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Ver 1.2 2nd June 2006
HHO Dry Cell
The electrolyzer shown in Figure 1 is based on the common-duct
series-cell electrolyzer concept originally developed and patented by
William Rhodes, Ernest Spirig, Yull Brown and later refined by Bob
Boyce, George Wiseman, etc… It uses an alkaline (NaOH, KOH) electrolyte
to split distilled water into hydrogen and oxygen components very
The produced hydrogen and oxygen gasses are not separated to separate
containers, but kept mixed. The produced oxyhydrogen gas is a
stoichiometric mixture of hydrogen (2 parts vol.) and oxygen (1 part
vol.) and can be combusted in vacuum.
The combination of series-cell topology is very efficient, because it
allows the cells to operate as close to their optimal cell voltage
(1.47V) as possible. The electrolyzer runs fairly cool, at about 30-50 C
depending on the current and electrolyte.
The electrolyzer shown in this report has about 80-90% total efficiency
when all things are considered (ambient temperature, ambient pressure,
accurate measurement of gas volume and current) when powered by straight
DC. Pulsing (PWM) or modulation of the input voltage waveform could
increase the performance further, as it is known that in the beginning
of each pulse larger current flows than in the steady state condition,
thus lowering the cell voltage needed to push thru a certain amount of
current and increasing the efficiency slightly. There are also claims of
various resonance phenomena (Boyce, Meyer, etc.) that supposedly
dramatically increase the gas production rate vs. input current when the
electrolyzer is driven with a certain type of PWM rich in harmonics.
However, this author has not been able to replicate any resonance modes
in any sort of electrolyzer.
The electrolyzer has 7 cells with a target input voltage of about
12.9-14.1Vdc depending on temperature. This makes the cell voltage about
Gas vent hole in each plateElectrolyte level ~20mm below gas vent
holeElectrolyte in each compartment is practicallyisolated from other
compartments, but thereare 3mm diameter electrolyte level equalization
holes drilled in the bottom corner of each plate (staggered)Gas output,
water input valvePlate spacing 3mm, active plate area ~170cm^2 per
sidePVC end plateStainless steel electrodesSoft transparent PVC spacers
Figure 1. Series cell electrolyzer cross-section
The eight electrolyzer plates (Figure 2) are about 0.8mm thick 160mm x
200 mm stainless steel (304 grade). A 10mm gas vent hole is drilled in
each plate. The electrolyte level is always about 25mm below the gas
vent hole. There are 3mm diameter liquid level equalization holes
drilled in the bottom corner of each plate (not shown) in such a way
that adjacent plates have holes in opposite corners. Staggering and
using small holes minimizes any efficiency loss due to current leakage
between cells, but makes electrolyte refilling and level equalization
significantly easier. The two end plates have a small SS piece welded
for electrical contact. After taking the picture the plates were sanded
with an orbital sander to expose clear metal and then cross-hatch
pattern was "engraved" on the plates with a rough file attached to a
wooden block. This is to increase the active surface area of the plates
and seems necessary for ultra high efficiency. Other methods to increase
plate area exist as well.
Figure 2. Stainless steel
hho plates (8 total)
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Nine spacers (Figure 3) were cut out of 3mm thick soft and transparent
PVC sheet with a knife. The wall thickness is 12mm. The PVC sheet is
originally designed for door material for large room-size refrigerators.
The small square PVC blocks were meant to keep proper distance between
SS plate centers, but they turned out to be unnecessary and were not
Figure 3. Soft PVC spacers rings
The end plates (Figure 4) were cut out of 12mm thick PVC plate. The size
of the plates was 200mm x 240mm. Eight 8mm holes were drilled for M8
size stainless steel through-bolts. A ¼" pipe thread was tapped in a
11.8mm gas vent hole. A valve and gas hose connector was epoxy glued to
the ¼" tapped hole in both plates. Other thread sealants may not be
compatible with the electrolyte so it’s best to use epoxy or teflon
tape. The valve was lined up with gas vent hole in SS plates. NOTE: When
the electrolyzer stack is tightened up the PVC end plates tend to bend
and bulge. Some form of metallic bracing should be used to prevent
bending or the end plates made out of thick stainless steel plate.
