You are correct that was what I was thinking about. So what engages the ford so called exhaust brake? I need to get the owners manual out.
You will not find anything in the manual about it. Myself and another member called Ford's Customer Service and they as well couldn't tell us anything about it and suggested I contact the dealership. Well, I did that and they did not have any information about on it so they sent a message to Engineering.
This is what engineering said....
• You have to be in Tow/Haul mode.
• The engine RPM has to be above 2000RPM before it will start working.
• The VG compressor also produces a small amount of back pressure as well.
The problem with this is it has no real world use in my opinion. Several times I have been on 2 lane roads and watched my speed increase 10-15MPH with a load. If you just take your foot off the fuel nothing will happen. At 60MPH and in 6th gear we are around 1300-1400RPM and in 5th gear we are around 1700RPM, nowhere near the 2000 RPM mark before it will work. When traveling at 60MPH it is not until the truck is in 3rd and sometimes 2nd gear before any kind of engine/exhaust assisted speed control will start happening.
A Ford diesel tech that is also a good friend said the turbo back pressure is simply a by-product of the high RPM that is all. Ford just turned this into an exhaust brake marketing tool.
Hope this clears it up for you... it sure did for me. Still not happy about it but non the less at least I have answers.