Better MPG Hydrogen Systems

Fuel Economy Modification Forums
HHO Dry Cell Retailer

Blog Post New Entry

HHO Tuning and Installation 101, a summary

Posted by Mike on July 5, 2011 at 12:05 AM

 (note:This article is a sample excerpt from our E-book "Better MPG Fuel Economy Modification and Tuning Guide", available in our store for $25.00 The book is much more detailed at 110 pages)

Purchase the full book by clicking HERE


There are many people that are installing Hydrogen On Demand systems in their vehicles all over the world, but not many people that are doing it correctly. If you have experienced mileage gains with HOD only to lose them over and over no matter what you try this article will help. I have spent the last 5 years experimenting with my own car and some others, and I have finally achieved the goal of consistent performance and results using HOD along with the proper engine and ECU tuning techniques. I want to help others avoid the frustration of not installing correctly the FIRST time. Most experimenters make the mistake of taking shortcuts. They install a MAP/MAF enhancer, but not an EFIE. They don't optimize ignition timing with the IAT sensor. The never use a scan tool to verify their mods are working. This guide will give you an overview of the professional way to install and tune an HOD system in a gasoline powered vehicle.

For some, the steps outlined in this guide will be too much, and for those people I recommend a " ECU flash module " such as the Volo FS2. The Volo will not compete with the results you will get with manual old fashioned tuning, but it will be simple and require less manual intervention. 

For those that want to try their hand at tuning our MAXIM series EFIEs and Controllers will give you everything you need to perform the mods outlined in this article. BetterMPG also supplies over the phone and e-mail tech support to help you tune. You can also build your own enhancers and tune them as described in our articles. 


BASELINE-This is THE most important step. Establish what your current highway MPG baseline is by doing a point to point 100 mile or greater highway mileage loop test. Purchase and learn how to use a scan tool. At 55-65 MPH cruise, log your Short-term and Long term fuel trim averages, MAP/MAF number, TPS number, ignition timing, and typical IAT and CTS temps. Repeat the test and the logging at least twice. If you don't know what your baseline is, you won't know if you've accomplished your goals.



This is the core of your HOD system. Just like a radio is of little use without a good antenna, an HOD system is of little use with a poor electrolyzer. Try as you might to increase engine efficiency, an inefficient electrolyzer will soak up most of any gains you might achieve by putting out too little LPM of hydroxyfor too much current from your battery/alternator.


With most vehicles it's important to stay under 30 amps of current draw to avoid electrical strain on the alternator/battery. At 30 amps you should be seeing atleast 3 LPM from your electrolyzer with minimal heat. (under boiling temperature) In most cases you shouldn't even need to exceed 15 amps of total draw for the supplemental effect of hydroxy to work.


Contrary to popular belief, it's not always best to run the maximum hydroxy you can produce. For 4 cylinder cars usually 1-1.5 LPM is plenty to get the job done. 6 or 8 cylinders get a little better kick from 2-4 LPM. The people out there onYouTube that are trying to build these "mega-cells" for HOD purposes are totally missing the point. Are you trying to run the car on water or simply enhance combustion? Pick one. Too much HHO and you'll actually force the engine to work harder, fighting the upward motion of the piston, screwing up engine timing, and more. A little water gas goes a long way, but at least .5LPM isessential to begin to do anything.


Do lots (and I mean lots) of research on electrolyzers. Dry Cells are the best LPM for the current draw, with the lowest heat. Although many people lie about their specs or use misleading statements like "best HHO kit in the world" or "most efficient design ever made" so use caution. Sensationalism should be easy to spot. Don't fall for it. 

Look for lasting build quality and know what's inside anything you purchase. Do not accept anything less than 316L grade stainless steel for electrodes. Even 304 WILL break down over time, so make sure it's 316L or better. Try to find positive postings or results with a specific electrolyzer before you purchase it, or just purchase from a reputable dealer that offers a satisfaction guarantee such as BetterMPG. Most do not. Many dealers will even lie about the grade of SS in their units but the dead giveaway is after running the unit for a day or two. If the water immediately changes to a dark brown color it's not 316L. Send it back and demand a refund! A little discoloration is normal, but dark brown water means you've been duped.

Mount your electrolyzer in a suitable place away from moving parts and away from the engine heat as much as possible. Wire the positive lead through a solenoid(relay) and an ammeter. Negative goes straight to a good vehicle ground. Use a ignition active source to fire the solenoid and a toggle switch to kill that circuit in the event you dont want to use the hydroxy. Use our wiring diagrams for more detail.


