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Gas Saving Gizmos & Gadgets



  • shiposhipo Posts: 9,148
    "First of all, potential changes in the volume of intake air required to compensate for a free flowing exhaust are not great enough to cause a loss of 6 miles per gallon IF THE AIR/FUEL RATIO IS KEPT AT THE MANUFACTURER'S RECOMMENDED SPECIFICATION."

    I'm not exactly sure I agree with that statement. Many engine makers use a technique called "valve overlap" to enhance cylinder scavenging. Reduce the back pressure well below that of the factory exhaust and too much of the intake charge flows out the exhaust valve before it closes. Needless to say, that condition will of course results in a measurable reduction in fuel economy even if the Air/Fuel ratio is bang on. The only way to counteract that problem for most engines is to change the cam(s) to reduce the amount of overlap commensurate with the new exhaust system. That said, many of the new VW & Audi engines use direct injection of the fuel into the cylinder, and as long as the exhaust valve is closed before the injector fires, even a long duration of valve overlap coupled with zero back pressure won't negatively affect the fuel economy.

    Best Regards,
  • 0patience0patience Oregon CoastPosts: 1,712
    Ok, first let me address that article. The author is an expert. He is published in many automotive mechanic trade magazines and is a leading professional in driveability and emissions.
    So you can disagree all you want, but his credentials are above repraoch. That being said, my rep ain't no slouch either.
    As for his claim, it was in response to a question, had you read it correctly. The guy asked why he lost 6 mpg when he bolted on stuff and the author, replied why.

    First of all, potential changes in the volume of intake air required to compensate for a free flowing exhaust are not great enough to cause a loss of 6 miles per gallon IF THE AIR/FUEL RATIO IS KEPT AT THE MANUFACTURER'S RECOMMENDED SPECIFICATION. As long as the mixture is correct, you can vary the total volume within that kind of range and not see much change in economy.
    Wrong. You contradicted yourself.
    If you open the exhaust flow, the air/fuel mixture will not be kept at the manufacturer's specs, because the computer will be trying to compensate for the flow.

    Increasing the total mixture volume while holding the air/fuel ratio constant will just result in needing to use a smaller throttle opening at a given speed.
    Sorry, still trying to make sense of that statement.

    Fuel injection computers are designed with a limited capability to adjust the mixture. They work fine, as long as the engine is kept stock.
    There is a reason for that. The govt specs what is allowable. Most bolt ons put those outside that range, then people have problems. The put these bolt ons on the vehicle with no reprogramming, then wonder why they have problems.

    I'm not gonna get into a debate about theory and all that, cause quite frankly it is a waste of my time.
    You can agree with me or not. Don't care one way or another.
  • 0patience0patience Oregon CoastPosts: 1,712
    Many engine makers use a technique called "valve overlap" to enhance cylinder scavenging. Reduce the back pressure well below that of the factory exhaust and too much of the intake charge flows out the exhaust valve before it closes.

  • zaken1zaken1 Posts: 556
    I hope this doesn't reopen the Pandora's box. There are plenty of engines out there with high overlap cams, which also use low restriction exhaust systems; and still get good gas mileage. I've owned several myself. The critical factor affecting whether or not the mileage is hurt is not so much the restriction or lack of restriction in the exhaust system; but rather the resonant behavior of the exhaust system. If the length of the exhaust system is poorly chosen (or not considered) it can cause reflected pressure pulses to travel back up the system and reach the open exhaust valve during overlap; those waves will then flow backwards through the cylinder and continue out through the open intake valve. And the resultant exhaust dilution of the intake charge will raise all kinds of havoc with the fuel mixture and volumetric efficiency at that particular RPM. On the other hand, properly tuned exhaust systems are designed so that a portion of the exhaust pressure pulses reaching the outlet end will reflect and travel back through the exhaust system to the engine, with the pipe length chosen so that the pulse strikes the closed exhaust valve and bounces back just before the valve opens. This second reflection of the pressure wave travels again through the exhaust system to the outlet end, drawing a lower pressure area behind it. The lower pressure behind the outgoing pulse helps to scavenge the exiting gas after the exhaust valve opens.

