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(FAST Wideband Air-Fuel Meter Installation, continued.)

The principle behind tuning with wideband sensors is simple. By knowing the actual air-fuel ratio of your engine's exhaust, you can make adjustments to the fuel metering to maximize performance. Moreover you can dial-in the optimum air-fuel ratio for each phase of engine operation. At idle and part-throttle you can tune the engine to run stoichiometric, a lean-best mixture of fuel-to-air to maximize fuel economy. Likewise, at wide open throttle you tune for a rich-safe mixture to prevent detonation and maximize horsepower. Naturally aspirated gasoline engines make maximum power around air-fuel ratios ranging from 12.5 - 13.3:1, while a richer (safer) mixture is desired for super/turbo chargers and nitrous.


To feed the signal from the FAST unit to the factory computer harness we'll modify the narrow-band sensor leads. Clip the connectors with about 5" of wiring as shown. You can use some old junyark O2 sensors if you don't want to hack up a good pair.

A good shop manual or the Ford Fuel Injection & Electronic Engine Control book will show you the pinouts for the left and right factory O2 sensor harness.

Based on the wiring diagram we identified the power, ground and signal leads on our connectors. Note that the black leads are actually the narrow-band signal carrying wires. The 12V source are the white wires (we marked with red tape.) The other white lead is ground.

We'll take the leads we made up and connect them back to the factory harness.

Finally, we extended the wires we uncovered from the FAST harness. Each sensor has a pair of wires; the gray wire carries the narrow-band signal and the black wire is ground. Connect them to the respective left and right sensor leads on the factory harness.

The 12V wires used to heat the factory sensors can be taped up as the wideband sensors are heated using the cigarette lighter power adapter. Or you can use the leads to directly power the FAST unit and ditch the cigarette lighter adapter.

With everything wired up and the harness cleanly routed, we're ready to program the unit.

When the unit is powered up you have the option to read air-fuel or select advanced options. We'll go into advanced options to configure the unit to send an analog signal for our narrow-band feed.

The option we'll select is the Narrow Band Simulator. This will generate a 0-1V signal which the engines computer will use in open loop mode.

With dual sensors you can configure the screen to display wide-band air fuel ratio as an average of both sensors or individually. We prefer individually to get an idea if both banks are tuned properly.

Finally, the unit will pre-heat the sensors before it can read the air-fuel ratio.

Once the unit it warmed up it will display the air-fuel ratio detected by each sensor. The unit is capable of datalogging up to 25 minutes (50 in single sensor mode.) Press the up arrow to log, and the down arrow to playback.
As you can see in the video (sidebar) the FAST unit can be wired in to your ignition so that the unit is activated when the engine is fired up. The narrow-band sensor output seems to work as intended. So far we've driven the car over fifty miles without obtaining a check engine light or noticing any hiccups in performance.

In our opinion the FAST product should be touted for its refinement and ease of use. The FAST device has a clean blue LED display and the entire unit is controlled and configured via the built-in interface. There is no need to connect to a PC as is the case with most other AF meters. The unit works reliably at every start. For the average guy simply wanting air-fuel ratios displayed while he is out tuning without the hassle of a PC, this unit is fantastic. Those wanting to download the data to their PC and then chart and crunch numbers with a software tool may not like the FAST unit's fully-contained simplicity. However, the analog out lead can be used to wire up a simple serial interface to a PC. Then one could use Excel or a similar program to visualize their datalog. That would be a bit to "techy" for us though.
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Watch a FordMuscle video showing the FAST unit installed in our 1967 Mustang.
 
 
 
 
 
 
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 





Sources:


FAST
3400 Democrat Road
Memphis, TN 38118
877-334-8355 - EFI HELP LINE

 

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