Better combusion != more fuel
 

I've been looking around and notice that a lot of people think that getting a better burn means you get more fuel injected because of the computer compensating for the better burn because of oxygen sensor readings. This is especially true of people trying to sell HHO kits or EFIE units. When an engine begins to experience better combustion, all other things being the same, there is in fact less oxygen in the exhaust stream.

Lets take an example engine, any engine, it doesn't matter. Running stoich your sensor will read just as it always does. If you increase the amount of fuel in the engine, leaving intake volume and combustion efficiency alone you end up with a rich mixture, less oxygen in the exhaust. A computer will pull fuel to compensate for this. If fuel is removed there will be more oxygen in the exhaust stream and more fuel will be added to compensate for this.

Since it is an OXYGEN sensor and a better burn leads to less oxygen then you end up with an engine that is now reading rich, even if it isn't, and the computer will actually remove fuel as a result of the better burn trying to alleviate what it sees as a rich condition.

Actually it is more complicated than that because the CAT is actually two stages and it breaks down the Nitrogen compounds containing oxygen and releases more O2 to combine with unburnt Hydrocarbons and Carbon Monoxide to form water and Carbon Dioxide and some left over oxygen in the process. The HHO pretty much just adds some heat to the process and combines to make more water if it burns completely.

Yes, but that is read by the downstream O2 sensor that has nothing to do with air fuel mixtures.

Better combustion is a product of maximum effective compression. By driving your conventional vehicle with the lowest possible engine on cycle, relative to engine off, you are creating more maximum effective compression for a shorter period of time, instead of lower compression in a constant mode.

This does not mean high revolutions or wide open throttle. It means more available oxygen packed into the same combustion chamber area.

This amplifies the leverage created by the expanding mixture as it heats up during combustion.

In most cases the mixture will be slightly more rich than under low load operation, but the real peak is at maximum BSFC which gives you the most power for a given amount of fuel. After that point unburned hydrocarbons will skyrocket if the mixture is enrichened, without substantial increases in power.

regards
gary

Don't forget that HHO generators also release Oxygen. and the raio of fuel to oxygen molecules actually goes up.

Don't forget that HHO generators also release Hydrogen. It is a stoich mixture and unless HHO doesn't burn completely there will just be more water in the exhaust. No extra hydrogen and no extra oxygen.

Yup...HHO generators split water into hydrogen and oxygen. Then, when you burn it in the engine, the combustion of it is a matter of recombining the oxygen with the hydrogen to make water again.

you state "If fuel is removed there will be more oxygen in the exhaust stream and more fuel will be added to compensate for this."
That much is true. but we are not just taking away fuel. better combustion means all the oxygen is being burnt up with fuel left over. Then the computer decreases fuel flow to where it should be.
So where does all this put you? now you dont have to ope the throttle quite as far to generate the same amount of power.

Less throttle increases manifold vacuum which reduces the effective compression. Best engine efficiency is achieved when effective compression is highest.

regards
gary

How do you know for sure that there is less oxygen in the exhaust when you get better combustion?

No matter whether it's stoich @ 14.7:1 or lean at 16:1, 100% efficient combustion will leave less oxygen than 95% efficient combustion.

Try an experiment, get a small sealed room and a propane fired bunsen burner, see if you pass out quicker running it on yellow flame or blue flame. ;)

Let's say you do achieve 100% combustion, what is the exhaust composed of then?

100% combustion at 14.7:1 AFR or richer would leave no free oxygen in the exhaust upstream from the converter.

One would have some oxygen left over in the exhaust if there was a misfire/no ignition (even at 14.7 to 1) or if you had 100% fuel combustion but were running leaner that 14.7:1- although running lean with high combustion temps might make at least some of the excess oxygen combine with atmospheric nitrogen to form Nox.

100% combustion yields CO2 and H2O.

Unfortunately, in the real world, you end up with a little NOx and CO in there too.

You don't understand how an O2 sensor works.
https://www.mummbrothers.com/SRF_Stuff/images/Stoich.gif

https://www.team-integra.net/images/B...fSmogChart.jpg

Peak power happens at the maximum AFR where there is no O2 left in the exhaust aka 12.5-12.9 AFR.

Peak fuel economy happens at 15.4-16 AFR which also happens to be the nox peak.

Hmmm how so? O2 sensors really only measure O2 balance between outside air and exhaust stream from this they infer mixture, if everything is working right, but when it comes down to it, all they measure is the oxygen content. Thus if you have a misfire, your fuelling just goes richer, nice huh?

In California, when you have your car smogged they give you a detailed chart of all the gasses coming out your exhaust. Usually a properly functioning car running at stoich (14.7afr) has 1% unburned O2 in the exhaust. That correlates perfectly with the chart above. A car running rich will have near 0% O2 and a car running lean will be over 1% O2

Is the yellow shaded range (HC) hydrocarbons? if so, why do they increase along with oxygen when you go really lean (say 18:1)? Is it misfiring at that point?

Yes. Some engines like honda Vtec-E are designed to create swirl in such a way to not misfire at super lean AFRs like 18+. Most other engines have a hard time running at 18+ AFR. You get 'lean surge' where you feel the car surge back and forth as it periodically misfires.

I'm in the process of megasquirting my Mercedes using a wide band O2 sensor. The engine is perfectly happy around cruising around at 15.4 AFR. It'll even run around 16-17 afr. But as soon as it goes leaner than that it starts to surge. Idle is at 14.7 afr (from the stock 13.5) and wide open throttle is set to between 12.6-13afr. Best of both worlds.


This is an old version of my AFR target table. The new one has a lot of the 12.9s at 4000rpm+ changed to 12.6. The 20KPA row is irrelevant above 1200rpm because the injectors will be turned off on over run.
https://www.fuelly.com/attachments/fo...98b6cd5c42.jpg

While those are good, and true, points. What does that have to do with me not understanding how the O2 sensor works?

The O2 sensor reads O2. If you get a more complete combustion O2 stats fall which the computer reads as rich, just like your chart shows.

If you are slowly leaning out lean surge isn't a complete misfire. It feels like one and you lose power like one, but the gasses still burn if you have the ignition source to light it. It just burns so slowly that the cylinder never reaches a good working cylinder pressure. Lean surge is very bad for exhaust valves because the air fuel mixture is still burning when it passes over the valve. That's the stage where people ruin valves from running lean and why it is considered a bad idea to lean out past stoich.

You have it totally backwards. Complete combustion (AKA maximum FE) happens near the noX peak and HC minimum where there is still 1-2% unburned O2 left in the exhaust. The O2 sensor will show a LEAN mixture in that situation.
What is your goal? To burn all the O2 going into the engine or all the fuel? You can't do both at the same time. In order to burn the last 1% of O2 inside the engine instead of the catalytic converter, you need to burn an extra 14% fuel over stoich. Great for peak power, not so great for FE. Most people around here want to burn all the fuel because they have to pay money for it, as opposed to the O2 which is free.

No no no. I said "all things being equal" as in the same amount of air and fuel in the cylinder you just get a better burn, like HHO is supposed to do your O2 stats will fall.

I said nothing about changing AF ratios to accomplish a better burn.