Perfect Power SMT8Y User manual

In Association with:
Introduces:
SMT8Y DIY TUNING MANUAL
Table of Contents: Page No:
1. INTRODUCTION.........................................................................................1
2. HOW DOES IT WORK?................................................................................1
3. CALIBRATION ...........................................................................................3
3.1 AMP CALIBRATION ..............................................................................3
3.2 ENGINE TEMPERATURE CALIBRATION ...................................................4
3.3 RPM CALIBRATION..............................................................................5
3.4 TPS CALIBRATION ..............................................................................7
3.5 DISPLAY OPTION ................................................................................8
3.6 DYNO (SPEED/DISTANCE) OPTION........................................................8
3.6.1 FREQUENCY INPUT .......................................................................9
3.6.2 PWM INPUT .................................................................................9
3.6.3 SPEED/DISTANCE INPUT...............................................................9
4. TERMINOLOGY.......................................................................................9
5. KNOW YOUR ENGINE..............................................................................9
6. SMT8Y PIN-OUT ................................................................................... 11
7. COMMUNICATION WIRING (WITH POWER).............................................. 12
8. POWER WIRING ................................................................................... 13
9. STARTING THE PC ................................................................................ 13
10. PROFILES: PC SCREEN SETUPS.............................................................. 14
10.1 PROFILE OPTIONS ............................................................................ 15
11. SMT8Y SIMULATION ............................................................................. 15
12. BASIC WIRING: RPM ............................................................................ 17

13. BASIC WIRING: TPS ............................................................................. 19
14. IGNITION WIRING................................................................................ 20
15. DISPLAY WIRING ................................................................................. 20
16. SYSTEM SETUP .................................................................................... 22
17. SUPPLIED MAPS................................................................................... 22
18. MINIMUM INSTALLATION AND WORK ..................................................... 22
19. ANALOG: AMP...................................................................................... 23
20. ANALOG: AFR ...................................................................................... 24
21. INJECTION .......................................................................................... 24
22. BOOST CONTROL ................................................................................. 25
23. IGNITION CONTROL ............................................................................. 27
24. APPLICATIONS: LIMITING AN AMP SIGNAL.............................................. 28
25. APPLICATION: MODIFYING AN AMP SIGNAL ............................................ 29
26. APPLICATION: MODIFYING THE TPS SIGNAL ........................................... 30
27. APPLICATION: PROVIDING EXTRA FUEL AT BOOST VIA AN EXTRA INJECTOR
30
28. APPLICATION: MODIFYING LAMBDA ....................................................... 31
29. APPLICATION: IGNITION MODIFICATION ................................................ 32
30. APPLICATION: BOOST CONTROL ............................................................ 33

DDS DIRECT –SMT8Y DIY TUNING MANUAL www.perfectpower.com 2016/03/03
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1. INTRODUCTION
Congratulations on the purchase of the SMT8Y. This piggyback unit is the result of 20
years experience in the automotive industry and is the latest design in the range of
SMT8 piggybacks.
It is similar to the Perfect Power SMT8T in size, but packs more features. In one
aspect the SMT8Y deviates from all other piggybacks: It has been designed and is
destined for the DIY market. My definition of DIY is: A person who is enthusiastic
about and understands engines and is able to work on his own engine for the
purpose of improving the vehicles performance.
The SMT8Y is a tool that can be installed to achieve that performance. This manual
will explain in a structured fashion each connection, the use and purpose of outputs,
and in general everything associated with the SMT8Y. Once the unit is installed you
will need the Let Ripp V2 software, and the DDS DIRECT SOFTWARE USER GUIDE as
well as a PC or laptop and a communication cable to get started. This manual can
also be used for training professionals because the terminology is common to all
Perfect Power LETRIPP products.
If you are an experienced engine mechanic, then you will find some of the
terminology strange, and you don’t have to read all sections.
2. HOW DOES IT WORK?
The SMT8Y ‘modifies’ engine signals. The signals are used by the ECU to ‘drive’ your
engine in a pre-determined fashion. By modifying the signals, we can change the
ECU’s response.
Example #1:
We all know that an engine runs richer when cold. So, if you want to run the engine
richer, you modify the temperature wire so that the ECU thinks that the engine is
cold. Then the ECU will enrich the fuel mixture.
Example #2:
Your engine has a Lambda loop. This means it controls the fuel mixture by a probe in
the exhaust. By modifying the probe output you can now ‘direct’ the ECU to change
the mixture to lean or rich.
Example #3:
The ignition point is derived from a crank sensor. By ‘delaying’ this signal you can
retard the ignition.
Note: The SMT8Y can also advance, but we will not go into detail here.
In most cases the ‘modification’ involves the cutting of a wire (the signal wire) and
routing the engine side (source) to an SMT8Y input. Then the signal is modified
inside the SMT8Y and presented as an output, which is then connected to ECU side of
the cut wire.

