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Old 09-18-2014, 08:50 AM   #15
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my overflow tank radiator cap is a 16lb vented cap? is this correct for the cummins 400 hp isl? don't think we have ever replaced the radiator cap and should we?
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Old 09-18-2014, 10:33 AM   #16
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Take the cap to almost any auto parts store, NAPA is a good choice, they can match it. I believe it is 17psi rated.
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Old 11-20-2014, 12:02 AM   #17
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Regarding Jake (engine) brake. The jake actually works by holding the exhaust valve slightly off the seat. That way when the piston comes up on the compression stroke sit is forced out of the cylinder making a compressor out of the engine. Forcing air thru the partially open valve takes energy or horsepower. That is what slows the coach. If the exhaust valve was allowed to close the compression would force the piston back down. That would NOT make a compressor out of the engine
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Old 11-20-2014, 11:59 PM   #18
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Quote:
Originally Posted by Stretch View Post
Old r ver
Regarding Jake (engine) brake. The jake actually works by holding the exhaust valve slightly off the seat. That way when the piston comes up on the compression stroke sit is forced out of the cylinder making a compressor out of the engine. Forcing air thru the partially open valve takes energy or horsepower. That is what slows the coach. If the exhaust valve was allowed to close the compression would force the piston back down. That would NOT make a compressor out of the engine
I believe I saw in the manual that the Jake brake randomly drops cylinders by cutting the fuel. On the low setting it drops 3 cylinders randomly, on the high setting it cuts the fuel to all 6 cylinders.
On the ISC ?, 350 hp the exhaust is blocked by a butterfly valve in the exhaust pipe.
As for using the up and down arrows to manually shift your transmission, remember that you will need to press D or arrow back up to 6th gear once you are back on level ground.
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Old 11-21-2014, 03:42 AM   #19
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Not sure about the jake randomly dropping 3 cylinders on low setting. I guess with the electronic controls it would be possible. However with the non electronic engines it is the same three cylinders that the fuel is turned off and the exhaust valve is held open. The other braking method, the exhaust brake is just a butterfly valve that closes off the exhaust pipe entirely causing pressure to build like a compressor. Again that takes energy holding the coach back.
The engine or Jake Brake is far the better braking method.
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Old 11-21-2014, 08:37 AM   #20
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On any modern electronically controlled diesel, whether Cummins, Cat, etc when the throttle is closed, there is ZERO fueling.

With a two speed engine compression brake (aka Jake brake), low activates three cylinders, high activates all six cylinders.

It requires a LOT of work to push a piston up-- compressing roughly 17 volumes into one. In coast mode (engine brake off) most of that work is returned after the piston passes TDC (Top Dead Center).

Lifting the exhaust valve at the end of the compression stroke releases all the energy used to compress that 17 or so volumes into one (out the exhaust).

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Old 11-22-2014, 07:25 PM   #21
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FWIW - Alpine owners only, with ISL engine, other brands don't reply.


1. Never go down a hill faster than you go up it. Leaned that in CDL school, don't follow what the other guy is doing, be safe, if you went up at 40, go down at 40 till you get to the bottom.
2. Regardless of others, in my Alpine, when I push the engine brake, it does couple of things, first shifts transmission into 4th gear (50 MPH or below)(over 50, you could OVER-REV the engine and blow it up-Cummins told me specifically when I asked, never over rev the engine in any situation, acceleration or deceleration period, he was fixing a Monaco Coach whose owner had used the engine brake and over revved the engine, to the tune of a rebuild, lots of dough for that. The ISL redlines around 2300-2400 RPM's, the Allison will shift it correctly when accelerating. It also closes or almost closes the intake/exhaust valves, and shut off fuel delivery to the cylinders. Making the engine a braking compressor if I understand the principle correctly.
3. I switch between high and low engine brake going down a hill, as high will slow me down real good, below 40mph, so then I switch to low, which allows the coach to build up speed, prior to 50, I switch back to high. This works for me, but, I never go down faster than 50, unless I know the road, and it is not a long downhill stretch.
4. Once I am near the bottom, I turn off EB and accelerate a little to get the transmission to shift into it's correct gear. Normally I never need to touch the transmission going downhill.
5. Going uphill, since I want max RPM's turning my Hydraulic pump so I get max RPM's out of the cooling fan assembly for the radiator, I keep my engine RPM's in the 1900-2000 range, using whatever gear is required to keep it at that RPM. I don't worry about MPH going up a hill. We don't carry more than 33K in weight, (max GVWR for the coach) so we can normally pass most trucks, they will also normally stay in the right lane or the shoulder so traffic can pass. I use the arrow keys on the keypad to downshift as needed, remembering to use the up arrow to get it back into 6th, then I use the EB to go down.


Other drivers have their own system, and the recommendation of their MH builder. If you don't have an owners manual, believe it can be downloaded from the ACA tech library, or an owner can make a copy and get you one.
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