    Since the length of time between exhaust valve openings is halved as engine RPM doubles, while the speed of the reflected exhaust pulses changes relatively little; the exhaust reversion will go into and out of harmony with the valve timing as engine speed changes. A well designed tuned exhaust has an effective range of resonance which closely matches the engine's torque curve.

    As long as the exhaust resonance is harmonious with the valve timing, the carburetion will work like it was intended to do, and there will be good potential for torque and fuel economy. But when a mismatched exhaust system creates pressure waves that upset the intake flow; the carburetion becomes unstable, and it becomes impossible to tune the engine to run efficiently. And that's when and why the mileage falls off.
  • shiposhipo Posts: 9,148
    No argument to any of the above. In my simplistic statement I written above I was too lazy to drill too deep. Glad you did. ;-)

    Best Regards,
  • zaken1zaken1 Posts: 556
    WOW, what a pleasant surprise to see your reasoned, positive response. I was beginning to feel like I was on the wrong planet, and was just about ready to quit posting on this site.

  • shiposhipo Posts: 9,148
    A "one chip fits all cars" device, yikes, I wouldn't plug that thing into a dead skunk much less one of my cars. :P
  • gunga64gunga64 Posts: 271
    I would switch to syntheic oil and make sure my tires are inflated properly to get better MPG. Also keep off the brakes and coast to a stop when possible and don't put the pedal down so fast when driving.

    I really don't think running the AC effects MPG as much as many think. You may get 1/2 MPG more but watched mythbusters and it wasn't all that much to drive in the heat.
  • zaken1zaken1 Posts: 556
    I agree with the points you raised, but many people already use synthetic oil, drive conservatively, and keep their tires inflated. Here are a few things those people, and everybody else, can do to get better mileage.

    1> Don't warm your car up by idling for long periods when you first start the engine. Tests have shown that over 95% of engine wear takes place in the first 5 minutes of running. Much of that wear is caused by excessive fuel from rich cold starting mixtures washing the lubrication off cylinder walls. The rich fuel mixtures used during cold running also cause a huge drop in fuel economy. The sooner you get the engine up to normal speed, the quicker it will warm up. The higher engine speed and earlier warm up both enable the air/fuel mixture to lean out faster. The best technique is to let the engine run for 15 to 30 seconds after a cold start, and then drive gently, at moderate speed, until the temperature comes up.

    The practice of letting the engine idle for long periods when cold was common in the days before cars used multigrade oil, when engine tolerances were much looser than they are today. But the tighter tolerances in modern engines, along with thinner, more effective oils, have now made that practice unnecessary.

    2> Many late model cars have a built in design feature that wise owners can use to improve their mileage. It is called a detonation sensor, or knock sensor. The way these devices work is to automatically advance the engine's ignition timing as far as possible, until it begins to ping or knock. The more spark advance an engine has, the better its fuel economy will be. However, prolonged knocking can lead to engine damage, so the timing cannot be safely advanced beyond the point where the engine knocks.

    In a car equipped with a knock sensor; using premium fuel will permit the timing to advance further than it can with regular fuel, before the engine begins to knock. This will improve the fuel economy over what it was on regular. The difference will vary between fuel brands, car models, and type of driving; but sometimes it can be quite significant. So even on cars where the manual recommends regular, premium fuel can often give better fuel economy, and more power as well.

