Thread Tools Display Modes
Old 06-10-2016, 12:55 PM   #71
Mod free 5er
Join Date: Mar 2008
Location: Concord, NC
Posts: 24,342
Originally Posted by Cowracer View Post
Any engine is basically an air pump. If you block off the exhaust (which is what an exhaust brake does) the engine turns into an air compressor. Air can get in, it cannot get out, and it takes energy to compress air. Any engine will function like that with the exhaust blocked (or partially blocked) off.

A Jacobs "jake" brake opens the exhaust valve at the time the injector or spark plug would normally fire. Energy is used up in the compression of the air in the cylinder. Its basically the same function as an exhaust brake, but the action occurs at a different place in the engine.

With all that being said, exhaust brakes (of any kind) are most effective on diesel engines because they do not have throttles. They gulp in the same amount of air no matter how far you press the accelerator. Gassers usually have the throttle closed for deceleration, largely limiting the amount of air that can be compressed to aid deceleration.

What some new computer controlled gassers with throttle by wire are doing is killing the ignition spark and fuel injection pulse, and opening the throttle WFO while in "exhaust brake" mode. In that case, they can be just as effective as one on a diesel.

Fully aware of how exhaust brakes work, they just don't put them on gas engines due to the fact that the compression is too low to be effective. Been a gearhead all my life.

OldCoot is offline   Reply With Quote
Old 06-10-2016, 09:42 PM   #72
Senior Member
mike.t's Avatar
Join Date: Sep 2014
Location: Norcal
Posts: 2,008
On racing motorcycles years back it was called a compression release. Jacobs had a law suit against towns that had posted signs that said do not use/engauge jake brakes in town because they were not all Jake brake by design.

2015 Salem 27RKSS
2015 Ram 2500 CC 4x4 Cummins
55' Chevy Bel-Air
Burgers on the BBQ and a cold beer
mike.t is offline   Reply With Quote
Old 06-10-2016, 09:54 PM   #73
Senior Member
B and B's Avatar
Join Date: Jun 2013
Location: Wilmot Twp, Ontario, Canada
Posts: 9,165
Originally Posted by Time-Travelers View Post
We don't have that weight yet, still 'making it ours'. Should be close to 'fully' equipped and weighed by the end of the month. Dry weight of our 8289WS is 8125 with a CC 1208.
Flat towing no problem when i did it with F 150 but over weight from day 1! Trailer brakes ran pretty high to slow it.

2017 Heartland Bighorn 3575 Elite with Reese Sidewinder
2016 Ford F 350 SD PS 6.7 SRW Crew Pucks and Reese 18 K Elite

2013 Rockwood 8289WS 2012 Rockwood 2703 SS TT 2007 Golden Falcon 38FLA PM 1983 Corsair 21RB
2015 Ford F250 PS '13 F150 3.5 Eco '09 F150 5.4 l 1987 Merc Grand Marq 1982 Ford E250 CW
B and B is offline   Reply With Quote

fifth wheel, wheel

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

» Featured Campgrounds

Reviews provided by is not in any way associated with Forest River, Inc. or its associated RV manufacturing divisions.

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 05:35 AM.