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General HHO Usage Theory / ECU Functioning
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Jrvalid1 Offline
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Post: #1
General HHO Usage Theory / ECU Functioning
Understanding how your car's computer works:
First off, to work through getting better gas mileage in your vehicle, we should understand how your engine control unit (ECU) works. For our purposes what we need to know is how much fuel the engine is getting at various times.
In your ecu, there is a a grid that looks like a spreadsheet table that is something like 16 columns by 16 rows. On the x axis, is load. On y is rpm. See sample diagram. In each field is a preset amount of fuel in terms of injector duration and adjusted for intake and water temperature.
In vehicles 1996 and newer there is also what is called short and long term fuel trim. What happens is as the engine is running, it passes through various fields based on load and rpm (and other large scale adjusters like Intake Air Temp (IAT), Coolant Temp, etc). When it is in a specific field, it uses the data from that breakpoint for how long the injector should pulse. At the same time, it matches up what the oxygen sensor is telling the ecu as far as whether it is running lean or rich and uses that information to adjust the fuel mixture. Short term fuel trim is what is adjusted based on what has happened recently in a given field. Long term, as one might suspect, uses a longer series of data to make the adjustment. So for example, if this was possible, your injectors might as they get older release more fuel per millisecond than when they were new. In this case, your ecu would notice that the vehicle is running slightly rich and balance it out by adding a short term trim in the negative trim of say 5%. Since this issue would be constant, it would carry over into long term fuel trim. Then, any short term trim issues would likely center around -5%, perhaps bouncing around -3 to -8%.
The easiest way to wrap your brain around engine load (x-axis) is to get a vacuum or vacuum-boost gauge. Many current ecus, use a manifold air pressure (MAP) sensor to determine load. So, if you have this guage, you can easily tell how efficient your engine is being since the less vacuum being shown, the more gas is being injected.
Now there are two ways ultimately that you can get better gas mileage as far as your ecu goes. You can either experience a negative trim situation where you somehow cause the ecu to believe it doesn't need as much fuel (This is what O2 sensor extenders do), or you can do something that causes the ecu to run the engine in a lower load setting.
To help clarify these ideas, everyone knows that when you tailgate a tractor trailer, you can improve your mileage. So why is this the case considering our thoughts? Well, as you follow closely, the engine is under a lighter load and is thus working on a lower part of our grid. And since the lower parts of the grid use less gas, you get better mileage.
Another example is going down a hill. When you descend, the engine is under a very light load and you are operating in a lower part of the grid where fuel economy is great. Some cars will actually kill fuel to the injectors completely, like my 96 Honda Accord, when you are decelerating fully.
HHO application theory:
So the ultimate question is, which type of fuel savings should we try to attain as we install and operate our HHO systems? First, let's think about what an ecu will do when it encounters HHO.
When the gas mixture enters our intakes, it doesn't change the vacuum characteristics of the intake because it is not adding pressure or taking it away. It is just being sucked in, like the rest of the air. So from the intake side, it will not change the map sensor's reading, and thus change the gas mileage. From the exhaust side the O2 sensor(s) might read there is more oxygen and thus think the engine is running leaner and give it more gas, right? I don't think so. I believe the added oxygen to the engine will not be left unburned. This is conjecture, but is based on a my using of oxy-acetylene torches. When you run the Acetylene, it is a sooty, poorly burning flame, but when you add the oxygen, the heat is bumped up to a couple thousand degrees. In fact, I think the added oxygen will cause the mixture to ignite with more volatility, thus giving more power per stroke. We all know the Hydrogen part of this HHO system will act as a fuel, so when it is burned, with it's ridiculous flash point (1000 times faster than a petrol air mix), it makes a more volatile explosion. A more volatile explosion is not a bad thing. It is what we want. It directly gives us more power.
So the ultimate question then is, what will give us better gas mileage if the intake and exhaust scenarios are ultimately unchanged? I believe the answer lies in analogy to following the big truck. A relatively nasty explosion in your cylinders with the HHO vs. without means your vehicle will go faster than you anticipated. Thus to maintain the speed you desired, you will subconsciously lighten up the accelerator and put the ecu in a lighter load level.
To play this out, the larger the production of HHO you can generate, the more explosive your combustion will be, and the less you will have to hit the gas. However, this can't too easily be taken to it's logical conclusion, that is, why not just produce enough HHO to totally run the engine at all times? The problem is the flash point. HHO mixtures ignite, from what I've read, 1000 times faster than an atomized petrol mix. So if the HHO mixture extends beyond a certain point, engine damage would occur, because the ignition is set for a flash point associated with petrol.
Most of us know that our car's ignition systems advance the ignition timing at various loads, and this is done because it takes a while for the mix to ignite. When we add HHO to the mixture the engine can still work with advanced ignition timing because it is thin enough that it doesn't have the volatility to blow a hole in the pistons. Once the addition of HHO is increased to some specific critical mass, the ignition timing would have to be retarded to achieve the highest efficiency and prevent detonation. If anyone is feeling saucy, you can purchase a piggy-back ecu controller (like the AEM Fuel Injector / Controller) and retard your ignition timing based on load if you have crazy HHO production.
O2 sensor extenders:
I am not a big fan. Gasoline engines are set to run at a 14.7/1 Air/Fuel mixture. This means 14.7 pounds of air is sucked in for every pound of fuel injected, ideally. When we really nail the gas, especially on turbo-charged cars, the rate can go down to 11/1 so that the extra fuel can cool the turbo along with the exhaust valves. One of the purposes of choosing this mixture of 14.7/1 is the exhaust valves. Exhaust valves run at temperatures from 900-1200 degrees f. and up. These temperatures are uncomfortably close to the melting points of the metal that the valves are made of.
If you choose to fool your ecu into thinking that it needs less fuel than it does by using these extenders, you can significantly shorten the life of your exhaust valves thus requiring either new valves or a valve job in a much shorter time than possible. I am not saying that there aren't ways around this. You just need to figure out how to cool your exhaust valves and/or turbo. I've heard HHO production causes a cooling effect on valves, but this is hard to substantiate.
Bottom Line:
I think, if you are going to run an HHO system, my gut feeling is not to mess with trying to fool the MAP or O2 sensors unless you are sure you have dealt with the exhaust gas temperature. If you are not sure, I am not sure if I'd risk it unless you are willing to do a valve job if all goes bad (or worse). If you add an HHO system, give us fuel economy figures based on decreased load levels, not tricking your computer. If you tell us all we should give inaccurate data to our ecus and all of our cars need valve jobs in three years, this is not progress.
Thanks for reading! Good luck with your HHO projects!