    3> In my 27 year career as a performance tuning specialist, I quickly found that the better an engine runs, the more differently it responds to various brands of spark plugs. If you change brands of plugs in an engine that is not in good mechanical condition, or is not sharply tuned; it often doesn't make much difference. But a sharply tuned engine will frequently show definite preferences in spark plug brands. And often, the brand of plug that runs best, and gives best fuel economy, is not the brand the vehicle manufacturer recommended. I've seen many engines run best with Champions, which is why that has become my favorite brand. But my fiance's BMW would not run well on anything except Bosch. And one client's Mazda ran best on NGK. Each brand of plug works best under a certain set of conditions. If you are willing to invest the time and effort, your mileage and performance may be improved by changing plug brands. Spark plug manufacturers frequently offer optional plug designs which have premium features. Champion makes a line of 'Platinum Power' plugs, which I've found work better in Toyota V-6 engines. Bosch 'Fusion' (with iridium/platinum electrodes) work better in my Geo Metro than any of the dozens of plug types I've used in that engine during the last 15 years. And plain ordinary nickel electrode Autolites work best in my heavily modified small block Mopar.
  • vchiuvchiu PARIS, FRANCEPosts: 564
    Not sure if this already posted or not.

    This web site claims to have the solution to increase Fuel mileage by X.

    Simply looking at the figures let me think that it is a scam.
    Moreover, the principle of EGR (Exhaust Gas Recycling) is already known. Would this be so great, I can't believe car manufacturers would have been so dumb as to overlook this.

    Any thoughts ? I did not find any thing about this on the EPA web site.
  • texasestexases Posts: 8,638
    Yep, it's a major scam, I'm dealing with it here, if you're interested:
    Discussion in Hydrogen Fuel Cell Cars
  • steverstever Posts: 52,683
    Device promises to save 60% at the pump (

    Maybe Tex's link is already doing that? I don't follow the hydrogen/hybrid boards.
  • texasestexases Posts: 8,638
    Pretty hard to believe. It takes as much or more energy to do the electrolysis as you get when you burn it, and the car would have to generate that energy, so why would it work? If this did work, we could create perpetual motion machines.
  • steverstever Posts: 52,683
    The part that bugged me was the baseline - why didn't they check the mileage driving around town for a month, then do the dyno, then do the oil change, then do the gizmo, and then do another dyno, another oil change, and another month around town without the gizmo?

    Dyno's have a reputation for tweakability.
  • texasestexases Posts: 8,638
    Yes, same concerns here. Also, they reported '61%' improvement...using their numbers, it's more like 147%!!! But (suspiciously) the web site talks of up to 60%, so you wonder....
  • texasestexases Posts: 8,638
    I just heard back from the reporter. Here's how they did the 'dyno' part of the test:

    "Here's how we did it. We filled up our tank and let the pump shut off automatically. We then put it on the dyno with a starting milage on the odometer of 125,691. We ran it 20 minutes at 55mph and put 21 miles on. We then topped the tank off, and put 2.216 gallons in our tank. Divde 21 by 2.216 and you get 9.4. We then repeated the test a month later. We filled up, and started the dyno at 126,566. We ran the machine for 20 minutes at 55mph. We put twenty miles on. We then filled up again, and put .862 gallons in our tank. Divide 20 by .862 and you get 23.2mpg.
    Now take the difference between the amount of gas that we put into each tank. 2.216 minus .862 equals 1.3. Take the 1.3 and divide it 2.216, which was the original amount of gas we put into the tank. That equals 61-percent."

    So their number is based on less than a gallon used - major potential for error.
  • steverstever Posts: 52,683
    Sounds bogus to me.

    Nice job tracking down the source. I hope you invited him to join in here. :-)
  • shiposhipo Posts: 9,148
    Some of this math is HIGHLY suspect. Many of the problems have already been identified, and here's one more example:

    "We ran it 20 minutes at 55mph and put 21 miles on."

    Ummm, last time I checked, 55 mph was less than a mile per minute, however, they managed more than that. So, either they ran @ 55 longer than 20 minutes (more like 22 minutes 54 seconds), or they ran at a higher speed than 55 (more like 63), or they ran it for less than the 21 miles they reported (more like 18.3).

    As is often said on other web sites, "I call shenanigans." :P

    Best Regards,
  • texasestexases Posts: 8,638
    "I call shenanigans."