Figure 4. PVC end plates with gas valves attached
The first stainless steel plate and one PVC spacer ring are shown in
Figure 5. There is a PVC spacer ring also between the PVC end plate and
first SS plate. A 35mm piece of 8mm ID 12mm OD rubber hose is slid over
the bolts to isolate the bolts from the plates and hold the plates in
place. Note that it would have made more sense to drill the gas vent
hole to the upper left corner of the plates, so that draining the all of
the electrolyte out of the electrolyzer would have been easier.
Figure 5. First SS plate in place with the PVC spacer shown
A side view of the cell stack with several SS plates and PVC spacer
rings in place is shown in Figure 6. Note the soft PVC sheet material in
the background with the cut outline drawn with a permanent overhead
transparent marker pen.
Figure 6. Partly assembled cell stack
The finished electrolyzer is shown in Figure 7. The two PVC end plates
are clamped together with 70mm long M8 stainless steel bolts with Nyloc
nuts. After initial tightening the electrolyzer was submerged in hot tap
water (about 60 C) with the gas vent valves closed. This softened the
PVC gaskets and allowed the stack to be tightened up even further to
provide an excellent seal. Note that the 12mm PVC plates are quite soft
and some bulging is visible. Two additional bolts would have been useful
to equalize the bolt forces more evenly around the plates.
Figure 7. Assembled stack
The finished electrolyzer equipped with a bubbler is shown in Figure 8.
The bubbler is absolutely essential to prevent backfires from blowing up
the electrolyzer. The electrolyzer may be filled with slightly acidic
water (use vinegar) to neutralize any residual NaOH vapors in the output
gas. It would be wise to use a non-return valve between the electrolyzer
and bubbler to prevent bubbler water being pushed back into the
electrolyzer in case of backfire.
Figure 8. Finished electrolyzer with bubbler
Figure 9 shows the electrode plates after the electrolyzer had been used
for some time. The chemical reactions occurring in the electrolyzer have
slightly darkened the electrolyte. The use of 316 SS electrodes would
probably have prevented this. Note how the other side of the plate is
relatively clean, while the other side has a darker deposit. Note also
the sanded and crosshatched electrode surface.
Figure 9. Electrode discoloration due to chemical reactions (NaOH & 304
1) Gas production is directly proportional to the current draw only. At
STP conditions (0 deg C, 1 atm) you need approximately 1.594 Amps for
each LPH per one cell, while you need less if you measure the gas volume
at room temperature.
2) The ideal cell voltage would be about 1.48V, and anything above it is
wasted efficiency. The lowest practical cell voltage seems to be around
1.8V-2.0V. The voltage is only needed to push the current thru the cell,
it has no relation on the amount of gas produced. The cell overvoltage
(above 1.48V) is determined by electrode materials, current density,
electrode spacing and conductivity of electrolyte.
3) Power or total efficiency is defined as the amount of watts needed to
produce one LPH. Series-cell designs seem to have the best efficiency in
the range of 2.5-3 Watts per LPH. The most efficient electrolyzer would
have a large number (100) of cells in series with narrow cell spacing
(3mm) at a low current (10A).
4) Many people build simple single-cell car hydro-booster type
electrolyzers and control the amperage by using weak electrolyte. The
cell voltage is often around 13V, and they put just enough electrolyte
to pass 5A or so. 5A creates only 3.5 LPH of gas, so the efficiency is
very bad at 18.5 Watts per LPH. Properly designed 7-cell series
electrolyzer would produce 7 times that amount or 24.5 LPH gas at the
same input power.
5) The cell voltage is also dependent on the current density (current /
electrode area). Smaller cell area is less efficient because it requires
higher voltage to pass the same amount of amps. Good practical current
density is around 0.5A/Sq.inch or 0.1A/cm^2. The electrolyzer shown in
this report had an effective plate area of about 170cm^2, with a target
current of about 20A.
6) The higher the current thru the cell (higher current density) the
higher the cell voltage. Power efficiency decreases as the current
increases if the plate area is kept the same. To keep the power
efficiency the same increase the plate area in proportion with the
current (keep current density the same).
7) The smaller the electrode spacing the lower the cell voltage. In
practice 3mm electrode spacing is good up to about 10A. At higher
currents the electrolyte starts foaming and crawling up the plates
(reduces efficiency) and the electrolyzer starts spitting electrolyte
foam out. For 10-40A use 5mm-8mm spacing.
