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July 2006

Emissions Analysis With Hydrogen Boost


          I hooked up our 5 gas emissions analyzer and computer to an inverter plugged into the cigarette lighter of my Saturn SL1.  With the Hydrogen Boost system shut off I had my wife drive around town as I recorded the readings on the readout of the analyzer, which was on the computer.  The following is what I found:


At idle for extended periods of time the ECU of the vehicle was quite good at optimizing the fuel ratio to take advantage of the catalytic converter, bringing the emissions down to fairly low levels. 


          CO at times could actually get down close to zero.

          HC at times could get down fairly low.

          NOx took a while but eventually got down below 50.


          During acceleration the emissions would climb considerably and during deceleration they would climb even more.  Then once again if the throttle was set steady the ECU would work out an optimum fuel ratio to minimize the emission once again.  The problem is that any change in throttle setting would send the emissions readings into a gyration.  For a steady cruise on a flat road this would work fairly well in keeping emissions down.  But changing throttle settings are a reality of vehicle operation and most throttles are not steady for more than a few seconds, even while using cruise control.


           With the stock vehicle operating normally I noticed that the emissions readings on the readout were as follows:


          CO at times would climb to 7.82%

          HC at times would climb to 400 PPM

          NOx at times would climb to 800 PPM


          The reason for these bad readings is that whenever the throttle setting is changed there is an immediate change in fuel ratio which does not meet the criteria of the perfect burn that the emissions control system is designed to handle.  Whenever the fuel ratio is too rich the CO and HC are elevated, and when the fuel ratio is too lean the NOx is elevated.  And since the throttle setting is almost always changing, the fuel ratio is always wrong for the design and the emissions are higher than they could be. 


          There are a couple things that can be done to improve this situation.  One is to increase the speed at which the ECU changes the amount of fuel being injected, and the other we will discuss later.  Enhancing the adjustment speed of the ECU will not completely take care of the gyrations because they are caused by fuel already injected and sitting in the intake manifold during deceleration.


          Present day electronic fuel injection systems are a vast improvement over carburetor and early fuel injection systems.  But much could still be done to make the combustion more efficient and reduce the emissions further. 


Let us address the efficiency issue first.  Liquid fuel doesn’t burn until it is first vaporized.  Heating of the fuel can vastly improve the rate at which the fuel will vaporize and thus hasten when it will combust.  This is why the Hydrogen Boost system has a fuel heater.  


Another thing that could be done to improve efficiency is to ignite the air/fuel mix quicker so the advanced timing can be reduced to a minimum so the combustion and compression are not fighting against each other during the initial part of the combustion, which is actually done during the later part of the compression stroke.  This is one purpose of the added hydrogen (Brown’s gas) to the combustion chamber with the Hydrogen Boost system. 


The third thing that can be done is to lean the target air/fuel mixture to the mixture that gives us the greatest power per stroke (greatest torque).  This is the purpose of the Hydrogen Boost system’s electronic control circuit.  At the moment the circuit is relatively crude and in need of more sophistication in optimizing the fuel ratio.  We would certainly like to accomplish that goal in the future.


Of course a couple things could be done to improve the efficiency of the vehicle that have nothing to do with combustion but are indeed incorporated into the Hydrogen Boost system.  One is to make the inside of the engine more slippery so there is less friction and drag.  We have done this with the addition of the XCEL PLUS permanent engine treatment and XCEL PLUS upper cylinder lubrication treatment.  And the last thing we could do is to get the vehicle to roll down the highway with less drag.  We have done this by increasing the tire pressure beyond the vehicle manufacturer’s recommended pressure but within the tire manufacturer’s safety limits.  We have addressed this in our February 2002 newsletter.


How do each of these affect the emissions of the vehicle?  Let me address that question.  First heating the fuel, this could increase evaporative emissions if you had a leaky fuel system, but that would only be for defective vehicles.  Certainly combustion of vaporized fuel can only cause less CO and HC emissions because the fuel can burn more completely while it is still in the combustion chamber.


The addition of hydrogen in the combustion mix also gets more of the fuel to combust while it is still in the combustion chamber so that is also good.


Leaning the fuel ratio slightly will decrease CO and HC emissions because it insures enough oxygen to combust all the fuel to completion but it can increase NOx production because the presence of excess oxygen in the combustion chamber during hot combustion allows the nitrogen in the air to combine with the excess oxygen and form NO2 and NO3.  This is not a good thing but it can be minimized in two ways.  Firstly, most engines have a system to do this called the EGR, or exhaust gas recycling system.  The other way is to decrease the temperature of the combustion so the needed energy to combine the nitrogen and the oxygen is not present.  This may be a task that might actually reduce our engine’s efficiency because we really would like to operate at the highest exhaust gas temperature to get the highest torque.  The methods we could use to reduce the exhaust temperature is to further lean the air/fuel mixture or to trade some of that excess heat for increased pressure by adding some water mist into our air/fuel mix.  This would capture the energy of the excess heat and turn it into torque.  I have not tested this option at this writing because the idea just came to me as I was writing this report.  I have tested the addition of water mist in relation to fuel economy with the Hydrogen Boost system and found no benefit, but I haven’t tested the possible benefits of reduction in NOx emissions by adding water mist because at the time of testing I didn’t own an emissions gas tester.  I have tested further leaning the mixture and am reporting on that here.


When testing the emissions with the Hydrogen Boost system turned on and operating I recorded the following:


CO emissions were always as low as the scale would go, basically zero.

