All the information on this website is based on my personal experience. I am not a licensed car mechanic, nor am I a physician or chemist. I do not take any responsibility and/or liability for whatever outcome a person or company might experience based on information found on this website. Read and use this information completely at your own risk


A HHO Booster is a kit that can be installed in your car’s engine compartment and can give several benefits. The most import ones are:
– increases fuel efficiency with 10-60%
– increases engine power
– reduces harmful emission
– cleans out built-up carbon deposits in engine
These kits are sold under names like H2O car kit, H2O booster kit, HHO car kit etc. and are priced between 300 and 1100USD. When I found one of these kits for around 400USD I decided to buy one and put it to the test.

Flow diagram-s

How does it work?

Basically power is drawn from the car’s battery to split demineralised water into hydrogen (H2) and oxygen (O2), via electrolysis. This H2/O2 mixture is then led into into the air intake of the throttle body, into the engine’s fuel mixture. Click and see the schematic diagrams on the right to get an idea of how this works in practice. For more detailed information and theoretical background, see any of these links:

Wiring Diagram-s

Increased O2 value

With a HHO kit, H2 + O2 will be fed into the air intake of the car and hence the O2 value in the exhaust gas will increase as well. Most cars with fuel injection will have an O2 sensor/lambda sensor to measure the amount of O2 in the exhaust gas. If the measured O2 value is higher than the factory set value, the ECU/PCM thinks the fuel+air mixture is too lean and will increase the amount of injected fuel. So without some sort of remedy for this, when using a HHO kit, the mileage of the car will decrease for most fuel injected engines. This issue is normally not applicable for carbureted engines.

Remedy 1: Install EFIE chip to adjust the ECU/PCM signals to the injectors
These chips are standard supplied with some HHO kit suppliers. If you want want to buy the chip loose you can get these at Volo Performance Inc.
These chips are not compatible with all cars. The Volo chips for example only work with OBD2 compatible cars. To learn more about OBD2 click HERE.

Remedy 2: Reset factory default O2 value in ECU/PCM
By disconnecting the car’s battery and draining the capacitors, a vehicle can reset the stored O2 reference value. After reconnecting the battery, the ECU/PCM will build up a new O2 reference value. This remedy is not a 100% sure to work either, since this reset procedure does not work on all cars.

The opinions regarding whether you need a chip or not depends strongly on which supplier you ask:

Global Energy Devices -> No you do not! E.F.I.E’s are a mess to work with….
source: www.globalenergydevices.com/faq

Green Fuel H2O -> Absolutely YES you do !…
source: www.greenfuelh2o.com/FAQ_s/25.htm

TIP: Do your research before deciding to by a kit, ask the supplier first if your car is compatible. If you have a car that is OBD2 compatible, you’re pretty safe I think since you can try to either reset the default O2 value or a chip.

Break even point

See chart on the right (example: with a 10% fuel efficiency increase, you need approx. 60 full fuel tanks in the USA to save the equal amount of money on fuel that the kit purchase would would cost. After that you’re saving money compared to having no kit. For Western Europe this is approx. 30 full fuel tanks).
Not included in these costs since they have very little impact are:
– costs of demineralised water: approx 2.5 USD/Gallon
(I use approx. 200ml on 600km)
– costs of electrolyte: approx. 25USD/kg
(I don’t think I will use the full 1 kg in the next 2 years)
Kit comes supplied with a small bottle of electrolyte (KOH).

Break Even-s

The Scirocco Conversion

Having had this kit installed previously in my Mercury Capri without experiencing any improvements, I still decided to give the kit another shot and built it into my Volkswagen Scirocco GTX from 1988. I had high hopes for this car, since it is so old the mileage is not so good to start with, so I expected a decent improvement here. Further more it is a carbureted engine; no ECU/PCM interference due to increased O2 value in the exhaust gasses (see “Increased O2 value”).

The HHO Kit

– Supplier: Global Energy Devices
– Kit Type: Solo/single kit for engine size up to 5.5L
(not for sale anymore, comparable with current 250 S model)
– Price: 350-450 USD
– Increased O2 in exhaust remedy: Default O2 value reset
– Ampere/current meter: optional
– Current control for HHO cell: Current can only be adjusted indirectly
by diluting or adding electrolyte.

The Car

– Make/Brand: Volkwagen Scirocco GTX
– Year: 1988
– Mileage at time of kit install: +/- 200.000km
– Engine: 1.8L gasoline (benzine), 4 cylinder, 8 valves, singe carburetor
– Other info: Car has no O2/Lambda sensor


The results from my initial mileage measurements with the kit installed, compared to my reference point (mileage before kit installation), didn’t yield the overwhelming improvement results I was hoping for. In fact the results were so inconclusive, that I decided to make a new set of measurements including a new reference point: it seemed that driving style (city/highway/average speed) had more influence than the kit itself. Unfortunately the second set of measurements, keeping the driving style as much the same as possible, didn’t show any clear mileage increase either: an average of 0.7% improvement. Click Scirocco mileage measurements for the full sheet of latest measurements.


Increased Mileage
Click Scirocco mileage measurements to see the full measurement chart with detailed results, where the comments below refer to.

