Hands-On: Effective Data Logging Through An Autometer Tachometer

An old saying goes: “How fast you want to go is based on how much you want to spend.”

The very same analogy can be applied to data recording; how much you want to know about your car can be based on how complex a data recording system you’re willing to invest in.

Known as the Ultimate DL Playback Tachometer, the “DL” stands for data logging, and is a step into recording the essentials of your engine and related drivetrain.

Some of today’s typical Pro Modified, Pro Stock, and outlaw drag racing competitors can utilize extremely complicated data recording systems. These systems monitor every intake and exhaust component and motion within your racecar, with 75 channels recording up to thousands of pieces of data per second.

Fundamental Knowledge

On the other end of the data recording spectrum is a system which substantially expands one of the most fundamental data displays mounted within every car running down the dragstrip; that is, the tachometer. Autometer Products has taken the analog (needle) display of your engine RPM and has expanded the electronics within its large “monster”-style tachometers. The DL tach records not only engine RPM, but also the related driveshaft RPM. These two selections of logged RPM data are the most essential drag racing parameters that can impart priceless knowledge to the sportsman racer.

The tach itself is a straightforward Autometer four-wire hookup. All the sensor and laptop connections consist of two pre-wired harnesses.

Racers can now easily view a timed graph of what their engine RPM is doing compared to the RPM output at the transmission. Knowledge based around the torque converter, transmission shifting, and transbrake operation is now just a laptop click away. You can even gauge what may be going on behind the driveshaft, such as launch characteristics and tire spin.

Motivation Behind the Tach

“I began with some market research when Autometer developed the innovation of a data-recording tachometer,” explains Marc Erickson, Director of Autometer Motorsports and Data Acquisition. “I asked racers from multiple sportsman classes what they would want to monitor with a simple data logger. The almost unanimous results included engine (RPM), driveshaft (RPM), air/fuel ratio, and then a pressure recorder. Obviously, a high majority of racers want to record fuel pressure.”

These engine, transmission, and drivetrain recording points may spark your interest, but like the gentleman on television says, “but wait, there’s more.”

The O2 sensor assembly is ordered as a package, including a quality heated sensor, header installation bung, and wiring harness. The harness is pre-assembled with Deutsch connectors.

The Data the DL Tach Provides

The Ultimate DL records more than just engine and driveshaft RPM; within the tachometer body, it also records wideband air/fuel ratio and a user-definable pressure channel. It also includes three-axis g-force meters to show exactly how the vehicle is moving down the track.

The tach can measure a racing engine’s simple air/fuel ratio by utilizing an O2 sensor installed on your header. You can monitor your tune-up, not just as the engine is idling but during your entire pass down the dragstrip, displaying any changes in your racing engine’s tune-up, be it rich or lean.

Like those sensors used with many electronic fuel injection systems, the Autometer wideband O2 sensor is a quality heated oxygen sensor. For a racing application, this sensor is mounted into the header collector area with an included threaded bung.

There’s a straightforward programming procedure for accurate O2 recordings that refers to the Stoichiometric (Stoich) ratio. The Stoich ratio is defined as what proper air-fuel ratio is required to chemically complete the combustion process. This ratio you program into your logger can vary greatly, for example, between leaded race fuel and methanol/ethanol.

An Autometer chart indicates what Stoich number to program into your tach for it to read out and record if your air/fuel mixture is possibly rich or lean. If you happen to change fuels, this Stoich setting can be easily changed in your tach controls.

What is called a single user-defined pressure channel has a very diverse application.

“You can use the pressure channel for nitrous pressure, boost pressure, transmission pressure, engine oil pressure, air bottle pressure, or fuel pressure,” Erickson explains. “It’s your choice.”

Out of the box, the DL Tach comes with a 0-to 15-psi sender that is typically connected to your fuel system or other applications. Racers can choose different pressure senders to match whichever pressurized system they wish to record. It is then only necessary to scroll through the toggle setting on the tach face and select the type of pressure the data logger will be receiving.

The USB port to connect our laptop is a component of the DL Tach wiring harness. The ample harness length allowed us to mount the port near the passenger door for easy hookup. The Autometer website offers free software updates and extensive tutorial videos that make downloading and analyzing each pass very easy.

The driveshaft speed sensor is a two-wire circuit connecting to one another between a magnetic pickup and the tach. Customers must custom fabricate a mount that locates the sensor within .2-inches from the driveshaft magnets. It goes without saying that great care is necessary when fabricating your driveshaft sensor mount so as not to allow it to flex or vibrate and come into contact with the spinning driveshaft magnets.

