injector cranking primer enrichment evom

All modern EFI systems also have one or more knock sensors, microphone-like devices that are tuned to detect a range of frequencies typical of the sound of abnormal combustion ignition timing is generally retarded in response to such a signal, even though such a signal might be 'false' (such as when different internal engine components alter the sound characteristics of the engine, or external parts like exhaust systems physically rub against the vehicle's chassis). The Coolant Temperature Sensor (CTS), as you may guess from its name, gives a voltage to the ECM that varies with coolant temperature low temperature readings will cause the ECM to take actions such as entering cold-start enrichment mode, while high readings might cause the ECM to activate cooling fan(s) or retard ignition timing to avoid detonation. Other Sensors: Various other sensors exist on EFI systems that do not have to do with measurement of the intake or exhaust stream, but have important functions nonetheless. So-called wideband O2 sensors are now used on some newer EFI systems these can detect a much wider range of AFRs including those present under wide open throttle. Most factory O2 sensors are of the 'narrowband' variety that can only indicate AFRs close to stoichiometric (14.7:1) and therefore have no use for anything beyond part-throttle driving conditions. These sensors enable 'closed loop' feedback control capability where the EFI system can make slight adjustments to fuel delivery to dial in AFRs as close as possible to those desired. Too much oxygen indicates a leaner-than-stoichiometric condition, while too little oxygen indicates a richer-than-stoichiometric condition. Also known as lambda sensors, they output a voltage (typically 0-1 V) that varies with the oxygen content of the exhaust, which is an indication of the air-fuel ratio (AFR) of recent combustion events. Oxygen (O2) Sensors: With most other sensors located in or about the intake tract, these are typically the only sensors located in the exhaust stream. Also, we're largely ignoring small details like Idle Air Control (IAC) valves and like tangential equipment that has come and gone as EFI has evolved, though some may be mentioned where they happen to come up. Still, it's worth noting that while spark plugs still ignite the mixture in the cylinder, distributors and the snake's mess of spark plug wires have become a thing of the past as computer-controlled individual coils now send the energy to the plugs. The reader's basic knowledge of the four-cycle spark-ignition engine is assumed for the purposes of this article, and we'll leave the components of the spark side largely out of the equation. Since then, EFI systems have evolved tremendously, advancing in step with increases in computing power, tightening of emissions limits, and desires to improve fuel economy. The first production cars with EFI systems date back to the late 1960s (with some notable aborted attempts a decade earlier), but it didn't start showing up under the hoods of GM muscle machines until the mid-1980s. After all, there's a lot of unseen business that goes on between the time gas is pumped into your tank and it ends up as motion down the road this article should be a good first step at figuring it all out.

To love EFI requires knowing the ins-and-outs of how it functions, so we figured a 'get to know your EFI' article was in order. Back then, many saw it as a hindrance to backyard mechanics fixing or modifying their own vehicles. These days, you probably take EFI as a given, but it wasn't like this 15 years ago. Back then, GMHTP readers were a distinct minority compared to those who thought carburetors would forever reign supreme, but today even the most diehard old-school aficionados have been converted after seeing the incredible combination of power levels and drivability EFI makes possible. EFI so revolutionized hot-rodding that the original High-Tech Performance magazine was born (and became GM-only in 1998). You love late-model muscle cars, but do you understand what makes them tick? Do you know why your '10 Camaro SS not only has more power than equivalent cars of the '60s, but also with vastly better drivability and fuel economy? Why the 1980 Turbo Trans Am was a lackluster machine, but the 1989 model was such a killer? There are a lot of reasons that engines experienced such improvement, and so many of them boil down to Electronic Fuel Injection.

Injector cranking primer enrichment evom