1. Measurements before HHO kit installed
With these measurements I created my reference point; the mileage of the car before kit installation.
Mileage: 13.01 km/L (average of 3 fuel tanks)

2. Measurements with HHO kit installed, kit switched ON
Mileage: 13.86 km/L (average of 17 fuel tanks)
Improvement compared to 1. : 6.5%

3. Measurements with HHO kit installed, kit switched OFF
The individual 17 measurements of 2. still fluctuated so much, that I wanted to exclude the mileage increase/decrease due to driving style (city/highway/average speed). With this set of measurements 3., I created a new reference point and this time kept my driving style as constant as possible: Highway driving between 100-120km/h. The results from this set of measurements 3., showed an even higher mileage increase than the results from 2.. For me this confirmed my suspicion: Measurements 1. and 2. where inaccurate, since the driving style had too much influence. Thus the 6.5% improvement of 2. compared to my initial measurements / reference point 1., could not be allocated to the kit in my opinion.
Mileage: 14.67 km/L (average of 4 fuel tanks)
(Improvement compared to 1. : 12.7%)

4. Measurements with HHO kit installed, kit switched ON
Like with the measurements of 3., during this set of measurements I kept the driving style as constant as possible: Highway driving between 100-120km/h. The improvement that I measured with this set of measurements 4. compared to 3., was so minimal that in my opinion it was out of range of the measuring accuracy: No mileage improvement with the kit switched ON compared to with the kit witched OFF.
Mileage: 14.77 km/L (average of 4 fuel tanks)
Improvement compared to 3. : 0.7%
(Improvement compared to 1. : 13.5%)

Increased engine power
The power of the car doesn’t seem to increase notably with the kit switched ON, compared to the kit switched OFF, or before kit installation.
Two Dyno runs, (one with the kit ON and one with the Kit OFF)  would eliminate any doubt.
An even better comparison would be, to compare a Dyno run before kit installation with a Dyno run with the kit ON, like I planned with the Capri. I didn’t do a Dyno run beforehand this time since I wanted to see an increased mileage first before spending any more money.

Reduced Emissions
I didn’t do any measurements.

Conclusion & Personal Opinion

With mileage increase between 10-60% stated on the supplier’s website, my average of 0.7% improvement is disappointing. Especially after I didn’t get any improvement in the Capri either. It could be that these kits perform better in more modern fuel injected cars after +/- 1996 (see HERE). But if that is the case, this should be stated more clearly on the website of the supplier. Also the power of the car has not improved in a way that I can really feel a difference. has not improved in a way that I can really feel a difference.
For a moment I thought that if the carburetor needed adjustment/tuning, or if the catalytic converter would be clogged, this might contribute to the fact that I don’t see any improvement. However, I just got my car back from its yearly safety inspection and asked my mechanic whether in his opinion the carburetor, or cat. converter are in bad condition. He told me that if that was the case, he would have seen it immediately on the exhaust emission test (which was done with kit switched OFF). He told me that the emission measurement was actually quite good for this old car. To eliminate any doubt whether the kit itself or my car is the cause for not gaining any results, I actually need to test the kit in a car from 1996 or later with OBD2 and a chip (see Increased O2 value further up).
If I buy another kit in the future, I would contact the supplier first to:
-let him comment on my current measurements
-discuss if in his opinion my car is compatible
-see if there is a “money back guarantee” in case it doesn’t yield any increased mileage



Install Picture 5-s




Contact with Global Energy Devices (GED) regarding the Scirocco

Especially during the initial installation of the kit in the Capri I’ve had a lot of contact with GED. With their kit in this second car (Scirocco), I’ve sent them my results now and then to discuss.I asked them to comment on my latest set of measurements. Here’s their reply from 2015 April 29th:

Good Morning Rodolphe,
As expected you were very scientific and complete in your information and data. We can appreciate this as you know thing will vary from application to application. We would ask that you only share your honest opinion, and experiences with the systems, but also hope that you may be able to work with the system in an application where you see the larger % gains as expected. We are steadily growing still as a company and getting more feedback from customs daily. There are always variables involved, and gains will vary from one vehicle to the next. I personally was talking with a customer with an Off-the-Road truck yesterday who was getting 10.8 MPG unloaded, far above anything he had ever seen on the vehicle to date. I wish that your experience would have gone more as expected, looking forward to future applications and feedback from you as well. Thank you.”

Tips & Notes

Below are some of my personal notes based on my own experience:

For an extensive list of frequently asked questions with answers, see any of these links:

Amperage Meter
Initially I bought this kit without an amperage meter to save money, but I bought one separately after reading the manual: you cannot see what you’re doing without one. I highly recommend to buy a kit which has an amperage meter included, unless you have one yourself already.

Amperage reading, quantity of electrolyte
Note that when you read the amperage that the kit draws when you add the electrolyte, to determine the right quantity, the (current) value is very dependent on how long the kit has been ON:
When you’ve been driving for an hour, the amperage (current) value can be 2x higher than when you just start your engine.

Can I install the kit myself?
The kit is supplied with a clear manual. Anybody who is a little bit handy and knows about basic car mechanics can install the kit. If you have it installed by a professional car mechanic, I guess it would take them less than 4 hours to install.

Is this kit for everybody?
In my opinion NO. If you’re the person who never checks the fluid levels of you car, then my advice is not to buy this kit. But if you’re a little bit handy and interested in this technology, go for it.

Hose Clamps
The hoses connecting the reservoir and the HHO cell kept leaking over and over again with the original hose clamps supplied with the kit: I replaced them at least 3 times. This can create a mess, since the KOH solution is corrosive. I advise to use fully round hose clamps. After my last replacement with these fully round ones, they haven’t leaked (so far). I suggested this to the supplier of my kit as well. They said to take this into consideration.

If you have any more specific questions regarding the kit for which the answers cannot be found on the website of the supplier, you can always send me an e-mail. If I can answer it, I will post the answer on this page or reply via e-mail.


Hose Clamps-s