“Tuning” is a mysterious word… lots of people claim to be “tuners”, but are they really? A whole genre of cars popped up called “Tuners”, but are these hopped up sport compacts really in tune just because they’ve been hosed down with aftermarket parts?
Truth be told, the majority of these cars are going to be way out of tune when compared to a factory setup. And that’s not a commentary on the quality of the parts or the installation… it’s merely a reflection on how well the factory parts played together as opposed to their new aftermarket brethren.
So what is the real definition of “tuned”?
According to popular dictionaries, an instrument is “tuned” when it is adjusted as to be appropriate or brought into harmony. Think about how this definition applies to cars… they’re Tuned not when they’re merely modified or adjusted, rather, they’re Tuned when the parts are all functioning harmoniously together. A car is Tuned when it’s performance level is maximized.
Until recent times, measuring performance tuning levels meant spending time on an engine dyno or on a Race track making adjustments to the vehicle until its maximum performance level… most power, best lap time, fastest quarter mile… was reached. When the car went its fastest, the driver could assume that it was in the best state of tune it could be in. That is, until someone with more knowledge than he came along and showed him a trick or two to go faster.
The trick seems to be to hone-in on a real measurement of the tune state. One way to do this is to measure the air / fuel ratio being blown out the tailpipes and try to achieve the magic number under various conditions.
MAGIC NUMBER
Fuel Air Spark Technologies (F.A.S.T.) is marketing a new wideband Air / Fuel Meter, a device that “sniffs” the exhaust and displays the ratio of unburned fuel to oxygen in the exhaust gas. Chemistry dictates a perfect combustion event will yield a 14.64:1 air / fuel ratio, where all the fuel and all the oxygen in the combustion air will balance each other out. This condition and corresponding air / fuel ratio is termed stoichiometric. Theoretically, if your engine is running and and the air / fuel ratio is stoichiometric, you’ve got the best tune possible.
Theoretically.
The F.A.S.T. Air / Fuel meter requires you to punch a hole in your exhaust system to install the oxygen sensor. If you spring for it, you can run the two-sensor version requiring you to install two supplied oxygen sensors in your exhaust system. When the engine is running, the oxygen sensors are heated up, and they generate an output voltage signal read by the meter which you install in the car. The less fuel present, the lower the voltage signal sent to the meter. Conversely, when there is a high presence of unburned fuel in the exhaust gas, the meter receives a lower voltage signal. The F.A.S.T. air / fuel meter than translates the voltage signals into a ratio displayed on the face of the meter. The F.A.S.T. meter is a true wideband system, which means the oxygen sensors send out a wider voltage range than the factory on-board oxygen sensors used by fuel injected cars. This increased voltage range translates to higher resolution, and more accurate data.
The F.A.S.T. meter incorporates several features which make it a valuable tuning tool. First off, it can be used with one or two oxygen sensors, and it can display the data in a variety of ways. Should you run the two oxygen sensor mode, it can either show the air / fuel ratio for each sensor individually, or it can average both to show one number making it easier to follow.
Another great feature of the F.A.S.T. meter is its ability to datalog. The F.A.S.T. meter can record up to 25 minutes of two-sensor data and 50 minutes of single sensor data allowing you to play the run back later when you’re not driving. This is a great safety feature.
Next, the F.A.S.T. meter has provisions for analog output to an external datalogger. If you have a stand-alone data logging device or a laptop with the appropriate software, you can record as much data as your machine can store, than view and analyze the data with a spreadsheet program like Microsoft Excel to get a graphical picture of what the car is doing.
We welded in the supplied exhaust fittings, connected the sensors, and were measureing our A/F ratio in minutes. What we found didn’t please us, but at least we finally were able to see an accurate, measured state of our cars tune. It turns out that we were running dangerously lean, which prompted us to start a week-long tuning session in which we attempted – and succeeded – at bringing our car’s A/F ratio in to our desired range. Harmony, if you will. Which is what tuning is all about.
Here's what our AFR looked like after we made some tuning changes to fix it. This shot shows the what it looks like when you capture the F.A.S.T. meter's analog output with an external datalogger on a laptop.
The end result is the FAST Wideband Air Fuel Meter is a great tool for dialing in your tune on a fuel injected or carburated application. It's easy to use, easy to read, and the benefits of knowing exactly what your Air/Fuel ratio is will help bring any combination to life.
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