Drinking too much
beer in Munich ;)
Join Date: Feb 2012
Location: I would rather not say
I've done some more testing. I've never really closely looked at the EGR control before, it seems we usually think it closes at about 2000rpm. Wrong !
In gears 1 to 4 I've had the EGR open at 3500rpm. (recorded the EGR control signal, not actual EGR valve position)
In all gears the EGR closes when the load goes beyond a particular threshold.
At low rpm, say for example 6th gear at 60mph, the EGR closes at about 0.7Bar pressure, but as the revs rise the point when the EGR closes completely varies depending on load level, turbo boost and rpm.
My guess is that the slow pick up experienced when letting the EGR work normally is because at part throttle and mid load conditions, with revs at 2250rpm, when you press the accelerator quickly there is a lag before the EGR closes, and the turbo boost pressure rises. With a full blanking plate the turbo is already completely responsible for the flow of air in the intake, so it is able to respond more quickly to the driver's wish.
There is no EGR activity when there is no fuel going in the engine, such as when you're on overrun. No fuel, no EGR. A little throttle, a little bit of EGR, typically about 30%, and as the load and revs rise the EGR opens to over 50%