THE BUBBLER- A simple container of water with an inlet port draws the HHO through a tube and to the bottom of the water. From there it bubbles up through and is released through the outlet port, to your engine. This simple device serves as your guardian and protector for two reasons: 1. In the event of a flashback (usually triggered by a back fire) the water in the bubbler serves as an isolator to prevent the hydroxy gas from exploding all the way back to the electrolyzer and possibly destroying it. 2. It serves as a "scrubber"to effectively remove traces of your electrolyte from the hydroxy before itgets sucked into the engine. Sodium Hydroxide, Potassium Hydroxide, and baking soda all can cause damage to your engine if they make it directly into your intake manifold. It is extremely important to take precautions to prevent any electrolyte from making it to the engine. Our patent-pending tank designs at BetterMPG already do this for you. Use our install guide in the documents section for more info.

 Hook a hose from your electrolyzer output to the bubbler inlet, making sure it's theside with the tube under water. Hook a hose from outlet of the bubbler to a hydroxy injection port on your AIR INTAKE. Do NOT use the vacuum manifold for HOD systems under any circumstances. The vacuum manifold supplies max suction when we least need it and increases your chances of getting electrolyte into crucial engine parts.


THE FUEL LINE HEAT EXCHANGER- This device, when used by itself will not produce fabulous increases in fuel economy, but when included with HOD it makes a very notable improvement, which is why I include it here. It's just a simple assembly of metal pipe fittings with in/out ports. We sell a pre-made fuel heat exchanger with magnets inside that works great with HHO systems. (I have also used the water4gas design and it works well) You seat the device to your radiator hose for heat exchange and re-route your fuel to it before the injection manifold. The fuel is then pre-heated for better vaporization when it gets to the injectors. The device is wrapped in aluminum foil and header wrap to act as a thermal blanket and heat the unit/fuel throughly. To install just follow your gas line from the rear of the vehicle to your injection manifold. If you have a fuel pressure release valve on your injector rail use it first to release the gasoline pressure, then cut into the line and re-route using high pressure fuel line hose and brasshose barbs to your heater, then back to the injection manifold. Lastly, wrap the heater in foil and wrap and use ties to lock into place. Use crimp type hose clamps for the connections and be sure to check regularly for leaks toprevent any danger of fire. (see installation photos in our gallery)


THE EFIE DEVICE (for narrowband O2 sensors)- If you were to install the above but do nothing else, chances are for most cars your MPG would either stay the same or get worse. Why? because the hydroxy is creating a different combustion environment inside your engine. It's an environment your car's ECU and sensors are no longer addressing properly, because you have deviated from factory specs. You are now burning your fuel better and reducing hydrocarbon deposits in the exhaust. Your o2 sensors are not seeing anywhere near the normal amount of hydrocarbons (pollution) in the exhaust and in fact see more clean oxygen. Why is this a problem? Because factory programming tells the ECU that a lean burn condition is taking place when in fact it is not. The ECU can't allow leaner mixtures than the factory set AFR, so it will add more fuel to see the level of hydrocarbons and less oxygen it's used to seeing. Any gains created by your HOD system are then swept away by the ECU increasing the fuel consumption.


Add the digital EFIE. The EFIE (Electronic Fuel Injection Enhancer) effectively tells the ECU through the O2 sensors that the oxygen content of the exhaust is normal, thus restoring the balance and allowing the HOD system to work in a positive direction with fuel economy gains. The EFIE "tells" the ECU everything is ok in the exhaust by adding a slight increase in the O2 sensors'voltage to offset the amount of voltage signal loss your HOD system is subtracting.


The EFIE can also be used to lean the fuel mixture very slightly by telling the ECU the exhaust is slightly rich in hydrocarbons, but this cannot be done easily without tuning other sensors on the car to coincide. Attempts to do so without tweaking other sensors usually results in a check engine light or trouble code.See the various sensor mods below for more on this.


 For cars post 1996 both the "upstream" and the "downstream" sensors will need to be addressed.


All EFIEs are NOT created equal. Most EFIEs are the old fashioned design that just adds avoltage to the O2 sensor signal. This works to a point, but on newer cars you can only add very little voltage before you're caught and the ECU triggers a check engine light. DO NOT USE OLDER STYLE EFIES OF THIS DESIGN ON UPSTREAM O2 SENSORS. They will work, then trip codes, work, then trip codes. Why? Because the O2 sensor signal is like a sine wave, or even a binary signal. It must havea low point (0,lean), and a high point (1,rich). When you start adding voltage offset all the time you're making the high point higher and the low point higher as well. Soon the low point is no longer low, (1111111) and therefore not acceptable to the ECU. You can use old fashioned EFIEs to address the less critical downstream sensors if needed, by using them to add a small 150-300 mv offset to the downstream signal at all times.