DDS DIRECT –SMT8Y DIY TUNING MANUAL www.perfectpower.com 2016/03/03
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SMT8Y
INPUT OUTPUT
Signal from
Engine ECU
FIGURE
1.
SMT8Y SIGNALS
The process by which the SMT8Y ‘modifies’ the signal is called MAPPING. The
mapping involves looking up a number from a table, adding it to the looked up
number from another table, adding it to the input value, and output the result.
SIDE MAP (S)
MAIN MAP
TPS
RPM
-5
+1
+
Signal input -4 Signal output
Selected map values: -5+1= -4
FIGURE
2.
MAPPING
The numbers which are ‘picked’ from the tables are selected by a TPS and RPM scale,
and in case of the ‘side table’ (the table on the side) from AMP or Engine
temperature scales.

DDS DIRECT –SMT8Y DIY TUNING MANUAL www.perfectpower.com 2016/03/03
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The above shows a typical ANALOG MODIFICATION screen, which does NOTHING.
Of course the user can set the scales applied to the tables. The process is called
CALIBRATION.
3. CALIBRATION
It is a necessary evil requirement. For starters you can ignore it, but eventually you
will need to calibrate the SMT8Y for optimum results.
3.1 AMP CALIBRATION
Calibration principle:
Let’s assume a linear sensor, such as the AMP. You need to know 4 values to
calibrate it.
A LOW voltage and the associated LOW pressure
A HIGH voltage and the associated HIGH pressure
A standard 1.15 bar AMP sensor has the following points:
LOW: 0.25V at 0.25bar
HIGH: 4.8V at 1.1bar
You can try and get the datasheet specification for the sensor, or you can do it as
follows:
Use the LOW setting: 0.25V at 0.25bar
Then use as the high setting the value obtained at ATMOSPHERIC pressure, which is
1.0 bar at sea level. Therefore:
HIGH: Input reading (V) at sea level=1.00bar
Of course the LOW/HIGH points don’t have to be at the end of the scales.

DDS DIRECT –SMT8Y DIY TUNING MANUAL www.perfectpower.com 2016/03/03
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3.2 ENGINE TEMPERATURE CALIBRATION
The engine temperature is a little different, because the SMT8Y first LINEARIZES the
input voltage. Here is what you do:
Let the engine cool down over night, and measure its temperature. Let’s assume it is
18°C. Then use the displayed input reading (V) at point #6.
LOW: Input reading (3.5V) at 18°C, at point #6
Then warm up the engine until it has reached operating temperature. Let’s assume it
is 85°C.
HIGH: Input reading (1.25V) at 85°C, at point #18
You can shift the points up or down to cover your expected operating range.

DDS DIRECT –SMT8Y DIY TUNING MANUAL www.perfectpower.com 2016/03/03
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3.3 RPM CALIBRATION
The RPM calibration is a little different. You can only specify the LOW/HIGH end
points.
Let’s assume we use 600 to 6000 RPM and the LINEAR function.
The same scale in UNLINEAR looks as follows:
Apply Linear

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The UNLINEAR RPM scale looks crazy. BUT: Each RPM step is by the SAME
PERCENTAGE higher than the next one. Why? In this way the change in engine
parameters are constant.
Then there is the CUSTOMIZE option: You can type in the complete scale.
Apply Unlinear

DDS DIRECT –SMT8Y DIY TUNING MANUAL www.perfectpower.com 2016/03/03
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The result of some customization may look like the following:
3.4 TPS CALIBRATION
Each car has a different TPS sensor. The calibration is needed to adapt the SMT8Y
range to the mechanical range of your sensor.
The UNLINEAR function is chosen. This is the preferred one, because the airflow
changes dramatically with very small butterfly openings. But, the other LINEAR and
CUSTOMIZE options are available.

DDS DIRECT –SMT8Y DIY TUNING MANUAL www.perfectpower.com 2016/03/03
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3.5 DISPLAY OPTION
The SMT8Y has an external display option installed after version 119. This option
allows the use of the AUX bin as a display output. For wiring check the BASIC
DISPLAY wiring.
The AUX output has 4 possible drives as indicated in the drawing below:
FIGURE
3.
SMT8Y DISPLAY
The AUX pin can drive up to 8 displays, each display can display one engine
measurement from the DISPLAY list in the PC.
The choosing of an item (from the list) for display does not switch the AUX pin to the
required configuration. This must be performed with the SYSTEM DEF. Finally the
Display can be switched off, which leaves frees the AUX pin to a 2k2 pull-up resistor
for other purposes.
Applicable items from the SYSTEM DEFINITION:
Freq. Mod Tick for Frequency modification, otherwise PWM mod.
Boost Output Tick for Boost output, otherwise Freq. or PWM operation.
Display on AUX Tick for display output, otherwise any of the above is output.
Display off Tick to switch display off
3.6 DYNO (SPEED/DISTANCE) OPTION
The AUXIN pin… can be used for three purposes:
As a Frequency input
As a PWM input
As a Speed/Distance input for DYNO operations