Addendum:
So after reading around the site a bit, (I wrote this before I even heard about your site) I did read that the main reason we would want to adjust our Narrowband O2 sensors is because of all the extra oxygen the system is getting and that that leads the ecu to think it is running lean and thus causes it to use more gas. I would love to see meticulous guys' findings in this area, because I tend to not want to agree with that. I don't mind being wrong though.
I have been running a 4 by 4” dry cell with 13 or so plates on my 2002 6cylinder dodge ram along with pulstar plugs and my hwy mileage went from around 19 to 21.5 and my system's only pulling 18 or so amps.
I am looking forward to installing a similar system on my 96 honda accord because it has a turbocharger and an AEM Fuel Injector / Controller which can monitor and hack both O2 sensors' voltages based on a map, and has a controllable map for Fuel +/-, Ignition Timing +/-, MAP sensor +/-, two maps for random 0-5volt outputs, and a Wide-Band Input. And what's better is that I have a Wide-Band O2 sensor that this unit can log for me.
I would love to get your feedback on these thoughts.        
(This post was last modified: 09-02-2009 07:22 AM by Jrvalid1.)
07-20-2009 07:10 PM
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Jrvalid1 Offline
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Post: #2
RE: General HHO Usage Theory / ECU Functioning
Below is an email a received that I believe will add to this conversation. I hope he doesn't mind...

"This has been a nice read and well informed and to the point its about time for info posted in this site has some good info on it there are many of us stuck trying to figer out what our problem is if I may run this past you and see what you think.
I have a 1998 V-10 ford triton I have 6000 miles on my HHO system I have a idea how to control the HHO to the engine by turing off the HHO during high vacuum or idle times I think this is when the ecu says to much Oxgen more fuel and this sets up the long turm program for more fuel and kills our MPG so by cintroling the HHO during lean times and only dumping during loads times this would be far better for MPG. What would be the maxum High time a person could run on our Exhaust Temp. on a V-10 1998 ford this is a RV 32' Thank you for the info."

