6.3 Tuning fuel 6 TUNING THE MS3PRO
MAP based or TPS based AE? If you have a variable Throttle Position Sensor, we’d recommend 100% TPS
based AE as a starting point. MAP based AE does the trick if you’re running an engine without a usable TPS, but
TPS based AE is generally easy to tune to the proper sensitivity level such that it activates when you want it to,
and not when you don’t.
Setting the TPSdot/MAPdot Threshold Levels First up, you need to determine what your TPSdot or MAP-
dot threshold will need to be. Below the line graph charts, you’ll see a TPSdot threshold and a MAPdot threshold.
These are the minimum amount of change of TPS position or MAP pressure reading, respectively, that are needed
to trigger acceleration enrichment. Your goal is to set these high enough that the acceleration enrichment won’t
accidentally trigger at steady throttle, but low enough that it’s sensitive enough to catch small or slow throttle move-
ments as well. Setting it too high can mean the AE won’t kick in when you need it.You want it as low as you can
get it without it causing AE to trigger when it’s not supposed to, such as during steady throttle.
Getting this dialed in can be done methodically, or by trial and error. Here’s the methodical method. You’ll need
to have a safe way to accelerate from the bottom to the top of a gear, preferably your 1:1 ratio gear, and you’ll want
to datalog your engine idling, as well as these WOT pulls with your MS3Pro and TunerStudio. Ideally this is done
on a dyno. Two to three pulls is better than one, but there’s no need to get carried away. Then you can stop the
datalogging and load this log up into MegaLogViewer.
In MegaLogViewer, on the left using the drop-down boxes that let you select what data you are viewing in your
logs, set one of these to TPSdot, and/or MAPdot. You can set another to TPS to show you what throttle position
you were at as well. Additionally, monitoring injector pulsewidth (select PW in the log to view that data) is helpful
too, as you’ll be able to see the commanded injector pulsewidth including the extra fuel added during an AE event.
Lastly, near the bottom right corner of MegaLogViewer you’ll see four indicators. Accel, Decel, Bit 7, and Bit 8. If
either Accel or Bit 7 are active, that’s a Accel event and AE is adding fuel. If Decel or Bit 8 are active, that’s a Decel
event and AE is pulling fuel if configured to do so. (Accel and Decel are used for TPS Driven AE, and Bit7/Bit8 are
for MAP Driven AE).
Next, look at the datalog section of the car idling. The TPS signal should be rock solid, no movement. If it’s
jumping around, you have a noise issues on your TPS signal. This can be caused by ECU sensor signal wiring
that’s been routed too close to high voltage sources such as ignition coils, plug wires, the distributor, etc. Re-
routing those wires away from those high-voltage sources is always a good idea. Additional possibilities for noise
to get in the TPS signal could be a bad sensor ground (be sure you’ve grounded it the MS3Pro sensor return wire),
or a faulty TPS sensor. Similarly noise on the MAP signal could be electrical, but is more likely to actually be real
movement in the manifold pressure, at least at the source you’re grabbing the vacuum signal from, meaning the
port on your intake manifold that’s connected to the MAP sensor.
If you’re seeing AE events at idle, your TPSdot or MAPdot threshold is set too sensitive (too low of a number).
You’ll see the pulse width bounce around when this happens as well; AE is just doing what you told it to do.
Now look at the datalog sections for the WOT pulls, step through these in the logs and look for any time AE
activated (Accel or Decel). It shouldn’t be active at all on WOT pulls, because you’re at Wide Open Throttle, you’re
not moving the throttle around, so AE is not needed. Again, if you are seeing AE activate during WOT pulls, your
threshold is too sensitive.
In either case if you’re triggering AE when you shouldn’t be, you’ll want to increase the threshold value a bit
above the highest TPSdot (or MAPdot) value you see it reach in the logs. This is the lowest you can set your
threshold in order to be a sensitive as possible while not triggering at steady state throttle (or idle, which is also
steady state throttle, it’s the steady state of NO throttle).
Note this setting is also the same setting you should use for your lowest (slowest rate of change) TPSdot or
MAPdot field in the next section.
Tuning the tables Now that you have these, it’s time to tune the PW adder line graphs. To tune these, start
with the lowest speed throttle change position, and practice “tipping in” at that rate of speed. Use the real-time
line graph at the bottom of the page to see how fast you’re tipping in. Once you are able to consistently obtain
a TPSdot reading equivalent to your lowest TPSdot on your acceleration enrichment curve, watch your wideband
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sensor readout. You want to be able to determine what’s happening when you stab the throttle at that rate of
speed. Is it going lean or rich? Note that it’s hard to see this on a gauge, as often it will go one then the other
really fast. You want the first response; if it goes lean then rich you’ll usually see it hit 20:1 or maybe 22:1 for just
an instant, and then as it goes back to running purely the table it may go to 13:1 or whatever... you want to watch
that initial response, and if the first response is to go lean, then you want to add fuel; if the first response is to go
rich, you want to reduce fuel (PW).
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 118
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