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Old 11-17-2013, 10:43 AM   #29
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Something I think is worth noting is that if you have a true compression brake, the braking action is inversely proportional to how close to redline your engine is. To say it another way, the closer to redline you are the more braking action you will have. If you leave it in 6th gear you will have a slower turning engine until you manually downshift it. I like having maximum braking power the moment the Jake comes on. JMO
Yes , you are correct but,
When mine comes on at 65mph,1800 rpm's is plenty for me even with a exhaust brake. When I loose only 15 mph it is downshifting to 5th and picking up rpm's again. I do not operate mine at "red line" at any time especially with exhaust braking as it seems to be really hard on manifold gaskets, engine braking using the engine valves does not have this problem and works a whole bunch better. All the semi's I drove had 3 stage engine brakes and worked fine and I down shifted as needed. RV's are setup like this I think because not everyone was a truck driver at one time in their life. My next Coach will most likely be a 600-650 hp with a 3 stage braking.
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Old 11-17-2013, 03:18 PM   #30
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Yes , you are correct but,
When mine comes on at 65mph,1800 rpm's is plenty for me even with a exhaust brake. When I loose only 15 mph it is downshifting to 5th and picking up rpm's again. I do not operate mine at "red line" at any time especially with exhaust braking as it seems to be really hard on manifold gaskets, engine braking using the engine valves does not have this problem and works a whole bunch better. All the semi's I drove had 3 stage engine brakes and worked fine and I down shifted as needed. RV's are setup like this I think because not everyone was a truck driver at one time in their life. My next Coach will most likely be a 600-650 hp with a 3 stage braking.
My original comment was caveated to apply only to compression brakes. What you do with your exhaust brake is completely unrelated.
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Old 11-17-2013, 03:29 PM   #31
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My original comment was caveated to apply only to compression brakes. What you do with your exhaust brake is completely unrelated.
But they are related Joel, The exhaust brake is just a less expensive, less effective answer to the higher priced engine added (Head mounted) compression engine brake. They both share the end result of backing up the exhaust gasses. And yes they both work on rpm's of the engine and their effects on slowing anything(RV'S, semi's,dump trucks, etc.) is governed by the rpm's as to its performance.
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Old 11-17-2013, 04:57 PM   #32
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But they are related Joel, The exhaust brake is just a less expensive, less effective answer to the higher priced engine added (Head mounted) compression engine brake. They both share the end result of backing up the exhaust gasses. And yes they both work on rpm's of the engine and their effects on slowing anything(RV'S, semi's,dump trucks, etc.) is governed by the rpm's as to its performance.
All I was trying to say is that I have no knowledge of how exhaust brakes are affected by engine rpm in relationship to engine redline. What I said about compression braking was what I had learned from the Jacobs website relative to their compression brakes. I wasn't saying that there isn't such a relationship for exhaust brakes, simply that I wasn't professing to know it. I try not to make technical statements that I can't back up and in the case of exhaust brakes I know little more than the basics.
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Old 11-17-2013, 05:13 PM   #33
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The engine brake is banned by local law in many cities,
That's only true for the older unmuffled engine brakes, the new ones are all muffled and are fine to use.
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Old 11-17-2013, 05:29 PM   #34
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The best answer to gain the ability to "coast" - in my opinion, is to have the Cummins engine software reprogrammed as to how it activates the brake. The default programming is usually to activate the brake when the throttle is released. This virtually eliminates the ability to coast. On my 09 Journey, I had the Cummins dealer reprogram the engine so that the engine brake is activated when the brake pedal is depressed and remains activated (whether or not the brake pedal remains depressed) until the throttle is depressed/activated. Coasting is now as simple as taking your foot off the throttle. To me this makes much more sense that the default method although purists could argue there is a split second delay in engine brake operation using this method in an emergency.
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Old 11-17-2013, 05:54 PM   #35
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When your Coach is hooked up at the Allison shop and if one gets a chance to look at the selections and different options of how their transmission can be changed with a click of a mouse........ most would be amazed of the different options to select from in the Allison program.
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Old 11-17-2013, 10:35 PM   #36
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That's only true for the older unmuffled engine brakes, the new ones are all muffled and are fine to use.
I have never seen that caveat on any of the signage. It just states NO engine brakes.