Thanks for the compliment on the post! I followed you for most of what you're saying, and I at the very least it would be better for our brakes if we didn't have HHO going while at idle or braking. I have been toying with the idea of using a variable output on the AEM FI/C to actuate the HHO allowing me to kill it during high vacuums. But as I thought through this, I realized that in my truck, I have gotten used to the fact that I can coast forever with HHO on and my driving style has adjusted. I think high vacuum times can still benefit from HHO. However, it doesn't account for what you're saying. If what you say is really happening, then all of the oxygen is not being consumed in a low load range and giving your computer a lean reading from the O2s.
Here's what I'm gonna do. I realized that I could put another relay in line for powering the cell, but use the always on side of the relay (so we must have a 5 pin version), and hook it up to my brake light actuator. If your RV is automatic, which likely it is, then when you are at lights, you'll have your foot on the brake anyways. When you are decelerating, you'll still get production and will be able to coast longer equalling better mileage. When you need to stop, the HHO will shut off and your brakes will work better.
I don't know how in the world you could, on a regular ECU, get a wire or signal that backyard mechanics could tap into to shut down the HHO. Relays are abundant, and most brake pedal switches I know of give a positive when actuated.... But it doesn't matter anyways, because with the relay you can trigger it with a positive or negative.
Then as you drove the RV, that lack of HHO during idle because of the new brake relay would cause the long term trims to level back out.
A little caveat to all this. I am not convinced that not all of the available oxygen is being consumed at idle. My understanding of combustion in general is that if there is a fuel and oxygen present, as much of the fuel as possible will burn along with ALL of the oxygen. To be convinced, I would want to see an OBD II readout of the long term trims at idle on an engine that has been running HHO, before the HHO install & after. If a Narrowband O2 sensor sees a rich condition, it is seeing no oxygen because it has all been burned up and fuel is left over. If it sees a lean condition, it sees oxygen because all of the available fuel has been burned and it sees oxygen left over.
I am not convinced that such a volatile gas as hydrogen, especially with it's nasty flash point, along with the petrol/air mix will not consume all of the available oxygen in each cylinder.
So here's the bottom line. If after checking the OBD II readout on long term trims, you see that they have not gone down by at least a few percentage points from pre HHO, then you are right. If the trim is down to perhaps -5% or lower, then the hydrogen is still helping fuel your idle. If your scenario is correct, the brake pedal relay will alleviate 20+ amps of load off of the electrical system and save gas. If my scenario is correct, I would just want to get off of the brake once I'm stopped so production turns back on and helps my engine idle.

I think this is a great point to bring up and I will post it to the thread.

Good luck!
09-09-2009 06:31 AM
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Gary Offline
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Post: #3
RE: General HHO Usage Theory / ECU Functioning
I'd like to see these ideas discovered to their conclusion. I've been thinking of a motion switch the would shut off the unit when going uphill or accellerating, to relieve the engine of the alternator drag when it needs power. HHO does-not-produce-power per se.
09-14-2009 04:23 PM
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Jrvalid1 Offline
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Post: #4
RE: General HHO Usage Theory / ECU Functioning
(09-14-2009 04:23 PM)Gary Wrote:  HHO does-not-produce-power per se.

Really... Respectfully, I beg to differ. First off, if we are getting better fuel economy with an additional load on the alternator, then the HHO must be resulting in additional power to compensate for the load. I recently took my ram which has a tiny 4 by 4" cell on a v6 and towed a 1500 lb pop up camper and a whole lot of gear, including firewood for 8 hours total and I got 18 mpg. In the past I would have gotten something like 14 or 15 in that situation. I was in the mountainous part of VT for a while and it was on all the time.

HHO is a volatile gas being sucked into an engine with the intent, at least in part, of being the fuel for combustion. If it did not produce power, we'd be doing something else. I know some will argue that the HHO allows for the exhaust valves to run cooler, thus enabling a leaner condition, but if this is true, it is only an ancillary benefit to the fact that it is producing real power to the ground instead of / or in addition to the petrol mix.

