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Discovering Data: Laying The Ground Work, Presented by Racepak



By Scott Clark

Photos Courtesy of Racepak

In our last article <<HERE>>, we helped you plan a system and hopefully by now you’ve made decisions, purchased a logger or ECU, and you’re ready for the next phase: installation. When it comes to installing electronics in your car, there are things you need to be concerned about that affect both the quality of your data, and the ease (or difficulty) of accomplishing your goal.

As you unbox your new equipment, take a little time to read the instructions! Do it privately if you fear someone may catch you reading them. You’re at the stage where careful installation will make or break the quality of your data gathering efforts; incorrect power or grounds, improper wire routing, even running the wrong spark plug wires can make your data sketchy and useless, so pay attention!

One of the first things you’ll notice about most EFI ECUs and Loggers is that they strongly tell you to run power and grounds directly to the battery itself, and not to a chassis ground or a power distribution panel. In our experience this is an absolute must, because shared power wires (with other electrical consumers such as water pumps, cooling fans, even incandescent lights) can and will cause noise problems that interferes with signals that will cause major frustration later. Follow the manufacturers guidelines for power and grounding, which is nearly always direct to battery.

If you’re making your own wire harness, most manufacturers recommend mechanically crimped connections, not soldered (because copper will eventually harden and break at soldered joints). Make sure to use a high quality adhesive heat shrink sleeve around each of these connections. Once you have the system powered and grounded, consider connecting your laptop and powering up to configure the system before adding any actual sensors; the idea here is to validate the system goes online before you spend hours installing other sensors.

After the system is installed, powered up, and talking to your laptop, it’s is a good idea to install firmware updates. Firmware is the “operating system” of all electronic controls, and manufacturers frequently provide updates that include new features, and sometimes bug fixes. Now is the time to make sure you’re on the latest firmware, and your hardware manufacturer will have clear instructions online how to accomplish this task. Whether you’re using an EFI controller or a Racepak logger, don’t skip this important step.

Now it’s time to start installing sensors. If you’re using VNET modules with a Racepak system, these simply plug in and all you have to worry about is routing the cables. If you’re adding sensors to your EFI ECU, then the task is a little more involved. Pressure and position sensors—such as suspension travel or manifold pressure—run on +5-volt power supplied by the EFI ECU itself. They will also use a special ground often called sensor return, or sensor ground, supplied by the ECU. It’s important to use these power and grounds for each sensor that requires it, as it helps avoid noise problems in the final installation.

In regards to electrical noise, there are other concerns as well: the most susceptible sensors and wires in your car will be any inductive sensors and their cabling to the ECU or logger. These are usually crankshaft, camshaft, and driveshaft speed sensors often reading flying magnets in a reluctor wheel, but they can also include the crankshaft sensor in late-model engines such as the Ford Coyote or Modular. These sensors go by a few different names: VR (variable reluctance) and Inductive are the most common. They are easily identified as they use only 2 wires, are self-powered (no need for 5v power or sensor grounds), and often use shielded cable. These are the wires that you want to route away from ignition and coil wires, including the control wires for an ignition coil, not just the spark plug wires.

Racepak has a YouTube channel ( gets you there). It’s full of great technical and product videos that will help you configure, test and use the company’s products. We’ve used these videos with great success in our own projects.

Speaking of spark, here’s something else you need to consider: almost all electronics manufacturers ask that you run resistor spark plugs. This is because non-resistor plugs send a noise through the power and grounds of the chassis, not a major concern when all you ran was a magneto or a CDI coil; but now, you need to be aware of potential noise problems, and the spark plugs and wires are usually contributors to it. You also must use suppression-core plug wires. A good way to test the noise suppression capability of your wires is to measure the resistance—you’re looking for 50-70 ohms per 12 inches of cable. This is the sweet spot where spark energy isn’t compromised but there is satisfactory suppression of spark noise. The same goes for spark plugs, you want to use resistor plugs that fit your application. If they’re not available, you can purchase spark plug boots that have resistors built in, which are reported to work well. Resistor spark plugs will measure around 1,400 ohms from top to electrode, and they go a long ways towards reducing potential noise problems with all electronics in the car.

Other sensors like square-wave speed sensors (often called Digital, Hall, or Optical) are less susceptible to ignition noise than VR sensors, but are very susceptible to power and ground noise in the chassis. It’s not a bad idea to use an oscilloscope—it can be a shop scope, an older analog scope, or even an inexpensive hobby scope to be able to see these signals (both VR and square wave)—so you can observe any power or ground noise in the signals themselves. Some tuners carry a scope with them at all times! And remember, test each sensor as you add them in the car, don’t be tempted to wire up 30 channels only to find you need to troubleshoot a problem later. This approach is akin to searching for a needle in a haystack, and can be very frustrating!

You may be wondering how sensors are tested in the shop before taking the car to the track; this is done using real-time monitoring (also called realtime telemetry) with your logger/ECU. This is also a good time to familiarize yourself with the software and documentation, and perhaps live technical support. All of these systems will allow you to test your new sensors individually, and it’s wise to do this for each channel before you go to the races. If you’re using Racepak, check out the company’s YouTube Channel (Racepak Media), it’s full of great how-to and product videos to help your installation go smoothly! Make sure you have a few practice logs before you head to the track, and are comfortable with the triggering method. You’ll want to make sure you capture data each pass, perhaps even each time you start the engine, so plan a file naming convention that makes it easy to go back and find logs from earlier sessions. Hopefully by now you’re just about ready to go to the track and make passes, and start learning more about your car’s performance—and improving it!

If you’re making your own wire harness, be sure to use good quality components like these connectors and kits available from Racepak. Be sure you test each crimp and connection before sealing with a quality heat shrink sleeve.





Author Bio

Scott Clark is an independent EFI tuner who works with a variety of different engine management and data capture systems. He focuses mainly on engine and powertrain electronics, and has tuned engines in a variety of venues including land-speed, drag racing, Engine Masters Challenge and even emissions-compliant stationary engines. Scott also teaches EFI installation and tuning classes through his company RealTuners,

Mike Galimi
Mike Galimi is the Director of Content & Marketing at ProMedia Publishing and Events with nearly 20 years of experience in motorsport writing and photography.