My car has a carburetor which I want to change to an EFI. I want to know what are the possible challenges in doing so, what I can think of are:

  1. Finding a match of an EFI which seamlessly replaces the carburetor
  2. Fixing it professionally, like maybe its not a DIY

what else?

PS: I am mainly doing this for fuel efficiency.

  • what car do you have?
    – Shobin P
    Commented Jun 16, 2015 at 10:51

3 Answers 3


Depending on the application, there are lots of options for changing over to EFI from carburetor. Your best bet, especially if you're not a professional, is to find a system which is plug-n-play. Trying to find one which is compatible by retrofitting it from another vehicle would not only prove difficult, but would be very frustrating when it comes time to tune the system.

My suggestion is to look at systems such as ones by FAST or Holley (there are others available). The reason for these has to do with self tuning. All you do is install the unit, plumb the fuel, update the fuel pump, apply power, add in the sensors, put in your engine parameters, and the unit will self evaluate and update as needed for optimal performance/fuel economy.

With all this said, you probably won't see a huge improvement in fuel economy. What you will see improvement in is driveability. The engine will run smoother in most every running situation (as long as everything is installed correctly).

  • You changed the whole point of the question, even if every thing is installed correctly I still wont see fuel economy? why are EFI cars more efficient then?
    – shabby
    Commented Jun 16, 2015 at 11:00
  • 6
    I didn't say you wouldn't see an improvement in economy. I'm simply trying to temper your expectations as to how much of an improvement that might be. You will see an improvement in fuel economy, but overall, it won't be that much (you may pick up say 3-5% improvement, but not something like 15-20% - those are just numbers I'm throwing out there). As stated, the main thing you'll gain is how well the engine will run in all conditions. Start up in cold weather, especially. Commented Jun 16, 2015 at 11:17

Converting Carb to EFI is possible , it can be a DIY if you know what you are doing. You can start by looking for the below basic things to get a rough idea of the work you are going to do.

  • Fuel Injectors
  • Throttle Body
  • An ECU
  • All of the sensors(MAP,O2 etc)
  • New Ignition system(Recommended not mandatory)
  • Fuel Pump
  • Fuel Pressure regulator
  • A whole lot of electical wiring.
  • Finally "TUNING"

Doing it for the Fuel Economy is not a good idea since a professional conversion including labour would cost you around $1500 to $2000 that money can be spent on the fuel itself and prevent fiddling with the engine and not messing it up.

Basically its not a good ROI(Return on Investment) if you want to install a EFI in your Carb vehicle unless you do a lot of hill climbing or need performance.

  • with due respect, with you point considering the ROI, i would never buy a hybrid as well
    – shabby
    Commented Jun 16, 2015 at 11:07
  • Well , I have a carburated vechicle myself and newer versions of the same vehicles which are fuel inject give 10%extra fuel economy compared to mine which is the same except carburettor but the newer models cost 22% More. So While new cars are very efficient , only fuel injection does not determine the efficiency , the type of engine, the power , the driving , all these determine the efficiency. Simply installing a EFI on a 6.8liter V8 wont make it efficient.
    – Shobin P
    Commented Jun 16, 2015 at 11:10
  • @shabby Well, yeah, hybrids are typically a bad value proposition too. They're currently more status symbols. :-) Commented Jun 16, 2015 at 14:32
  • 1
    "not a good idea" is a personal opinion. If he wants to save fuel to do his part to reduce demand for fossil fuels then it IS a good idea. The ROI is a valid argument since it comes from a particular (financial) perspective.
    – CramerTV
    Commented Jun 16, 2015 at 20:05

Depending on the make/model/engine, you might be able to find a newer version of the engine that already had EFI installed. If this is the case, you can search local junkyards and ebay to find a wiring harness, ECU, sensors, intake and exhaust manifolds.

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