Whats the practical difference
Logistics Pro
Joined: Mar 2005
Posts: 3,552
Likes: 2,511
From: West Michigan
[QUOTE=mptjelgin;18848300]
Oh, I totally agree with that. My point was that T/H mode is a lot more than just a braking mechanism.
Tow/Haul doesn't just use transmission to slow you down, it also changes the shift points and Torque Converter behavior (locks up quicker). /QUOTE]
I think that changing shift points and locking up the converter still qualifies as using the transmission to slow you down. My point is that the EB makes the engine a much more effective brake as well, working in conjunction with the tow/haul mode and the transmission.
I think that changing shift points and locking up the converter still qualifies as using the transmission to slow you down. My point is that the EB makes the engine a much more effective brake as well, working in conjunction with the tow/haul mode and the transmission.
Thread Starter
|
Posting Guru
Joined: Nov 2010
Posts: 1,430
Likes: 6
From: Alabama
I believe we're all in sync on what/ how T/H assists (tranny logic magic); I'm still unclear on HOW the engine brake works.
I was once told EB is not an exhaust brake - so what magic is it performing?
My using both of them together was very effective in keeping my speed down so I could enter these blind twistys without burning up my brakes.
I was once told EB is not an exhaust brake - so what magic is it performing?
My using both of them together was very effective in keeping my speed down so I could enter these blind twistys without burning up my brakes.
Thread Starter
|
Posting Guru
Joined: Nov 2010
Posts: 1,430
Likes: 6
From: Alabama
I decided to ask google this question, almost immediately I found this:
and this:
I note both sources label it as an engine - exhaust brake.
What is the Engine-Exhaust Brake?
The Engine-Exhaust Brake has become an integral part of the Super Duty’s turbocharger. When activated by flipping a switch located at the top left of the centre stack, the engine brake will automatically adjust the vanes on the exhaust side of the turbocharger in order to generate engine pressure.and this:
DIESEL ENGINE-EXHAUST BRAKING
The 6.7L Power Stroke® Turbo Diesel incorporates a driver-activated engine-exhaust brake. It restricts the turbocharger’s exhaust flow to generate back pressure and slow the vehicle, providing greater control while traveling downhill, regardless of vehicle load or road grade.I note both sources label it as an engine - exhaust brake.
Thread Starter
|
Posting Guru
Joined: Nov 2010
Posts: 1,430
Likes: 6
From: Alabama
Looking at some maps I can add a better location for you rowdy bikers to play on.
It is within the Chattahoochee National Forest (Georgia), state highway 19, several miles south of Lake Trahlyta, GA.
It is within the Chattahoochee National Forest (Georgia), state highway 19, several miles south of Lake Trahlyta, GA.
Tuned
Joined: Jul 2003
Posts: 274
Likes: 20
These terms get mixed and matched quite a bit. In gasoline engines when we talk about engine braking we are talking about the natural ability of an engine to provide a significant amount of resistance because of the throttle valve (butterfly) and the vacuum created. No extra device or technology is required as gasoline engines provide quite a lot of "natural" engine braking.
Diesel engines normally employ some extra device or technology to provide significant engine braking, and it is often described as an exhaust brake. The big rigs use a Compression Release Engine Brake, aka Jake Brake which modifies the exhaust valve sequence to provide braking, and makes a heck of a lot of noise in the process. So when you see a sign that says "No exhaust brakes allowed" that is what they are talking about.
Lighter duty trucks like ours use a device that simply restricts the exhaust. In early trucks it was a butterfly mounted in the exhaust, activated by some time of switch to restrict flow. Our current Fords utilize the variable geometry exhaust vanes in the turbocharger to accomplish the same thing. All of these things are a sort of engine brake, and more specifically in diesel trucks, exhaust brakes. But they aren't Jake Brakes and we don't have to turn them off when we see one of those signs!!
Diesel engines normally employ some extra device or technology to provide significant engine braking, and it is often described as an exhaust brake. The big rigs use a Compression Release Engine Brake, aka Jake Brake which modifies the exhaust valve sequence to provide braking, and makes a heck of a lot of noise in the process. So when you see a sign that says "No exhaust brakes allowed" that is what they are talking about.
Lighter duty trucks like ours use a device that simply restricts the exhaust. In early trucks it was a butterfly mounted in the exhaust, activated by some time of switch to restrict flow. Our current Fords utilize the variable geometry exhaust vanes in the turbocharger to accomplish the same thing. All of these things are a sort of engine brake, and more specifically in diesel trucks, exhaust brakes. But they aren't Jake Brakes and we don't have to turn them off when we see one of those signs!!
FTE Legend
Joined: Jul 2005
Posts: 65,938
Likes: 1,432
From: Millersville, MD
Another thing I haven't seen mentioned when using either of the above brakes AND select the speed control to whatever speed you wish to maintain, the tow/haul and speed control WILL do a great job to maintaining that speed - to within (I believe) 5 MPH . Also great to use in mountainous areas .
Hotshot
Joined: Oct 2015
Posts: 19,726
Likes: 12,873
From: Wyoming
As near as I can tell, tow/haul alone won't use the turbo to help slow you down. But, you do get engine braking due to compression.
The tow/haul will hold the shift points (higher RPM before the shift) as you accelerate through the first three gears. After that, it doesn't hold the RPM in the upper three gears.
The tow/haul will hold the shift points (higher RPM before the shift) as you accelerate through the first three gears. After that, it doesn't hold the RPM in the upper three gears.
Thread
Thread Starter
Forum
Replies
Last Post
Jeremy2792
1999 - 2016 Super Duty
19
Aug 3, 2008 03:50 PM
