down, inspected and serviced every 2 to 3 years, or 50,000 for direct injection style systems, up to every 5 years or 100,000 kilometers for port style/throttle body style injection systems.
To maintain optimum performance, vehicle fuel injection systems should be serviced every 2 to 3 years.
There are several reasons that injection systems have to be properly cared for. In all engines, over time, unburned carbon deposits and impurities in the fuel build up in the air and emissions passages, as well as on the tip of the injector, distorting the spray pattern and interfering with the atomization. Even the newest direct injection systems, where the injectors inject directly into the combustion chamber, are not immune to distortion, and can even partially melt or corrode due to chemical reactions that occur in the chamber. Also, every injector has its own filter, which can become restricted due to particulate matter from the raw fuel itself.
What does a healthy fuel injector look like?
The design and engineering of injectors, pistons and combustion chambers has become ever more advanced and they are machined to ever more stringent tolerance requirements in order to deliver, on a consistent basis, the quality of performance consumers have come to expect. Equally, engine management systems (EMSs), the computers that manage the flow of fuel through the injectors, are getting very adept at accurately delivering tiny amounts of fuel in up to 1.5-50 milli-second bursts. Fuel is delivered at between 35-100psi for port/throttle body injectors, and somewhere between 1,500-20,000psi for various forms of direct injectors (including those in Diesel engines). All fuel injectors must match that accuracy to the engine to perform as promised at the time it was still on the showroom floor.
Critical factors for optimal fuel delivery
The critical factors in delivering fuel into the combustion chamber is a combination of the amount of fuel being delivered, the spray pattern and the atomization of the fuel. Poor atomization can cause fuel pockets and rich running, which leads to poor economy, excessive carbon buildup in the cylinders, and eventually low power. These conditions can cause problems in starting, as well as rough running. If the wrong amount of fuel is delivered, this can cause rich or lean running, resulting in various forms of engine damage.
For the technically minded...
This is a direct injection set-up. Direct injection is currently the most efficient system, which can be found on most modern vehicles.
Below is an older port/throttle injection setup, where the fuel is atomized before it reaches the combustion chamber (cylinder).
Your injector system has multiple running modes.
Here are two of the most commonly used injection strategies that are running most newer direct injection engines:
Homogeneous Charge Injection Strategy:
This strategy has been the primary mode of operation for all fuel injection systems since they were invented. The fuel injector fires it’s burst of fuel during the intake stroke, when the piston is sucking down. In throttle body and port injection systems, this is done behind the intake valve and the vacuum inside the cylinder pulls the fuel through the valve. In direct injection systems, the injector is located in the cylinder head and fires the fuel directly into the combustion chamber. This results in an even distribution of atomized fuel throughout the entire combustion chamber, maximizing power efficiency and clean-burning of all fuel when the piston rises on the compression stroke and the spark plug ignites the fuel. Under normal conditions, this strategy varies the air/fuel ratio anywhere from as rich as 10:1 to as lean as 25:1, the perfect ratio being 14.7:1. It’s ideal for when lots of power is required.
Stratified Charge Injection Strategy:
This injection strategy is one of the newer ones that uses advanced software control. The burst of fuel is fired into the combustion chamber during the compression stroke, right before the spark plug fires. This results in a rich fuel pocket around the plug, but a leaner mixture at the edges of the cylinder. Less fuel is required to fire the cylinder, sometimes going as lean as 40:1 air/fuel ratio. While it is ideal for fuel economy, it does not provide much power and so is utilized mostly during light load, steady cruising, or idling.
Complex systems require complex testing
With modern computers being so fast, (some are able to change commands to engine components like fuel injectors every 5 milliseconds!), your car’s computer can not only monitor what you are doing with your car every second, but it can even predict what you will do in the next second and change the dynamics of your engine’s running condition stroke by stroke. That’s right; your car’s computer can decide to change how it’s running the motor in between each individual piston firing and you don’t even know it’s happening.
Vehicle computers have more control over how the vehicle works than ever before, increasing the challenge for modern day technicians in diagnosing running issues. Despite this impressive computer sophistication, there is and always will be, wear and tear and build up of deposits - especially in such a high-pressure, dynamic environment. Because of the complexity of the operating environment, some issues can be so difficult to diagnose it may take weeks before the exact right circumstance occurs for the computer to give that one command that is actually causing the problem in the first place.
The EMS can only compensate for approximately a 15% variation from ideal. Beyond that variation, a warning light may illuminate on the dashboard. However, a lot of damage can be done to an engine before that point is reached, if the injectors are not properly serviced on a regular basis. When the EMS detects a weak or abnormal combustion, its response is to deliver more or less fuel, even though the correct amount of fuel may be delivered but in the wrong pattern. This compounds problems as now the cylinder may have excess fuel that causes carbon build-up, excess burning on the piston crown, bore wash, sticking of exhaust gas recirculation valves, and clogging or possible damage to the catalytic converter.
A lot of damage can be done to an engine if the injectors are not properly serviced on a regular basis
There’s only one way to fix this, and we have it!
While there are sophisticated tools that enable a technician to identify the existence of a problem with the injectors when the engine is fully assembled and running, the spray pattern cannot be properly diagnosed, evaluated, measured or corrected while the injectors are in the engine. The engine’s EMS cannot analyze spray patterns. The only way to check and rectify any of these problems is to remove the fuel injectors, use the special fuel injector bench test machine & various other test tools that we have at The Garage. This equipment enables us to replicate and physically see any issues with injectors in a safe, low-pressure environment. This has the added advantage that, generally, if there is a performance issue, we can identify faulty injectors and often partially rebuild and service them, rather than having to make costly replacements, especially if we can test and service them before irrevocable damage occurs.
This is the world’s leading fuel injection service bench, made by ASNU in the UK, which we have at The Garage.
In this test, only the number 3 injector is delivering the correct amount of fuel and performing properly. The other injectors have irregular spray patterns that reduce efficiency in the combustion chamber.
(Click the image to enlarge.)
Have you had your injectors tested recently?
Every type of injection system has a recommended regular service interval. Contact us to find out what your vehicle-specific service interval is.
If your vehicle has done more than 100,000 kilometers, we highly recommend this simple and effective procedure to protect your investment in your vehicle.