8) Best electrolyte is NaOH (1 part NaOH 4 parts water by weight) or KOH
(28% by wt). These give the lowest practical cell voltage.
9) The best electrode material would be nickel, but nickel plates are
very expensive. Nickel plated steel plates would also work. The most
practical electrode material is stainless steel. The electrode surface
conditioning is very important at minimizing the cell voltage. Best to
sand (crosshatch pattern) the electrode plates to create lots of fine
10) Bubbler is absolutely essential to prevent backfires from blowing up
the electrolyzer. Bubbling the gas thru a water bath is the only safe
way to prevent backfires, provided that the bubbler is strong enough to
contain any backfires and that the water level in the bubbler is high
enough. Alternatively the bubbler can have a pop-off lid or a rupture
11) The electrolyzer as shown will not be able to take any pressure
without leaking. For pressurized operation use a pressure-proof shell
(metallic). If you need to store oxyhydrogen gas for a short period of
time, put a large balloon on the bubbler lid. The balloon will store the
gas at atmospheric pressure and will not be very dangerous if it
explodes due to a backfire. Remember to wear hearing and eye protection.
Faraday’s First Law of Electrolysis:
where V = volume of the gas [L], R = ideal gas constant = 0.0820577 L*atm/(mol*K),
I = current [A], T = temperature [K], t = time [s], F = Faraday’s
constant = 96485.31 As/mol, p = ambient pressure [atm], z = number of
excess electrons (2 for H2, 4 for O2).
Assume that you have STP (Standard Temperature and Pressure) conditions
and the electrolyzer runs at one Amp for one hour:
T = 0 °C = 273.15 K
p = 1 atm
t = 3600 s
I = 1 A
Total oxyhydrogen volume is hydrogen volume + oxygen volume:
This corresponds to about 0.627 LPH/Amp or 1.594A/LPH per cell.
If for example you have 7 cells in series and put 11A through the
electrolyzer, according to Faraday’s Law you would produce 0.627
LPH/A*11A*7 = ~48.3 Liters per hour at STP conditions.
It is impossible for an electrolyzer to be anything else than 100%
Faraday efficient, unless there are significant leakage currents between
cells. Passing one Amp thru a single cell will always produce gas at a
rate of 0.627LPH when reduced to STP conditions, no matter how the one
electrolyzer cell is constructed.
This however applies only at STP (0 deg C and 1 atm ambient pressure).
At room temperature (25 deg C) the same amount of gas has higher
apparent volume. Substituting T=25 deg C gives the efficiency as 0.684
LPH/A. Stated the other way the Faraday efficiency would appear to be
about 109.5% if the gas volume was measured at room temperature, unless
the correct efficiency value for room temperature (0.684LPH/Amp per
cell) was used.
The thermoneutral cell voltage is ~1.48 V, which means the voltage at
which all input energy for the electrolysis process comes from the
electrical input energy. At 1.23 V (reversible cell potential) part of
the energy comes from ambient heat and electrolyzer is about 120%
voltage efficient. Note that 100% efficient hydrogen oxygen fuel cell
would produce 1.23V. The thermoneutral voltage of ~1.48V is considered
to be the 100% voltage and power efficient electrolysis. Combusting the
produced gas will release exactly the same amount of energy that was
used in making the gas.
The 100% power or wattage efficient electrolyzer would consume 1.48 V *
1.594 Ah/l = 2.36 W/LPH when gas volume is measured at STP. At room
temperature the 100% efficiency is 2.16W/LPH.
In the literature the electrolyzer efficiency is usually defined as the
ratio of the thermoneutral voltage (1.48V) to the cell voltage. At 2.0V
cell voltage it would imply a total efficiency of 74%. This also shows
the inefficiency of single-cell hydro-booster type electrolyzers
operating at automotive voltages (~12-14V), leading to a total
efficiency of about 10%.
