Exhaust Brake:I Kind of Have to Agree - Ford Powerstroke Diesel Forum
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post #1 of 49 Old 04-04-2011, 06:47 AM Thread Starter
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Exhaust Brake:I Kind of Have to Agree

Came across this test that GM did on a boating site and I kind of have to agree with the findings.

I still love this truck and have no regrets, but the so-called exhaust brake like I have mentioned in the past is a major disappointment for me. Hopefully Ford will figure this out and make it better for future truck owners.


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post #2 of 49 Old 04-04-2011, 07:45 AM
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I thought the ford had to be below 20mph before the exhaust brake to work

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post #3 of 49 Old 04-04-2011, 07:49 AM
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Originally Posted by stroke11 View Post
I thought the ford had to be below 20mph before the exhaust brake to work
You might be thinking of the hill decent control.

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post #4 of 49 Old 04-04-2011, 08:00 AM
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You might be thinking of the hill decent control.
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.

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post #5 of 49 Old 04-04-2011, 08:05 AM
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exhaust brakes have no place on a light duty diesel engine. especially with an automatic transmission. ever heard a new dmax using the exhaust brake? it literally sounds like the engine is screaming in pain, like it's going to fly apart. GM built a good truck no doubt......but i still believe the ford will outperform the dmax in the real world, long term.

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post #6 of 49 Old 04-04-2011, 08:20 AM Thread Starter
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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.

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post #7 of 49 Old 04-04-2011, 10:56 AM
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My 03 Duramax without an exhaust brake did very little holding back. I put it in low gear to descend a 20 mile 8% grade in BC. I was pulling a 15000 lb trailer. The truck accelerated until the engine reached nearly 5000 rpm. Two things happen as the truck and engine speed up that work together to prevent further acceleration -
1.) as the engine accelerates it pumps more air through the exhaust system which produces some back pressure even without an exhaust brake - this back pressure tries to prevent the piston from rising up on the exhaust stroke creating a negative torque on the crankshaft. This torque is then multiplied through the gear ratios of the transmission and differential and if it is equal to the torque created by the weight of the truck and trailer on the incline the truck will stop accelerating.
2.) as the speed of the truck increases more air resistance is produced so there is less torque required to prevent further acceleration.

The amount of rear axle torque needed to prevent the truck from accelerating can be easily calculated if the weight of the truck and trailer are known as well as percent slope of the grade.

The amount of torque an exhaust brake will produce can also be easily calculated once you know the engine displacement and the back pressure in the exhaust system. Because none of the exhaust brakes allow high back pressure to be produced, in order to prevent engine damage, there cannot be allot of negative torque produced at the engine crankshaft by this type of engine brake. The thing is this low torque can be multiplied through the transmission by gearing down. Because gearing down both increases the back pressure (and therefore increases crankshaft torque) and multiplies this torque through the transmission it is essential that gearing down be involved in engine braking with this type of engine brake. I suspect the new Ford will do just fine in holding back a load once we get it in our heads that we need to manually gear down with heavy loads.


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post #8 of 49 Old 04-04-2011, 11:07 AM Thread Starter
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I suspect the new Ford will do just fine in holding back a load once we get it in our heads that we need to manually gear down with heavy loads.
I have been doing just that and finding that I need to be in 3rd and sometimes 2nd gear depending on the grade going 60MPH in oder to keep off the brakes. So I am embracing the manual shifter.

After pulling my work trailer with a '11 Duramax I noticed I really did not have to do any brake tapping or manual shifting with it in Tow/Haul or with the Engine Brake switch ON.... when I took my foot off the fuel it somehow knew to try and maintain speed going down hill with down shifting and using the engine's exhaust. And in the video you can kind of see that... the Ford just kept skating down the hill with out doing anything other than removing the fuel.

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post #9 of 49 Old 04-04-2011, 11:21 AM
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I think you are right on - the GM is almost doing the thinking for you as it gears down. I personally prefer having control over the amount of engine braking by manually shifting the transmission up and down to control my speed - as long as it ultimately has the capacity to hold the load back. I am really looking forward to trying it out this weekend. Anyone know of any good long grades on route from Emory TX to Des Moine IA and on to Great Falls MT. I will be pulling a descent load of 19000 lbs.

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post #10 of 49 Old 04-04-2011, 11:38 AM Thread Starter
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The first leg will be fairly flat then the second leg will be all up hill.... I think.

What are you going to be hauling?

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