SAFC Installation and Tuning (By RS_Guy)

Tuning the SAFC for the 2G 420A

Please note that this is all based on my experience and your results may vary. I am pretty sure that all the info presented here is correct, however, should you use any of it, you are doing so at your own risk, and I am not liable for any of your actions, mistakes or misunderstandings.

As this is going to be a quite large discussion, I have chopped it up into parts:





Gauges & Sensors

Guidelines Reading your Gauges





Lo-Throttle Tuning

Hi-Throttle Tuning

Blue Wire Mod





I am writing this Help file, to try and help all you people out there with SAFCs (Super Air Flow Converter from A�PEXi). I know how hard and frustrating it is trying to get help on something, and I hope that this answers most of your questions. This is all based on my experience, and what I have learned from others. If you have some comments to make, or some information tips to add, please feel free to submit them.

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Quick Background Information
The SAFC is a computer that modifies the MAP Sensor (Manifold Absolute Pressure) signal to the PCM (a.k.a. ECU) of the car. This is really useful because it can "lie" to the car�s PCM about how much air it is getting. Accordingly the PCM will give more or less fuel to the engine, thus helping you tune. Added use of the SAFC comes from the fact that you can play with the settings throughout the RPM range with different throttle positions.

The SAFC does not officially support our Engine. Our MAP sensor is NOT listed in the manual. However, this isn�t terribly crucial to the way the AFC works. All that the SAFC does is a signal (in our case, a voltage). So, don�t worry, the SAFC works perfectly fine, and what follows are some setup suggestions that have worked for me.

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Gauges & Sensors
Before I start to talk about how to tune your SAFC, you have to know to whether your car is in tune or not! To do that there are a few things to note...

The [b][i]best[/b][/i] way to know if a car is running lean or rich is to use a wideband 02 sensor (Oxygen Sensor). But these cost way too much (in the region of $800 and up!). The next best thing to do is read the signal off your existing 02 sensor.

Basically, the voltage read from the Stock 02 sensor can be translated into three categories: Lean (too little fuel), Correct (Just Nice), and Rich (excess fuel). Unfortunately, the differences between the three categories are sometimes slightly blurred and it is hard to tell. For that reason

To make your life easier, I recommend a A/F Gauge (the Air/Fuel Gauge displays the 02 Sensor Voltage). By digital, I mean with a numerical readout. Any gauge that just has blinking lights is extremely confusing, and pretty much useless. The gauge I would recommend is the By getting this gauge, you are also supporting a fellow DSMer.

Along with your A/F Gauge, you an EGT gauge (Exhaust Gas Temperature). The EGT gauge is used as a backup/check tool for the A/F Gauge. You basically tune the car using the A/F Gauge and you keep an eye on the EGT Gauge making sure that the temperature is within safe limits.

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Here are some guidelines for reading your gauges:
For reading the 02 Sensor voltage (remember all readings are taken at Full Throttle). From OV - 0.88V (lean), 0.92V (just nice on pump gas) and 0.96V - Up (rich). Note: When you are at partial throttle (or when the car is idling), the 02 sensor voltages will cycle from and display anything from 0.2V and 1.0V. So don�t panic, it�s normal!

If the temperature probe for the EGT Gauge is placed on the exhaust manifold, the temperature should exceed 1650�F (I would recommend using 1600�F as a max just to be safe). If your car is Turbocharged, and your probe is placed on the Downpipe (after the turbo), use 1400�F as your max safe temp (1450�F is cutting it dangerous).

OK, now that all that is clear, let�s get on to using the SAFC.

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Setting Up the SAFC Correctly
Once you have installed the SAFC, there are a just few things that you should set up before you can start tuning.

First turn the key in the ignition all the way to the end, without actually cranking the engine. Basically you wan the SAFC to turn on with the engine off, so that you can set the initial SAFC settings without accidentally screwing up the engine.

I am assuming that you have read (or at least skimmed) through the SAFC manual. You should know things like where to find the Settings or the Display menus.

In the Menu, go to This is where you tell the SAFC which settings it should use. I recommend 35%, and 50% throttle. This is based on my driving habits; you should drive around a little and see at what throttle percentage you consider "low throttle".

Back again in the Menu, select This is where you set the RPM increments for which you would like to later tune the SAFC. The points that I recommend are 1000rpm, 2000rpm, 3000rpm, 4000rpm, 45000rpm, 5000rpm, 6000rpm, 7000rpm. I like the 4500rpm setting because you need that extra point for tuning at 4500rpm, as the 4000-5000rpm range is quite crucial especially at high throttle.

In the menu, go to and select Start off with For some unknown reason (maybe because the SAFC was NOT made for our car??) the setting works better in some cars.. It doesn�t depend on the year of the car...

Now, Go back one screen and enter the menu and choose and the arrow pointing

This basically covers the crucial settings. The can play with the rest of the settings like VFD Bright later (Vacuum Fluorescent Display Brightness, basically the brightness of the screen!).

Now turn on the car and make sure it idles! It will probably take two tries to turn it on the first time. This is because when you installed the SAFC, the car battery was unplugged and the ECU had lost all power. You did disconnect the battery..right?

Of course if the car doesn�t start, then make sure that the battery is hooked up :-) Lost of people forget this because they are so excited after the install...

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Tuning

I will give you any preset settings. This is for many reasons. All cars set up differently, and EVERY car has unique settings that you have set (no two cars are 100% identical, even if purely stock). Also, I am sure that someone lazy would just skip to this step, stick in some numbers, and do something stupid to their engine. Even though I am not liable, I still care....