The tach is very simple to use. We morphed some of our playback designs into this DL tachometer and incorporated our data recording technology. – Marc Erickson, Autometer

More Features

One advantage of Autometer’s design is the auto-activation of the recorder. Though a flip activation switch is an option, an automatic RPM-activated recorder start can be pre-set to begin data logging automatically when your pre-launch engine RPM is reached.

Most racers set this activation RPM just a couple of hundred RPM below their starting line limiter; the system records for 60-seconds — ample time to record any complete pass. You can also install a trigger switch within the wiring harness if you want to arm the data recording manually.

“On top of monitoring data points, for sportsman racers, this is an effective diagnostic tool,” Erickson states. “Monitoring such characteristics as torque converter slip in high gear can immediately take the guesswork out of diagnosing the source of a performance problem.”

Manipulation of the data logging parameters is accomplished through a four-button control. You follow a small digital readout with multiple choice settings. This digital display can also show real-time data of driveshaft RPM, your pressure channel, air/fuel ratio, or G-forces.

Knowledge is Power

I personally can recall many times when my 60-foot time or overall e.t. would fall off; it’s then a guessing game of diagnosing the source of the problem. With the DL tach, engine, torque converter, ignition, or any other potential issues can be solved by reviewing your logged data and/or comparing data with previous passes.

The three-axis G-meter system is housed inside the Ultimate DL tach with no external wiring needed. The G-meter offers accurate tracking of the movement and position of your car during each pass. This three-axis design records the forced related to lateral, longitudinal, or vertical forces.

For your driveshaft speed sensor, Autometer offers a unique approach of including a package of JB-Weld to adhere a set of magnets directly to your U-joint bearing cups. If you choose, an option is available to use a removable magnet collar that fastens around your front or rear driveshaft yoke.

Once the tach installation is complete, you move through the calibration process on the tach readout. With your car running and on a small stretch of track, the tach will direct you to “hold” and then “go.” Accelerate the vehicle in a straight line for under 2-seconds, and the tach will learn its relative position.

Unless you change any mounting angle of the tach, you will not need to re-calibrate the G-meter again.

One more additional feature included is a user-defined readout as a second use of the small digital readout display that generally is used to program the tach. When the tach is in normal operating mode, this digital display can show a real-time digital readout of engine RPM, driveshaft RPM, the pressure channel, air/fuel ratio, and lateral, longitudinal, or vertical G-forces.

An interesting suggestion spelled out by Autometer is the opportunity to install multiple pressure sensors at different points. By easily relocating the connecting wire harness between sensors, you can change which pressures are recorded.

Replaying your passes is also very straightforward; we use a standard USB cable connected to our laptop outfitted with the Autometer Data Pro Software. As an option, many racers utilize the tach face playback feature when in round-robin eliminations scenarios. Not only can you store and review your passes on your laptop, but you can also playback engine and driveshaft RPM right from the tach needle display. This option allows you to quickly review your last pass between rounds without connecting your laptop.

The tach will store up to four passes; if you’re meticulous about storing each pass, it takes as little as 5-seconds to download a pass. The Data Pro Software is a “racing logbook.” You can also manually add 18-additional categories of data into each recording, such as corrected altitude, e.t., MPH, track location, date, and more.

Every sensor includes clearly marked harness extension with dedicated Deutsch connectors that removes confusion, eliminates cross connections, and eases assembly of your system.

With proper Autometer written and online videos that teach you how to operate the software, the sensor graphs on the screen make it visually easy to analyze a pass or compare to previous passes.

Another feature included in many Autometer tachs and not neglected here is the shift light. The Ultimate DL tach has the capability of indicating up to four separate shift points — just set the RPM you’d like the shift light to activate for each individual gear change. During a pass, the tach will automatically move to the next shift point in sequence when it sees a 450 rpm drop following a previous shift light activation.

The jump between a complex data recording system and a playback tach may be broad. Still, the difference between the Autometer Ultimate DL playback tachometer and only racing by the seat of your pants is much more significant.

“Straightforward” is the best description possible when using the data-logging tach from Autometer. If you’re scrutinizing every complex point for a heads-up application, where every ounce of tuning data is for you, then yes, the vast data retrieving options from a high-end recorder system are essential.

When you question if your car “spun a little,” or why it picked up or fell off in elapsed times, it’s not a matter of guessing why, but rather looking at the basic data readily available from your tachometer. If you’re looking for a system that will provide you with leagues of information for Super Gas, Super Comp, bracket racing, and even your basic heads-up racing, this playback tach is a viable and price-conscious data-logger.

Article Sources

About the author

Todd Silvey

Todd has been a hardcore drag racing journalist since 1987. He is constantly on both sides of the guardwall from racing photography and editorship to drag racing cars of every shape and class.
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