EGR Valve, EVP Position Sensor & Stainless Exhaust Tube
Meters inert exhaust gas back into the intake manifold under part-throttle cruise to suppress peak combustion temperatures and NOx.
Role in the System
What This Assembly Is
Connected from the rear exhaust manifold up to the neck of the intake plenum via a corrugated stainless-steel tube is the vacuum-operated Exhaust Gas Recirculation (EGR) pintle valve and its top-mounted linear-potentiometer EGR Valve Position (EVP) sensor.
Mechanics & Physics
How the Subcomponents Work Together
Why Diluting the Air Charge with Exhaust Cools the Flame: Oxides of nitrogen (NOx) form exponentially whenever peak combustion chamber temperatures exceed ~2,500°F. At part-throttle highway cruise, the EEC-IV applies modulated vacuum to the EGR diaphragm, lifting the tapered steel pintle to blend 5–10% inert exhaust gas (CO₂ and H₂O vapor) into the intake charge. Because inert molecules absorb combustion heat without burning, peak flame temperatures drop by several hundred degrees—cutting NOx formation while the top EVP sensor reports exact pintle lift in millimeters back to the computer.
Other Assemblies in This System
Split Front (Cyl 1–3) & Rear (Cyl 4–6) Exhaust Manifolds
Two separate nodular-iron 3-into-1 exhaust manifolds that eliminate thermal warping and scavenge paired 240° firing pulses.
Thermactor Air Pump, Diverter Valve, Check Valve & Rail
Belt-driven rotary-vane air pump and 6-branch cylinder-head manifold that inject fresh oxygen to light off the catalytic converters.
Dual-Stage TWC Catalytic Converters, Muffler & Tailpipe
Dual-branch Y-pipe, heated oxygen sensor, two-stage monolithic honeycombs, tri-flow muffler, and over-axle tailpipe.