If that can be improved a heater shutoff/bypass will be next but there's no point if I can't reduce the entry temp.
My two pence worth…
The cooling dynamics of our modern Ford engines is precarious and sometimes counter intuitive. It would appear that these modern engines with stats on the cold side of the radiator at the bottom of the engine behave completely different to older cars with stats on the radiator hot side, or at the top of the engine. The GDI and Duratec are both configures this way with stats lower down. These stats use combined hot and cool coolant paths that merge together in the stat housing to regulate the running temp. I beleive that the coolant from the heater matrix also flows directly into the stat housing, so any intervention that changes the amount of heat carried into the housing may well change the stat’s open/close point with respect to the actual head temp. I would guess that the knock on is that the overall engine running temp may change a little.
I came up against this when I put a more efficient rad in my little 1.8 engined Duratec. The larger rad reduced the bottom hose coolant temp flowing into the stat housing, so the engine had to work harder to raise the bypass coolant temp that also entered the housing (from within the block on a Duratec) in order to make up the deficit to open the stat. And that caused the engine to run a little hotter
On a differnt theme, thought the pic below may be of interest showing the temp of my old 1.8 heater matrix enclosure. I snapped this with a thermal camera after thrashing the car, stopping and quickly lifting the bonnet to record the intake temp.
![[Linked Image]](https://dl.dropboxusercontent.com/s/o4lcbx2lmxkns9m/thermal.jpg)
The ambient temp at the time was 17/18C.
Have fun with your mods
