Combining Old and New - EMI Interference
Combining Old and New - EMI Interference
Hot rodding embodies the fusion of classic aesthetics and contemporary conveniences. For some, advanced electronics are cleverly integrated, while others make them a focal point of their project. Regardless of your approach, challenges often arise when incorporating modern technology into a custom vehicle. Issues like radio crackling, malfunctioning PCM, erratic gauges, and sporadic A/C operation commonly stem from EMI, or Electro-Magnetic Interference.
What is EMI?
Electromagnetic Interference (EMI) in a vehicle refers to the disruption or distortion of electronic signals and communication systems caused by electromagnetic radiation emitted by various components within or external to the vehicle. These emissions can arise from sources like the vehicle's ignition system, electrical motors, radio transmitters, or even external sources like cell towers and power lines. When EMI occurs, it can lead to malfunctioning or degraded performance of essential systems such as the radio, GPS, engine control modules, and other electronic components. Minimizing EMI is crucial for maintaining the proper functioning of a vehicle's electronics and ensuring safe and reliable operation on the road. This is typically achieved through the use of shielding materials, proper grounding, and electromagnetic compatibility (EMC) design practices.
How do I Identify if I Have an EMI issue?
In the context of a vehicle, electromagnetic interference (EMI) problems often manifest as anomalies in a system or component, characterized by a recurring "pulsating" or "scrolling" pattern. This indicates that the affected element is undergoing rapid cycles of activation and deactivation, such as a screen scrolling or performing unintended actions in a rhythmic and repetitive fashion. This distinctive behavior is a key indicator of EMI-related issues within the vehicle's electronic systems.
What Are the Causes of EMI Interference?
Two primary systems contribute to EMI interference:
The ignition system: The combination of high voltage and a mix of old and new components within the ignition system can lead to a range of issues. Arcing is the primary problem associated with ignition system EMI interference, occurring anywhere downstream of the coil. This arcing can manifest in the rotor, plug wires, or even the spark plug itself. An open arc generates a radio or electronic signal, which can negatively impact various vehicle systems. The familiar rhythmic crackling or buzzing heard near power lines on an AM radio exemplifies the weak audio representation of EMI signals. Identifying ignition system-generated issues often involves observing fluctuations in intensity alongside engine RPM changes.
Motors and switches: While this concern is relatively minor in the industry, it's still important to note and troubleshoot if necessary. If EMI interference is experienced even when the engine is off, the likely source is a motor or switch. A constant issue typically stems from an electric motor like a fuel pump or fan, whereas intermittent disturbances are commonly linked to a switch. In both cases, the underlying problem involves the generation of an electrical arc that exceeds FCC regulations, emitting EMI at a strength sufficient to disrupt other electronic systems. To pinpoint the source, a practical method involves systematically removing fuses with the key on until the interference ceases, with the responsible component corresponding to the removed fuse.
OK Great, Now I Know Where the Problem Is How Do I Fix It?
Arcing is the issue and sometimes it's easy to see, other times it's hidden. Let’s take a look at some of the causes and fixes relating to arcing and EMI interference.
Spark Plugs: The most common use on older vehicles are the use of non-resistor spark plugs. When the spark traverses the gap, it generates a burst of high-frequency energy known as RFI, or radio frequency interference. True to its name, RFI introduces radio static and disrupts other electronic devices, including the vehicle's onboard electronic control units (ECUs). To mitigate this issue, resistor spark plugs emerged in the 1960s, curbing a portion of the spark's energy and thus reducing RFI to an acceptable level. In most resistor spark plugs, a monolithic resistor composed of materials like graphite and glass is employed. This resistor functions to filter the electrical voltage as it courses through the center electrode. Interestingly, while resistor plugs impede some spark energy, non-resistor plugs deliver a more potent spark. This attribute makes non-resistor plugs a common choice for racing applications. However, in the majority of automotive scenarios, a resistor plug is essential for correct vehicle operation. Using non-resistor plugs in vehicles designed for resistor types can lead to issues such as uneven idling, misfires at high RPMs, and abnormal combustion. Just about every spark plug out there has a resistor and non-resistor variant available. Lastly, carbon tracking in spark plugs can be a source of EMI interference. Grime or water in the boot or a failed plug can all show carbon tracking.
