Carb Vs. EFI Vs. DFI??

Discussion in 'Bubba's Outboards' started by turtle1173, Jul 19, 2006.

  1. turtle1173

    turtle1173 Member

    Mayfield, KY
    Hi all,

    OK, I know what all the lettering stands for but I'm interested in a simple practical explanation as to what this should mean to me :roll_eyes: I understand how a carbed motor works but my knowledge ends there.

    It doesn't seem like I hear as much about the Direct Fuel injection as I do EFI. Is this something newer? How much better are the latter two than a carbed engine?

  2. Mr.T

    Mr.T Active Member

    I'd rather have a fuel-injected engine than a carbureted engine any day.

    A few of the obvious advantages:
    * The computer is smarter than you are and cold starts are almost *always* easier on an EFI engine than a carbureted engine. The computer knows what the fuel/air mixture needs to be and adjusts things so it's correct.
    * The computer is smarter than you are and there's no need to choke the engine or play games trying to get an EFI engine started. Pump up the fuel bulb till it's firm, turn the key and go fishing.
    * The computer is smarter than you are and will adjust the mixture on the fly to avoid running too rich or too lean. The result? Maximum fuel efficiency.
    * There's no carburetor to get gummed up.
    * Oh - and the computer is smarter than you are.

    As for how a fuel injector works on a 2-stroke engine, that's all black magic as far as I'm concerned - I've tried to study the diagrams, etc. for my 200 hp EFI Merc but it doesn't mesh with what I understand about how a 2-stroke carbureted engine works. Bottom line for me is I don't really care how it works; it works so well that I don't need to know too much more.

    I'm not positive, but I think DFI and EFI are pretty similar, and I'm not sure that DFI engines are still made - Mercury sold "DFI" motors back in the 90's but I don't recall seeing any with that designation lately.

    If there are any advantages to a carburetor over a fuel injected engine, I really don't know what they are.

  3. Bubbakat

    Bubbakat New Member

    I like the fuel injected engine my self.
    We really don't have a carb on an out board they are really fuel metering devices because they don't have a fuel throttle pump.

    That was a very informative post MrT on the fuel system.

    With the injected system there is less danger of some one tinkering with you settings to mess them up. In the old days when they had two settings one low one high most people on the water when having trouble would grab that Ole 39 cent screw driver and go to fiddling with the carb adjustments. If they got to going again they would forget about it and say well I fixed it and in reality it would either be running rich or lean and in turn burn a piston and off to the shop.
    Most times it was under warranty so the company's went to the fixed high speed jet.
    With the injection system you don't have nothing to adjust the computer does it all and if it is programed right it will out think us every time so lot less heavy repair done.
  4. duxsrus

    duxsrus New Member

    SW Ohio
    I found this info regarding DFI on another site:

    Conventional gasoline engines are designed to use an electronic fuel injection system, replacing the traditional mechanical carburetion system. Multi-point injection (MPI), where the fuel is injected through each intake port, is currently one of the most widely used systems. Although MPI provides a drastic improvement in response and combustion quality, it is still limited due to fuel and air mixing prior to entering the cylinder.

    To further increase response time and combustion efficiency, while lowering fuel consumption and increasing output, systems may use direct injection. Gasoline direct injection engines are engineered to inject the gasoline directly into the cylinder in a manner similar to diesel direct injection engines.

    Direct injection is designed to allow greater control and precision, resulting in better fuel economy. This is accomplished by enabling combustion of an ultra-lean mixture under many operating conditions. Direct injection is also designed to allow higher compression ratios, delivering higher performance with lower fuel consumption.

    All new Merc Optimax's and Evinrude E-tec's are DFI.
  5. jim

    jim New Member

    Jacksonville NC
    The clean air act has virtually killed carbs.Most outboard companies now only offer EFI which is the older technology I believe and DFI engines.For the most part I say good riddance and the same for the automotive engines.It is hard to find a carb anymore.90% of the problems I see on here are carb related in older engines and those are exactly what injection/computers eliminate until they break of course.As T says pump the primer bulb,turn the key and go.This is not to say that the new engines can't have problems,because they can,its just you don't have to worry so much with idle adjustments,rebuild kits ,jet sizes etc etc.I think California has mandated all carb 2 strokes be off the water soon.Carb,EFI or DFI remember todays gasolines are crap and you should use stabilizer all the time and some sort of inline filter.:smile2:
  6. turtle1173

    turtle1173 Member

    Mayfield, KY
    Thanks a lot guys! Lots of great information there.