This is probably the hardest tuning to do, because the 02 Sensor Voltage is cycling while you are trying to set your settings.

First start off by going to the Menu and by choosing There you will see a graph. The let you select the RPM setting at which you want to tune at, and the arrows let you change the percentage, in 1% increments.

Start off at 1000rpm. This is the most important setting for people with raised fuel pressures, or bigger injectors, because it basically helps you set your idle. What you want to do is make your car idle 99.9% of the time most cars idle RICH (i.e. too much fuel). First you take note of the cycling voltage. You will notice that the voltage keeps flashing a maximum value. This is the value that you should keep paying attention to. If the value is 0.92V, you have to start leaning down the fuel. On the SAFC press the down arrow and do it slowly so that you do it in 1% increments. You want to keep on leaning the fuel until the maximum voltage that shows up is around 0.88V-0.92V. Once you have that set up, let it idle for 30 seconds and make sure that it is still cycling with a correct max value. Sometimes the PCM tries to compensate for the SAFC changes. If the value has changed a little, then just simply lean it down or richen it up as necessary.

Now you can keep doing this tuning routine for other RPMs by slowly stepping on the gas pedal to rev and hold the engine at 2000rpm. This is actually quite hard and requires some practice. After you tune 2000rpm, tune 3000rpm. At this point you have a pretty good idea of the graph you are setting up, and in my experience, for every next rpm increment just go down 1% from the previous rpm setting.

1000rpm -16%, 2000rpm -15%, 3000rpm -14% etc...

HOWEVER, when you reach 6000 & 7000 rpm 2% from the previous values

4000rpm -13%, 4500rpm -12%, 5000rpm 6000rpm 7000rpm

This is a good technique to use as a starting point for tuning.

What you have to do next is take a nice little drive on a long empty road, You need the passenger, because you run off the road otherwise! You can really get carried away staring at the cool blinky-lights!

OK so, now you get to about 2000rpm in gear and make sure that the SAFC is displaying rpm and throttle position (you to make sure that your TPS value is less than what you set the Lo�Thrtl � about 3 5%).

Now, just drive keeping the TPS below you Lo-Thrtl setting and checking your rpm and 02 sensor voltages. Remember if the value is 0.92V at a certain rpm, just richen it a little (up arrow, to increase fuel) and if it is above 0.92V lean it up a little.

Remember, sometimes, it takes more than a 1% change on the SAFC to make the O2 sensor voltage change.

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Hopefully by now, you have a good idea of how the tuning works, and you are comfortable playing around with the SAFC.

First, start off by filling in the values for 1000rpm and 2000rpm. These should be set at the same values you used for Lo-Thrtl. When you are flooring the gas pedal, these rpms fly by so fast that it really doesn�t matter. As a baseline for the 3000rpm setting, use the value for Lo-Thrtl at about 3% richer.


LO-THRTL: 1000rpm -16%, 2000rpm -15%, 3000rpm -14%
1000rpm -16%, 2000rpm -15%,

For the 4000 - 7000rpm start off with the SAFC at values at 0%.

Well, you know the routine by now: floor the car in watch the 02 sensor voltages and make tuning adjustments. Remember don�t make huge drastic changes in once step. Do it reasonably gradually. Also don�t ever forget to keep your eye on the EGT gauge. Lookout for excessively hot EGTs (see above for the values, depending on your setup).

Some things to note:
The settings at 6000 & 7000rpm are usually pretty similar to each other. At these rpm settings, I would usually recommend running like at about 0.94V. This is to be on the safe side in order to try and prevent knock which usually can occur at these high rpms.

Some other things to note for both Lo-Thrtl & Hi-Thrtl. After you have tuned the SAFC to run nicely in the first four gears, remember to check the settings in fifth gear. Due to the gear ratio of the fifth gear, sometimes the settings at higher rpms are too lean/too hot (EGT). The only way that we have found to get around this is to re-tune the car, on the fly, to run richer when you are going to be traveling at high speeds. In any case, you should always keep an eye out for your EGTs. This is your warning that something is running lean.

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Blue Wire Mod

What is it? Well, after you have installed your SAFC, you will notice that some wires from the harness are unused. That is because they are there for applications of the SAFC in other cars.

One of the unused wires is and the idea here, is to hook it up to the 02 Sensor. If you do that, and you go to the menu and select the option, under #2 you will see your 02 Sensor voltage.

Now this may sound very nice and convenient, because it means that you don�t need a Digital AIF Gauge. However, personally, Here are a few reasons why:

- It�s a pain navigating between the and settings and the Sensor Check menu, especially while when you need to be able to make adjustments and see the results very fast, so that you can continue adjusting the tuning graphs.

- People have reported getting wrong 02 Sensor readings when using the blue wire mod. It is suspected that the SAFC puts too much extra load on the 02 Sensor reading and so the reading is somewhat affected. This is especially true if you have hooked up more than one gauge to the 02 Sensor.

- The blue wire is actually meant for a second Air Flow Meter on some Nissans. Some people suspect that the SAFC sometimes tries to send a signal back through the wire. Now if it�s connected to the PCM (ECU).. . .you can guess the rest.

Do you like this? Any Suggestions? Do you have any ideas that you want me to add? Feel free to email me about it at dsmguy@hotmail.com




SAFC

Document statistics: Last modified on 2006-09-29 07:52:15 by DR1665