Can anybody explain how these E85 conversion kits work?

Discussion in 'General Electronics Chat' started by smp375, Mar 21, 2009.

  1. smp375

    Thread Starter Member

    Mar 21, 2009
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    I see these E85 conversion kits all over the internet which use a pot to increase the duty cycle of the fuel injectors by approximately 30% to counter the lower potential energy of ethanol as a motor fuel. The basic premise is that the electronic control unit on the cars are more capable of -remapping than they are +remapping, so with the unit installed after about a hundred miles the ECU creates a macro allowing the vehicle to then run on gasoline or E85 without sacrificing the stochiometric air/fuel ratio of 14.5:1. The fuel injectors are basically on a PWM circuit with the frequency varied as necessary, the conversion kit simply increases the PWM frequency across the board. Can anybody explain the circuit for me?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    282
    I don't see a circuit to explain.

    My understanding is that there are a number of critical seals in the fuel system that have problems with high concentrations of alcohol. I would want to identify and replace those seals before even trying to mess with that kit.

    As further insurance, I would want to find some disinterested party to install and evaluate the conversion before trying it myself. Some outfit like Consumer Reports or even one of the car magazines.

    Locally, E85 is about $.10/gallon less than unleaded. With the lower mileage it delivers, that means it is quite a bit more expensive to try to run on the E85 blend. I don't see any savings.
     
  3. smp375

    Thread Starter Member

    Mar 21, 2009
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    0
    First, the statement that critical seals in fuel systems fail due to ethanol use is a myth. Fuel systems have very few seals to begin with, all of which are simple o-rings, and for over 20 years they have been made with neoprene, which is not damaged by ethanol. Second, There is already one conversion kit that is approved by the EPA, and many others on their way to being approved; I would consider the EPA a "disinterested party." Third, I have already been using ethanol in my car at 50% for several thousand miles, and have only seen a 4.5% drop in city fuel economy, no loss in highway economy, and no "critical seals" have failed; plus my oil lasts longer. E85 is 105 octane, and therefore should only be compared to premium unleaded; also my car benefits greatly from the higher octane E85 delivers, as do many other high performance vehicles. Locally, premium unleaded is $2.23 while E85 is $1.67, so for me it is cost effective to use ethanol. Also, the fuel economy loss with ethanol depends greatly on the engine management system of the vehicle it is used in. While some vehicles suffer a 20-30% drop, many others only suffer a 2-8% loss. These numbers do not reflect poorly on the fuel, they reflect poorly on the auto manufacturer. Ethanol has significantly lower emissions and drastically lowers combustion temperatures, which will increase the life of the engine, oxygen sensors, and catalytic converters; these are things very few people consider when thinking about the cost of using ethanol. Lastly, when I buy ethanol, because it is produced here in Wisconsin, the majority of the money I spend benefits people and families locally, which is very important to me, and another cost factor that is rarely considered. Personally, I just want to know what these people are doing to alter the duty cycle because I'm convinced its smart guys like you that are building units for $25 and selling them for $350; and I'm jealous. I have no intention of building or purchasing any of these units, I simply want to know how they work to satisfy my curiosity; when I'm ready to convert I will simply have my computer reprogrammed, which is cheaper and the better way to go.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    The schematics and other details don't seem to be readily available. You may choose to accept their word for it, or not.

    It's clear that it will require a wider pulse to the injector to put more fuel into the cylinder to compensate for the lower energy content of E85. They do seem to have some ability to to do.

    I might wonder if a kit that does not monitor the ECU sensors can do an accurate job under all conditions. The increased pulse could turn out to be a bit like running a carburetor with the choke pulled on to richen the mixture. If it can't adapt to operating requirements, it's going to be wasteful of fuel.

    Altering the control parameters in the ECU would seem to be much more satisfactory.
     
  5. smp375

    Thread Starter Member

    Mar 21, 2009
    14
    0
    No, there's very little information about them available; presumably to avoid saturating the market. The thing that is interesting about these units is that they do not modify any sensor signals to the ECU, allowing the ECU to maintain full control over the engine, even the increased duty cycle on the injectors. What I know about ECU's is that they are able to adapt to the new settings the conversion kits create by remapping itself to accommodate the new condition. As far as the ECU is concerned, the oxygen sensor tells the ECU what's going on, and once the conversion kit is installed with gasoline in the system, the oxygen sensor reads a rich condition which the ECU adjusts for. However, the conversion kit creates a situation that is now outside of the ECU's parameters, so it simply writes itself a macro, saves it in it's memory and uses that macro to correct the rich condition. Once the ethanol is added to the system, the computer no longer needs to use the macro so it reverts back to it's original parameters until it needs to call the macro back into play. My Saab has a pretty advanced ECU that adjusts for a great deal of conditions that most other systems wouldn't be able to handle; if you're interested in learning more detail about how this all happens google "saab trionic" and somewhere in the results you'll find a tutorial on exactly how the system functions.

    EDIT: I agree that it's much better to alter the ECU parameters, that's why I choose that option for myself. However, for many vehicles that's not an easy task; and for some people that's a frightening endeavor. The thing people like about the conversion kits is that they are somewhat universal, so they can be transferred to another vehicle; and they can be removed allowing the ECU to return to it's basic parameters.
     
    Last edited: Mar 21, 2009
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