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Old 02-28-2008, 01:11 AM   #11
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Now until I discovered Gassavers, I thought fuel injection was the best that you can get. Then I learned about lean burn and low emissions. Coming from California, I grew up with the California versions of cars getting worse mileage and lower performance.
I'm not so sure that nitrogen is "burned" as much as NOx is a side reaction product of higher temperature combustion. NOx reacts with hydrocarbons to form smog. Smog annoys people in LA. Since they have juice and money the rest of us have to play along. For now.

One of the earliest ways to reduce NOx was the EGR valve. EGR, or "exhaust gas recirculation" took some of the engine exhaust and fed it back into the intake manifold. This was done to change the chemistry of the fuel air mixture, to change how the combustion process unfolded. The change caused a reaction shift away from NOx products. This also reduced the amount of energy in the mixture - since you were replacing air and fuel droplets with exhaust gases. Get a malfunctioning EGR valve and you'll soon know what I mean - stalls and other stuff.

Even the old Hondas, I think, had EGR valves.

Another way to reduce NOx is to use the energy in gasoline to reduce NOx back to nitrogen and oxygen.

Converters are touchy animals. They require just the right amount of gases at just the right time. Too lean and they do not work. Too rich and they super heat and the catalyst beds melt. Usually it's best to let the mixture cycle to allow for proper cooling.

If we did not need to feed the converter we'd have more energy to move us here and there. They are a net drain though properly fed and cared for they work well. The cycling also permits the use of cheap "switching" narrow band Oxygen sensors versus more expensive "wide band" sensors.

Another method to reduce NOx is to change the timing. I've read that the most efficient combustion occurs just short of "pre-detonation". However this is the same timing that causes a lot of NOx emissions.

So by changing the timing away from this area you get less NOx emissions, but you pay for it with a loss of power. So you have to push more gasoline into the engine for the same amount of power.

Lean burn also requires a proper match of detonation sensing technology to combustion chamber geometries. For example, Hemis running lean are exquisitely sensitive to detonation. They require very agile det sensors. In the bad old days of very rich mixtures detonation wasn't a big deal.

Honda's CVCC used a funky internal chamber to combust the fuel mixture. Trouble is, I think, that the valves cut close to the piston. If the timing belt should break the tears start to fall.

Honda CVCC technology does require a cat converter. Older Honda motors cannot pass emissions checks without a reasonably well maintained catalytic converter. My 1990 CRX failed two years ago because I did not have a fresh converter. Once I purchased one and properly installed it my checks went through easily.

Yeah, the standards "tightened". What else is new?

Gene
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Old 02-28-2008, 01:39 AM   #12
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Now here's another idea as far as smog and possible mpg experiments go. I plan on building an HHO generator, with the extra hydrogen making the O2 sensor read rich and lean the engine out, will the added O2 and hydro lower overall NOX?
You're going to add hydrogen so that you get more oxygen? You'll probably end up using more energy to make the perquisite amount of hydrogen than you'd save changing the mixture. Water takes a lot of energy to break up, and guess where it comes from? Yes, your motor itself.

Be a lot easier to either insert a very low value resistor or length of wire into the oxygen sensor harness. Both are "tampering" and illegal, but they will lean out your mixture. They'll also confuse the heck out of your ECM.

See, here's the deal.

The older ECM used tables to generate proper mixtures and timing retardation. I suspect that they're a bit more sophisticated today but probably not much beyond some sort of table system.

The manufacturer develops the original figures from dyno studies. They put a test subject in a dyno and work a table. Once in the field the ECMs probably "fine tune" by using the motor's performance to feed back into itself.

You're about to change the chemical composition of the fuel. The possible results are pretty hard to predict.

Now, if you had access to a dyno and a way to remake the fuel tables I'd suggest working up an interim table, than fine tuning it on the dyno. No need to add hydrolysis machines. Just run more lean.

If the valves can take it - to a point the leaner the more heat they take - and you can avoid detonation, and you can handle the power issues from going too lean, you'll be fine.


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Also it would take a huge amount of build time, but constructing a Geet Pantone fuel super heater, making fuel a gas, I wonder how smog would be effected. The guys at Geet say 90% less emissions, but that's on a carburated vehicle. With the ECU, FI, O2 sensor controlled cars of today, what would come out of the tail pipe?
Don't know. If turning gasoline into a vapor was so good it would have been done decades ago. I don't know of anyone who does it. Even up to the bitter end of carbs the goal was to atomize the fuel, not vaporize it. Two phase flows.