Spark plug wires: Like spark plugs, non-RF (radio frequency) wires can also produce significant levels of interference. Solid core wires, including racing plug wires, are particularly prone to causing EMI problems. Effective EMI and RFI suppression is crucial to minimize the propagation of electrical noise generated by the ignition charge along the wire. This noise has the potential to disrupt a wide range of devices, from AM radios to crucial engine and transmission control computers. Beyond noise suppression, another concern arises from arcing. Arcing can originate internally due to wire breaks or loose connections at the plug or rotor. These internal issues can be more challenging to detect. The most easily identifiable problem is open-air arcing of the wires. This can be observed by turning off the garage lights or inspecting the engine bay at night, looking for any visible arcing on the wires. Such arcing could occur from the boot to the engine block, across wires, or even on the rotor.
Rotor arcing: This presents one of those challenges that often remains hidden from plain sight but can be conveniently tested. Occasionally, there might be an arcing phenomenon occurring from the rotor button towards the distributor base, cap, or even spanning to a spark plug terminal. All of this transpires within the cap while the engine is in operation. A straightforward approach to assess this situation involves applying dielectric grease to the rotor button vicinity. It's important to note that dielectric grease functions as an insulator, not a conductor. Its role is to impede arcing, not to enhance connectivity. This distinction should be kept in mind when using it.
Rotor phasing: This is another one of those hard to find but common EMI issues. Rotor phasing plays a pivotal role in mitigating EMI interference within ignition systems. The alignment of the rotor within the distributor cap significantly impacts the timing and sequence of spark delivery to each cylinder. A precise rotor phasing ensures that the firing of spark plugs corresponds accurately with the engine's rotational cycle, reducing the likelihood of arcing or crossfire between adjacent terminals. By synchronizing the rotor's position with the engine's firing order, EMI interference caused by untimely sparks or erratic firing can be minimized. This meticulous adjustment aids in maintaining a harmonious flow of electrical impulses and contributes to overall system efficiency, leading to smoother engine operation and a reduction in unwanted electromagnetic emissions.
- Alternator/Voltage regulator: In the past, when vehicles didn't have computers and networks, if an alternator produced AC voltage or ripple in the electrical system, it could lead to flickering lights and ignition issues. Nowadays, excessive ripple voltage can cause problems with communication networks and trigger communication trouble codes in various modules. Vehicle computer modules and sensors rely on a stable direct current (DC) voltage level provided by the charging system. However, alternators generate alternating current (AC) through electromagnetic induction. Inside the alternator, a rectifier converts AC to DC using diodes. These diodes channel the negative AC current to ground, converting it into cleaner DC current with a minor amount of remaining AC, usually absorbed by the battery. When a diode fails, the DC current decreases, and sometimes AC current enters the vehicle's power supply, causing issues. The easiest way to test this is to simply unplug the alternator and check if the issue still exists.
- Motors (blowers, fans) This is a common sight that often goes unnoticed. Have you ever peered into the end of an electric motor and observed those tiny sparks as the shaft rotates? Some of these sparks result from the electrical current bridging a gap, but excessive occurrences can lead to EMI interference. Why does this occur? It could be due to wear and tear on the motor or even a subpar rebuild.
Why Do We See This More and More When We Didn't Know About This a Decade Ago?
There are two main reasons why we are witnessing a surge in these occurrences.
- Firstly, the advancement of technology has prompted more builders to integrate sophisticated electronics into vehicles. This is coupled with the trend of retrofitting older products with newer versions.
- Secondly, the period post-2020 has revealed significant turmoil in the supply of electronic components. Factors such as factory backlogs spanning years and the entry of subpar or incorrectly labeled parts into the market have become all too common. These issues encompass electronic elements like resistors, diodes, chips, magnets, and wiring – essential for crafting ignition and electrical components. The decline in material quality has cast a shadow over numerous industries, from automotive to consumer electronics. The fault doesn't lie with distributor manufacturers, who continue to procure their standard core components. The root of the problem often lies upstream with incorrect or substandard component parts. Our tests on HEI distributors, comparing versions from a few years ago to the present, overwhelmingly indicate that the newer parts are more susceptible to EMI interference.
As enthusiasts blend vintage charm with modern advancements, such as digital gauges, cutting-edge infotainment systems and other electronics, EMI emerges as a modern challenge that must be navigated carefully. Fortunately, many EMI issues stem from problems that are straightforward to identify and resolve. This guide aims to equip you with the foundational knowledge to tackle EMI troubles effectively, ensuring that your integration of new technologies into classic designs is both seamless and satisfying. With this information, you can diagnose and address EMI concerns efficiently, allowing you to return to the pure enjoyment of your drive!