Mixture control

[larryg]

Came across this on the net, have any of you experimented with this type of thing? seems easy enough to build, thought I might try to put one together and test it.

http://better-mileage.com/memberadx.html

[MetroMPG]

There's no doubt that by spoofing the O2 sensor, you can lean the mixture and increase fuel economy.

But leaning the mixture will also increase production of NOX emissions in engines that weren't specifically designed to run lean (e.g. through combustion chamber design, or intake charge concentration, like the Honda lean burn motors).

[omgwtfbyobbq]

That's where H2O injection comes in. Lowers the intake charge temp and limits peak combustion temps, so it will allow you to run leaner w/o risk of detonation, as well as do work when it soaks up some of the heat and goes from a liquid to a gas. Just gotta be very careful with the system, don't want it to break and dump water in there.

[MetroMPG]

Or I suppose you could introduce more EGR...

Problem is you're flying blind unless you also have a way to monitor NOX.

[SVOboy]

Originally Posted by MetroMPG

There's no doubt that by spoofing the O2 sensor, you can lean the mixture and increase fuel economy.

But leaning the mixture will also increase production of NOX emissions in engines that weren't specifically designed to run lean (e.g. through combustion chamber design, or intake charge concentration, like the Honda lean burn motors).

I might disagree. At a certain point on a stock engine, overly lean condiutions will result in poor mileage. I posted an article about this on the RSX a while back that nailed 15.5 or something like that as best for that engine.

[omgwtfbyobbq]

I've seen old (supposedly working) smog machines pop on Craigslist for a hundred bucks or so, and when I get things sorted out, it's something I would definitely grab if I had the chance. Also, by virtue of limiting peak combustion temps, NOx is limited by a certain amount for certain engines. I suppose we could do some back of the pad calcs and have a reasonably good estimate of how lean/how much water we'd need to equal stock NOx levels. And there's also just going to the smog guy and paying him the going rate, maybe more, maybe less, to measure the output.

[zpiloto]

Originally Posted by MetroMPG

There's no doubt that by spoofing the O2 sensor, you can lean the mixture and increase fuel economy.

But leaning the mixture will also increase production of NOX emissions in engines that weren't specifically designed to run lean (e.g. through combustion chamber design, or intake charge concentration, like the Honda lean burn motors).

From Tony fuel saving page

The three "regulated pollutants" are unburnt hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx). All three are serious human health hazards. NOx is nitrogen with added oxygen; HC and CO represent incomplete combustion. What the catalyst does is to remove the oxygen from the NOx and give it to the HC and CO. The result is plain nitrogen, carbon dioxide and water, all of which are essentially harmless. But to work, the lambda value must be just right. If the mixture is too rich then the oxygen in the NOx is not enough to give to the HC and CO, so they pass through unconverted. If the mixture is too lean then the "spare" oxygen is given to the HC and CO, and the NOx passes through unconverted. The overall effect of lambda on post-catalyst emissions is like this:

There is a very narrow "window" between lambda 0.99 and lambda 1.00 where all three pollutants are effectively cleaned up. It is precisely because the engine must operate in this "window" that modern engines are fitted with lambda sensors.

Now, under most circumstances the lambda sensor will correct for any fuelling deviations introduced by the "fuel saving device". But the sensor has limited "authority" - it can only add up to about 10 - 15% additional fuel, since otherwise a faulty sensor could result in an extremely rich mixture, leading to engine problems. If the deviation exceeds this limit, then the lambda sensor can no longer compensate and a lean mixture is the result. So the result of fitting one of these devices may be a lambda around 1.05 - 1.10. This will give a small improvement in fuel consumption (about 2 - 5%) and, as the graph above shows, reductions in HC and CO. This sort of result is often shown by makers of such devices as "proof" of emissions reduction. However, the NOx emissions will increase massively - perhaps 20 times - as the catalyst can no longer clean them up. Since NOx is not usually measured by workshop test equipment, this is not picked up. The overall effect is a very large increase in toxic pollutants, which does not fit the "green" claims of such devices.

(On a vehicle without a catalyst, leaning the mixture will greatly reduce CO and significantly increase NOx. HC may go up or down, depending on the engine and the test conditions.)

[cfg83]

omgwtfbyobbq -

Originally Posted by omgwtfbyobbq

I've seen old (supposedly working) smog machines pop on Craigslist for a hundred bucks or so, and when I get things sorted out, it's something I would definitely grab if I had the chance. Also, by virtue of limiting peak combustion temps, NOx is limited by a certain amount for certain engines. I suppose we could do some back of the pad calcs and have a reasonably good estimate of how lean/how much water we'd need to equal stock NOx levels. And there's also just going to the smog guy and paying him the going rate, maybe more, maybe less, to measure the output.

When you say smog machines, do you mean a water injection device ?

EDIT : Wait a minute, you mean smog machines as in what the guy at the smog place uses to test emissions. For a minute I thought you meant a "smog generator" or some other strange gizmo.

CarloSW2

[cfg83]

omgwtfbyobbq -

Originally Posted by omgwtfbyobbq

That's where H2O injection comes in. Lowers the intake charge temp and limits peak combustion temps, so it will allow you to run leaner w/o risk of detonation, as well as do work when it soaks up some of the heat and goes from a liquid to a gas. Just gotta be very careful with the system, don't want it to break and dump water in there.

Would the hydrogen generators (electrolosys) serve to accomplish the same thing as the water injectors? The lower combustion temps sounds like the same behavior that Fran Giroux, the hydrogen-boost guy, claims.

CarloSW2

[omgwtfbyobbq]

Ha, that would be something. Water injection that's masquerading as a H2 generator... I wouldn't be surprised, especially when considering that H2O injection can result in upwards of 10% better mileage.