Palehorse, do you think the Allison programing that will not permit the engine to over-rev in any gear, will protect the engine as designed? I know the Allison in my Chevy dually will up-shift to prevent engine damage from over-reving. The Allison owners manual for my MH states it works the same way, it will up-shift to prevent engine damage. If blowing an exhaust gasket is a concern, leaving an exhaust brake on continually generates a lot of heat and back-pressure unnecessarily.
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Old 11-18-2013, 04:48 AM   #37
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Yes Ray the Allison transmission is set up to protect the engine against over reving. Just because one leaves the "brake switch" on all the time does not mean is is being used all the time. Mine only comes on when my pedel is in a "closed" position (off the pedal completely) I set mine up the way I want it to perform and it does just that, and that is why the menu for the transmission has so many different selections and configurations to select from based on ones desires, but.........now if you just want to buy it, drive it and leave it set up like you bought it that is OK to. Most people do not know of the different options that there is to select from or for the biggest part......understand if they make a different selection .....what is it going to "act" like. One of biggest reasons for staying in 6th gear is my tranny is set up to "hold" my speed while on cruise control so if my speed when set goes over 2 mph my exaust brake will come on and when it is 2mph below set point it goes off, When this is going on I did not need the transmission downshifting to 4th gear. Driving with the cruise control setup like this is a real joy now. Factory settings are just a "default" setting set up as a base line but to personalize it is your choice.
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Old 11-18-2013, 07:15 AM   #38
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I have never seen that caveat on any of the signage. It just states NO engine brakes.
The reason these signs don't matter is that they violate federal law and, therefore, are unenforceable:

The Noise Control Act of 1972 (now codified at 42 U.S.C. § 4917) authorizes the Environmental Protection Agency (EPA) to promulgate uniform national noise emission regulations for motor carriers engaged in interstate commerce. The federal statute expressly prohibits the states and their political subdivisions (including municipalities) from adopting or enforcing noise standards applicable to any motor carrier engaged in interstate commerce unless the standards are identical to the federal standards (see § 4917[c][1]). (The current version of the EPA’s regulations is codified at 40 C.F.R. § 202.20.) Therefore, unless the noise standards in an engine braking ordinance are identical to the federal standards, the ordinance is unenforceable as applied to motor carriers engaged in interstate commerce.

Since Jake brakes aren't prohibited by federal law they can't be prohibited by local municipalities.
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Old 11-18-2013, 08:49 AM   #39
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When I engage my PacBrake exhaust brake the Allison tranny automatically shifts down to 2, BUT at highway speed it doesn't actually go to 2nd gear until the speed drops way down to where it's safe for the tranny to be in 2nd! So even though it says it's in 2nd the tranny is not reducing the speed any if you are at higher highway speeds.
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Old 11-18-2013, 12:07 PM   #40
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The reason these signs don't matter is that they violate federal law and, therefore, are unenforceable:

The Noise Control Act of 1972 (now codified at 42 U.S.C. § 4917) authorizes the Environmental Protection Agency (EPA) to promulgate uniform national noise emission regulations for motor carriers engaged in interstate commerce. The federal statute expressly prohibits the states and their political subdivisions (including municipalities) from adopting or enforcing noise standards applicable to any motor carrier engaged in interstate commerce unless the standards are identical to the federal standards (see § 4917[c][1]). (The current version of the EPA’s regulations is codified at 40 C.F.R. § 202.20.) Therefore, unless the noise standards in an engine braking ordinance are identical to the federal standards, the ordinance is unenforceable as applied to motor carriers engaged in interstate commerce.

Since Jake brakes aren't prohibited by federal law they can't be prohibited by local municipalities.
That reg is for veicles engaged in interstate commerce. Commercial plates,cdl,highway use taxes. It does not apply to RV's thus the local ordanences are legal and enforcable.
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Old 11-18-2013, 03:40 PM   #41
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That reg is for veicles engaged in interstate commerce. Commercial plates,cdl,highway use taxes. It does not apply to RV's thus the local ordanences are legal and enforcable.
Sure, but since >90% of Jake brakes are on trucks many (most?) of which are engaged in interstate commerce, I'm sure that not much enforcement effort is spent tracking down motorhome offenders, all of which have muffled compression brakes, anyway. IMHO this is an unnecessary "fear" that I know I'm not going to lose sleep about, nor would I attempt to convince someone not to buy a compression because of. I surely don't think this is an argument for why it's better to own a less effective exhaust brake because you won't get a ticket for something you won't get a ticket for anyway.
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Old 11-18-2013, 10:03 PM   #42
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Thanks for that information DocJ. Makes sense to me.
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