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Hydrogen Powered Commodore 

 By Darren Chandler


fig. 1.    The Commodore after it’s first Hydrogen road test.


While I have an interest in cars, it is not an all-encompassing interest, just one of many interests.  I am actually very narrow minded with cars- I am really only interested in one brand, Holden!  I suppose it is because I grew up with Holdens.  They were always big, comfortable, reliable and uniquely Australian.  Another interest I have is alternative fuels.  I believe that one day we will either run out or not be able to afford petroleum fuels, meaning that hundreds of millions of petrol driven cars could be rendered useless to their owners unless we can convert them to operate on a new, sustainable fuel.

Converting a car to run on Hydrogen is a passion that I have had since I was quite young.  The idea of being self-reliant and creating my own hydrogen fuel from water through electrolysis and then powering my car on it, no longer relying on petrol companies has always been a dream.  I also like the fact that a vehicle running on hydrogen emits mainly steam from the exhaust.  Assuming the power used to obtain the hydrogen is produced in an environmentally friendly manner, cars powered by hydrogen actually improve the surrounding air quality, because pollutants in the air are burnt inside the engine and no new pollutants are produced.  This is why hydrogen powered internal combustion cars are sometimes called “minus emission vehicles”.

fig.2.  the exhaust is mainly harmless steam 

In 2003 my father handed over the keys to his 1980 Holden VC commodore, the goal was to “do it up”. I decided that the VC would become my first attempt at a hydrogen conversion.

The plan

While the VC was 26 years old, the aim was that the conversion could be applied to almost any petrol driven car, including modern fuel-injected types.  The conversion also needed to be as safe as possible and with minimal tendency to ‘ping’ (pre-ignite the hydrogen fuel).  The car was also to be a ‘dual fuel’ conversion, meaning it could switch between hydrogen and petrol.

While cars have previously been converted by introducing hydrogen into the air intake, this method is flawed as it creates a large volume of mixed hydrogen and air inside the intake manifold.  Due to the extremely high flame speed of hydrogen, this is dangerous for the engine, as any pre-ignition event could cause a very large “backfire” inside the manifold, frightening everyone nearby and damaging the engine.  Pre-ignition is one of the main problems with hydrogen, as the flame speed is faster than that of any hydrocarbon fuel, if the ignition timing is not set at top dead centre right through the rev range, the flame front inside the cylinder will burn back through the still partially open intake valves and ignite any fuel/air mix inside the manifold.  This is not the only thing that can cause backfiring, even before it is ignited the hydrogen can self-ignite when entering the cylinders, just from contact with a “hot spot” inside the cylinder.  This is one reason why it was decided to use a sequentially injected system on the car.  This would involve using specially made “gas” fuel injectors, one for each cylinder, and each “firing” just before it’s corresponding intake valve opens.  In addition, the ignition timing would need to be able to be altered from inside the cabin both when tuning the car, and when changing between hydrogen and petrol fuel.  Compressed hydrogen would be used, initially obtained from a local gas supplier..  Two “E” size cylinders fit in the boot easily and these are filled to just over 2000 psi giving a range of around 30km just enough for testing purposes.

The conversion

The first part of the conversion involved extensive modification of the ignition system.  The existing ignition system on a VC is a conventional one for 1980; a distributor, reluctor system, using a single coil and a rotor button to distribute the high tension to each of the six spark plugs.  Timing is controlled by weights inside the distributor that, by centrifugal force, rotate the reluctor assembly, advancing the timing as rpm increases. This works well when running on petrol, however to run on hydrogen, there needs to be no ignition advance.  Additionally, the sequential fuel injection system needs to know the position of the engine at all times to enable the correct injector to fire at the right time, and this engine, being a carburetor engine, has no sensors to determine engine position. This meant removing most of the existing ignition system, retaining the distributor and reluctor only as an engine position sensor.  The centrifugal weights were clamped so they could not move, and an optical sensor was fitted to the distributor case.  The only function of the rotor button now is to trigger the optical sensor.

fig. 3.  Modified distributor. Arrow indicates optical sensor.  

This optical sensor now gives a reference signal, and the existing reluctor provides the six “firing points” needed to determine the position of the engine.  These signals are fed into a “sequencer box”, which drives six separate ignition coils.  This consists of a PCB containing logic circuitry, which drives two, 3 channel coil driver devices, pictured in fig.4. This also provides the signals used to drive the fuel injection system.

fig. 4. sequencer box which drives the six coils

fig. 5. the six ignition coils can be seen here.

The ignition advance is controlled by a PIC based controller inside the cabin, which has two pre-set programs- one firing at T.D.C across the rev range for hydrogen fuel, and one giving the advance curve needed for petrol operation.  These programs can be changed with the push of a button.

fig. 6. the PIC based device used for ignition timing control.