Today with injectors they're still doing it.

Propane and LNG may be handled differently. I do not know.


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One reason this intrigues me is I saw the camera shot inside the cylinder of a Ford Taurus on its combustion cycle. With the injector aimed right at the intake port, I was amaised at how much unatomized fuel is squirted inside the chamber and how incomplete the burn is. From the old days of a propane carburator convesion, I wonder if there is a port injected propane update?
Dunno. I've heard of Honda Civics that use natural gas. How they do this I am not sure.

You will need AT LEAST different fuel tables for your ECM. I think that the Honda GX uses a higher compression motor to take full advantage of the chemical properties of natural gas. Just to use ethanol you have to modify the mixtures.

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I'm forever trying to figure out how to make a car go 100 miles on an eye dropper of fuel.
You'd need more energy than that to walk 100 miles, Scott. You're talking of using that much to move you and the car too?

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Old 02-28-2008, 05:00 AM   #13
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If turning gasoline into a vapor was so good it would have been done decades ago. I don't know of anyone who does it. Even up to the bitter end of carbs the goal was to atomize the fuel, not vaporize it.
http://www.race-cardrivers.com/Shell%20Opel.htm

Yes, I realize this wasn't done for actual normal driving, but vaporizing the fuel DOES work.

Honda runs a vehicle on natural gas, and maintenance and wear are reduced SIGNIFICANTLY. Same on propane. That's why you see propane conversions, and HUGE amounts of city busses are now running on propane or natural gas as well. Less maintenance because there is less wear on the engine.

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If we did not need to feed the converter we'd have more energy to move us here and there.
True. Older Hondas with the CVCC engine WITHOUT the catalytic converter DID pass emissions, btw. They changed emissions standards in CA because of that, changing to a PPM basis, which is what allows Hummers to pass although they belch much more TOTAL pollutants into the air. Get that to change and we'll see small cars rule the road.

Propane, LNG/CNG ("Clean natural gas" which is the same thing as Liquid Natural Gas) have so much less emissions than gasoline! WHY? Because gasoline is also partially formulated to have emissions! LEAD used to be added to gasoline *ON PURPOSE* and guess what came out of the tailpipe? Lead is so cheap it's not funny, and that's one reason why gasoline was cheaper, among many.

At least one person on here has made a vehicle that gets over 200 MPG (Ryland?) IIRC. There are thousands of personally built or kit vehicles in the US that get over 60 MPG but they are not huge behemoths of SUVs and the car industry wouldn't make a ton of money on them, so they don't sell them.

You'll also note that Honda only makes a BIG car that runs on natural gas, one with lots of extras. They don't make a high-mileage vehicle that runs on natural gas, only a luxury car. But look at the low emissions on the Civic GX. The only thing lower is an electric vehicle.

Running on vapor would be the absolute best NOX emissions on the planet, and it's cheaper, but the secret stays hidden for almost everyone.
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Old 02-28-2008, 07:46 AM   #14
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Propane, LNG/CNG ("Clean natural gas" which is the same thing as Liquid Natural Gas) have so much less emissions than gasoline!
<snip>

You'll also note that Honda only makes a BIG car that runs on natural gas, one with lots of extras. They don't make a high-mileage vehicle that runs on natural gas, only a luxury car. But look at the low emissions on the Civic GX. The only thing lower is an electric vehicle.
CNG officially stands for Compressed Natural Gas, mebbe the other definition is marketroid speak.

One does need some space for the CNG tanks, and a manufacturer officially offering a CNG model needs to put them in a place where they are unlikely to be damaged in an accident or they'll have a pintogate thing on their hands. Hence, until there are purpose designed CNG vehicles, we aren't likely to get many small ones.
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Old 02-28-2008, 11:35 AM   #15
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Scott -

Quote:
Originally Posted by Scott View Post
...

So on my future mpg machine I now plan on a Scan Gauge, EFIE, an air fuel ratio gauge, and a pyrometer.

