Re: Pontiac EGR Valve

Posted by Chris Vangel on September 07, 2004 at 20:49:10 from (68.75.155.219):

In Reply to: Re: Pontiac EGR Valve posted by TheRealRon on September 07, 2004 at 03:45:02:

True, EGR operation may not commence until engine operating temp is up, some do-some don't, depends on manufacturer, model, and engine.

Absolutely EGR flow occurs during acceleration.
Oftentimes, A fully warmed up engine will open the valve when you rev the engine in park.

Early systems were simply opened using Ported vacuum, which is available any time the throttle is off idle. The further you open the throttle, the more ported vacuum you have up to about 15"-18". This is if your vehicle is has a carb.

Later systems used a solenoid that simply switched manifold vacuum off and on to the valve.

A popular valve from GM used three solenoids which opened three different valves in one assembly to provide more controlled delivery of EGR gases.

The latest uses a motor that dials the valve open and closed at small increments for exact control. This one is called a Linear EGR Valve.

Manufacturers may wait for the engine to warm up first because the opening of the EGR valve on a cold engine can cause a flat spot in acceration on a cold engine. Timing is adjusted (advanced) by the ECM to supplement performance. The Knock sensor watches to ensure timing is not overly advanced.

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