Cheap Home Made DIY Turbo Timer for your 4wd

Land Rover Defender 200tdi turbo timer
Nissan Patrol TD42 turbo timer

This has been used in two diesel vehicle with no computers etc, so all
that is needed is for the fuel pump cut-out solenoid to be kept open in
order for the engine to be kept running. Nissan Patrol engine: TD42 and
a Land Rover engine: 200tdi.

Petrol engines are a different story - whereby +12V will have to be
switched to the coil and the fuel pump once the ignition is turned
off and keys taken out. However, once computers are introduced things
start to become a different story. I have no knowledge for this kit to be
used with these vehicles. It may be wise to purchase a professional timing
device and have it installed properly - how much do you value your late
model common rail turbo diesel?

On both vehicles, I have a push button sitting on the dash with a single
toggle switch next to it which enables a one minute delay (using the 2200uF
capacitor) and a three minute delay (using the 4700uF capacitor).


I have talked to a lot of turbo gurus and most of them have said three
minutes is ample even if the turbo has been working hard for hours, any
longer and it is just wasting fuel - which surprised me actually.
Water cooled turbo's hardly even need a timer, however I still always use
the 40 second setting regardless.


Before I turn the ignition off, I select either one or three minute
setting using the toggle switch (S2), then press the push button (S1),
turn the ignition off. The relay will keep its contacts closed over the
ignition for one or three minutes, after which the relay will drop out,
open the contacts, and vehicle will stop.

From here, you can wire the timer up in two different ways:

If, after the timer has been activated and is running, pulled the keys
out etc, if I want to stop the engine immediately, the timer can be wired
up so that by pressing and holding the push button (Switch 1) for about a
second, other accessories will drain the capacitor nearly instantaneously,
and the relay will drop out. The engine will then stop straight away.
Call this the turbo timer kill switch when wired and used in this way.


The other alternative is to wire the timer so that you can activate 'on'
without having to have your keys on you. Why would you wanna do this for?
No idea really, but if your just ducking out to grab something out of your
car, and your gonna be 3 minutes doing it, flicking the switch to 3 minute,
and pressing the push button will give you 3 minutes of doof doof music.
Wire in another push button to go in parallel with the starter solenoid,
and you can start and run the engine for 3 minutes. Again, no idea why,
unless you wanna move your car forwards or backwards just a tad and cant be
bothered going to get the car's ignition keys.


So I use the one minute timer running around town etc, and the three
minute whenever I pull up suddenly after driving hard (ie > 2000 rpm)
or long distances (ie > 100 klicks)


I cannot advise on which wires to cut and connect to the relay on the
ignition switch for your vehicle. I found the wire that runs from the
ignition to the fuel solenoid engage/cut-out via fuse, found a 12V line,
then soldered these two wires to the relay. After testing, I rolled
everything up in a bunch of electrical tape and tied it to the steering
column.

For Nissan Patrols with sub-tanks, there are two 'ON' wires at the
ignition barrel (pins 5 and 6), along with Accessories being Pin 3.
Pin 6 'ON' and Pin 3 'Accessories' need to be energised in order to make
the sub-tank circuit happy, otherwise the sub tank LED will come on and
stay on. The battery will then need to be disconnected for 20 to 30 minutes
to reset everything.



extra:
Diagram one shows the original printed in the article. Diagram two is
what I made for my two vehicles.
On a 1999 Y61 GU Nissan Patrol (probably the same wiring for all GU TD42
vehicles), connect neg earth, +12v from pin 2 of ignition plug to the timers
+12v SRC, and then +12v 'out' from the timer to both pin 3 'accessories, Black
with white tracer and pin 6 'ON' White with red trace. Pin 5, the other 'ON'
is not needed. Accessories is needed in order to keep power to the sub tank.
If this is not done, it will upset the sub tanks electronics.
Install an on-off-on switch and a single push button. One side of the three way
switch is for 40 seconds, other side if for 4 minutes (roughly) and centre is
engine turn-off or turbo timer kill switch. The push button is wired to turn on
the timer and charge the capacitor that is selected.
Press the button just before turning the vehicle off. Doesn't take long for you
to become accumstoned to doing this and next thing you know you will be pressing
it everytime before turning the vehicle off without even realising it.

Diagram one shows the original printed in the article. Diagram two is
what I made for my two vehicles.




Article slightly modified from "Teeny Timer: a low-tech timer for your car",
Silicon Chip, April 1997.


The heart of the Teeny Timer is a Darlington NPN transistor, Q1.
When current is fed to its base via the 10k resistor, the transistor
is turned on and the realy is actuated to operate whatever you want -
the ignition. The diode across the relay is there to absorb the back
MEF generated by the relay when it turns off.


The circuit operates as follows. When switch S1 is closed, it feeds
+12V to the 1000uF capacitor and the 10k resistor. This turns on the
transistor and operates the relay. When the switch opens, the 1000uF
capacitor continues to feed bias current to the transistor and so the
relay stays on until the capacitor is substantially discharged.
There is not much more to it than that. The +12V supply is fed via an
inline fuse.


Varying the delay
The time delay can be varied by varying the size of the capacitor.
On our version, the 1000uF capacitor gave a delay of about 38 seconds.
470uF would give about 17 seconds; 220uF about seven seconds;
100uF would give about four seconds and anything smaller you wouldn't
bother about.
Longer delays could be obtained by using bigger capacitors.
For example 2200uF should give about one minute and ten seconds while
4700uF should give about three minutes. The actual delay will depend
on the capacitor tolerance, the gain of the transistor, the ambient
temperature and the supply voltage and whether you've had too much to
drink lately.
Not precise enough for you? Hey, this is a low-tech, low-cost design.


Building it
In a thrownback to the dim distant past, we built the circuit on a
5-way tagstrip. The relay is a standard automotive type with SPST
contacts and rated at 20-30A. THey can be purchased from any automotive
parts outlet. The relay is mounted with a single screw and nut, to the
base of the plastic case. You can either solder the connections direclty
to the relay or fit the wires with spade lug connectors, as we did.


Testing it.
This is the easy part. Connect the circuit up to a battery or 12V supply
and operate the switch. The relay should operate immediately. Then turn
the switch off. The relay should stay closed for your desired delay time
and then give a click to show that it has opened.


We mounted the whole lot in a plastic case and the leads all came in via
a grommeted hole at one end. If you are going to mount the Teeny Timer in
the engine bay of your car, keep it as far away from the hot spots as
possible. Mount the case so that the wire entry hole is at the bottom, so
that water splashes do not become a problem.

Parts List
1 12V automotive relay
1 SPST toggle switch or push button (S1)
1 inline 5A fuse and holder
1 plastic case
1 BD679 or BD682 NPN Darlington transistor (Q1)
1 1N4004 silicon diode (D1)
1 1000uF 16VW electrolytic capacitor
1 10K ohm 0.25W resistor
1 5-way tagstrip
1 grommet
1 screw and nut to suit relay

Miscellaneous
1 DPST toggle switch (S2)
1 8000uF capacitor - roughly five minutes.
1 4700uF capacitor - roughly three and a bit minutes.
Spade lugs, hook up wire, solder.








Created: Nov 2007
Updated: 4th Sep 2016.