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The Delta Throttle Timer Breakthrough

Judges how you're driving and then switches things on and off to suit...

by Julian Edgar

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Imagine having a car that can sense how you’re driving. One that knows when you’ve started going hard and adjusts systems to suit. Like, turns on an intercooler water spray even before intake air temps start to rise. Or switches the auto trans from Economy to Power modes automatically. Or turns up turbo boost when you’re driving hard and turns it back down when you’re driving just gently.

It’d be good, wouldn’t it?

Well stop dreaming and start installing – now you can put a cheap electronic module in your car that does exactly that.

The Delta Throttle Timer uses unique breakthrough technology to constantly watch your accelerator movements. It does this by taking a signal feed from the throttle position sensor. When you push down on the throttle quickly – like after a fast gear-change or when you want max acceleration – a relay is tripped. With that relay you can switch on or off anything that you like. But it’s even better than this. Built into the module is a timer that keeps the relay clicked in for an adjustable period after your last quick throttle movement.

Let’s look at a couple of uses.

Just the Start...

You’re lined up next to a challenger at the lights and you want to trigger your intercooler water spray. A quick blip of the throttle and the spray automatically comes on, cooling down the intercooler. But you don’t want to have to keep on revving the engine to keep the spray running, so you’ve set the timer to 10 seconds. The spray will therefore stay on for that long after your last quick throttle movement. The light goes green and you blast up through the gears, the timer being extended each time you push down fast on the throttle. Race over, you go back to the speed limit - and gentle throttle movements - and the spray automatically turns off.

Neat, huh?

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Or maybe you’ve got an auto trans car with ‘Power’ and ‘Economy’ settings. The trans is a pain – set to Power mode it never changes into top gear, while in Economy mode getting part-throttle down-changes is like extracting teeth.


But fixing the problem is just a case of wiring the Delta Throttle Timer’s relay in parallel with the trans Power/Economy selector switch. Leave the switch set to Economy and whenever you start going for it, the trans will automatically switch to Power mode. Set the timer to give a delay of (say) 20 seconds and a line of fast corners will automatically be despatched in Power mode and the following long straight in Economy. And switching to Power mode is as easy as a single quick foot movement away. On the road the result is just awesome – and in fact we’ll cover this modification in detail next week.

Note that you don’t need to actually floor the throttle to trip the Delta Throttle Timer – just a quick downwards movement anywhere within the accelerator travel is enough to do it.

But the more you think about it, the more uses that arise for the Delta Throttle Timer...

Er, Delta What?

Since there’s nothing like it on the market, a new name for the product was needed. ‘Delta’ means change, so Delta Throttle means ‘change in throttle’. The Timer bit we’re sure you can work out.

The Delta Throttle Timer

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So where did this brilliant module come from? The Delta Throttle Timer was developed and designed by Silicon Chip electronics magazine. It is one of a number of projects that will be covered in a unique Silicon Chip publication - High Performance Electronic Projects for Cars - which will be available from newsagents in Australia and New Zealand, or online through the AutoSpeed shop.

The book will be an absolute must-have for DIY modifiers.

The electronics design and development of the Delta Throttle Timer were carried out by the skilled and modest electronics engineer John Clarke, while I came up with the concept and did all the on-car development. (During this period I wore a different hat to an AutoSpeed contributor, working for Silicon Chip Publications as a freelance contributor.) So while by no means should the Delta Throttle Timer be seen as an AutoSpeed-developed project, we’re very happy to endorse it.

The electronics kit for the Delta Throttle Timer is available from Jaycar Electronics stores or the AutoSpeed Shop for AUD$24.95. Alternatively, the module can be bought fully built and tested for AUD$75.95 - go here AutoSpeed Shop for the details.


Note that is some places the Delta Throttle Timer is known as QuickBrake. This is because the first application of the module used it to quickly turn on the brake lights when the throttle is abruptly lifted (as you do before standing on the brakes in an emergency). This approach was covered in the March 2004 Silicon Chip magazine (Increase your driving safety with Quick Brake) and will also be covered later in AutoSpeed.

The Module

If you have assembled other electronic projects before, the Delta Throttle Timer (or QuickBrake) kit shouldn’t cause you too much trouble. There are 18 resistors, 13 capacitors, 13 semi-conductors, assorted terminals, the relay and two trim-pots. Solder and hook-up wiring is supplied. Follow the instructions carefully – in fact to gain the article in full colour (important when following a component overlay) we suggest that if you're building the kit yourself you subscribe to the on-line version of the article at Silicon Chip.

