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SMT8-T | Frequently Asked Questions


Frequently Asked Questions.


What do the values of the SMT8-T's ignition map actually mean on the engine's timing?

The SMT8-T doesn't know what the engine's timing is, but it can advance or retard it. Positive values in the ignition map will advance the timing and negative values will retard the timing. Any value used will be added or subtracted from the base ignition timing. Zero entry will be the stock or base timing.

I am trying to wire the SMT8-T to my 1989 E30 BMW 325i. Can anyone tell me what this means on your wiring diagrams : "5 ECU 47 Engine SMT 13 Crank + SMT 3 ECU 27 1 Engine Power SMT 10 Red ECU 2 2 Engine Ground SMT 1 Black ECU 53 3 Engine TPS signal SMT 15 Grey 4 ECU 7 Engine SMT 8 AFM signal SMT 14."?

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I am tuning with the SMT8-T software in Durban. Can someone in your technical division please explain to me how to map a combined start up as well as a warm fueling analogue map according to engine temp. I have calibrated engine temp & configured my LetRipp viewing profile to show side eng temp amp.

You will have to adjust the engine temp side map to add more fuel under cold conditions.

Which wire should I start the installation of the SMT8-T with and which wires should follow thereafter?

Wiring the switched 12 volts and ground first makes it possible for you to communicate with the unit. Connect the crank signal next by teeing onto it first; this way the engine will start and the RPM can be displayed in the software. Then set up the settings correctly so that the software and rev counter display the same RPM, then proceed with intercepting it. Connect the TPS and check it in the software. Intercept the MAF or MAP sensor voltage with the Ana1 in and the Ana1 out. After doing this the car should still start. Check that in the Ana1 Map "F3" when a number of 50 is entered (on the green cursor) (the engine RPM will change). You should now have control over the fueling and timing.

Where should the SMT8-T piggy-back unit be fitted?

It should be fitted inside the cab where it will not get exposed to water (moisture) or overheating.

Can SMT8-T modify a frequency based Air Flow Meter?

No, the SMT8-T piggy-back cannot, however the SMT8-L and the SMT8 have this ability.

Does the SMT8-T have two maps?

The SMT8-T has been designed with 1 map in mind.

Can the SMT8-T modify a narrow band circuit?

No, however you can tee onto the signal so that it can be displayed in the software.

Can the unit be tuned using the MAP sensor instead of the TPS?

Yes you can, just wire the MAP sensor voltage into the TPS input.

Can I fit a narrow band lambda sensor if the car is not fitted with one?

Yes, this will only be as an indication of what the fueling is doing.

What is in the SMT8-T user kit versus the SMT8-T kit?

The user kit contains all the necessary parts for fitment and tuning. The User Kit contains the SMT8-T unit, SMT8-T harness, RS232 communication cable and software CD. The kit contains only the unit and harness.

Will the SMT8-T unit ever come out with USB communication?

The units are constantly being upgraded as the electronic industry changes and gets better, faster and smaller. USB communication will definitely be introduced into the SMT8-T in the near future.

My laptop has no RS232 connector. How will I communicate with the SMT8-T piggy-back?

The only way to communicate is with the use of a prolific converter.

I have connected the USB prolific converter but cannot connect to the SMT8-T?

Verify in Windows, in the Device Manager, under com ports that the converter has been assigned to COM port 1. If not, then go into the advanced settings and reset it to COM port 1.

I have changed the Com Port setting but the unit still does not communicate?

Check in the LetRipp software under Tools, Communication Setup, that it is set to RS232-115K and that COM 1 has been selected.

The green cursor is in the middle of the map and not in the left column as it should be?

The TPS scale has not been set up correctly. By pressing : "Shift F7" the TPS config map will open.

I cannot find the TPS percentage display in the Data Display list?

The SMT8-T will not display the TPS% but will display the voltage. To get the % take the present displayed voltage, divide it by 5 and multiply it by 100.

I lost my communications cable. Where can I get a replacement?

The RS232 cable is a generic cable and can be bought at any computer store.

What is the biggest injector I can use with the SMT8-T?

The SMT8-T unit can safely control a 6 ohm or higher.

How do I calculate the amp draw of the extra injector if it is 2 ohms?

12 volts divided by the injector resistance, in this case it is 6 amps.

How can I test to see if the extra injector is working on the SMT8-T piggy-back?

Pulse the injector at idle. To do this you will need to enter values into the Main Injection Map and the AMP side table, enter a 200 into the main map and a 1 into the AMP side table where the green cursor is when the engine is idling. You should hear the engine note change and depending on the injector type you could feel it working or hear it "ticking".

Do I need to fit a manifold pressure sensor to tune the extra injector?

It is not 100% necessary but we do recommend fitting one as it makes the tuning a lot easier as it is possible to make the extra injector active only when there is boost pressure.

How will fitting an extra AMP sensor make tuning easier?

On most after fit turbo application the OEM MAP/MAF sensor has not been calibrated to measure boost pressure. By using the additional sensor we can trigger the extra injector to only operate when there is boost and to increase the fuel amount as the boost pressure increases.

Why does the SMT8-T unit have CB1+ and CB1- in and out?

Some manufacturers use a magnetic crank sensor which supplies the OEM ECU with a balance signal that is a positive and negative signal. If you intercept only one of the signal so as to modify the timing the OEM ECU will detect a fault, so the unit can modify both signals at the same time.

Can the SMT8-T modify a Crank and CAM signal?

The SMT8-T unit can only modify a Crank signal. If you need to modify cam signal then you would need the SMT8 unit.

How would I know what signal the crank shaft sensor generates?

Check the factory service manual or use an oscilloscope.

Can you make a 0-5 volt crank signal into a bipolar signal?

Yes, by using Pin 3 as the output back to the ECU.

Do I have to cut the crank signal for the unit to operate?

No, as long as you tee the crank "in" onto the crank signal for the unit to get some sort of RPM.

My ignition map is all zeros. Does this mean my ignition timing is at zero degrees advance?

No, the SMT8-T will add (advance) or minus( retard) from the existing ignition curve. The unit does not know at which degree the engine is currently at, but it can modify it. With zeros in the map the ignition timing is standard, positive numbers will advance and negative numbers will retard the timing.

The engine does not start after cutting the crank signal?

The incoming crank signal from the sensor may require a pull up  voltage in order for the unit to "see" it. The OEM ECU normally supplies this, but now that it has been cut and wired into the SMT8-T the pull up voltage is gone.

What does "analog" mean in the pin out?

Analog means that the incoming signal is a voltage-based signal between 0 and 5 volts. The signal can be from an AMP (MAP) sensor, a TPS sensor and boost pressure sensor.

Can the SMT8-T piggy-back control a boost solenoid?

Yes, but with the loss of the extra injector output.

When I use the SMT8-T to control the boost on my turbo car the engine light keeps coming on and the error code is about the N75 valve. How do I fix this?

The ecu was controlling the N75 valve but now you have cut the wire to the N75 valve so the SMT8-T can control it directly. What you need to do is wire a 1 kilo ohm quarter watt resistor onto the ecu wire and onto switched 12 volts.