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Engine Brake Question

Yahoo Message Number: 89253
My previous coach had an exhaust brake only. I understand the Cummins in the Allure has a true Jake (compression) brake. The 'engine brake' switch on the dash has two positions; a forward and backward position and center 'off.' Is there a difference? I've moved it to both positions and could not really tell a difference but I haven't really driven this coach in much steep terrain yet. Compared to my two axle Journey, this Allure has outstanding service brakes.

Gary

2007 Allure 470 #31578

Re: Engine Brake Question

Reply #1 –
Yahoo Message Number: 89255
Check your manual to be sure on our coach, but back is low, forward is high. (Low = 3 cyl; High = 6 cyl.) On the Cummins ISL in our coach, the difference is not profound, as these are medium size block engines. But, the High does definitely provide more 'braking horse power' then the low.
Also on certain ISL's (I don't know about your era.), Cummins did have to go back in and adjust settings under the valve cover. Our High, was only partially closing the valves, and thus were not getting the full benefit of the High setting. Cummins Cal Pacific here in San Diego area (El Cajon), went in and reset the settings under the valve covers for us as part of a condition of our coach purchase. It made a difference, but again the comment about medium size block engines, still not a BIG CAT or ISM/ISX when it comes to Braking Horsepower:)!

Best of luck on your rig, and enjoy, Smitty
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)

Re: Engine Brake Question

Reply #2 –
Yahoo Message Number: 89257
We had a similar problem. Stage #1 & #2 produced the same amount of braking. Cummins Coburg Oregon found a leak in the oil line under the valve cover that accuates stage #2 (a pipe plug had fallen out).

Jim 07 Allure #31570

Re: Engine Brake Question

Reply #3 –
Yahoo Message Number: 89259
In my case I have found it all depends on the quality of the engine oil you use and the resulting oil pressure. Now that I use Valvoline instead of Rotella with the same weight, 15-40, my down the road oil pressure is around 42 to 45 lbs, and when the engine brake engaged over 60 lbs. Where be fore the engine oil pressure was around 35 and the braking pressure under 50. If I am descending a 5% grade with the switch on low I can easily hold 54 mph in 4 th gear. In the high position almost 7% grade. Driving around Colorado where the speed limit on the roads is in the 30's and low 40's in the Mountains I leave the switch in high. My transmission was set up to seek 2 nd gear with the engine brake engaged. Which means I don't have to take my eyes off the road and can keep both hands on the wheel while driving mountain roads, say from Durango to Ouray for example, or west bound over Wolf Creek pass or east bound on I70 going into Denver from Eisenhower tunnel. I found this set up especially valuable while driving back east from Chicago to Portsmouth NH. Driving the hills of Virginia, West Virginia and Tennessee, the set up was quite valuable. It makes driving the Grapevine and the Sierras in California and the Cascades in Oregon and Washington, I5, trouble free. Its especially valuable crossing the coastal range mountains from HWY 101 and 1 over to HWY 99 or I 5. As we live at the base of the Rocky Mts no matter which way we go we find the set up valuable. TWI 2004 Intrigue 42' 11731

Re: Engine Brake Question

Reply #6 –
Yahoo Message Number: 89267
I always remember CAT Man Wolfe (A few other sites well respected member, and moderator of some.)comment about his 'favorite gear'. He says that gear is 'coasting', as it really improves MPG:)!
I use the Jake set in High or 2nd Stage while in heavy city freeway traffic. And of course I used it in mountain driving. I prefer to drop into 3rd, or 2nd, as needed. As opposed to needing to frequently 'stab the brakes' to slow back down to the speed I wish to maintain. These are heavy rigs, and brake fade protection is recommended as a normal habit of driving.
I was chuckling at myself, as it was a full year before I learned that: -When Jake is first engaged, and on my coach it drops into 4th, that I then need to use the 'Down Shift' button 3 times, to drop it into 3rd, or a 4th time to drop it into 2nd gear. (The trans may reflect '4', but the Allison brain remembers it was in 6th.) -That the Jake will engage while using cruise control. It just has about a +5mph fudge factor before kicking in. (If in cruise control at 55mph, it will be about 60mph before the Jake kicks in.) -And as a reminder of what you have probably read many times. The combo of the Cummins and Allison computer brains, will not allow you to hurt either. So if you are say driving at 70mph, and turn on the Jake, it will not engage due to the RPM's will be too high.
As someone mentioned on another thread, these coaches provide an ongoing opportunity to learn. Year, after year...
I also think it is important to understand that Jakes and Engines make a difference. A BIG BLOCK CAT or Cummins ISM/ISX (Most with 3 Stage vs 2 Stage.) will have different characteristics. Toss in the Allison vs CAT Transmissions into this mix too.
I mention this, because when helping other board members with your tips on Jake's Best Practices, please include your engine. As the bulk off CC coaches are Allison, maybe as an exception please let us know if you have a CAT Transmission too?
Many, many experienced drivers on this board that are very generous with their school of hard knocks lessons:)!

Best to all,
Smitty

04 Allure 31017 (40' Tag with ISL370)
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)