However, if you’re not confident with component identification, component polarity and soldering, buy the fully built and tested version – then only a few simple connections to the car are required.

Neither version comes with a box, however the Delta Throttle Timer (we’ll call it DTT from now on!) fits straight into a 130 x 68 x 42mm plastic electronics ‘jiffy’ box. Alternatively, you can put it in any box that you want, making sure that the bottom of the printed circuit board can’t come into contact with anything metallic (which could cause shorts).

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When you have either built the kit or received the built-up module, have a good look at it. Orientate it so that the relay is on the right. Now you’ll have two sets of terminals on the left and a long strip of six terminals on the right. The top-left terminal connects to ignition-switched 12V – that is, a battery positive supply that is on when the ignition is on. The terminal right below connects to ground – in other words, to the car’s metal body. The lower left terminal has two inputs but as they’re connected together, either one can be used. This input is for the wire that connects to the throttle position sensor.

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Before you can connect the signal input to the throttle position sensor you need to find the right wire on the sensor. To do this you’ll need a multimeter. Set the multimeter to Volts DC and connect the black lead to the car’s body. Turn on the ignition. With the other multimeter input, back-probe the working throttle position sensor until you find a wire that has a voltage on it that varies with throttle position. Typically, this will be in the 1-4V range and the voltage will rise when the throttle is opened. This is the wire that you tap into for the DTT signal.

Connect up these wires to the DTT (note that the throttle position signal wire doesn’t need to be cut – the DTT just taps into it).

The next step is to adjust the two trim-pots. Turn Pot 1 (Sensitivity) anti-clockwise as far as it will go. Note that these are multi-turn pots so you may not come up against a positive ‘stop’ when you get to the end of its rotation. Turning the Sensitivity pot anti-clockwise increases sensitivity. Next turn Pot 2 (Time) clockwise to decrease the period that the timer will stay on. Finally, check that the moveable link on the board is in its left-hand position (note: this is the opposite position to where it is located when being used in QuickBrake, so if you are building the kit version keep this point in mind.)

Switch on the ignition, wait for 10-15 seconds and then quickly push down on the throttle. The LED should come on and the relay pull-in for a short time. (The 10-15 second delay after switch-on is needed because the DTT has a built-in pause to avoid false-alarming when power is first applied.) Then turn the Time pot anti-clockwise to extend the relay’s ‘on’ time. The range of adjustment is from 1/10th of a second to just under 2 minutes. Set the Sensitivity and Time in keeping with your application - you can fine tune it later.

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The next step is to connect the DTT to whatever you’re triggering. If the load is less than 5 amps (around 50 watts) you can run it straight from the relay on the DTT. Connect 12V to the ‘Normally Open’ terminal and then feed the load from the ‘Common’ terminal next down. Earth the other side of the load.

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If you are switching an even heavier load, use a normal automotive relay in conjunction with the DTT.

Throttle Lifts as Well

In addition to detecting when the throttle is being pushed downwards quickly, by simply swapping the position of the on-board link the DTT can detect when the throttle is being lifted fast. Uses? Well again there are heaps. Here’s two: triggering an electronically-controlled blow-off valve and switching on the brake lights in an emergency decel... even before you touch the brake lights! We’ll be covering both of these in future articles.


The Delta Throttle Timer has the ability to read the driver’s behaviour and then take appropriate action.  Whether the driver actively uses the DTT to trigger a device (eg a conscious quicker push on the throttle to change transmission modes) or whether it just happens as a part of normal driving (eg fast gear changes switch on the intercooler water spray), the results are brilliant.

However, if you’re not confident with component identification, component polarity and soldering, buy the fully built and tested version – then only a few simple connections to the car are required. AutoSpeed Shop

Tech Summary

0-5V throttle position input signal – works with all standard throttle position sensors
Adjustable sensitivity to speed of throttle movement
Adjustable timer 1/10th – 110 seconds
Link Position 1 – detects throttle movements downwards
Link Position 2 – detects throttle movements upwards
DPDT 5 amp output relay – can switch two independent circuits either on or off
LED relay indication – LED can be mounted on dashboard for driver indication

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