Howdy Fellas,

So they say my new 6.7 F350 has exhaust breaking. In my buddy's Dodge, the exhaust break is very noticeable. Pretty loud and slows it down quite well.

I have put my truck in "tow/haul" but I didn't hear or feel much. What am I missing here?

Brandon

 

This should get interesting!

 

You are missing nothing...the EB in your truck is completely integrated with the tow/haul mode system in your truck. It is not as strong as the Dodge but it works well after you understand how it operates. There are several long threads here regarding the EB...look for posts by Painted Horse. He has posted his experiences often with accurate descriptions.

Regards

 

Thanks. I'll do some searching here.

 

The EB on the Ford 6.7L is not as strong as the competition. Why I don't know. During the years that Ford used the 6.0L engine, Is was limited mostly by the valve springs. The powerstroke used 40psi springs vs GM/50 and Dodge/60 psi springs. So the EB could not create as much back pressure on the Powerstroke or it would cause the valves to float. I'm sure there is something similar that limits how many ft/lbs of Braking in the 6.7L vs the competitions engines.

With the understanding that the 6.7L is not going to win in the EB competition, We still have an exhaust brake and it does offer some braking, The trick is learning to utilize what we have and get the most of it.

I tow almost daily. I frequently pull a 4H GN trailer that weighs 13,000lbs in the mountains of Utah.I've made numerous trips up Logan canyon and down into Bear Lake towing either my Skid Loader or Mini Excavator. So I have some experience towing in the 10,000 to 13,000 lb range. Can't speak for those towing heavier loads. I also had the B&D Exhaust Brake on my 6.0L truck to give me some experience with an after market EB.

The trick with our trucks is to be in the right gear to get the most of your exhaust brake. This means selecting a gear which will push the engine RPM's to around 3000-3500 rpm. Unfortunately we don't have a gear that will run at 3000-3500 rpm at 55 mph. 2nd gear hits the right rpm at 40-45 mph, 3rd gear hits those rpms at 65-70 mph. So we have a gap in gears that allows the truck to gain speed at 55-60 mph.

I focus on trying to make sure I'm in the right gear as I summit and grades. The downhill into Bear Lake is 5-7 miles of 7-8% grade. It has numerous 35-40 mph curves. So I set my cruise at 40 mph and lock out any gears above 2nd. My truck will hold the 40 mph all the way down with out me touching my foot brake.


Now coming down I-80 from Park City to Salt Lake is 20 miles with 7% grades in the upper stretches. It has a run away truck ramp to catch vehicles that might loose their brakes. I don't want to slow to 40 mph and I don't want to go as fast as the cars at 75-80 mph. I slow to 50 mph at the summit and set the cruise. My truck does a good job of holding 50-60 mph with my 13,000lb trailer. I do on occassions have to touch my brake pedal usually because I'm in the slow lane and over take a semi crawling down the grade.

There are a lot of variables involved. How fast you enter the grade, at what speed you want the truck to hold the grade, how heavy your load and if you are willing to touch your brake pedal. I don't think its all bad to use my brake pedal several times on a grade as long as I don't over heat my brakes. I don't think we will see an aftermarket exhaust brake like we did with the 7.3L and 6.0L, so we will have to make the most of the factory EB. Experiement with yours and see what speeds and gears work for you.

 

Wow. Thanks. That is a great write up.

Brandon

 

Painted Horse,

Your picture is a great illustration of the conditions needed for the exhaust brake to be effective. Notice the boost gauge. If you aren't making boost, there is no braking.

Ford really should rethink the gear ratios of the 6R140. Their current ratios are the main reason that the Chevy dominates them in racing up mountains and exhaust braking comparisons. The truck works great as it is, but some refinements would make it the best available by a large margin.

 

I don't agree with this. Remember that the exhaust break functions by increasing backpressure in the exhaust to resist the movement of the engine. Boost is measured in the intake system and has no bearing on the exhaust braking function.

You're right that most of the time when the exhaust brake is functioning you will notice boost on the gauge, but it's not always there and isn't a good indication of whether or not the brake is functioning. I remember that under high RPMs my work truck's Cat C15 would make boost when coasting down a hill, and this was without a VGT or exhaust brake. Absolutely no braking function at all and there was boost...

 

You have to remember that we have an engine brake, not an exhaust brake. Our system, used w/ tow-haul mode, is nothing more than a computer controlled downshifting of the engine to get the RPM's up. If I use manual shift mode, disabling the tow haul mode, I get the same engine assist braking. I tow 18-20k, the engine brake works marginally at speeds of 40 or below, above that you need to really pay attention or you will get in over your head pretty quick. The last comparison of the "big 3" shows how dismal Ford's engine brake is. Some will say it wasn't used right in these tests etc however my personal experience is and has been the system is a major over-sight on Ford's part for a truck rated at 30k GVW. I love my truck but it def isn't perfect.

 

 

Tom, spend some time with AE on one of these trucks and your opinion would likely change. I've said it plenty times before and I need to just accept the fact that people are always going to tell me that I have no clue about things I've done the research on.

VGT exhaust braking will always make boost if the vanes are closed up to create backpressure and thus braking. The vanes are closed to create backpressure and that forces all the exhaust thru the turbo wheel spooling it up and creating boost on the other side. Pressurizing the intake side aids in creating the braking force as well as restricting the exhaust does.

Ford simply is not closing the vanes very much during their attempt at exhaust braking. Once AE is available for the 6.7, I will show you that it is working the same way that aftermarket tuning provided exhaust braking on the 6.0.

 

I have no issues with the engine brake on my truck.. i thought it did quite well going down the grapevine in California..i had the cruise set, and the truck downshifted itself and kept the speed I had it set to.. didn't have to touch the brakes..was quite funny watching all of the other idiots ride their brakes down that hill..
Since I am a commercial truck driver, I have to agree with Painted Horse.. it's all about selecting the right gear and speed BEFORE going down the hill..you can't go flying down the hill in high gear and whine "oh, my engine brake sucks"..because it's not slowing you down well.. even the engine brakes on the big rigs don't work _that_ good... so what if Mr. Duramax and Mr. Dodge brag about their engine brakes, you can laugh at them later when they pass you going down hill with that white smoke coming out of their wheels, because they didn't downshift and slow down when they were supposed to.."i didn't have to downshift and slow down because my D-max has the best engine brake, blah blah"

 

Great feedback. Thanks, fellas.

 

painted horse.

your post has been very helpfull. i was wondering how this works today.
what is you total weight with your 13,000 lb trailer.

 

My truck is about 8500lbs, add in any additional passengers, So with 4 horses and 4 riders in the truck, the truck will be 9400-9500lbs, add the trailer at 13,000 and the total is 22,000 to 23,000 lbs

One of thngs that I find very interesting, Is that my #4 pyros temps really climb when I'm engine braking.It often is almost double or triple the #1 pryos temps during the down hill grade. any ideas why?