Thoughts on a successful SAFC install (S4 NA)
04-22-05, 12:11 AM
#1
Rotary Freak
Thread Starter
Thoughts on a successful SAFC install (S4 NA)
... the SAFC forum ate my post! Plus, this is kind of 2nd gen specific.
Well, I've done a lot of research, and have successfully installed a SAFC in my S4. I thought I'd share a few things that seem to come up fairly frequently with regards to the process. Some of this should apply to the S5s as well, but they can use the stock throttle sensor.
I got mine (black) from a vendor on eBay, roughly $260 shipped. The entire goal of the unit is to improve fuel economy significantly. My FC is a highway cruiser, and I feel that it can do significantly better than stock mileage. Power gains are a plus, but not the primary purpose. I have no emissions control equipment, so I don't have to worry about frying cats with higher than normal EGTs.
My SAFC is hooked in using the boost sensor (yes, it's a boost sensor on a NA) for throttle position, and also has the O2 sensor hooked in. I remove the O2 feed from the ECU, to prevent the ECU from going into closed loop mode. Most people with a SAFC see a 10% or so improvement in fuel economy, but the ECU will still go into closed loop mode with the SAFC and hover around 14.7:1. By disconnecting the O2 sensor, I hope to run significantly leaner on the highway, and get better mileage.
In preparation for the installation, I read through the manual, the install guide, and located the required pins on the ECU. The additional lines I had to find & mark were the boost sensor feed and the O2 sensor line.
I chose to install the unit by soldering it in instead of using the little clamps. When dealing with the fairly low voltages of car engine electronics (generally 5V signals, with a usable range of 2-3v), a soldered connection is much better. I did use the plugs for the AFM lines, but I soldered the plug connectors onto the wires after crimping them. Most of the taps can be made by using wire strippers, cutting through the insulation, and pushing the insulation back away from the plug. Be careful you don't cut a wire, because there's not much slack (I cut one, and just soldered it back together, but it's still a pain).
The other change I made was in how I wired the O2 sensor. Stock, the O2 sensor runs into the ECU directly. I think I can out-do it, but I'm not sure yet, so I wanted to leave it able to be reconnected if needed. To do this, I used the yellow Y-splitter cable included with the kit. I put a receptacle on the line coming from the O2 sensor, a plug on the ECU side of the line, and the blue wire from the SAFC already has a plug. This allows me to connect the O2 sensor to the SAFC, ECU, or both, without having to resolder anything.
You can't directly monitor the O2 reading from "Monitor" mode, but you can read the voltage coming off the sensor in the "Sensor Check" mode (off the etc menu). It's a narrowband, so it'll mostly show "rich" or "lean", but you can use this to confirm that your changes are having an effect.
When you set up the throttle sensor, you'll want to set it as "Up" arrow mode. The pressure sensor's output voltage increases with pressure. Note that you will be seeing 100% throttle with the engine off - this is correct. There's full atmospheric pressure on the boost sensor, so it will be reading it's full voltage. With a turbo pressure sensor this won't be true, but you'll still set it up the same way.
After playing around some, I set the low throttle point to 50% and the high throttle point to 70%. This may change, but it seems to be a good ballpark.
You'll also notice driving around that the throttle hits 100% very early on in the pedal travel at low RPM. This, again, is normal. It doesn't take full throttle plate opening to allow the full airflow at lower RPM. One theory has it that learning this "full pressure" curve will give slightly better performance, due to higher primary port velocity with the secondary ports not wide open. YMMV.
As for tuning, I'm still working it out, but I have confirmed that I can cruise with -30% at 3000 RPM (light load) without the engine missing. I get noticeable stumbling at -40%, so I have a range to work with. I also added 10% at idle (as suggested in a lot of threads) and the engine seems happier.
That's about it for my thoughts on the matter. Soldering the connections is a Good Thing!
-=Russ=-
Well, I've done a lot of research, and have successfully installed a SAFC in my S4. I thought I'd share a few things that seem to come up fairly frequently with regards to the process. Some of this should apply to the S5s as well, but they can use the stock throttle sensor.
I got mine (black) from a vendor on eBay, roughly $260 shipped. The entire goal of the unit is to improve fuel economy significantly. My FC is a highway cruiser, and I feel that it can do significantly better than stock mileage. Power gains are a plus, but not the primary purpose. I have no emissions control equipment, so I don't have to worry about frying cats with higher than normal EGTs.
My SAFC is hooked in using the boost sensor (yes, it's a boost sensor on a NA) for throttle position, and also has the O2 sensor hooked in. I remove the O2 feed from the ECU, to prevent the ECU from going into closed loop mode. Most people with a SAFC see a 10% or so improvement in fuel economy, but the ECU will still go into closed loop mode with the SAFC and hover around 14.7:1. By disconnecting the O2 sensor, I hope to run significantly leaner on the highway, and get better mileage.
In preparation for the installation, I read through the manual, the install guide, and located the required pins on the ECU. The additional lines I had to find & mark were the boost sensor feed and the O2 sensor line.
I chose to install the unit by soldering it in instead of using the little clamps. When dealing with the fairly low voltages of car engine electronics (generally 5V signals, with a usable range of 2-3v), a soldered connection is much better. I did use the plugs for the AFM lines, but I soldered the plug connectors onto the wires after crimping them. Most of the taps can be made by using wire strippers, cutting through the insulation, and pushing the insulation back away from the plug. Be careful you don't cut a wire, because there's not much slack (I cut one, and just soldered it back together, but it's still a pain).
The other change I made was in how I wired the O2 sensor. Stock, the O2 sensor runs into the ECU directly. I think I can out-do it, but I'm not sure yet, so I wanted to leave it able to be reconnected if needed. To do this, I used the yellow Y-splitter cable included with the kit. I put a receptacle on the line coming from the O2 sensor, a plug on the ECU side of the line, and the blue wire from the SAFC already has a plug. This allows me to connect the O2 sensor to the SAFC, ECU, or both, without having to resolder anything.
You can't directly monitor the O2 reading from "Monitor" mode, but you can read the voltage coming off the sensor in the "Sensor Check" mode (off the etc menu). It's a narrowband, so it'll mostly show "rich" or "lean", but you can use this to confirm that your changes are having an effect.
When you set up the throttle sensor, you'll want to set it as "Up" arrow mode. The pressure sensor's output voltage increases with pressure. Note that you will be seeing 100% throttle with the engine off - this is correct. There's full atmospheric pressure on the boost sensor, so it will be reading it's full voltage. With a turbo pressure sensor this won't be true, but you'll still set it up the same way.
After playing around some, I set the low throttle point to 50% and the high throttle point to 70%. This may change, but it seems to be a good ballpark.
You'll also notice driving around that the throttle hits 100% very early on in the pedal travel at low RPM. This, again, is normal. It doesn't take full throttle plate opening to allow the full airflow at lower RPM. One theory has it that learning this "full pressure" curve will give slightly better performance, due to higher primary port velocity with the secondary ports not wide open. YMMV.
As for tuning, I'm still working it out, but I have confirmed that I can cruise with -30% at 3000 RPM (light load) without the engine missing. I get noticeable stumbling at -40%, so I have a range to work with. I also added 10% at idle (as suggested in a lot of threads) and the engine seems happier.
That's about it for my thoughts on the matter. Soldering the connections is a Good Thing!
-=Russ=-
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