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Carb vs EFI

Discussion in 'Technical and Troubleshooting Torque' started by davidp1984, Aug 17, 2009.

  1. I apologise if this has been asked before but I did more then 1 search and couldn't find anything.

    Basically, can anyone shed some light on the pros and cons of each.

  2. Carburetors are relatively easy to tune by varying the size of the main jets, for example, and when tuned well they provide good performance and fuel economy.

    The drawbacks of carburetors are that they are unable to recognize and accomodate changes in atmospheric air pressure. For example, a carburetor tuned properly for operation at sea level along the coast won't perform very well in the mountains. The higher the altitude, the lower the ambient air pressure, the fewer molecules of air per cubic foot. But the carburetor only knows how many cubic feet of air flows through it. Consequently, the sea-level-tuned carb delivers too much fuel for the amount of air pulled through it in the mountains, meaning the engine will run too rich.

    Emissions controls are much more complicated and difficult with a carburetor.

    Efi delivers more power and lower emissions. Efi is simpler, requires fewer components, and as such is more reliable and durable. Efi is completely controlled by computers and can be adjusted to provide exactly the correct amount of fuel to each cylinder in virtually every conceivable situation. E10 is fine to run in an efi engine, but not a carburetorred engine for this reason.

    The downside is the days of home tuning are over.
  3. The major advantage of EFI over carbs is that it needs less tuning and balancing. As a bike grows older, the carbs become unbalanced. As the air filter clogs up, less air flows in and the carbs run rich. All this means maintenance.

    Carbs also tend to clog up with evaporated fuel residues from their float bowls. Carb needles are also sensitive to small particulate matter in the fuel. Whereas fuel injection lines are under pressure and less likely to clog up.

    Fuel injected vehicles often can compensate for temperature, making cold starting much easier.

    As kowls mentioned, fuel injection can compensate for atmospheric pressure/oxygen levels.

    In the real world, it gives more power, better fuel economy and lower maintenance.
  4. There are certainly ways of making carburettors respond to atmospheric pressure, though I don't know if they were ever employed on a motorcycle.

    Is your question theoretical, or are you wanting the information to help choose a bike?
  5. +1, nowadays EFI is also significantly better tuned then in old EFI systems, as well, less "snatching" when coming off closed throttle, near infinitely adjustable tuning, better efficiency. Downsides are proprietary software systems used, and more expensive equipment required to reprogram stock ECMs.

    Home tuning is still alive though, you just need to use something like MegaSquirt! (No, it's not a porno.)
  6. Carbied engines also sound different for some reason?
  7. A little bit of both.

    Thanks everyone for the very good info.

    I basically took from it that if given the choice of an exact model bike with a difference of only carb or efi majority of people will go for efi. Right?
  8. New or near new bike yes.

    for older bikes it's not quite as clear. Bike EFI has only gotten good in recent years. So the performance advantage isn't that great on older bikes.

    The guys above are right in that carbies can become troublesome with a few years on them (12-15), but temper that against the cost of an efi system that becomes troublesome.

    If you've got a problem with an EFI bike in either fueling or ignition, it becomes a multi-hundred dollar guessing game at least.

    Mine for example is running a tiny bit rich at the moment. I'm hoping it just needs a new air filter. If that doesn't work, then who knows what's next. The tuneboy alone is about $600, to look at the software.

    $600 gets you a fair amount of carbie work.
  9. The BMW EFI they were doing on the K models in 1983 was and still is very good.