Dual Performance Chips
Many performance enthusiast, must have heard or read about dual chips. Dual chips are chips that their memory capacity doubles the memory capacity of the original chip, so two different, same size programs can be written inside of the new chip, so it can be selected between them on the fly, simply by using a small switch.
The idea is useful for selecting between the stock program and the performance or fuel economy program. That is, a “Normal” and “Sport” or a “Normal” and “Eco” options switch. Also, if your performance chip doesn’t pass smog tests because of a performance chip you like, the stock program can be selected in a flip of the switch at the time of the inspection test, then it can be switched back to performance when tests are completed.
If the stock or “Normal” program is not to be used anyway, then the dual chip can accommodate two different performance programs like “Mild” and “Aggressive” options.
If the original chip is small enough in memory capacity or the new chip is large enough, there can be installed more “versions” or “power levels”, but a more complex switching would be needed. We will cover here the dual program chip only, using a 27C512 (64KB) EPROM where the original is a 27C256 EPROM (32KB).
If you don’t have or don’t know how to use or manage the chip burning equipment, you may ask somebody skilled on this to do the burning part. If using the “Normal” and “Sports” version, then you would ask the stock program to be burned in the lower memory page of the chip (0000h-7FFFh) and the performance program in the higher memory page (8000h-FFFFh). This is done by attaching one programs into the other in that order, making a single binary file, but double in memory space.
There are many products out there to do this dual chip switching. An example is a chip socket with jumpers, averaging between $30 and $80 , like the Moates product, which is a very nice product, but if you need to do it in many ecus or simply don’t have much to spend, then this trick will be useful.
You will just need a 1k-ohm resistor, a small switch and some thin electrical cable. Below is the simple schematic:
The connection diagram is something like the one blow:
The resistor must be soldered directly in the pins #1 and #28 of the chip. Do this with the chip out of the socket or you will ruin the socket. Solder must only cover the upper part of the chip leads, or the chip could not be reinserted in the socket. Then, the switch must be wired to leads #1 (carefully, in the same spot as the resistor) and #14 in the upper part of the leads also. Now the chip can be carefully reinserted in the socket, but VERY IMPORTANT pin #1 must be hanging out the socket, unconnected, nor touching any part of the socket’s metal contacts.
The above is done because pin#1 is used only when programming (writing) the chip and it is of no use for the ECM (the ECM only reads it, it does not write), but for some reason, Honda and many other manufacturers wire it directly to the +5V supply of the ecu. That, will cause a short circuit that WILL damage the ecu when the switch is flipped to the ground position (Pin#14), which corresponds to “Normal” mode. All this is prevented by leaving the lead of pin#1 hanging out of the socket floating.
There are two details about this installation;
(1) In some cars, switching on the fly will have no effect. In these cars, for changes to take place, the car must be turned off, the switch flipped, and then the car turned on again. Now changes are available.
This is because in those cars, as soon as turned on, the ROM chip is read and then transferred to a faster RAM memory. That is called ROM shadowing or ROM masking. When the car is turned off and then on, it is forced to re-read the ROM and with the switch already flipped, it will read the newly selected program and transfer it to RAM.
(2) In most cases, the cables for the switch must not be longer than 12 inches. That is why we recommend to install it in the ECM body instead of the car dash. This is done to prevent any electrical noise to be picked up by the switch wires, just like an antenna would peak Radio Frequency Interference (RFI). Electrical noise can cause that the switching of programs become unstable and turn on the check engine light or might also cause the ecu to act erratically or make it to lock up.
The method described above, is a precise one and have been tested with no problems. It is offered as an economical option for implementing a simple system like this, but, if you don’t have, or have insufficient experience or knowledge in electronics to do this, we recommend that you either do not try it or bring it to a trained person that can do it for you. A trained person might charge a small fee, but damaging the ECM can be really expensive.