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Installing an APEXi AVC-R 
Electronic Boost Controller
(continued)
At this point the actual installation should be complete (unless I've left something out). The next step is to program the AVC-R.
 
There are some ground rules that apply here:

  • When making boost adjustments, always get a friend to drive. This frees you to make the computer adjustments. You are heading for a crash if you are trying to drive under extreme boost conditions and fiddling with the little buttons at the same time. Trust me on this.

  • Always make sure the pedal is fully to the floor when reading the boost. Make sure your driver understands this.

  • Make sure you have straight roads with little or no traffic. The desert is perfect if you are anywhere near one.

  • BE PATIENT. Remember, this is a process that you will continually fine tune as you become more familiar with it. Concentrate on getting the desired result under a single set of conditions, like, "I don't want to overboost when going to WOT in 4rd gear." When you can achieve that and know HOW and WHY your adjustments worked, you can proceed.
     
Here's the basic theory behind the settings, at least as far as I understand them. Remember, I'm no expert, but I've picked up enough information to tune my AVC-R fairly reliably.
 
The amount of boost you generate is dependent upon engine speed, selected gear, throttle position, and inertia of the turbine/compressor wheel. In a perfect world, you would simply set the amount of boost you want, and the system would be smart enough to maintain that level.

However, that would require a sophisticated computer and automated sensor/feedback system with near-instantaneous response time. With the AVC-R, you get the computer part, but the sensor/feedback system is less automatic and more manual. On the plus side, that gives you more control, but setting it up for the desired result can be tedious.
 
The Boost setting sets your target boost level, and the Duty setting controls the percentage of time that the solenoid is activated to keep the wastegate closed.

Start Duty and Engine RPM-Specific Boost Duty are your key settings, because they provide the level of fine-tuning control you will need to keep boost at the target level you desire without overshooting under changing conditions.
 
In my case, my ultimate goal was to reach 1 bar of boost under all conditions, without over- or under-boosting. Here's the procedure I used.
 
Turn off Learn Mode by setting the values for each gear to "X" (Page 29 in the AVC-R manual). Whenever I used the learn mode, all it did was screw up all my settings. I have heard this same complaint from other users.
 
Set Feedback speed to 5 for all gears (Page 28 in the AVC-R manual).
 
Set NE Points to a Minimum 3000 rpm, Maximum 6500 rpm. Increment 500 rpm (Page 27 in the AVC-R manual).
 
Set the Boost to .8 (or lower) to be on the safe side. At this setting, your goal is 0.8 bar. You can change this after you get continual, reliable boost levels (Page 22 in the AVC-R manual).
 
Set the Duty to 70% -- you will probably have to change this later (Page 22 in the AVC-R manual).
 
Set the Start Duty in each gear for -25% (Page 30 in the AVC-R manual).
NOTE: This is "minus 25%". Use the UP ARROW and DOWN ARROW keys to increase/decrease the Start Duty. The range is Minus (-)50% to Plus (+)50%
 
Set Engine RPM-Specific Boost Duty to 70% in each range (Page 24 in the AVC-R manual).
 
OK, that should do it for initial settings.

With a clear road ahead, bring the car slowly up to 3000-3500 rpm in first gear, then have your driver go to full throttle until he hits 5000 rpm or so, then let off. You will probably see the boost spike when the pedal is initially depressed, then back off a little. That initial "spike" is controlled by the Start Duty setting. It will be different for each gear. Most likely, you will end up with a setting of -5% to -10% in the lower gears, and a figure around -20% to -25% in the higher gears.
 
Repeat this procedure in second and third gears until you eliminate any spikes when the pedal is first cracked wide open. If you go too far, you will get the opposite of a spike, e.g., the boost will be lower when the pedal is first cracked wide open, then it will build. Remember, the Start Duty setting only has an effect in those first few moments when the turbo goes from little or no boost to full boost.

Note: Concentrate on the lower gears, as you'll be traveling pretty fast at 3500 RPM in fourth gear. Use the lower gears as your "training ground", then you can apply what you learn to the upper gears.
 
When your Start Duty setting is reliably limiting boost spikes, concentrate on getting RPM-Specific duty set. For me, this seemed to work best in second and third gears. At each rpm level, see if the boost remains EXACTLY where you want it (.8 bar). If the boost creeps at some rpm levels, decrease the percentage at that rpm. If it drops, increase it.
 
If none of your settings result in AT LEAST .8 bar, go back to the main Boost/Duty setting, and increase the percentage on the duty to a higher number. Don't change it by more than 5% at a time.
 
You will see how boost builds differently depending upon the gear you are in and the engine rpm. Once you are familiar with the way changes to the settings affect your boost profile, you will be able to get the boost to go to .8 bar immediately and stay there, with no overshoot.
 
Now you can apply what you've learned to the boost in the higher gears. Since it's a bit tougher to find a wide open road for testing, this may take some time. One thing to remember is that you will likely experience a more severe case of initial overboost in the higher gears. At least, that was my experience. I typically needed to set the Start Duty in the upper gears in the range of -20 to -25%.
 
Once you've mastered this procedure, you can start adjusting the RPM-Specific settings in each RPM range. You'll need to get into full-boost conditions in each RPM range to see how each setting affects the boost.
 
With the Start Duty and RPM-Specific settings adjusted, you can increase the Boost setting to .9 or 1.0 bar, and most of the other settings will be very close to their correct settings.
 
This procedure will take time to implement, but you will gain an understanding of how each of the settings interacts with the others. Ultimately, you will squeeze the most performance out of your turbo without risking overboost conditions. That is the whole reason to use a tool as complex as the AVC-R, as opposed to a simple manual boost controller. If you don't take the time to master it, you've simply spent all that money on a fancy flashing LCD display panel.
 
I encourage other users to provide feedback on whether their results are similar to mine, and to offer further tips for using the AVC-R to its full advantage. You can email me at mr2@turbomr2.com.
 

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Dave Martin
1993 MR2 Turbo