Series-cell electrolyzer voltage and current measurements
The current thru the series-cell electrolyzer is extremely sensitive to
the voltage across it. This is because the electrolyzer acts as a very
non-linear resistance, with pn-junction like characteristics. It takes a
certain cell voltage until the current starts flowing ("knee voltage")
and increasing the cell voltage above this voltage will increase the
Figure 10 shows measured and modelled
electrolyzer current vs. voltage graph for the 7-cell series
Note how increasing the electrolyzer voltage from 13.2V to
13.9V (5%) will cause a five-fold (500%) increase in current (from 2A to
Electrolyzer current vs voltage7-cell series-cell electrolyzerElectrode
area = ~170 cm^2, gap = ~3mm 024681012141618200246810121416Electrolyzer
voltage [V]Current [A]MeasuredI = 1E-11*exp(1.972*U)
Figure 10. 7-cell series electrolyzer current vs. voltage
Note that even the insertion of a current meter in series with the
electrolyzer may cause high enough voltage drop that significantly
reduces the electrolyzer current. Thus it is absolutely essential that
the current meter is in place when the electrolyzer gas output rate is
This extremely non-linear resistance of the electrolyzer also causes the
current thru the electrolyzer to be modulated very strongly with any
small changes in the electrolyzer voltage. This is especially true if
the electrolyzer is powered by rectified AC, for example from a
transformer based battery charger or power supply.
The oscilloscope pictures of the 7-cell electrolyzer voltage and current
waveforms are shown in Figure 11. The power supply was a mains
transformer followed by a bridge rectifier and a large filtering
capacitor. Note how the electrolyzer voltage (trace 2) has a small
ripple on top of it, which causes the electrolyzer current to be
modulated between zero and peak current (trace 1), with appearance
similar to half-wave rectified AC. The current draw waveform may be
easily measured with oscilloscope by connecting the oscilloscope probe
across the multimeter terminals wired in series with the electrolyzer in
the current measuring mode. Thus the oscilloscope shows the voltage drop
across the multimeter current shunt resistor.
Figure 11. Series-cell electrolyzer voltage and current waveforms
The pulsed current waveform causes significant measurement inaccuracies
if normal digital multimeters or analog current meters are used. Normal
current meters respond to either straight DC or perfectly sinusoidal AC
waveshapes correctly, but show significantly lower current values for
pulsed DC type waveforms. True-RMS multimeter is required to measure
pulsed waveforms correctly (the RMS value represents the equivalent
"heating value" of any current or voltage waveform). Figure 12 shows
comparison between current readings of an analog current meter and a
Fluke True-RMS multimeter, while measuring current draw of the 7-cell
electrolyzer powered by a transformer-based power supply (actual current
waveform as shown in Figure 11). The analog current meter shows
approximately 7A while the correct RMS value is 10A, which would cause
the electrolyzer to appear 143% efficient based on the analog current
meter reading which is not true!
Figure 12. Comparison between current meter readings for pulsed
For the most accurate measurements straight DC should be used,
preferably from a battery which is not connected to a battery charger.
If any other power supply is used, True-RMS measurement equipment is
needed for accurate results.
Series-cell electrolyzer current limiting
As the series-cell electrolyzer has very non-linear voltage vs current
characteristic, it is important that some form of current limiting is
used to prevent current runaway. While the electrolyzer is operating it
will get hot and heat will decrease the required cell voltage to pass a
certain number of Amps, thus increasing the electrolyzer current draw if
the electrolyzer voltage remains the same. This is likely to increase
the current draw very significantly, which may cause electrolyte boiling
and other problems.
PWM current limiting
The best way to limit the current is to use PWM or pulsed DC and to
adjust the duty cycle to maintain the average current. A fairly straight
forward way is to use a Hall effect current transducer (such as LEM
LTS25-NP), which outputs a voltage proportional to the current and use
this as a feedback to a PWM controller chip (TL494) to adjust the PWM
duty cycle. For the switch FET IRFZ44 (N-channel 17.5mΩ49A, placed
between electrolyzer negative and ground, switched on with positive
voltage) or IRF9Z34 (P-channel 140mΩ18A, placed between electrolyzer
positive and battery positive, switched on with negative voltage) may be
For the PWM controller a ready made DC motor speed control unit will do
fine. It usually has a potentiometer to adjust the duty cycle, which can
be replaced by circuitry to automatically adjust the duty cycle based on
measured current draw. If automatic set-and-forget operation is not
required, the PWM controller may be used to control the electrolyzer
current draw manually.
For most accurate current limiting the RMS current value may be
calculated with for example MX536A or AD536A True RMS-to-DC converter
For minimum parts count a microcontroller (e.g. Atmel AVR series) may be
used with the Hall effect transducer output routed to the AD converter
input and the duty cycle adjustment and RMS current calculation
performed in software. The switch FET may be directly driven with the
Capacitive current limiting
Capacitive current limiting (Figure 13) may be used for electrolyzers
powered by rectified AC. It is based on putting a capacitor in series
between the AC source and the bridge rectifier. The reactance of the
capacitor will limit the current to a certain value, but will not
dissipate any power like a current limiting resistor.
