Grounding Gremlins
Computer controlled engine management strategies started finding their way into new vehicles en-mass as early as the 1970’s. By the mid-1980s, well over half of all new vehicles had computer controls. By 1996, ALL new vehicles used electronically controlled fuel injection. On-Board Computers control ignition, fuel delivery, evaporative emissions, camshaft positioning (variable valve timing), transmission controls (shift solenoids, torque converter lock-up, etc.), dash gauges, OBD communications, CAN network communications, traction control, air bags, and a host of other things. They receive both digital and analog inputs that tell them the state of the vehicle operation. They then make decisions and send signals to drivers/actuators to make things happen. All these signals — both input and outgoing, both digital and analog — all reference a common ground. Typically, this is the negative side of the battery, and the vehicle’s body.
Some of the components used on vehicles generate electrical “noise”, referred to as EMI — or Electro-Magnetic Interference. Major culprits include the ignition coils (probably the biggest villain), fuel injectors, actuation solenoids, relays, and even the radio. Factory engineers do a fairly decent job of including noise filters in the electronics to eliminate (or at least reduce to a tolerable level) EMI influence; so long as the grounds do their job.
The negative side of the battery is connected to the engine block and closest body part; often an inner fender. Most vehicles have a ground strap that connects the engine block to the firewall. Sidebar: I “fixed” a cantankerous Cadillac Escalade that had drivability, transmission, and even gauge cluster issues by simply adding a bunch of grounding wires between critical points. The engine-to-firewall ground strap was a green brittle archeological artifact making absolutely no electrical connection. The grounding issues didn’t end there. I removed and cleaned the remaining factory ground wire connections, which were categorically corroded beyond serviceability.
A company called Nology offers a rather high-priced grounding package they claim adds 7 dyno HP on a Subaru WRX. You may ask, “Just how important is grounding?” Consider this; a Narrow-Band (NB) oxygen sensor outputs a 0 to 1.25 volt signal. It is extremely “high impedance”, which means there’s no “oomph” behind it. An analog volt meter will show 0 volts all the time, because the meter sucks the life out of the sensor’s signal, as it is Low Impedance. How critical is this signal? The oxygen sensor is the heart of the AFR (Air-to-Fuel Ratio) feedback system. If the engine is running rich, the O2 Sensor shows high voltage. If lean, it outputs a low voltage. If the grounding system is askew, the oxygen sensor output signal could vary by at least a few millivolts (1/100 of a volt), or maybe more. Considering the sensitivity of the signal, this could force the computer to erroneously add fuel to restore nominal O2 Sensor voltage. Bing!! Wasted fuel! Poor fuel economy! What’s the fix? Repair poor grounding issues.
In addition to the O2 Sensor, analog inputs include intake air and coolant temperature, throttle position, and many other critical signals. Poor grounds can allow these signals to vary by millivolts, or more. The result is poor performance, fuel economy, emissions, and perhaps even serious drivability issues (like with the Escalade).
If I were a technician charged with adding ground wires, I would add an 18 AWG (minimum) ground wire between battery negative and the fender, and the engine, and the firewall. I would add an additional ground wire between the left and right fenders. I would run more ground wires between the factory body ground points and battery negative (stuff I did to the Escalade).
In addition to all that, here’s one you probably never saw coming — the exhaust! The mere flow of air, especially hot exhaust gasses through a metal pipe (the exhaust system) disrupts electrons and creates ions. There is a technology called “ionic propulsion” that uses the attractive and repulsive forces generated by ions to induce thrust. As the exhaust gasses pass through the exhaust system, they generate massive voltages and ions; both positive and negative. The ions inhibit the flow of the exhaust gasses like magnets — basically they become an invisible restriction. By simply grounding out the exhaust pipe(s), this invisible restriction disappears, and the exhaust system flows better! (See Exhaust Explanations.) As an added benefit, the oxygen sensor references the exhaust pipe in which it is mounted as part of its electro-chemical process. Skew the voltage on the exhaust pipe, and it alters the ECU’s perceived AFR. Secure the exhaust pipe’s ground source, the oxygen sensor suddenly becomes more accurate, and more exhaust gasses freely flow through the pipes. In short, performance and economy are improved (as suggested by the Nology dyno test).
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MPGenie Basics 051 Training - Grounding Gremlins