Next, the fuel injection system was constructed.  The fuel injectors were ordered from a company in the U.S.A.  They are specially designed for gaseous fuels, and can be used with hydrogen, compressed natural gas (C.N.G) and propane.  They are rated at 80 psi input pressure for hydrogen, and are “peak and hold” type injectors, meaning they need a special type of driver which delivers full (6 amps) current initially to open the injector, then reduces the current to 1 amp to hold the injector open for the rest of it’s  “open” cycle.  A special mounting bracket was fabricated to accommodate the fuel injectors, along with the fuel rail, which was salvaged from a later model Commodore that featured fuel injection.

fig. 7. two of the fuel injectors and fuel rail.

Ports for the fuel injectors were machined from brass plumbing fittings and ” copper tubes carry the hydrogen from the fuel injectors, through the intake manifold and to within 2 cm of the intake valves.  What this means is that, because the injector will only fire when it’s intake valve opens, there is minimal mixing of hydrogen and air within the intake manifold, which minimizes the extent of any pre-ignition event.

fig. 8. here the ”tubes carrying hydrogen fuel can be seen.

The injection system is controlled by a potentiometer which is connected to the throttle cable; when the throttle is depressed, the potentiometer reduces the voltage supplied to a voltage controlled oscillator (V.C.O), and this reduces the frequency of the square wave output of the V.C.O. The cable is an additional throttle cable which works in parallel with the original throttle cable.

fig. 9. potentiometer attached to throttle cable. Mounted to firewall.

This V.C.O signal is fed to the injection control box, which consists of flip-flops and counters.  When an injector is fired, a flip-flop is set and stays set until it’s counter has received 128 pulses from the V.C.O, when the flip-flop is reset and the injector is turned off.  If the V.C.O frequency is reduced (throttle pedal depressed), those 128 pulses take longer to occur and so the injector stays open longer.  This is how throttling is accomplished.  Fine tuning of the V.C.O is possible using the controls inside the car and this allows for idle speed and throttle range adjustment.

fig. 10. peak and hold injector driver and control box.

fig. 11. injection control box with cover removed.

Solenoid valves are used to turn the petrol and hydrogen supplies on and off when necessary..  These are operated from the fuel selection switch in the cabin.

fig. 12. V.C.O box in centre console.

The hydrogen fuel cylinders are mounted laterally in the boot in special brackets, which hold the cylinders securely.  The regulators mount directly to the cylinders and are two stage regulators, set at 80 psi. 10 mm I.D hose carries the hydrogen up to the fuel rail under the bonnet.

fig. 12. cylinders mounted in boot.

fig. 13. dual stage regulator.



The VC was test driven on hydrogen and after some adjustment of fuel injection timing it performed well.  As expected the power was approx 80% of that when running on petrol.  The VC was driven at over 110 km/h and on flat roads achieved 13-15 km per cylinder of Hydrogen.  When the engine is hot and under heavy acceleration, some pre-ignition is still occasionally apparent, however it is not severe and the future planned is to add a water injection system which should solve this entirely.  A further plan is to test the car on C.N.G as this is currently the most feasible alternative fuel in this country, and the idea of filling the car with C.N.G at home is appealing.

fig. 14. first test run on hydrogen fuel.


    This project took almost three years to complete due mainly to other commitments and projects happening along the way. It was a learning process and it has paved the way to creating a fairly economical conversion system which, in the future, can be utilised to convert other, newer vehicles. On the subject of cost, here are some figures for the higher cost items in Australian dollars;-

6x gas injectors:                                   $1200
peak and hold driver:                           $400
2x ignition coil drivers:                         $400
6x ignition coils:                                    $360
2x dual stage hydrogen regulators:    $800

total                                                     $3160     

All other major parts for the conversion were designed and constructed by the author, so the main cost here was time, however the remaining parts / materials cost would be no more than another $1000, so the total cost of the project was approx $4160.

As mentioned earlier, while the conversion was primarily designed for use with hydrogen fuel, it is equally suited to operation on C.N.G, a fuel which is plentiful in Australia.  Unfortunately, it seems Australia is a country of governments whom are reluctant to embrace change, presenting a big challenge to any new or developing technology.  While other countries encourage the use of C.N.G in cars, it is an unknown fuel in this country, and while there are hydrogen refueling stations in the U.S to encourage research and improvement of these types of cars, the Australian government has just decided to offer a $2000 rebate to anyone converting their car to liquid propane gas just because petrol prices have gone up!… An abhorrent waste of money, which could be spent with a view beyond the next election.  For these reasons, some specialized parts (i.e. the injectors) were impossible to obtain locally, as there is no automotive hydrogen or C.N.G industry here.

However, when we do finally move away from petroleum fuels and hydrogen does become readily available, this type of conversion will mean motorists will be able to continue driving their internal combustion vehicles, and all of the energy and materials put into their manufacture will not be wasted.





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