If there is ever a time to lighten the alternator load, it is going to be when power is not needed. So stopping, not decelerating, and being stopped are two potential times when this could be helpful. And for this a brake light actuated relay would be an easy solution. However, I am being led to believe that stopping may be the only time we need to cut the HHO, unless the alternator can't keep up with the cell at idle. I have come to enjoy the fact that the ram seems to coast forever. It reminds me that the distance of the coast is like free gas mileage.

I think the bottom line is that production should not depend on differing engine loads, such as going up a hill or not, but on when it is going to be fought by the brakes. If I had the resources, I would love to have a valve that shut off the HHO right at the point of entry, exactly when the brakes were applied in order to decrease the lag time when you hit the brakes and the engine continues to suck the gas in, even if the cell has stopped producing. I would also put a specified second delay on HHO production so it still made more for a little while while it is capped. It could alternatively be driven by a pressure sensor inside the tank or bubbler, so that when it hits a certain psia, like 15.7 psi absolute (1 psi) it shuts off. This would be great for stop and go traffic and would give you a little boost when you hit the gas pedal again.

In my accord, I have put so much stuff in the engine bay (with the turbo) that I could not find a way to get a full sized bubbler in the engine compartment. So I got 20' of polyethylene tubing and ran it from the trunk. Now it will be super easy to hook up a relay to the brake lights given that they are right there in the trunk, allowing the cell to turn off when brakes are on, but there is a 20 foot section of tubing that can be diffused with normal air when brakes are hit. ...Perhaps the solution may be to put a bubbler in the engine compartment.

However, I digress. So Gary, what logical end are you looking for?


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09-16-2009 06:40 AM
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Gary Offline
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Post: #5
RE: General HHO Usage Theory / ECU Functioning
Well, as we are discussing it as we understand it, so I'll concede that there is a certain type of power developed that will overrun normal mileage at a certain rate of production/amps balance. But I also know that it works on lean throttle. Guys have tried to use HHO for power on the strip and found that it takes MEGA amounts of gas to do any noticable effects.
That is not to say that it doesn't clean out your engine and create lost power, and therefore feel like it's making HP.
I don't see why you'd want to cut off the HHO on decelleration, as it's not costing anything. Upon accelleration, the "power" gains are far less than the amperage drag, as our little Toyoty can attest to: I shut it off climbing a hill and feel the forward surge of our mighty ground-pounding 100hp 4-banger.
(sarcasm here) But this is a car that you have to shut off the air conditioning to pass someone as well.
On my v-8, I can't tell with it on or off, so I'm just going by the smaller engines noticable effects.
09-16-2009 01:32 PM
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Jrvalid1 Offline
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Post: #6
RE: General HHO Usage Theory / ECU Functioning
(09-16-2009 01:32 PM)Gary Wrote:  Upon accelleration, the "power" gains are far less than the amperage drag, as our little Toyoty can attest to: I shut it off climbing a hill and feel the forward surge of our mighty ground-pounding 100hp 4-banger.

That makes sense. The only reason I was going to cut it during deceleration was because it was putting additional wear / heat on my brake pads and dusting wheels on both the car and truck. And as far as my car goes, since I added the turbo, there is upwards of 200 - 300 hp so we won't notice any drain on the system. In fact, the cell I put in the Accord is a 21 plate dry cell at 4 x 8". If it draws enough amps, I could always add an alternator or put a stronger alternator on there. If I drive it hard, then since I haven't upgraded the brakes, I wouldn't have much engine braking and it could cause them to fade. So clearly, the application is a bit different.
09-16-2009 03:12 PM
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Gary Offline
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Post: #7
RE: General HHO Usage Theory / ECU Functioning
I see. You're one of the few I've seen posting about better coasting from the HHO, not that others don't get it also. I don't notice anything, but perhaps it's because I'm in a continual state of hypermiling, which means I use the least amount of throttle and the least amount of brakes as possible without hindering traffic. I will coast down hills at an idle when steep enough to maintain or gain speed (or lose a bit if there's a reason to) and I'll think that the lessened usage of brakes would be balanced out if there were a forward coasting "problem" (good problem to have, huh?).
I worry more about wearing out my shift linkages shifting into neutral all the time! I've gotten pretty expert at re-engaging at the right rpm's without doing a neutral bomb, even tho the car and truck are totally different in the way you do it.
09-16-2009 04:15 PM
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