OK - I seem to have struck out at the www.ImpalaSSForum.com (http://impalassforum.com/cgi-bin/ult...=002360#000007) so I'm bringing my LT1 PCM question here.

Like the link says, a friend and I have a theory that while at cruising speed, the full displacement of the engine is not really needed (as seen in the new OEM engines that have a cylinder deactivation system).

The theory further states that if we were able to fully open the EGR valve while cruising down the highway (assuming, say, low MAP numbers and TPS under 35%...engine not working hard) this would displace some of the combustable mixture in the cylinders with inert exhaust gas, thereby reducing the amount of fuel required to maintain AFR at any given RPM.

Call it redneck cylinder deactivation.

The big question is what tables/values does that PCM look at to decide 'when', and 'how much' to activate the EGR...I want to experiment with those values.

Thanks for your input...hope I made this understandable. - JM.

 

It won't work as you planned. Even with the EGR vacuum commanded 100% the valve senses exhaust back pressure and will close when theres not enough pressure. I can't get the valve to open at all on my car with the headers due to lower back pressure. Unless you change to a different type of valve its not gonna open like you want.