Safety Boost Indicator - Zed4life

on Monday 19 November 2007
in A-Z Index - Everthing is listed in here > Boost

Safety Boost Indicator

1: Easy Safety Boost Indicator (SBI) -Approx $10 in materials
2: Manual Boost Controller (MBC)

1:Easy Safety Boost Indicator (SBI)

The idea for this came from both Gonzales and Maciej but I wanted a circuit anyone (even a hack like me) could follow and I wanted a little more control over the way it worked.

What is Safety Boost? This is where your ECU has decided to cut back the boost a little to compensate for certain scenarios it has diagnosed. The usual culprits are when your engine temps are below 60°C or you have a faulty code in the ECU (Code 34 for sure) or your car is detecting detonation. There are probably other causes but these are the main ones.

The ECU compensates for these conditions by doing a range of things including :
* lowering the boost by about 2PSI to around 7PSI via the wastegate solenoids (pics below),
* richening the fuel mixture
* possible retarding the timing

The usual indications of "safety boost" is boost reduces to about 7PSI but unless you are gunning it and have an aftermarket boost guage and are acutely aware of your engine's power output, in general everyday driving you may not even notice the reduced power. In fact many new zedders buy a TT which is in safety boost and being unfamiliar with their power outputs, think that it is normal power. After all, even 7SPI is still a kick in the pants under full throttle. When they discover safety boost and fix it, their faces light up when they realise they have an extra 40-50 odd horsepower for free usually just by fixing or bypassing a faulty det sensor with a few cents worth of parts and 15 minutes...

Knowing when you are in fact in safety or normal-full boost would be useful from a preventative maitenance point (ie: still in safety boost even after it is fully warmed up indicates you may be experiencing detonation or the detonation sensor is malfunctioning) and from a performance point (no more guessing when you have full boost or not indicating your true power baseline from which to plan extra mods against).

The rationale is this SBI gives you a visual indication of when your ECU is in safety boost or normal-full boost mode. The cause of safety boost can be a variety of reasons and this system doesn't isolate the cause, just alerts you of the condition. Like a TWD, it's an early warning device which indicates a problem requiring fixing.

This applies to stock wastegate solenoids, boost jets and should still work with aftermarket boost controllers. In fact, if you have disconnected your wastegate solenoids and running a boost controller, this might be even more useful as you may not even know you are in safety boost map.

Here's what the Wastegate Solenoids look like. You don't need to really know this nor do you need to open the bonnet for either of these mods but it's nice to know more about your zed!

Normally the two solenoids are hidden under the turbo plumbing on each side of the engine or sometimes they are visible. The wiring connector plug is supposed to be secured to either side of the plenum but is often just hanging down. It is a black unit about 50mm x 25mm x 25mm and has a skyblue and red/black wire attatched.

How does the factory safety boost system work? The standard turbo wastegates are controlled by the wastegate solenoids above. When in Safety Boost, they are normally 'open' and therefore do not pass any extra boost pressure to the wastegates which are set at about 7PSI. They are wired into 12V ignition power (red/black wire) and earthed by pin 25 of the ECU (skyblue wire). When in Safety Boost, the ECU floats (disconnects the earth signal) to the solenoids and they are inert. When in normal-full boost mode, the ECU sends an earth signal to the solenoids via pin 25, the solenoids activate and 'close' thereby increasing the boost pressure by approx 2PSI to a total of 9PSI stock max boost. Boost Jets will raise safety boost and normal boost levels. Aftermarket boost controllers almost always recommend to disconnect the standard wastgate solenoids but the ECU pin 25 wire is still intact.

Here is the factory service manual page.

We are simply splicing into the pin 25 wire for SBI.

Here is the diagram we will be working on, roll over and then off the image below to see the circuit in action.

Safety boost mode = ECU 'floats' pin25 earthing wire = (no earth to normally open wastegate solenoids so 7PSI safety boost) - the relay is not earthed and RED LED is on via relay pin 87a circuit (or manually off via switch)

Normal mode = ECU earths pin 25 earthing wire = (wastegate solenoids are actived and closed and therefore 9PSI normal boost) - the relay is energised and Green LED is on via relay pin 87 circuit (or manually off via switch)

SO: Red means : Car is in safety boost mode, Green means goforit, max boost is available.

Tech Rating: Basic Wiring experience

Time to complete: About an hour or so

Tools Required:

* 10MM spanner
* Phillips and blade screwdrivers
* Soldering Iron and solder (optional but recommended)
* Razor blade
* 6.5MM drill bit and Drill


Parts Required (You could get everything from Dick Smith Electronics or equivelant):

* Light gauge wire (about 2 metres black and 1 metre each of red and green - $3.00ish)
* One Single Pole Double Throw 5 Pin relay (DSE part #P8035 - $4.96
(If you are tight and/or don't care bout your cruize control, you can just use the black relay inside the fuse box in engine bay or pick one up from wreckers for a dollar).
* One 3a Diode (DSE part # Z3222 - $0.25c)
* One 1K Ohm Resistor (DSE part # 1474 $0.10c)
* One 5mm LED (DSE part # Z4071 or similar two colour design of your choice - approx $1.00)
* LED Bezels 5mm (DSE part # H1934)
* Ten Electrical connectors (DSE part # H3209) / solder / quality electrical tape
* One pack Cable Ties (DSE part # H1955)
* One Optional (3amp+) 3 pin switch "On1|Off|on2" style to manually turn LEDs off if desired -approx$2.50)
* One Length of coat hanger about 450MM long

Total- approx $10.00

Installation: (Read all the steps before starting)

1: Disconnect vehicle’s battery. Expose ECU (help) & remove retaining screws to gain access to the loom & connector. Remove connector cover carefully & locate pin #25 (skyblue)as in 'help' link and diagram above.