Now here's another idea as far as smog and possible mpg experiments go. I plan on building an HHO generator, with the extra hydrogen making the O2 sensor read rich and lean the engine out, will the added O2 and hydro lower overall NOX? Also it would take a huge amount of build time, but constructing a Geet Pantone fuel super heater, making fuel a gas, I wonder how smog would be effected. The guys at Geet say 90% less emissions, but that's on a carburated vehicle. With the ECU, FI, O2 sensor controlled cars of today, what would come out of the tail pipe?

...
This is exactly what I want to do. Use the hydrogen generator to lower the NOx under lean burn conditions. Unfortunately, I think I need a NOx sensor to verify my results in real-time. It looks like these sensors are in development, especially in the EU, but are not ready for prime-time :

Smart NOx Sensor
http://www.vdo.com/products_solution...nox-sensor.htm


(NGK) Sensor Technology
http://www.ngk-detroit.com/prod_sensortechnology.html



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Old 02-28-2008, 11:09 PM   #16
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Propane, LNG/CNG ("Clean natural gas" which is the same thing as Liquid Natural Gas) have so much less emissions than gasoline!
I've heard this on an anecdotal basis. The other possibility is that most natural gas burning engines are used in industrial equipment or in vehicles that have access to regular maintenance.

A well maintained vehicle will burn clean.

Of course "natural gas" is mostly methane. Methane doesn't contain sulfur or other impurities.

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LEAD used to be added to gasoline *ON PURPOSE* and guess what came out of the tailpipe? Lead is so cheap it's not funny, and that's one reason why gasoline was cheaper, among many.
Tetra-ethyl Lead was used as a "anti-knock" additive. You could add it to pretty poor quality gasoline and it would boost octane levels to the point that you had pretty good quality gasoline.

Once lead was removed from gasoline the gasoline itself had to be of a higher quality. You need to expend more energy to reform crude and intermediate products so that its anti-knock properties were close to those of leaded gasoline.


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Running on vapor would be the absolute best NOX emissions on the planet, and it's cheaper, but the secret stays hidden for almost everyone.
Maybe...

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Old 03-02-2008, 09:49 PM   #17
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I'm having a thought. Maybe it's just my imagination going wild again, so bear with me.

What if the normal compression stroke of our motors creates enough heat to boil/vaporize fuel due to the adibiatic process?

Let's assume that ambient air is 75*F and 14.7psi absolute pressure. During normal cruise my engine runs with about 13"Hg vacuum. According to the conversion at www.stealth316.com/2-converters.htm that much vacuum equals 5.893835 psi absolute pressure. Using those numbers in the online calculator here www.stealth316.com/2-turbotemp.htm shows cylinder temps at TDC might reach around 948*F assuming a compression pressure of 155psig (taken from a compression test of my car) and assuming 95% efficiency. Using 100% efficiency gives a compressed temp of 904*F. Using 90% efficiency yields 996*F. I'm at a loss to figure out the actual temperature in the combustion chamber since some of the heat will be absorbed by the cylinder head, piston top, and top of the cylinder wall. The compression stroke happens quickly enough that there isn't much time for the heat to be absorbed, so what might the final temp be?

According to the various sources at http://www.hypertextbook.com/facts/2...istopher.shtml Gasoline vaporization temp is around -50 to -45*F, and an autoignition temp of 495 to 536*F.

It's hard to imagine temps in the cylinder at TDC of the compression stroke dropping by several hundred degrees below these estimates, but it must, since the spark plug ignites the air/fuel mix and not the heat of compression.

A wiseman once told me 'If a problem raises more questions than it answers, then the problem is smarter than you'. Hmmm...
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Old 03-03-2008, 09:45 AM   #18
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I'd say it must be too, DRW. Because if we raise the compression ratio of a normal engine much above 10:1, we get preignition and detonation. So we're running compression temps just below the flash point.

Try not to think so much. As Jethro Clampett said, "I tried that, and it hurts".
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Old 03-04-2008, 10:02 PM   #19
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Yeah, I think I overexerted my brain muscle on that post and only touched half the problem. Oh well, it's good to flex the grey matter once in a while.
I think I'll take a nap now.
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Old 03-10-2008, 05:57 PM   #20
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I'm just sitting here absorbing. Really interesting...I had no idea that the NOx levels dropped off at a certain point.

Of course, this is also why I went to a pre-smog vehicle when I lived in CA...I did not want to have to deal with this.
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