HC emissions were always as low as the scale would go, basically zero.

NOx emissions would depend on power output and our electronic control circuit adjustment setting.


The first two above make perfect sense because with excess oxygen there is plenty of oxygen to combine with the CO and HC to make CO2 and H2O.  NOx emission would be elevated with any air/fuel ratio between stock and 20:1.  At around 20:1 fuel ratio the combustion temperature is low enough to keep the NOx emissions to a minimum but the available torque/power of the engine is less than what I like.  I prefer to run with a fuel ratio between 16:1 and 18:1 but at these settings the NOx emission are not so good.


Following are the readings of NOx I recorded versus air/fuel ratio settings:


A/F 15:1       NOx 200–1800 PPM

A/F 16:1       NOx 200-1800 PPM

A/F 17:1       NOx 200-1300 PPM

A/F 18:1       NOx 150-900 PPM

A/F 19:1       NOx 120-400 PPM

A/F 20:1       NOx 100-250 PPM


Remember we are comparing with stock vehicle NOx emissions of 50-800 PPM.


Below is a rough sketch of a graph of estimated emissions versus air/fuel ratio for the typical engine, based on the tests that we have run with the Saturn SL1.  Note that the normal ECU operation emission is likely to have a combination of emissions with higher total emissions than the lean burn operation of Hydrogen Boost.  The only exhaust emission that is likely to be higher with Hydrogen Boost is NOx emissions during heavy throttle operation.  Since Hydrogen Boost drivers are more likely to be interested in better mileage they are not likely to be using heavy throttle setting very often. 



Conclusion:  Compared to stock vehicle operation the hydrogen Boost system can virtually eliminate all CO and HC emissions while possibly elevating NOx emissions, except at an air/fuel ratio that borders on loosing available power/torque.  But, since the optimum air/fuel ratio that gives comparable NOx emissions as a stock vehicle is coincidentally the best fuel ratio for best indicated mileage (A/F 18:1), the present Hydrogen Boost system can drastically reduce total emissions when adjusted for best mileage.  Further testing will be done with more water mist or vapor injection in an attempt to further reduce the NOx emissions.  A slight modification to the present design of our hydrogen generator may be all that is required.  This would likely not increase the cost of the Complete Hydrogen Boost system.


Emissions Challenge


          A week later, after discovering an easy modification to the hydrogen generator that increased the gas production by about 30%, I took the Hydrogen Boost Emissions Challenge.  The challenge was intended to be an offer to a technician that owned a five gas analyzer and wanted a Hydrogen boost system.  The challenge was for us to install a Hydrogen Boost system on a technician’s vehicle and achieve better emissions without a catalytic converter than the stock vehicle emissions with a catalytic converter.  I had no takers on the challenge and now have my own five gas analyzer so I decided to take the challenge myself.


          I drilled a hole in the exhaust pipe in a convenient place in front of the catalytic converter and inserted the emissions tester probe and secured it to the bottom of the vehicle.  Then with the Hydrogen Boost system turned on I took an extended drive, testing all driving conditions and throttle settings.  The result was no surprise to anyone who knows about a catalytic converter and has read the above article. 


          Let me explain the workings of the catalytic converter.  The purpose of the converter is to insure that all CO and HC emissions in the exhaust pipe are encouraged to react with oxygen in the exhaust, and at the same time rob any oxygen from any NOx in the exhaust to supply it to the CO and HC.  At the perfect stoichiometric fuel ratio the converter does the job quite well, but as we have seen above, the stock vehicle never has the perfect ratio because it is always changing.  


          Now let’s get back to the emissions in the Hydrogen Boost equipped vehicle.  If there are no CO and HC emissions in the exhaust pipe there is no place to force the oxygen in the NOx to go, so reducing NOx is not done by the catalytic converter.  If there is no CO and HC in the exhaust and the converter can’t reduce the NOx without them, there is no need for the catalytic converter, and the emissions would basically be the same in front of the converter as they would be at the tail pipe.  I knew this before I did the test but I had to follow through to prove it.  Plus I couldn’t win the challenge and give myself the tester without following the challenge rules.


          Now I can say that the emissions were not always perfect in front of the catalytic converter, because there was the rare occasion that excess fuel vapors from the tank would increase the fuel ratio from our ultra lean setting.  You might think that this should show increased CO or HC in the exhaust pipe in front of the catalytic converter, but that is not the case.  Actually there was increased NOx at these times, which proves to me that the hydrogen generator and ignition system were doing a proper job of igniting the air/fuel mixture and there was still plenty of oxygen to burn the fuel.  The increased NOx was very short lived and on very rare occasion, like when accelerating after sitting at a traffic light for long periods at idle, which no self-respecting good mileage driver would do.


          Another rare occasion of increased emissions is when the engine would skip or buck, because of poor ignition.  This could be caused by a too lean mixture that the system is barely igniting and occasionally not igniting.  This show me that it would be nice to have some more hydrogen in the mix.  This has spurred me to investigate ways to increase our hydrogen production and I have already found one easy modification to increase the gas production of our latest production model generators by about 30%.  If you have purchased our system between January 2006 and July 2006 you can email me at hydrogenboost@roadrunner.com for the modification instructions.  The modification takes about 5 minutes if you have the hydrogen generator in your hand or have easy access to the top of it.


Related information:  The reduced emissions are closely related to the increased mileage benefits of the lean-burn ability of the Hydrogen Boost system.  See www.hydrogen-boost.com/complete.html for more details.


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