    I just have a picture of these guys "helping" this reporter run this test - fiddle with the dyno, fiddle with filling the tank, and then it gets broadcast as 'the truth' :confuse: :sick:
  • shiposhipo Posts: 9,148
    Whad'ya reckon the reporter is getting as a kick back? :confuse:

    Best Regards,
  • nortsr1nortsr1 Posts: 1,060
    "If it's too good to be true.....It is too good to be true"!!!! I feel this way about the above. If it was such a gas saving device and that cheap and easily installable....The manufacturers would have bought up that patent and immediately made that a OEM item in the vehicle.
    I googled it and there were "several" of those same type items for sale by different sources!!!!!!
    Seriously, don't you think GM, Ford, Chrysler, Toyota, BMW or some big company would have grabbed that "gas saving device" immediately????
  • gagricegagrice Pahrump, NevadaPosts: 31,432
    When an automaker will go to great lengths to beat the competitions mileage, you can bet they would be on a device that would change the course of the automotive industry. My belief is a product that is not available in any mainstream outlet, is a scam. I include Amway......
  • nortsr1nortsr1 Posts: 1,060
    Exactly, I wholeheartedly agree. I really don't know anything about Amway, as I have never used any of their products.
  • steverstever Posts: 52,683
    Amsoil will sell you oil and digestive enzymes.

    The enzymes are for you, not your crankcase. :P

    If Exxon/Mobile started selling multivitamins too, I'd start to wonder if they've gone MLM. Maybe they'll come out with a magic pill for the gas tank.
  • gagricegagrice Pahrump, NevadaPosts: 31,432
    I switched from Puritan Pride to Swanson. Not sure who has the best vitamins. I am not into anything sold by a MLM scheme. Too many con artists involved. I am sure there are good products sold by companies like Watkins and Tupperware. I just don't want to get involved in any cult like sales meetings.
  • steverstever Posts: 52,683
    Vitamins 'may shorten your life' (BBC)

    Just like some of the junk you can stick in your engine and ruin it...
  • steverstever Posts: 52,683
    "If BP (BP) could add something to its gasoline that made cars go farther on a gallon, cars would be lining up at the company's pumps.

    If General Motors could make its cars go significantly farther on a gallon simply by putting a device into the fuel line, don't think for a second it wouldn't be doing that. GM's car sales would go through the roof.

    "There are a number of these gas-saving devices that are generally useless," says Champion.

    But drivers who try them will swear they work. In reality, it's probably an automotive placebo effect, says Reed. Buy one of these devices or additives, and you're like to pay extreme attention to your fuel economy and how you drive."

  • shiposhipo Posts: 9,148
    The placebo effect is alive and well, of that I have no doubt. Why? Subconsciously at least, folks have to justify to themselves that their hard earned money was put to good use, and as such, they need some numbers to support the justification,

    Funny thing though, last summer I took our older Dodge Grand Caravan on a 2,000+ mile road trip, and decided to see just how much mileage I could squeeze out of it 3.8 liter mill. Prior to that trip, the best mileage I'd ever gotten in it was 25.9 mpg (although more typical highway mileage is something like 23.5), however, this time I had a straight 800 mile shot on relatively flat roads and I managed an astounding (for that van) 28.2 mpg. Funny thing though, I could have gotten over thirty. How/why? I believe that had I been able to avoid the two international toll booths with long queues, two internal Customs inspections, also with long queues, and one ten mile/one hour long traffic jam I crawled through, my mileage would have been over thirty.

    Now, had I just spent $1.200 on one of these Rube Goldberg devices, I might well have been inclined to claim that it was the device and not my highly altered driving style that had allowed such impressive mileage.

    Best Regards,
  • fezofezo Manahawkin, NJPosts: 10,357
    It is amazing what placebos can do. I happen to be on a really obscure "orphan drug" right now (this is not the way you want to be unique, BTW) and I got to read all through this stuff about it. They list the side effects with the medication vs with a placebo. Some were identical percentages, some looked to actually be related to use of the drug and in some cases those with the placebos were reporting more side effects that those taking the actual medication!

    Strange thing the human mind.
    2013 Mazda 5 Grand Touring, 2010 Toyota Prius IV. 2007 Toyota Camry XLE, 2004 Toyota Camry LE, 1999 Mazda Miata
This discussion has been closed.