Originally Posted by
In-Tech
Yes, I'm not sure LT1's ever had an EGR circuit that was active, however, all other ecm's have quite a few separate "tables" when the EGR is active. Or I should say, when the ecm thinks the egr is active.
I read all the time where people block their egr and wonder why they have a part throttle lean and knock issue. IF THE COMPUTER THINKS THE EGR IS OPEN IT PULLS FUEL AND ADDS TIMING!!! These are tuneable events and corrections. Changing a cam/exhaust/heads etc drastically alters the egr qualities.
Some egr's are basically on or off, other later ones are pulse width modulated and there are even more fuel tables and spark tables to work with that.