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Pressure in cylinder pattern in dependence on ignition timing: (a) - misfire, (b) too soon, (c) optimal, (d) too late. In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke.
Other problems may be implicated in the case of older vehicles equipped with carburetors. Weak, disconnected, or mis-connected throttle return springs, worn shot-pump barrels, chafed cable housings, and cables which jump their tracks in the throttle-body crank can all cause similar acceleration problems.
Although the IAC is supposed to last the vehicle's lifetime, various reasons may cause it to fail/malfunction prematurely. The most common failure mode is partial/complete jamming of the actuator (due to dirt/dust or even oil) where it cannot be smoothly controlled. The result is an engine that fails to maintain idle RPM and frequently stalls.
The intake manifold vacuum, with wide open throttle, is lower in these conditions, which causes the PCV valve to open and the crankcase gases flow to the intake system. [13] The greater flow rate of intake air during these conditions means that a greater quantity of blow-by gases can be added to the intake system without compromising the ...
A typical ETC system consists of three major components: (i) an accelerator pedal module (ideally with two or more independent sensors), (ii) a throttle valve that can be opened and closed by an electric motor (sometimes referred to as an electric or electronic throttle body (ETB)), and (iii) a powertrain or engine control module (PCM or ECM). [4]
Under full throttle and light load, other effects (such as valve float, turbulence in the cylinders, or ignition timing) limit engine speed so that the manifold pressure can increase—but in practice, parasitic drag on the internal walls of the manifold, plus the restrictive nature of the venturi at the heart of the carburetor, means that a ...
The anti-lag system (ALS) is a method of reducing turbo lag or effective compression used on turbocharged engines to minimize turbo lag on racing or performance cars. It works by retarding the ignition timing and adding extra fuel (and sometimes air) to balance an inherent loss in combustion efficiency with increased pressure at the charging side of the turbo.
The advent of concern about fuel economy and emissions had major impacts on engine design. Some of the trade-offs reduced throttle response. Most new cars employ a drive-by-wire system, which includes electronic throttle control and can itself either reduce or increase throttle response (Depending on whether or not it's being employed on a performance car).