He first removes the ECU from the car, making sure to remove the negative ground from the battery to prevent any shorts. With the ECU removed, the casing is opened up to reveal the main board. Older Nissan ECUs have the capability of using external memory via a daughterboard. The data is written to EPROM chips and fixed onto the daughterboard.

On the main board, he locates the com port. This area is first cleaned and then de-soldered. The cable that communicates between the main board and daughterboard is soldered into here.

You can see that the jumper on R021is moved to R020 to bypass the main memory and read from the com port.

Great care is taken when soldering as vibration can shake the solder loose and damage the ECU. Next, he moves the jumper from R021 to R020. This tells the ECU to read through the com port instead of the main chip. The opposite side is then soldered onto the daughterboard.

This daughterboard is compatible with different applications based on jumper selection.

He then prepares the EPROM chips by first placing them in a chip eraser to ensure that the memory is clear. While waiting for the chips, he prepares the data through Mighty Map. Once he's satisfied with all the changes, he places the clean chip into the chip writer. Each 28-pin chip is written, one odd, one even. The chips are then affixed onto the daughterboard and the ECU is reassembled.

The daughterboard fits inside the original casing of the ECU.

Making the right choice when it comes to tuning your project is important. It should be the final step in bringing your project together. Whether it's a piggyback, ROM tune or a standalone, make sure your choice is appropriate to your needs and budget.

Piggyback Computer Rom Tune Stand-alone
Fuel control Limited capability Yes Yes
Ignition control Limited capability Yes Yes
Map scaling No Yes Yes
Temperature, altitude, air-con compensation Done by factory Done by factory Done by tuner
Boost control No Yes With additional kit
Additional injector controller Limited No Yes
Change between MAF and MAP Limited capability No Yes
Diagnostic codes Yes, but may be incorrect due to altered factory signal Yes No
Installation Wiring required None Depends on system
User cost $200 - $1,000 $350 - $1,000 $1,200 - $10,000
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