By
Jennifer Szabo July 31, 2018Many racers have considered using mechanical fuel injection on their cars only to wonder what they should do and how to get started. If you are one of those people, you’ve come to the right place! If you haven’t already read our first article, you should:
What You Need To Know About Mechanical Fuel Injection.Continuous-flow, mechanical fuel injection has many benefits. It is relatively simple to set up with few parts requiring regular maintenance. Those parts are readily available world-wide from multiple suppliers. The different designs and layouts make the engine stand out in the car, as it is the most visible part of a racing engine. Multiple fuel lines, stacks, and large air inlets provide the appearance of stunning power levels. Let’s take a look at the different features and attributes of the different styles of mechanical fuel injection.
A current stack-type fuel injection setup on a Ford Flathead V8 racing engine. This configuration is based on setups developed in the late 1940s. This one runs a heavy dose of Nitro in the popular NHRA Heritage series for nostalgia drag racing.
Early mechanical fuel injection started out with a velocity stack-type configuration. It features one fuel injection nozzle and one throttle bore per cylinder. Common in drag, circle track, top speed, and other forms of racing, it often represents the ultimate image in power production from a naturally aspirated racing engine. Stack-type fuel injection is considered to be the standard in appearance by many.
Tuning
The fuel system tuning in a well-developed fuel injection setup like this involves simply changing a main bypass jet and/or a high-speed poppet pressure setting for variations in air density.For idle-to-full-throttle drag racing, the fuel mixture is simple to control with jetting for maximum power. For circle track racing, where the throttle is modulated–such as in tight turns around quarter-mile ovals–the low end can be set up with a secondary bypass circuit to provide a surge of fuel coming out of the turns for good response.Stack systems require adjustment of individual throttle plates, which may vary in seating at idle position with engine heat expansion, and that can strain the manifold. Some of the Kinsler stack-type setups go to great lengths to segregate manifold sections and throttle shafts to minimize this problem.
Drivability
The stack type is reported to provide the quickest e.t.’s over other fuel system alternatives in short course, tight dirt track or pavement circle track racing. Stack-type fuel injection is not considered very streetable however, since there is no fuel modulation with engine load. Although, with an automatic transmission and a high-stall torque converter, some setups work on the street. Stack-type fuel injection setups often appear in car shows such as Autorama and Goodguys events.Alcohol is the most common fuel used with this and other mechanical fuel injection setups. Gasoline is used by some, but it is a bit harder to tune. It is more susceptible to spark plug fouling, and as a result, it is not as popular, however E85 works well with mechanical fuel injection. Nitroromethane and methanol, in just about any ratio, can be made to fly with mechanical fuel injection.
Regulations
In drag racing, mechanical fuel injection is common in several drag racing nostalgia and bracket ET classes, and it is the standard in Pro Mod, Top Alcohol, and Top Fuel eliminators. In circle track racing, the stack type is common in most of the 305, 360, and 410 cubic-inch engine classes throughout the world, and is common in outlaw classes with oversize engines as well. It is also a frequent choice in drag, circle, and sprint boat racing.
Cost
New systems cost between $5,000 and $8,000, which is a bit more costly than a simple throttle body fuel injection setup or stock-type carb and manifold. However, it is a more-developed standard for quite a few racing classes. Many suppliers maintain inventory of low-cost used parts for sale for this combination to help with costs, along with their inventory of new parts.
This is a Rons Terminator-series system on a well-developed, single plane V8 intake manifold. You can see the simple barrel valve, fuel lines, and nozzles feeding each cylinder. Individual nozzles eliminate cylinder-to-cylinder fuel distribution variation such as in a carburetor alternative or throttle body EFI.
Throttle body fuel injection is a standard worldwide in many racing classes such as bracket drag racing. Both single throttle body and dual throttle body setups are common and have a very functional appearance, similar to that of singe and dual four-barrel carburetors.
Tuning
Tuning is a matter of matching jetting to the size of the engine. Throttle bodies such as the
Rons Terminators and T2’s with their rigid throttle assemblies remote from the engine, are probably easier to set the idle for than the stack-type fuel injection setups with multiple throttle plates.For high performance sports boating, this type of injection is often chosen instead of the larger-bore stack-type MFI. The latter may require more transition fuel circuit tuning against the load of a propeller in the water during prop recovery with RPM and speed, to get up on plane.
Drivability
This is not recommended for street use for all the same reasons as stack-type mechanical fuel injection. However, with a simple throttle body, it may be more streetable for those quick trips to and from motorsports events and car shows, where the engine is run mostly at idle or low speeds. A high stall-speed torque converter makes a setup more forgiving on the street.This type provides high power output, especially when combined with a well-developed manifold such as modern single- or dual-plane intake manifolds common with modern V8s.
Racing regulations
Throttle body setups are common in many drag racing, top-speed events, and boat racing classes where fuel injection is specified or allowed.
Cost
This type of fuel injection offers the lowest cost of any mechanical fuel injection alternative; a quality system is in the $2,000 range for a completely new system plus the cost of the manifold.
This low-cost dragster was put together in the ’90s by Bill Rutledge and Richard Buzdas. It ran Hilborn 4-port fuel injection on a stock 6-71 Roots blower. It was assembled to run the 7.90-second bracket drag racing class that was most popular at the time. The team had less than $10,000 in the whole setup built from mostly used parts. This car ran effortless 7.6 second e.t.’s during one of its early outings and remained there from then on.