The capacitor must be suitable for AC use (not an electrolytic
capacitor). For mains-powered operation power-factor correction
capacitors are the best. This is best suited for welders operating on
mains power (no heavy transformer needed) or hydroboosters running on
modified alternators (diodes removed). You can use any number of cells
(even one), but you need to figure about 2.0V per cell minimum. For
230VAC 50Hz you need about 14uF for each Amp.
Figure 13. Capacitive current limiting
Run #7: (3rd Aug 2005)
Electrolyte drain-cleaner grade 93% pure Potassium Hydroxide or KOH
pellets in medical grade purified water. Concentration 28% KOH and 72%
water by weight. 500 grams of electrolyte (about 450ml volume) was mixed
and poured into the electrolyzer. The electrolyzer was allowed to run
without collecting gasses for a few hours. During this time the
electrolyte temperature stabilized at 45C while the ambient temperature
The gas production rate was measured by collecting the gas in a 0.5L
coke bottle filled with water. The weight of the bottle with water was
measured. The bottle filled with water was turned upside down while
partly submerged in a cold water bath. The gas was allowed to bubble
through the water bath to the bottle and the time was measured. After
removing the gas hose and stopping the timer the cap of the bottle was
screwed on while still under water and the weight of the bottle filled
partly with water and partly with gas was measured. The weight
difference between start and end weights was recorded, as the weight
difference in grams corresponds to the volume of produced gas in
milliliters. The production rate was found to be 475ml in 30 seconds,
which corresponds to 57 LPH (liters per hour).
The cell was powered by a current limited (11A limit) battery charger.
The voltage and current across the electrolyzer were measured to be 12.9
V and 11 A during the gas collection. Thus the input power was 141.9 W.
At room temperature the Faraday efficiency would be 0.684 LPH/A per
cell. This electrolyzer should produce about 0.684LPH/A*11A*7 = 52.6
LPH, but it produces about 57LPH. This difference is most likely
explained by the gas volume or current measurement inaccuracy.
The power efficiency was determined by dividing the total power
consumption by the amount of gas produced. This is 141.9W / 57 LPH =
~2.49 W/LPH. The 100% efficient electrolyzer (gas volume measured at
room temperature) would be about 1.48V/0.684LPH/A = 2.16W/LPH. Thus this
electrolyzer has about 86.7% efficiency.
However, the cell voltage was 12.9V/7 = 1.84V. Thus the actual total
efficiency is 1.48V/1.84V = ~80%.
Running internal combustion engines on oxyhydrogen
The amount of oxyhydrogen needed to run an internal combustion engine is
spectacular. Idling a small engine (e.g. 5hp) would require 500-1000 LPH
(liters per hour), while idling a car engine would probably consume
about 3000LPH of oxyhydrogen. Driving down the highway would probably
consume 20000-30000 LPH of oxyhydrogen. The electrolyzer shown in this
report produced approximately 57LPH at 11A, which is not enough to idle
even the smallest 4-stroke engine (at least 300-400LPH would be required
to idle a small 1hp brush cutter 4-stroke).
One liter of gasoline contains approximately 30MJ of energy, while
oxyhydrogen gas would contain approximately 7-8kJ per liter. This means
that you would need approximately 4000 liters oxyhydrogen for each liter
of gasoline your engine currently uses, assuming the engine efficiencies
are approximately the same on oxyhydrogen than on gasoline.
Thus if your car uses 6 liters of gasoline per hour while driving down
the highway, prepare for 24000 LPH oxyhydrogen consumption. Assuming a
super-efficient series cell electrolyzer (2.5 W per LPH) you would need
60kW of electrical energy to run the electrolyzer. This corresponds to
about 80hp, which is significantly more than the amount of engine power
used at highway speeds (~20hp). Figuring in the alternator efficiency
(~50%) you would actually need 160hp on the engine shaft to produce
24000LPH of oxyhydrogen gas.
