Community Forums

kengardner · 09-29-2021, 12:26 PM

Hi all, I'm STILL looking at super C motorhomes and love the Entegra Accolade models which are on a Freightliner chassis. The price is a little higher than we budgeted for so I'm looking at some of the Ford F-550 chassis models. I can find nothing discussing exhaust brakes on the Ford models. I see the Dodge models come with one but I like the looks of the Ford better. Anyone have one ? Thanks, Ken

R.Wold · 09-29-2021, 06:57 PM

Ford 6.7 diesels come with an exhaust brake standard. So while brochures and dealers may not have info, a look at the chassis on the Ford website should have the info. Also mine in my 17 F250 is really quite effective. Holds speed on 6% grades 14k lbs towing 14,000.

From the website configuring an F550 cab and chassis:

Your Configuration: 2022 F-550 Crew Cab, XL, 4X2, DRW, 179", 6.7L 4 Valve OHV Power Stroke V8 Turbo Diesel B20 Engine with Manual Push-button Engine-Exhaust Braking, 10-Speed Automatic with Selectable Drive Modes, 4.10 Non Limited Slip Axle
Pricing shown for Zip code 95652 as of September 29, 2021 S2

https://shop.ford.com/build/chassis-....CRW.550CC.%5D

kengardner · 09-30-2021, 01:24 PM

Thanks R. Wold

ebenson24 · 10-23-2021, 10:25 AM

The Entegra / Jayco / Renegade on the Freighline S2RV chassis, F550, and Dodge 5500 (Dynamax) all use the exhaust brake. It is not until you jump to the Cummins 8.9 or DD8 or larger that you will get the true exhaust brake (Jake Brake).

We drove a Thor F600 (38' long) from CA to NY and the exhaust brake plus tow haul mode worked great. Never a time when I really had to use the brakes coming down a interstate grade.

Eric

wolfe10 · 10-23-2021, 10:32 AM

Quote:

Originally Posted by ebenson24

T It is not until you jump to the Cummins 8.9 or DD8 or larger that you will get the true exhaust brake (Jake Brake).

Eric

Sorry, this is INCORRECT information.

Smaller diesels (less than 8.9 liter Cummins ISL) can have either an EXHAUST BRAKE or VGT (Variable Geometry Turbo) as a brake.

The ISL can be ordered with either an exhaust brake or an ENGINE COMPRESSION BRAKE. The engine compression brake is more $$, so lower end coaches with the ISL may have the exhaust brake.

An engine compression brake (aka Jake brake) works entirely differently from an exhaust brake.

The engine compression brake opens the exhaust valves as the piston approaches TDC so all the work done to compress that 16+ volumes into 1 are released.

An exhaust brake is basically a "potato stuffed in the tailpipe". So the engine has to work to push exhaust out.

R.Wold · 10-23-2021, 11:12 AM

Quote:

Originally Posted by wolfe10

Sorry, this is INCORRECT information.

Smaller diesels (less than 8.9 liter Cummins ISL) can have either an EXHAUST BRAKE or VGT (Variable Geometry Turbo) as a brake.

The ISL can be ordered with either an exhaust brake or an ENGINE COMPRESSION BRAKE. The engine compression brake is more $$, so lower end coaches with the ISL may have the exhaust brake.

An engine compression brake (aka Jake brake) works entirely differently from an exhaust brake.

The engine compression brake opens the exhaust valves as the piston approaches TDC so all the work done to compress that 16+ volumes into 1 are released.

An exhaust brake is basically a "potato stuffed in the tailpipe". So the engine has to work to push exhaust out.

I was about to say the same thing but you saved me the trouble.

For Ebenson, a good analogy is that a Jake (Jacobs brake) turns the engine into a compressor, compressing air but no fuel, causing it to use power (created by decelerating or descending a grade) rather than making power. This is a good (and old) video on the subject.

https://www.youtube.com/watch?v=7FSkNSOeTWM

Wolfe, the one exception is that some high end ISL equipped coaches surprisingly and regrettably come with a VGT engine brake. The 35’ Newmar New Aire is a good example. I guess they figure a coach under 35,000lbs or so doesn't need it, but the VGT engine brake on my 30,000lb Ventana is barely adequate. A retarder would be a welcome addition, and is available as an option on the Allison 3000, but too much to hope for on a MH chassis.

kengardner · 10-24-2021, 06:07 AM

WOW, great information Wolfe and R.Wold !! This is vital to folks like me who have white knuckled it down a mountain pass in a gasser pulling a toad and praying the service brakes held out ! That's the main reason I'm looking at DPs. Unfortunately ( or maybe fortunately ) I have to look at older, higher end coaches to find the Jake brake I feel I need to be safe where I like to drive. You guys rock ! Ken

ebenson24 · 10-24-2021, 11:24 AM

Quote:

Originally Posted by wolfe10

Sorry, this is INCORRECT information.

Smaller diesels (less than 8.9 liter Cummins ISL) can have either an EXHAUST BRAKE or VGT (Variable Geometry Turbo) as a brake.

The ISL can be ordered with either an exhaust brake or an ENGINE COMPRESSION BRAKE. The engine compression brake is more $$, so lower end coaches with the ISL may have the exhaust brake.

An engine compression brake (aka Jake brake) works entirely differently from an exhaust brake.

The engine compression brake opens the exhaust valves as the piston approaches TDC so all the work done to compress that 16+ volumes into 1 are released.

An exhaust brake is basically a "potato stuffed in the tailpipe". So the engine has to work to push exhaust out.

Sorry, I did type too fast I did not use the correct terminology. Which class C or Super C RV can you with the 6.7 with the Compression Brake aka Jake Brake. Either they are using the camshafts to get engine compression (Jake) or creating back pressure in exhaust (turbo). At least in the Super C offerings, no one offers the true Compression Brake (Jake Brake) in the 6.7. The ford 550/600, Dodge 5500, Freightliner SVR2 cummins 6.7 are all exhaust or variable compression fancy wording you want to use but they are using exhaust back pressure instead of engine compression.

R.Wold · 10-24-2021, 11:45 AM

Quote:

Originally Posted by ebenson24

Which class C or Super C RV can you with the 6.7 with the Jake Brake. I fully understand Exhaust brake = turbo aka variable whatever they want to name it. Either they are using the camshafts to get engine compression (Jake) or creating back pressure in exhaust (turbo)

There is no 6.7 with a Jake. An after-market kit is available for the 5.9 and might have been tried on the early 6.7 (Load Leash by PacBrake) but I don't think it was successful on the 6.7 and there is currently no version for the 6.7.

For clarification (if anyone cares) exhaust brakes and VGT engine brakes are two entirely different systems, the exhaust brake restricting the exhaust flow post turbo, and the VGT restricting it by adjusting the vanes in the turbo, but yes they accomplish the same goal by more or less the same means.

A Jake (modern version including Cummins C-brake) uses oil pressure driven actuators to open the exhaust valves at a point where the cam shaft would otherwise keep them closed, utilizing the energy used to compress the air in the cylinders to slow the vehicle.

Just to confuse things a little, there is also a Jacobs exhaust brake (“Jacobs E Brake“) for the 5.9, 6.7, 8.3, and 8.9 engines, but it cannot be used in conjunction with a VGT engine brake. Apparently not compatible.