Dont know about Ford or Dodge, but the GM exhaust brake works with the turbo vains and transmission without having to be in tow/haul mode. It does not have a valve of any kind in the exhaust pipes. I am a little confused about the new Dodge (cummins) exhaust brake. Do they now have real "Jacob's brake rocker boxes" now like big 'ol trucks have??
No "Jake brake" Bob. Did you know the the "Jacobs aka Jake Brake" actually came about after Mr. Cummins, the Father of Cummins Diesel, almost hit a train, back in the 30's? Took him some time to develop it and by then ironically he ended up leaving the company he started. So, Jacobs ended up being the manufacturer, a marriage in more ways then one.
The big three all now use the turbo outer vane manipulation to control both boost and turbo braking, and it is very effective. Side benefits to the VGT variable vane turbo or VNT variable nozzle turbo as Ram calls it, is a waste gate is not necessary and by closing the vanes in a coast mode we get turbo-engine braking. And, the technology is already there so it is just some programming to add the turbo brake feature.
Fords new for 2015 larger turbo takes advantage of the VGT and resulted in several pluses. The two stage sequential compressor (it is not a "twin turbo") was replaced with a single larger compressor and full VGT manipulation.
The VGT allows the larger compressor to act like a small compressor at low speeds (throttle response - turbo lag) and being larger allows higher flows at higher RPMS and loads. The smaller sequential turbo was the achilles heel when the Ford's were compared to the GMC and Ram in the tow off challenges.
There was a reason GMC or Ram centric tow tests were done at plus 10,000 feet of elevation. At that altitude the Scorpion started to choke for air.
GM was the first IIRC to use the VGT technology and then Banks Performance took it a step further when they figured out you could manipulate those vanes to help you slow down, as well as accelerate.
I had the Banks "Speed Brake" on my 06 GMC. I had some issues with it and between myself and Banks Engineering we were never able to solve the problem with my truck so I had to remove it. But, when the brake worked correctly, it was awesome. On level 3 (of 3) and with no trailer, it felt as though and anchor was dropped out of the bed. It was so effective you could not just drive around with no load on level 3.
One of the techniques to get the most effectiveness out of the various engine "slowing" methods is the tow haul mode. Typical in tow haul is increased transmission line pressures, higher rpm up and downshifts and lower speed and gear range of torque converter lockup. My GMC locked the converter in 2-6 gears in T/H.
For anyone that is interested there are plenty of decent videos on you tube.
This first, the Ram engineer Dave Connor in this video is the brother of my partner at work.
http://blog.ramtrucks.com/ram-technology/cummins-6-7s-biggest-fan-pt-6-no-feet-with-exhaust-brake/
A white board explanation of VGT
http://www.youtube.com/watch?v=hdjsNPeCLQs&sns=em
http://www.youtube.com/watch?v=4AROIRu6tm4&feature=youtu.be
http://www.youtube.com/watch?v=Gc2awh0O0Bc&feature=youtu.be
I believe we had this conversation once.
or twice
or thrice