How about a 100cc scooter powered by a 60-cell series electrolyzer
running of an 120V inverter and bridge rectifier powered by the 12V
battery? Estimated gasoline consumption while riding at 70km/h would be
about 1LPH gasoline, which would convert to about 4000LPH of oxyhydrogen
consumption. Idling the same scooter would probably take 500-1000LPH.
The 60-cell electrolyzer would produce about 40 LPH per Amp measured at
room temperature. Thus you would need 100Amps thru the 60-cell to
produce 4000LPH. Because the electrolyzer has 60 cells, you need to
power it with about 120Vdc (assuming 2.0V cell voltage) from the
inverter. Assuming 100% efficient inverter, it would draw 1000 Amps from
the 12V battery to produce 120Vdc 100A. If the scooter had a fully
charged 5Ah battery it would last for 18 seconds at 1000A until it would
run out. The scooters "alternator" would produce probably about 5A
A common misconception is to think that you can dilute oxyhydrogen gas
with air and run the engine with very small amounts of gas. Oxyhydrogen
gas is in itself a perfectly proportioned mixture of hydrogen and oxygen
gasses, which combusts perfectly leaving no hydrogen or oxygen but only
water vapor and heat. Adding any air will make it combust imperfectly
and release less energy for same volume of gas.
An often quoted air:fuel ratio for hydrogen combustion in air is 34:1,
but this is a MASS ratio. This means that you need 34 grams (=27.76
liters) of air for each gram of hydrogen (=11.1 liters). Converted to
VOLUME ratio this is 2.5:1, which makes perfect sense because air
contains approximately 20% of oxygen by volume and you need 0.5 liters
of oxygen for each liter of hydrogen. Thus you need 2.5 liters of air
for each liter of hydrogen for perfect combustion (leaving nitrogen and
other atmospheric trace elements).
Assuming the engine has 100% volumetric efficiency, a 2.0L auto engine
running at 2500RPM would have have a total air intake flow of 150000LPH.
Running this engine fully unthrottled at 2500RPM to produce the maximum
power would take about 43000LPH of hydrogen gas and 107000LPH of air for
stoichiometric operation. The 43000LPH of hydrogen contains about
43m^3/h*2.8kWh/m^3 = ~120kW of power. Assuming 25% engine efficiency you
would get about 30kW or 37hp shaft horsepower.
Figure 14 shows the experimental setup that was used for idling a 6.5hp
200cc 4-stroke Honda copy on oxyhydrogen gas. The electrolyzer did not
produce enough oxyhydrogen to run the engine continuously, but the
oxyhydrogen gas was first collected in a balloon and then used to run
the engine. The 7-cell unit was used, powered by a current limited
welding transformer running at about 40A producing approximately 200 LPH
of gas. The gas was collected for 1-2 minutes which later ran the engine
for some 20 seconds. Approximately 600-800LPH of gas would have been
needed to idle the engine continuously. The engine timing was not
changed in any way. The electrolyzer gas output tube was routed to a
propane adapter bolted at the intake of the carb. The oxyhydrogen was
admitted thru a narrow (1-2mm) orifice to the intake of the carburetor.
The engine ran fully choked, with no outside air used at all. The engine
would not run without the narrow orifice or without being fully choked.
Figure 14. 6.5hp 200cc 4-stroke running on electrolytic gas
There is a common misconception that when the engine runs on oxyhydrogen
it operates by imploding the oxyhydrogen gas in the cylinders supposedly
creating a vacuum that pulls the cylinders up, thus requiring altered
One mole of water (~18ml) turns into 33.6 liters of oxyhydrogen gas.
Thus you get about 1860 liters of oxyhydrogen for each liter of water,
and correspondingly one liter of oxyhydrogen turns into 1/1860 = 0.53
milliliters of water.
But you only get a vacuum if the produced water vapor (steam) can
condense, and you only get condensation if the combustion chamber is
very cold. Steam will not condense on the hot cylinder walls of the
engine and you won’t get a vacuum in the cylinders as a result of
One mole of water (~18ml) will turn into 33.6 liters of oxyhydrogen at 0
deg C, but when the oxyhydrogen is combusted it will turn into 100 deg C
steam. Assuming the steam is at 1 atm pressure, it will occupy a volume
of about 30.6 liters (one mole of 100 deg C steam).
In reality the oxyhydrogen gas combusts in the engine just as any gas
(even though the flame front proceeds quite fast), creating a rapid
pressure/heat increase which then runs the engine