Boosted SAFC by Robert Pina

SEE ALSO SAFC INSTALLATION PAGE:

Well, you have installed your SAFC and it works great. The turbo crowd has always desired more out of the SAFC. Boost related fuel adjustments have always been sought after. You can in fact dial in the SAFC pretty well with throttle points. It does take a while, but you can do it. I was able to setup the non boost fuel adjustments and WOT fuel adjustments with a decent linear range in between. The problem I ran into however was on hills or heavy load. In these situations you run into partial throttle (~25%) but still are making at least 5 psi. This may be OK, but if you are aggressive on your low throttle settings, it can be a problem.

Inspired by a Talon owner, I wanted to setup the SAFC to adjust by boost instead of throttle. After having done this, I noticed that the characteristics of the throttle reading by boost are very similar to actual throttle position. However, now the reading can account for changes such as free flowing exhaust mods, hills, and other things that would raise boost at an otherwise identical throttle position.

How is this done? Simple, we already have a MAP sensor. The sensor operations from 0-5 volts (roughly) to see everything from high vacuum to ~14 psi. Applications over 14 psi will require a different MAP sensor, which I will talk about later.

Installation:

  • Remove Gray SAFC wire from harness
  • Locate PIM wire from ECU (or route it to your own MAP sensor output)
  • The PIM wire is the same one used for your FCD (see FCD install page)
  • Tap Gray wire into MAP Sensor (PIM) wire (do not cut)
  • Make sure for 3sgte engines that you have tapped in before the FCD
  • Re-Initialize SAFC once installation is complete (under .etc menu)
  • Set all adjustments back to zero before starting car
  • Go for a full boost run to have SAFC read max MAP sensor reading
  • Adjust throttle points, high and low
  • Adjust fuel points by RPM

Tuning:

SAFC tuning will be similar to before. Now, you can adjust by boost and RPM. Boost will appear on the SAFC as throttle %. Before doing any adjustments you should leave all adjustments to zero and use the monitor mode to watch the characteristics of boost according to what throttle % will be shown. After this, you will understand how tuning can take place. If you are unfamiliar with SAFC tuning, please wait till you are familiar before performing this mod. You have 2 choices for tuning. You can tune from the lowest throttle reading (vacuum) to the highest throttle reading (full boost). In between will averaged in a linear fashion for each adjustment point. This may not be ideal as you might not get the fuel adjustment you want at say 3 psi since it averaged for you. So you will need to play with and understand the averaging part. If you want more refined boost tuning, you can set your low throttle point to something near zero vac. This way the fuel adjustments start when you hit the point at which tuning is really needed, zero and above (positive boost). Most figures in vacuum are corrected by the computer anyway.

For those with 550s, you may want to start at high vacuum (the lowest voltage reading). This way you can set very aggressive lean conditions for when not at boost and try to save a little gas. Note that anything more than 25% lean may throw out an error code. Also always remember that any amount that you lean, always advances timing. Please be aware of what you are doing.

Limits:

You will find that with the tuning area between zero and full boost (let's say 15 psi) is pretty narrow. The stock MAP sensor is pretty close to a 2 bar MAP sensor. This means it measures vacuum and up to ~14 psi. If we upgrade this to a 3 bar MAP sensor, now the top reading will be around 25 psi. If we only use say 16 psi max, this leaves a much higher resolution between 0 and 15 psi than what we previously had. These run about $75. After one is installed, further testing will be done.

Tests:

3SGTE GEN II Stock Sensor

Pressure Reading Voltage Throttle %
Idle Vac 1.4v 26
Zero Vac/Boost 2.5v 65
7 psi 3.45v 90
9 psi 3.7v 100*

* - 100% will always be the highest reading you encounter, which was low boost in this test.

Note: Other Toyota MAP sensors such as MA70, and ST165 will have slightly different readings.

Gains:

This mod may not give you more HP. It will give you a greater tuning ability if used properly. It will help fill in "holes" that were previously left between boost/non boost transitions. Tuning will be a little more on and off this way, but I feel that more power and a smoother power curve could be attained. This is only a theory.


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