Perfect Power SMT8-T5 User manual

SMT8-T5
Technical Manual V5
LetRipp II

Table of Contents: Page No:
1.
INTRODUCTION.........................................................................................1
2. HOW DOES IT WORK?................................................................................1
3. CALIBRATION ...........................................................................................3
3.1 AMP CALIBRATION (Shift F4 ................................................................3
3.2 ENGINE TEMPERATURE CALIBRATION (shift F5 .....................................4
3.3 RPM CALIBRATION ..............................................................................6
3.4 TPS CALIBRATION ..............................................................................7
3.5 DISPLAY OPTION ................................................................................8
4. TERMINOLOGY ..........................................................................................8
5. KNOW YOUR ENGINE .................................................................................9
6. SMT8T_5 PIN-OUT ...................................................................................10
7. COMMUNICATION WIRING and SEt-up .......................................................11
8. POWER WIRING ......................................................................................11
9. STARTING THE PC ...................................................................................11
10. PROFILES: PC SCREEN SETUPS..............................................................12
11. DYNO DISPLAY ....................................................................................13
11.1 INSTALLATION .................................................................................13
11.2 CALIBRATION...................................................................................13
11.3 SETTING UP .....................................................................................13
11.4 PRACTICAL USE OF DYNO FEATURE ....................................................14
11.5 CALCULATING THE HORSEPOWER.......................................................14
11.6 PRACTICAL USE OF THE FUEL MONITOR ..............................................15
12. SMT8T_5 SIMULATION..........................................................................15
13. BASIC WIRING: FUEL MONITOR.............................................................18
14. BASIC WIRING: RPM ............................................................................19
15. BASIC WIRING: TPS .............................................................................21
16. IGNITION WIRING................................................................................21
17. DISPLAY WIRING .................................................................................22
18. SYSTEM SETUP ....................................................................................23
19. MINIMUM INSTALLATION AND WORK .....................................................23
20. ANALOG: AMP......................................................................................24
21. ANALOG: AFR ......................................................................................24
22. INJECTION ..........................................................................................25
23. BOOST CONTROL .................................................................................26
24. IGNITION CONTROL .............................................................................27
25. APPLICATIONS: LIMITING AN AMP SIGNAL..............................................28
26. APPLICATION: MODIFYING AN AMP SIGNAL ............................................28
27. APPLICATION: MODIFYING THE TPS SIGNAL ...........................................29
28. APPLICATION: PROVIDING FUEL AT BOOST VIA AN EXTRA INJECTOR ........ 29
29. APPLICATION: MODIFYING LAMBDA .......................................................30
30. APPLICATION: IGNITION MODIFICATION ................................................31
31. APPLICATION: BOOST CONTROL ............................................................32
32. AUXILARY OPERATIONS ........................................................................33
32.1 FREQUENCY MODIFICATION...............................................................35
32.2 PWM MODIFICATION .........................................................................35
32.3 BOOST CONTROL..............................................................................35
32.4 DISPLAY OUTPUT ..............................................................................35
32.5 DYNO DISPLAY .................................................................................36

32.6 FUEL MONITOR.................................................................................36
32.7 PULLUP............................................................................................36
32.8 SUMMARY AUXILARY OPERATIONS .....................................................36
Table of Figu es: Page no:
FIGURE 3. SMT8T5 pin out ..............................................................................10
FIGURE 4. SMT8T_5 DISPLAY ..........................................................................22
FIGURE 5. SMT8T_5 Switching.........................................................................34

LETRIPP II SMT8T V5 TECHNICAL MANUAL www.perfectpower.com 2011/09/22
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1. INTRODUCTION
Congratulations on the purchase of the SMT8T_5. 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.
The SMT8T_5 (SMT8T Version 5 is a further development from the very popular
SMT8T Version 3 and packs unsurpassed features in a very small size. The unit is
available through the dealer network as branded and public versions.
The SMT8T_5 is a tool for tuning and monitoring engine performance. This manual
will explain in a structured fashion each connection, the use and purpose of outputs,
and in general everything associated with the SMT8T_5. Once the unit is installed
you will need the LetRipp II Tuning software, and the LetRipp II Software User Guide
as well as a PC or laptop and a communication cable to get started.
If you are an experienced engine mechanic, then you will find some of the
terminology strange and can skip over familiar sections.
2. HOW DOES IT WORK?
The SMT8T_5 has two functions:
A Monitor signals for display purposes
This function is a great tool during tuning, but is also great for collecting and
displaying data.
B Modify signals for changing the engine performance
This is its traditional purpose!
The SMT8T_5 ‘modifies’ and measures 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 SMT8T_5 can also advance ignition, 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 SMT8T_5 input. Then the signal is modified

LETRIPP II SMT8T V5 TECHNICAL MANUAL www.perfectpower.com 2011/09/22
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inside the SMT8T_5 and presented as an output, which is then connected to ECU side
of the cut wire.
SMT8 T
Pin 12 of 16
Pin 13 of 16
CB1 + out
CB1 + in
ECU
Engine
Magnetic Sensor
Cut
CB1 - out
Pin 4 of 16
Cut
FIGURE 1. SMT8T_5 SIGNALS
The process by which the SMT8T5 ‘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 = A Signal output
= A ± (-5+1
= A - 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.

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The above shows a typical ANALOG MODIFICATION map, 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 SMT8T_5 for optimum results.
3.1 AMP CALIBRATION (SHIFT F4)
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 1.15bar
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 at position 1
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.

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3.2 ENGINE TEMPERATURE CALIBRATION (SHIFT F5)
The engine temperature is a little different, because the SMT8T_5 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 the expected operating range.

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3.3 RPM CALIBRATION
The RPM calibration is different. You can only specify the LOW/HIGH end points.
Let’s assume we use 600 to 6000 RPM.
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.

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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 SMT8T_5
range to the mechanical range of your sensor.