RX-7 Electronic Non-Sequential Switch
Thanks to Gene Felber for the writeup.
Original concept by Aaron Faupell with testing by Michael Smith and Andrew Ghali.
This is a very easy to do mod that allows one to choose from the stock
sequential boost pattern to non-sequential (i.e., parallel) boost.
This mod is not as effective as the full non-sequential mod
(where the wastegate is wired open, midpipe is used, and vacuum hoses spliced), but still offers some advantages, primarily no boost spiking at turbo
transition. Below is a table comparing advantages and disadvantages of
both configurations.
| Position |
Advantage(s) |
Disadvantage(s) |
| Stock (sequential) |
Higher boost at lower RPMs.
Good for autocrossing.
|
Boost spiking at transition,
particularly with extensive
aftermarket modifications.
Dangerous boost when balancing
a car through a turn at or
near transition point.
|
Non-sequential |
Consistent, reliable boost
without spiking
|
Good for track events.
Lack of high boost at low RPM
resulting in loss of
around-town driveability.
More lag than the true
non-seq. mod
|
The switch changes the way three solenoids/actuators work: charge control;
turbo control;, and charge relief. Charge control is on during sequential,
and gets turned off for non-sequential. Turbo control and charge relief
operate at different times determined by the ECU. These are both turned
fully on during non-sequential.
Parts/Tools:
- To configure this switch, you'll need a single pole, single throw switch (SPST). This is about the most common switch around so finding one at Radio Shack will be easy.
- 2 Three pole, double throw 12v relays (3PDT or TPDT). Four pole relays might be easier to find and you can use these without any problems, you will just be ignoring one set of contacts.
- 3 300ohm resistors.
- 18 gauge wire. Get as much as is required to mount the switch wherever you desire.
- Insulated butt connectors (optional). For splicing into the ECU to wastegate solenoid wire. RadioShack PN. 64-3037.
- Electronic solder. I like RadioShack clear flux solder in .063 diameter, PN 64-018C. Only a few bucks.
- Soldering iron. Your choice, but do not use very high wattage (>40).
- Wire strippers and crimpers (optional)
The idea is to connect the relays to each other and splice them between the wires going from the solenoids to the ECU. The switch then turns on the relays. Use the locations from the ECU diagram at the bottom of this page. Make your cuts and wire accordingly.
Understanding a relay:
A double throw relay has 3 contacts. A center contact that is switched to connect to one of the other 2 contacts. When the relay is not turned on, the contact is called the Normally Closed concact. When the relay is energized it switches to the Normally Open contact. The center contact is called Common. This configuration is repeated once for each "pole" the relay has, for example the relays we are using for this mod have 3 or 4 common contacts and 3 or 4 NO and NC contacts. Additionally there are 2 extra pins on the relay. These are for the coil. The coil is what turns the relay on and off. When there is 12 volts across the coil pins the the relay is ON.
Wiring the relays:
The idea is to connect the NC contact of one relay to the NC contacts of the other. The 3 common pins on the top relay are connected to the solenoids, and the 3 common pins from the bottom relay are connected to the ECU. Then the 3 NO pins from the bottom relay are connected to the resistors which are then connected to +12v. On the top relay, 2 of the NO pins are connected to ground and the remaining NO pin is not connected to anything. The pole with the unconnected NO pin must run to the 4T wire on the ECU as labelled below.
ECU Diagram:
4R - yellow & blue wire w/silver stripe
4S - pink wire w/silver stripe
4T - blue& black wire w/silver stripe
|