You need an EFIE that sets a higher high point but allows the low points to pass through to the ECU, satisfying it's need to see the full wave, and the full picture of what's happening with the AFR. A good EFIE simply tells the ECU the AFR is rich more often, but not ALL the time like an older EFIE. These good EFIES aresometimes called " true digital" EFIEs because they generate both the"1" and the "0"s the ECU must see to believe it's just the o2 sensor doing it's job. This is all we sell here. What you are changing with this EFIE is referred to as the oxygen sensor switch point, that is, the point at which an o2 sensor signal is translated to the ECU as a "rich" signal, or a digital 1.This switch point is adjustable, from 500mv all the way down to .050mv. In other words, the lower you set the switch point, the more often you're telling the ECU you're running rich, which will lean things out. Typical switch points for HHO tuning fall between 350-100mv on most cars with most o2 sensors.


Do not go down a whole lot in switchpoint until you address the other sensors on the vehicle, or you will run into check engine lights, rough engine, bucking,stalling, sputtering, pinging etc.


FOR AFR /WIDEBAND O2 SENSORS -For vehicles that dont have narrowband O2 sensors but instead have wideband or AFR style sensors, you'll need to purchase a Wideband or AFR EFIE. AFR sensors are current based devices instead of voltage based. Methods for attacking AFR sensors use a method to control current flow on the blue signal wire.

FOR DOWNSTREAM NB O2 SENSORS- If you watch the downstream O2 readings on your scantool you'll notice a different behaviour from them VS the upstream sensors.Typically a downstream sensor reacts in a more sluggish manner, with very few peaks in comparision to the upstream. An old fashioned analog EFIE that just adds a fixed voltage offset all the time should work fine to address your downstream sensors. Typically settings are about 150-300mv added. For downstreams that appear to hover around 700 to 800mv for long periods of time your car is probably using them for catalytic convertor temp readings, with a goal of keeping the cat hot to do it's job. This is bad for you because the car can dump up to 40% more fuel to keep the cat hot. If your scan tool gives a cat temp reading stream this is a dead giveaway that your car is using the downstreams for temp sensors. Contact Better MPG for a fix.


IAT(Intake Air Temperature) SENSOR MOD- We need to fool the ECU into thinking it's sensors are in agreement about the current conditions. You must unlock more lean fuel tables in the ECU by doing this mod. Sometimes the IAT sensor is incorporated into the MAF sensor as one unit. You'll need to track down thepair of wires that goes to the termistor to modify the stream. This mod also changes the ignition timing curve. THIS IS A MUST TO GET THE BEST MILEAGE YOU CAN FROM USING HHO. Do not skip this step!


The IAT has a big effect on engine ignition timing. When it comes to improving combustion efficiency ignition timing is everything. Raising the temp retards the timing and lowering it advances it. With a hydroxy system we are actually looking to retard the timing most of the time because of the flame propagation speed increase within the combustion chamber using the system. It's important to add that the next modification of the MAP or MAF sensor will advance the timing, so you're looking to adjust the IAT temp a little over the mark for timing so that ourfinal MAP/MAF adjustment brings the timing in perfectly. 40-85 degrees above ambient outside temp sounds dramatic, but is typically a good starting point. You will need to experiment with resistor values to find the right one for your vehicle. I used a 20k pot with a 500 ohm resistor in series to keep it from shorting out the sensor. This mod is also switched with a toggle after the engine warms up.This mod is sweet in that it allows me to "dial" in the correct valuefor the IAT, and find the optimal setting for economy. I adjust IAT for maxpower.

NOTE: A scan tool is a MUST for this mod. You need to know the IAT that the ECU sees to make the mod.


RE-ADJUST THE EFIE- Ok, the IAT sensor is tweaked for a slightly leaner mixture and retarded timing, so time to adjust the O2 sensors as well with the EFIE. Now that you have effectively "lowered your lean limits" to the ECU, we can drop more switchpoint on the EFIE and get away with it. No check engine light or trouble codes toworry about, just don't get carried away. Go a little bit lower, maybe 50-150mv more then you have previously set.


