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" Since I did my last story debunking hydrogen-on-demand, documenting an NBC Dateline story I participated in, my e-mail has been relatively free of the hydrogen-gadget feeding frenzy. Within a few weeks of that story last spring, the number of people vilifying me and accusing me of being in the employ of Big Oil was remarkably high. Now, maybe because the price of gasoline has come down, people aren&amp;#039;t so desperate. And as everyone is trying to weather the economic storm, it seems there&amp;#039;s no time or energy left over to try to circumvent the laws of physics.  The SEMA show this year is also blissfully short on bogus gas-saving gadgets. Few seem to be peddling fuel-line  magnets, intake-tract vortex generators, vapor injectors or other stuff that doesn&amp;#039;t work. It&amp;#039;s actually a refreshing change. Unfortunately, there are still some throwbacks selling additives and chemicals that claim improved fuel economy. Sigh. P.T. Barnum was right. There&amp;#039;s a sucker born every minute. And, of course, there are still die-hard hydrogen-on-demand holdouts out there, claiming dramatic improvements in fuel economy by burning water in your car. On the floor I even found a couple of vendors selling systems. Not just backyard systems, either. I&amp;#039;m talking engineered systems with remote water reservoirs and electronic controllers. I heard one pitchman trot out the same old blarney: &amp;quot;Your engine only burns 80 percent of the gasoline you&amp;#039;re paying for. Our hydrogen-enrichment device will let you burn 100 percent!&amp;quot; Rubbish. The level of unburned and partially burned hydrocarbons in the exhaust stream is only a few hundred parts per million. The percentage of carbon monoxide is less than 1 percent, all measured before the catalytic converter, which cleans up the rest. There&amp;#039;s a long way from a few hundred parts per million--or even from 1 percent--to 20 percent. Even if injecting hydrogen could make the combustion event perfect, there still couldn&amp;#039;t be a 20 percent improvement. I looked at one system from MPE Performance that sells for $1700, uninstalled. (MPE makes money selling custom exhaust systems.) It&amp;#039;s really intended for big-rig truckers, so it produces a lot of HHO--they claim 3 to 4 liters of product per minute. To make that much gas, the system sucks up 60 amps of 12-volt electricity. That&amp;#039;s more than half the alternator&amp;#039;s output on most vehicles. A spokesman for MPE claimed that rarely would that much current be a problem. Let&amp;#039;s see: 60 amps at a nominal 14 volts when the engine is running is 840 watts, more than a horsepower of extra load on the engine. In spite of claims, that&amp;#039;s extra fuel consumed: MPE&amp;#039;s staff asserted that the alternator &amp;quot;produces all that electricity anyway, so we&amp;#039;re just using it instead of wasting it.&amp;quot; Doesn&amp;#039;t work that way, folks. MPE plans to improve the performance of its next-generation hydrogen generator by using a DC-to-DC converter to up the voltage to 24 or 48 volts. Wrong again. One of the first things I learned in fooling around with HHO devices is that it takes only a couple of volts to disassociate the hydrogen from the oxygen in water. Using any more than 3 volts across an individual electrolysis cell just heats up the water more; it won&amp;#039;t produce any more hydrogen. A few minutes into a conversation with MPE reinforced what I&amp;#039;ve learned in years of debunking these devices: The people making and pitching them don&amp;#039;t really understand the physics behind their claims. Or if they do, they hope their customers don&amp;#039;t. We did find one decent gas-saver at the show, the T-Max transmission thermostat. Simple, really. It bypasses the transmission cooler in the radiator until the transmission reaches normal operating temperature. Hotter automatic transmission fluid (ATF) is less viscous than cold ATF, and has less hydrostatic drag. In the kind of urban driving cycle most people have, 30 minutes or so of stop-and-go driving followed by a cool-down, the reduced drag means reduced fuel consumption, and they have wind tunnel and dynamometer data to back up their claims. The T-Max received a PM Editor&amp;#039;s Choice award.  Still, most gas savers I&amp;#039;ve investigated don&amp;#039;t come with credible test results, just anecdotal testimonials. Caveat emptor, readers! "^^<http://www.w3.org/2001/XMLSchema#string>
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