WARNING: The author takes no responsibility for any damage or malfunction that may occur by fitment of this device and/or modification to your vehicle as a result. It is strongly recommended the vehicle battery be disconnected during this mod & ECU connection.

2: Trace the #25 skyblue wire (away from the connector) into the loom for about 100 > 150mm to make it easier to work on. Carefully remove 3 to 5mm insulation from the wire without cutting the wires. Connect a suitable length of the 2Metre black wiring to the exposed wire & insulate the join. Ensure the connection is secure with either solder or tightly wound together then insulate with sufficient electrical tape and a cable tie over the join for good measure.

3: Carefully remove the centre stereo dash panel (remove two clips covering two screws at top left and right next to vents and middle strip covering two screws, then carefully prise the panel out from the bottom- be careful, it may be brittle). Leave the stereo intact.

4: Feed the coat hanger down the left hand side of the centre cavity and toward the left footwell towards the ECU. Wrap the other end of the wire you attached to the ECU to the coathanger wire using tape and slowly remove the coathanger drawing the wire back up with it.

For ease of use, we will use the space above the stereo to mount the relay and main components.

5: Connect the black, red and green wires to the LED (use red for the longer LED probe (as this requires a 12+'ive) using a suitable securing method (solder etc) and insulate each wire with electrical tape where it comes out of the LED lens. A good idea is to label each wire NOW (ie: red, green, 12vPower).

6: Decide where you want to fit your LED. You can locate it in an unused warning lamp spot under the speedo or on the lower fascia as per K-Zed's TWD LED location. (I've located mine inside the speedo cluster next to the stock boost guage but that's because I am a pedantic obzessive geek and I don't recommend you install yours here unless you are extremely comfortable working around delicate instruments)

My 'geek' location:

Lets assume you are mounting it on the fascia like this:




Remove panel from between instrument cluster & steering column as per this Tech Article. Install LED, complete with wiring attached, into the panel directly below main instrument cluster. Requires a 6.5mm [17/64"] hole. Tip: do a trial fit on an old icecream container or similar, bezel goes in first - LED pushes in from rear.

7: Feed the LED wires back to the area above stereo. There are a few paths to take.


8a: Optional- Decide on your Switch location. A good place is under the dash somewhere easily accessible but not easily bumped when you enter/exit the car. Connect the wires to the switch as per the below diagram and feed them back to above the stereo. Install the Resistor incircuit back in the stereo area for each of future access (It does not need to be located near the switch).

8b: Locate a red or blue positive ignition or PREFERRED accessory feed using this chart or the FSM. NOTE: Ensure it is an accessory feed and and not a constant 12V source...

9: Wire up the SBI using the below diagram paying particular attention to the following:

* RELAY (If you need help identifying the correct pins key use this help);
* b: The diode must be installed in the correct direction, as it is transferring an earth signal, place it with the bar closest to the relay wire side (more help) . As the battery is disconnected and the wire will be disabled by the ECU in any case, so if in doubt, try connecting it to the negative battery terminal via a test light/ multimeter; You want to wire it so that the earth signal can pass from the ECU wire into the relay but not go back.

* c + d: Ensure the 12V sources is an accessory or ignition. NOT a permanent 12 V source;
* e: The resistor MUST be installed in circuit before you connect the LED to 12V or it will blow....

It might help to cut and label each wire first before you connect it all up.

10a: Secure and insulate all the wiring sufficiently in a suitable location. There are plenty of locations above the stereo area. use the cable ties to neaten up all wiring.

11: Refit the ECU and cover board (reversing step 1) ensuring the ECU connector is still securely connected to the ECU. If you removed the connector from the ECU for ease of working then rescrew the centre retaining screw down snugly and ensure each end is firmly pressed into the ECU.

12: Reconnect the battery and tighten the leads.

12a: (For optional Switch). Place the key to the accessory position and test the switch, it should light up RED if you have hooked up the LED wires correctly, (if it's Green, just switch connections 87 and and 87a on the Relay!).

13: Refit the centre panel.

14: Trial run. Remember the light shouldn't turn green until the ECU is satisfied that no safety boost conditions exist. Once safety boost conditions return (ie: engine cools down etc) expect the LED to turn RED again. If you fitted the optional switch, you can turn off the LED altogether.

Credits: Gonzales and Maciej and K-Zed

Stay tuned for part two: Manual Boost controller which essentially uses most of the components from this SBI.

Disclaimer: Although every care has been taken to ensure the details above are accurate you should make your own inquiries before acting on any suggestions above. Major overheating can cause a large repair bill so ensure you are completely comfortable with your ability to tackle these repairs/maintenance suggested. The suggestions work on our own vehicles but we cannot control what you do with your own car.


m: 0402 279373


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