Fuel Injection Conversion
These systems replace a carburetor with a fuel injection system. There are fuel injection conversion kits that make the entire process very easy. Older cars have carburetors, but electronic fuel injection (EFI) offers greater fuel efficiency and improved performance. One of the most difficult parts of the DIY EFI conversion is tuning the chip that runs the EFI.
Tools and Materials
- A wrench
- Injectors
- A laptop
- A conversion kits
- A throttle bodies
- Sensors
- An EFI system
- A wiring harnesses
- Machining tools (option: take it to a machine shop)
Remove the Carburetor
Take off the fuel lines and hoses that come from the carburetor. The carburetor is mounted to the manifold by nuts. Use a wrench to remove these and take the carburetor off. If it is in good shape, it’s possible to sell it as a used part; if not, then it can go to a junk yard.
Install the Throttle Body
The throttle body regulates the air going into the valves. Universal models are the easiest for conversions. Bolt the throttle body on and hook it up at the throttle linkage. This is connected to the accelerator pedal. An idle air controller is needed with the EFI throttle body. This goes into a small passage that pushes extra air past the throttle plates. It opens or closes the passage depending on how much air is needed in the manifold. Most throttle bodies come with an IAC already installed.
Install the Sensors
In order for the EFI system to monitor and change the injection, several measurements need to be taken. If they are not already in place, several sensors need to be installed. An oxygen sensor, manifold air pressure sensor, air temperature sensor, coolant sensor and throttle position sensor are needed. These are easy to install, as most easily screw into the engine. The kit should contain everything you need. If not, there are sensor packages available.
Adjust the Distributer
Because the new EFI system controls the timing and advance of the ignition, these will need to be locked out of the distributor. The vacuum and mechanical advance also need to be locked out. Most distributors will be fine with a bank-to-bank EFI system. If sequential fuel injection is used, then a dual sync distributor needed.
Set up the Electronics
The electronics are of main importance in an EFI system. The easiest way to install one is to get an aftermarket system, because it is very difficult to reprogram a factory control unit. All the necessary components are programmed in and by connecting the computer to a laptop you can customize the different settings. Most of the systems will simply need to be mounted and plugged in using a wiring harness. Once you have tuned everything to the desired performance, the vehicle is all ready to go.
Basic EFI Setup Procedure
The initial setup of an aftermarket self-tuning EFI conversion system is simple thanks to the plug-in handheld device that is provided with the kit. The device allows the EFI controller to be programmed with the basic setup information it requires to operate the system. This includes inputs such as engine displacement, number of cylinders, cam duration, fuel pump type (pulse width modulated with no regulator, pulse width modulated with regulator or non-pulse width modulated with regulator), desired idle RPM and rev limit. Some EFI conversion kits also have the ability to control ignition timing. If used this requires some additional inputs.
Once the engine is fired up with its initial settings, the EFI controller starts to adjust the air/fuel mixture using a closed loop feedback signal from the oxygen sensor. The O2 sensor signal is used for short term and long-term fuel trim adjustments at various engine speeds, loads and throttle positions. This generates a map of what adjustments are needed to maintain the proper air/fuel ratio during various operating conditions, ranging from idle to part throttle to cruise to wide open throttle.
It typically takes a couple of days of driving at various speeds before everything is really dialed in. From that point forward, adaptive learning will continue to fine tune the system as operating conditions change. Additional tweaks can be made on some systems with a laptop if further changes are desired.
However
- For old-school guys, computer controls, oxygen sensors and laptop tuning can be intimidating. If they are used to fiddling with a carburetor and have good carburetor tuning skills, they will usually stick with what they know rather than venture into the unfamiliar territory of EFI. These types of customers may be converted to EFI if they see the advantages EFI provides on somebody else’s engine. The self-tuning EFI kits also reduce the intimidation factor of converting a carburetor to EFI.
- EFI requires installing an oxygen sensor in the exhaust manifold. Most kits include only one wideband O2sensor. The sensor can be installed in either exhaust manifold or header collector on a V8 or V6 engine. This provides less than ideal feedback because the sensor is only reading one side of the engine. Even so, the single O2sensor setup simplifies installation and keeps the cost of the system down. OEM EFI systems always use separate oxygen sensors for each cylinder bank because it provides more precise fuel control.
Installing the oxygen sensor requires drilling a hole in the exhaust manifold or header collector and welding or clamping a bung on the hole so the sensor can be screwed into the fitting. The sensor should be positioned with an upward slant (10 degrees or more) so exhaust moisture will drain back into the pipe when the engine is shut off.
The basic idea is to position the O2 sensor, so it reads the exhaust from all the cylinders on that side of the engine. It will not work with individual “zoomie” style headers because the sensor would only read one cylinder.
Another requirement is that there must be some exhaust tubing beyond the exhaust manifold or header collector to prevent reversionary airflow between cylinder pulses from misleading the sensor. If air flows backwards into the collector where the O2 sensor is located, it can produce erratic or inaccurate readings that will upset the air/fuel mixture. Also, any air leaks (even small ones) at the exhaust manifold or header flange gasket or in the manifold tubing can mislead the sensor and upset the air/fuel mixture.
- EFI requires installing an electric fuel pump, a simple, in-line, high pressure electric pump or an in-tank pump. Most EFI systems require a pump that can deliver 45 to 70 PSI. A low-pressure electric pump that is designed for a carburetor will not work.
In-tank pumps run cooler and quieter than in-line pumps and are better protected from road hazards. But an in-tank pump is more of a pain to install in a vehicle that does not have an in-tank pump, and it makes pump replacement and service more difficult if the pump needs to be replaced later. Return-less EFI systems have the fuel pressure regulator in the tank as part of the pump module assembly. This eliminates the need to install a separate return line to route fuel back to the tank from an external pressure regulator. However, if a customer is installing a return style EFI system, a return line is required.
- EFI costs more than a carburetor. You can buy a carburetor for $400 to $1,500 depending on the size, style and modifications that have been made to the carburetor. A single throttle body EFI conversion kit, by comparison, will set you back $2,000 to $2,500, and a port EFI kit can cost upwards of $3,000 or more depending on the capabilities of the kit and what type of injectors, fuel pump and electronic controls are included.
- All EFI conversion kits require an ignition input signal to monitor engine RPM and to trigger injector pulses whether the EFI system controls ignition timing or not. Most kits will work with a GM HEI, Ford TFI, or other electronic distributor. If an engine has a mechanical contact point distributor, it will have to be converted to an electronic distributor. Some professional multi-port EFI systems use a crank position sensor for a trigger signal.
Finally
This type of setup is not for everyone, but for those who want something “different” it offers yet another powertrain option for repowering a street rod, resto rod, vintage muscle car or classic car. Each year the EFI systems become easier to install and operate as technology continues to improve these systems with EFI conversion.
