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EGR valve the top of box on top of the inlet manifold of a Saab H engine in a 1987 Saab 90. In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NO x) emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. [1]
The way they do this is during a deceleration of the vehicle when there is low absolute pressure in the intake manifold (i.e., a high vacuum present in the intake manifold relative to the outside air) the powertrain control module (PCM) will open the EGR valve and then monitor the MAP sensor's values. If the EGR is functioning properly, the ...
The crankcase air outlet, where the PCV valve is located, is generally placed as far as possible from the crankcase breather. For example, the breather and outlet are frequently on opposite valve covers on a V engine, or on opposite ends of the valve cover on an inline engine. The PCV valve is often, but not always, placed at the valve cover ...
The pump's air intake is filtered by a rotating screen or the vehicle air filter to exclude dirt particles large enough to damage the system. Air is delivered under light pressure to the injection point(s). A check valve prevents exhaust forcing its way back through the air injection system, which would damage the pump and other components.
How it works "The MultiAir system is elegantly simple. An electrohydraulic actuator, a high-response, electronically activated solenoid—controls the pressure applied to hydraulic fluid (engine oil drawn from the sump) that fills a thin passageway that connects the intake valves and the camshaft.
Balancing the percentage of cooled external EGR with the hot internal EGR generated by a VVA system, makes it possible to control the in-cylinder temperature. While electro-hydraulic and camless VVA systems offer control over the valve event, the componentry for such systems is currently complicated and expensive.
An internal wastegate is a built-in bypass valve and passage within the turbocharger housing which allows excess exhaust pressure to bypass the turbine into the downstream exhaust. Control of the internal wastegate valve by a pressure signal from the intake manifold is identical to that of an external wastegate.
For twin-cam or DOHC engines, VCT was used on either the intake or exhaust camshaft. (Engines that have VCT on both camshafts are now designated as Ti-VCT.↓) The use of variable camshaft timing on the exhaust camshaft is for improved emissions, and vehicles with VCT on the exhaust camshaft do not require exhaust gas recirculation (EGR) as retarding the exhaust cam timing achieves the same ...