Kinsler_Handbook_#32 December 2017

Kinsler Fuel Injection, Inc, 1834 THUNDERBIRD TROY, MICHIGAN 48084 U.S.A. Phone (248) 362-1145 Fax (248) 362-1032 72 A BRIEF HISTORY OF FUEL INJECTION CARBS TO CONSTANT FLOW, TO LUCAS MECHANICAL, AND FINALLY ELECTRONIC ON TO ELECTRONIC In the late sixties various auto companies started serious electronic fuel injection (EFI) programs for better economy, driveability, and emissions. What needed to be done was obvious, but the progress was slow because of the difficulty of developing good low cost injectors and electronic bits. The exciting thing about using electronics is that you can look at as many inputs as you want to for very little money. Why? With any mechanical device, either carbs or injection, it is quite cumbersome and expensive to sum more than a few inputs. With electronics it is easy and cheap to sum as many as you want. So while only throttle angle or intake vacuum combined with engine speed had been used in most mechanical systems, now you could sense air, water, oil, and fuel temperature, barometer, rate of throttle opening, etc. With computing ability, it became easy to have complex maps of fuel mixture vs. RPM for various throttle angles, acceleration enrichment, controlled enrichment from cold starting to hot running, etc. Bosch was the clear leader in the early EFI work, introducing the system on the 1967 Volkswagen. A drawback of both the Lucas and Bosch is that to get more than a simple straight line fuel curve you have to make a complex three dimensional fuel cam. Even today, an engine with a Lucas or Bosch mechanical system with the simple straight line fuel curve runs quite well, because the internal com- bustion engine is so beautifully forgiving... it puts out almost full power from about three percent lean to about six percent rich. CARBS TO CONSTANT FLOW Back in the fifties it was either carbs or constant flow fuel injection. The basic cost for an out of the box carb was quite cheap compared to injection. However, to get the mixture distribution right with the carb took a pretty smart person a lot of time, as both the air distribution and the fuel distribution were tough to get right, and they changed with engine RPM and load. A really good running set of carbs would wind up costing a lot more than the injection, and even then carbs did poorly with combinations of both straightaway acceleration and cornering as the floats and bowls hadn’t been developed far enough. Even today’s carbs don’t handle boating through rough waters well, as it’s impossible to meter the fuel if it’s bouncing off the top of the float bowl. Don’t get us wrong - we’re not knocking carbs, as tens of millions of them have done an admirable job for many years when used on the application they were designed for. If you bought a good set of individual runner injection, the air distribu- tion was just about perfect right out of the box, since all of the runners were cast the same and had a radiused bell at each entrance. If your unit had a properly matched set of nozzles the fuel distribution had to be good, since there was one nozzle in each runner. Other advantages of the injection was that you could change the fuel mixture quickly by just changing one jet (even from the dashboard while driving), and you could run alcohol and nitro. There were no carbs at the time that did a good job with these fuels. LUCAS MECHANICAL In the early sixties both Lucas and Bosch mechanical timed injection became popular because of several nice features because they use the stroke of a piston to precisely meter the fuel. The fact that they are timed allows you to inject the fuel at just the right instant to avoid letting any go through during valve overlap, thus giving better potential fuel economy. These systems also meter the fuel well during engine starting and idle which prevents washing off the upper cylinder lube. The nozzles are of a valve-and-seat design, so there is no dripping of the 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 two revolutions of the engine after moving the throttle pedal. Finally, the out- put of the pump is not a basic part of the metering system, so if the pump were to cavitate say 10%, it would have no effect on the mixture at all. All of these features make this system very popular for road race cars. Most of the early injection was of the constant flow design, which to this day is the most rugged and dependable system. The basic fuel metering is done by sensing throttle angle and engine speed. The throttle rotates a spool with a tapered ramp inside a metering block; it has a samll opening to the nozzles at an idle, which gets larger as the throttles are opened. Engine speed is sensed by using a positive displacement pump driven by the engine, so when the engine speed doubles, the output of the pump doubles. This system has always worked well for drag racing, where the fuel can easily be kept cool. In round track or road racing, the fuel gets hotter the longer you run, both from the track heat and the warm fuel returning to the tank. Because the light ends in gasoline boil at about room temperature, or even lower if you have any vacuum at the inlet of the pump caused by a restriction in the inlet line from the tank, the fuel pump doesn’t draw in all the fuel it should, which causes a lean condi- tion. The car will run just fine early in the race, but after a while it gets “lazy”.... the power and reaponse fall off and you may even burn a piston. The solution is to pressurize the pump inlet line so the fuel can’t boil. Our vapor separator tank is the heart of an excellent off-the- shelf system that can take care of this. A nice feature of the constant flow system is that you can tailor bumps and dips into the fuel curve using special metering pieces that we have available. While alcohol doesn’t boil as easily as gasoline, it still requires a carefully plumbed inlet line to the pump to prevent lean-out. 1963 Maserati Mistral Lucas me- chanical fuel metering system Walt Kolodziej’s ‘Blue Meanie’ small block Chev with Kinsler injection © 2017