MAP/MAFSENSOR MOD- The last mod, (probably the most important) is your load sensor mod, aka the MAP or MAF mod. These sensors give the engine an indication of load by measuring the volume of air coming into the intake. Higher pressures mean more gas is needed, lower pressures mean less gas is needed. Simply put these sensors translate the need for x amount of fuel into voltages which are sent to the ECU.


With hydroxy we don't need as much fuel as we did for everything before the system,even under load, so we can safely reduce some of this fuel. Even better, withthe IAT and O2 sensors now in agreement for a leaner mixture, tweaking theMAP/MAF should be a piece of cake. You can either build the LM317T voltageregulated MAP adjuster all over the net or purchase one from us for $23.95 and install it on theVREF line (NOT the signal wire) of a MAP. (usually 5v)I adjusted my VREF downto about 4.85v. Make it switchable as well so you can toggle between your adjusted MAP voltage and the stock 5v factory VREF.

For some MAFs it's alot more complicated. If the MAF has a VREF you can attack that, ifnot you can go for the fluctuating signal voltage and attenuate that with a POT, OR you can put a low resistance resistor (say 1-4 ohms)on the ground wire to generally knock the air values down. Generally speaking, you must find a way to reduce the air volume the ECU sees through either the MAP or the MAF sensor.You can do this electronically or mechanically.


One of the biggest mistakes people make is they use their MAP or MAF enhancer as afuel leaning device, and believe that no EFIE is needed if they use a MAP/MAF enhancer. This is completely wrong! Yes, it is true that lowering the MAP/MAFreadings will reduce the amount of fuel the injectors are sending. However, thefuel you are taking away with the enhancer can easily be detected with the O2 sensors. The O2 sensor readings go lean because there's less hydrocarbons coming out after you take away fuel with the MAP/MAF enhancer. The result is your long and short term fuel trims will actually go positive and ADD more fuel to compensate! This is why many experimenters report losing mileage or going full circle with gains and then losses using only a MAP/MAF enhancer. You MUST address both the load sensors and the oxygen sensors. If both are in agreement about less fuel being needed, you will then see a fuel economy increase. BetterMPG can teach you more about how to read what the ECU is"thinking" with your scan tool and adjust your mods and enhancers perfectly. By purchasing a MAXIM tuning unit you can address all your sensors and tune the system in accordance with this guide. We provide help every step of the way.

 If you've made it this far and have the above items installed and functional,CONGRATULATIONS! You've made it much further than most experimenters.BetterMPG will help you get the most out of the system with proper tuning on the fly, as well as some special tricks I have learned to further increase your chances of success. A BetterMPG tuning guide is on the way soon and will be offered here.

(note:This article is a sample excerpt from our E-book "Better MPG Fuel Economy Modification and Tuning Manual", available in our store for $25.00 The book is much more detailed at 110 pages)

Purchase the book by clicking HERE

Wishing you good mileage with your project!






Categories: None

Post a Comment


Oops, you forgot something.


The words you entered did not match the given text. Please try again.

Already a member? Sign In


Reply Bob Saga
11:46 AM on August 20, 2011 
This tuning guide has inspired me. It has given me enough information to make the jump and buy a system. I'm an old gear head, time to go electric. Thanks Mike
Reply DavidIIM
6:42 AM on April 2, 2012 
This is incredibly helpful information! I am looking forward to making these modifications and tuning for my HHO system. Can you give us some general mpg gains that you have experienced with this tuning process?

Looking forward to that tuning guide too!
Reply Djunkie
4:39 AM on April 30, 2012 
The ideas here will help me to continue my HHO dream project on a F-Exped 4.6L. I want to prove that it can go more than 100% also! more power Mike!
Reply takburon
1:35 AM on July 16, 2012 
Hello, i think that i saw you visited my site thus i came to ?return the favor?.I am attempting to find things to enhance my web site!I suppose its ok to use a few of your ideas!!

Become a BMPG member today! Join our live chat. Learn about fuel economy mods and post in forums, blogs, pics, get assistance with your project, and find out the latest offered from BMPG. All for free of course with NO SPAM!

Better MPG Skype Status: (click to contact on Skype)

My status

Don't pay so much

Better MPG, World-Wide Leader In HHO, Fuel Economy, and Emissions Reduction Technologies


Share on Facebook

Share on Facebook

Google +1 Button

Twitter Follow Button

Facebook Like Button

Google Translator

Did the information or services we provided help you accomplish something great? Please donate to keep us up and running so that we may provide you more information in the future. Thanks to everyone for your support!