Auto Extreme

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Author: Mike Ancas

Do you want crank you car’s performance level up a notch? Many experts today feel that the only way to go is with aftermarket programmable fuel injection, but there are also folks who feel that computers are for the office, not for racing. That real cars have a heart, and that heart is made of metal, not circuits. It’s the old argument: what’s better, carburetion or fuel injection?

One common viewpoint is: “fuel injected cars start easier, idle consistently, and you can easily control the fuel mixture to optimize performance.” A counterpoint endorses a more classic view of the automobile: “carbs are what gives a car it’s personality. They’re a simpler concept reminiscent of simpler times. You feel more connected to the car because you get more hand’s on involvement”. You can hear discussions similar to this one in garages all over the country, and the participants often become passionate about their views. But before we start duking it out, we thought it it would be a good idea to take a long hard look at the pros and cons of both systems.

POINT: Traditional Power by Mike Ancas

For the conversion to dual carburetors, we knew that we had to do everything just right in order to be competitive with aftermarket fuel injection. Most readers are familiar with the problems that can be encountered when dealing with hi-performance carburetion, but this poor reputation dates back to a time when carbs were generally unreliable and difficult to adjust properly.

There is a new generation of carbs that are much more user friendly and can always be set up quicker and easier than installing an aftermarket EFI system. TWM, one of the leaders in intake technology, sent us the latest in manifolds and linkage to take full advantage of the dual carb set-up. We turned to Advanced Engine Management in Gardena, California for our carburetors since they are the largest West Coast distributor of Weber and Mikuni. Steve Trinkaus at AEM knows both carbs and aftermarket fuel injection systems, and can assist with any intake or ignition need. AEM can also rebuild old carbs for around $125 each. We chose to go with Mikunis over Webers because they are externally adjustable, and Webers are not.
The next step was to deliver a consistent fuel flow of at least 3 psi to the carbs. That meant getting rid of the stock fuel pump. A new electric fuel pump was installed next to the fuel tank in the rear of the vehicle, and an inexpensive Purolator fuel pressure regulator was installed along the fuel line just before the carbs. Once the above steps were completed, all that was necessary was to remove the old manifold, carb and pollution control equipment. This turned out to be the most time consuming part of the project (took about an hour). Then the new manifold, carbs and linkage were secured into place - done. Everything just bolts right on. We chose to match all of the ports, both on the head side as well as the carb side, to further optimize intake flow. At this point in the conversion, we knew we would be way ahead of the aftermarket EFI project as far as ease of installation and time commitment.

COUNTERPOINT: Electronic fuel injection by Dennis Witt

Technology has a subtle way of changing our daily lives. The amazing advances in micro chip development has revolutionized the century old process of mixing a fuel and air mixture in the modern automobile engine. In a very short time span, the manner in which competitors have attempted to maximize horsepower and torque curves has been dramatically altered by the combination of computer power and fuel injection.

Historically, the fuel injected cars were a rarity, primarily due to the cost of the system and its mechanical complexity. Today what was once impossible is now feasible at a very reasonable cost in both time and money.

There are aftermarket systems available now which allow for the conversion of the old and outdated carburettored vehicles to take advantage of the powerful new electronically controlled fuel injection systems. Our comparison should validate the theory that a carburetor conversion “sucks” when compared to an electronic fuel delivery system that “injects”.

The heart of our fuel injected system is comprised of an intake manifold and throttle bodies supplied by TWM, who manufacture components that are compatible with both carb and EFI systems. Injectors and technical advice were provided by RC Engineering, who has just about any size injector in stock and can tailor a “wet” system for any vehicle.

The brains of our conversion was handled by a compact computer developed by Racetech. We quickly discovered that the name “Simple Digital Systems” says it all. No more having to rely on a laptop to set individual air/fuel parameters. The SDS computer is small, self-contained unit that can be programmed with ease. To summarize: Hardware = TWM; Wet system = RC Engineering; Electrical = SDS. We found, however, that with EFI systems: you get what you pay for. The SDS system is inexpensive, and it works, but not as well as a Motec or Electromotive.

Now a bit of advice for anyone attempting an EFI conversion: start with a fuel injected car! Converting a car that was not initially designed for fuel injection is a difficult process. Carbs only need 3-4 pounds of pressure, however it takes 40 to 50 pounds to run fuel injectors. If you start with a carburetored car, you will find that none of the existing fuel lines or hoses are capable of handling these higher pressures. So the first modification you face is how to get the fuel from the gas tank to the injectors without causing your fuel lines to burst. The solution requires the installation of a larger diameter stainless steel fuel line from the tank to the engine compartment (a difficult and dirty task). That having been accomplished, if you haven’t taken a sledge hammer to the car in frustration yet and still want to move on, you will now need a get high pressure fuel pump to keep the hungry injectors happy. We chose a pump manufactured by N.O.S and distributed by RC Engineering. This pump puts out over 100 lbs. of pressure at the outlet. Next, AN fittings need to be attached to the fuel pump and plumbed into a new stainless steel line. Not using the highest quality components could result in a rupture of raw gas spraying over both electrical and hot engine parts, resulting in a fuel fed fire rendering all of your hard work into a glob of melted metal and rubber.

We chose a 3/8” diameter steel line to handle the additional fuel flow, connected to a high pressure fuel filter to insure that no contaminants clog the expensive system. The stainless steel line conversion was one of the most difficult parts of the project.

Another frustration we faced was that the individual parts used to install an aftermarket EFI system come from different manufactures, hence the project is not an “insert part A in tab B” process. A significant amount of time was expended trying to figure out how the entire system would be tied together. If your header is not fitted to contain an oxygen sensor, then a hole must be drilled so that a 22 mm nut can be welded in position. Your EFI system won’t know what to do unless it get feedback from an oxygen sensor.

Additional problems encountered were that the Lucas injectors we wanted to use were not compatible with the SDS system, and there was a grounding problem that occurred when a wire inside the throttle position sensor was broken. When you choose which EFI system to use, make sure that you provide all necessary information to the injector supplier.

The moral of the story is that there are many things that can and will go wrong when you tackle a conversion like this. If you mentally prepare yourself to face these problems before you start, it could help preserve you sanity.

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