 |
 |
| The folks at MSD recently tested a mule engine on Westech’s Dyno in California. Take a close look. What follows is a pretty basic introduction to electronic fuel injection hardware. The engine in question was a 402 cubic LS-series small block, complete with Dart Pro One cylinder heads, a FAST-Wilson intake manifold, a 90-millimeter MSD throttle body and a complete MSD Blaster fuel injection system (amongst other hardware). By the way, the end result proves incredibly interesting, particularly from a drag racer’s perspective (as you’ll see here, and in the next issue of Drag Racing Online). | |
Over the years, Kinsler has sorted out this dilemma by pressurizing the pump inlet line so the fuel can't boil. When the system is sorted out, Kinsler claims a constant flow system can be precisely tailored to any fuel curve, even with bumps and dips in it, using special metering hardware that is currently available.
The Next Step: Timed Mechanical Fuel Injection...
Almost fifty years ago, both Bosch and Lucas released timed fuel injection equipment. Since they were both timed, they allowed the racer to inject fuel in a more precise manner. For endurance racing events, this meant potentially superior fuel economy. Kinsler notes that these systems also meter the fuel well during engine starting, which prevents washing the cylinder down. The nozzles are of a valve and seat design, so there is no dripping of fuel into the engine on shutdown even without a fuel shut off valve. The throttle response is very crisp, as you get the new fuel rate within one revolution of the engine after moving the throttle pedal. According to Kinsler, the output of the pump is not a basic part of the metering system, so if the pump were to cavitate by a margin of something like 10%, it would have no effect on the mixture at all. Because of these inherent features, timed fuel injection system became very popular for road race applications.
Were the Lucas and Bosch systems without faults? The experts agree that a drawback of both the Lucas and Bosch timed fuel injections units is the fuel curve. In order to obtain more than a simple straight-line fuel curve, you have to make a complex three dimensional fuel cam. Kinsler states that even today, an engine equipped with a Lucas mechanical system with the simple straight-line fuel curve is relatively competitive. Why? Kinsler points out that because the internal combustion engine is so forgiving, it produces almost full power from approximately three percent lean to approximately six percent rich. Because of this the engine can, more or less function properly with a linear fuel curve.
Early Electronics...
Toward the end of the sixties, a number of automobile manufacturers began to take a long hard look at electronic fuel injection (EFI) systems with an eye toward the superior fuel economy, vehicle driveability and lowered emissions those systems offered. As you can well imagine, the R&D process was tedious, since the manufacturers had to start with a clean sheet of paper. Items we take for granted today such as good quality, low cost fuel nozzles and reliable, small electronic hardware didn't exist. Eventually, this was overcome, with Volkswagen being one of the first to offer a simple Bosch EFI package as early as 1967.
Kinsler techs point out that perhaps the most intriguing aspect about EFI is the fact one can look at as many inputs as necessary for relatively little money. Why? With any mechanical device such as a carburetor or an early mechanical fuel injection system, the gathering of input is cumbersome. The more input data you gather, the more complicated and costly the system becomes. That isn't really the case with electronics. Typically, most mechanical injection assemblies will rely upon throttle angle or intake vacuum combined with engine speed for input parameters. In contrast, an EFI system can sense air, water, oil, and fuel temperature, barometer, rate of throttle opening and so on. Given the computing capability of an EFI system, it becomes easy to have complex maps of fuel mixture versus rpm for various throttle angles, acceleration enrichment and controlled enrichment from cold starting to hot running.
By the time the seventies rolled around EFI systems started to show up on an ever-increasing number of passenger cars. The transition for most vehicle manufacturers wasn't easy since an EFI system was still very costly when compared to a carburetor. A couple of the injection nozzles cost as much as an entire carburetor. In the case of a V8 engine, there could be as many as eight nozzles, a complex fuel rail arrangement, a number of expensive sensors, a complicated wiring harness and of course, the electronic control unit (ECU). So why make the switch to the EFI? It was a combination of political pressure due to fleet economy and emission requirements, startability and driveability (not to mention a positive marketing image). The overall consensus in Detroit was that volume use and further research would in turn lower the costs.
Less than two decades ago, the first race-oriented ECU's or "black boxes" made their debut. At first, they proved difficult to program. They were also expensive. Various sports car race teams tinkered with the new EFI systems and in Formula Vee, the complete series ran with it on an exclusive basis. Kinsler notes that much of this equipment was supplied first by Bosch, but other companies soon followed suit.