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Old 07-13-2022, 10:41 AM   #1
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Adding Jake Brake to ISC8.3

Hey there everyone, decided I would make a post because I have found zero info on the installation I am doing and figure there might be others interested. Backstory:
We recently purchased a 2013 Fleetwood Discovery 40G. It had the bunk beds, newer interior that my wife was after and I targeted 2011 or newer as it has the larger ISC 380/1050 engine. On the drive home (Washington to Oregon) it quickly became apparent that the exhaust brake was not sufficient for western topography. Through some research I found out that Cummins utilizes the VGT function as an ďexhaust brakeĒ on the newer ISC engines. Itís far less effective than a traditional exhaust brake in my opinion and incredibly anemic compared to the 3 stage engine brakes Iím accustomed to in the ISL9 powered fire engines at my job as a career firefighter.

My first inquiries were replied with ďIíve never seen true jakes on a newer ISCĒ. I had just about resolved myself to burning through service brakes until a google search happened to turn up literature from Jacobís on their 490A brake heads. I then found an install manual covering ISC8.3 2010 EPA models!

Multiple phone calls to Jacobís (unanswered, never returned, frustrating) and a couple calls to Cummins and no one could tell me how to source the parts. Luckily another google search turned up a for sale posting from Frontier Truck parts. In short, the ISL9ís frequently come fitted with the engine brakes and the parts are cross-compatible in most cases. In the case of my 2012 build, engine brake parts from a 2012 ISL9 crossover just fine.

There are many parts that you will need to accomplish the task and Iíll try to list them out here:
- Jacobís specific exhaust valve crossovers
- Engine brake compatible lash adjusters for exhaust rockers
- Engine brake compatible exhaust rocker bolts/engine brake mounts
- engine brake oil supply intake rocker hold downs for intake rocker 1 & 4
- Engine brake compatible rocker lever housing, with pass through electrical connectors
- Jacobís Jake Brake housings (490A for my engine model)
- taller engine brake compatible valve cover
- taller valve cover compatible EGR crossover tube

As long as you are decently mechanically inclined, this really isnít that bad of job actually! Once I gained access to the engine it took me about 5 hours of wrenching to tear down and get back to the point of ready to install the Jakeís themselves. You do need to be comfortable/familiar with adjusting valves and setting lash but thatís about as technical as it gets. All of the removal process and torque values for installation can be found on Cummins QuickServe via your ESN.

I will head to Cummins tomorrow for a 20-30 minute recalibration of the ECM from a VGT exhaust brake control, to engine brake control. Then I will have to add an additional switch to control the level of braking. Iím still waiting on access to my chassis wiring harness to determine if existing wiring is available or if I will have to add it. I hope this helps anyone interested and happy to answer any questions I might have also had.
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Old 07-13-2022, 12:48 PM   #2
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Great write up! Looks like a awesome upgrade as well

I can say the valve clearance adjustment is critical on these engines, I set them on the "tight" side of the adjustment... Meaning it takes a fair amount of effort to slide the feeler gauge across the rocker. I've seen them where the cross bridge falls out from a loose setting, makes instant engine miss and lots of raw fuel white smoke.

Just curious..... what it all cost?
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Old 07-13-2022, 02:31 PM   #3
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Great write up. Please let us know how it works?
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Old 07-13-2022, 05:36 PM   #4
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What happens to/with variable geometry turbo. Do they just disable the brake portion
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Old 07-13-2022, 06:32 PM   #5
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Good for you !

I know all about how inadequate a VGT brake is on a heavy coach !!!!
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Old 07-13-2022, 09:21 PM   #6
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Did you figure out how it ties to your regular brakes, transmission and cruise control? The hi/lo switch is pretty simple. Just a break-out on the ecm wire. It is one coming from the ecm and splits to 2. 1 of those 2 runs to the hi lo switch and back. Watch your voltage, it's a long run. A relay in the rear may be in order.
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Old 07-13-2022, 09:41 PM   #7
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Yes. Nice layout of your work. I purchased a 2002 Monaco Windsor a few months back and it has the 350ISC 1050 torque motor with the Pac brake 2 stage and bringing it back to Washington I was amazed how the brakes held coming down Mt Ashland in Oregon. Very impressed. Safe travels and Enjoy!
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Old 07-14-2022, 08:55 AM   #8
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Huh?......been all out West with my 2012 Discovery 40X and never had an issue with braking, including steep downhills on snow, with the VGT on my 8.3L ISC?

Did you verify your VGT was functioning properly before considering the modification?

Thanks.
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Old 07-14-2022, 09:09 AM   #9
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Originally Posted by Toribk View Post
Huh?......been all out West with my 2012 Discovery 40X and never had an issue with braking, including steep downhills on snow, with the VGT on my 8.3L ISC?

Did you verify your VGT was functioning properly before considering the modification?

Thanks.
Thatís a good question and the honest answer to that is no. I can verify that the transmission is targeting the lower gears (second by default) and you could feel SOME braking effect. But I donít know if the ECM would display commanded and actual functions for the VGT via Insight or not.

Also, admittedly, even at full function, the available braking horsepower is half of that available via the CBrake by Jacobís. Iím sure that the level of engine braking Iím accustomed to in the fire engines when Iím working influenced my sense of how effective it was.
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Old 07-14-2022, 09:19 AM   #10
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Quote:
Originally Posted by mackwrench View Post
Great write up! Looks like a awesome upgrade as well

I can say the valve clearance adjustment is critical on these engines, I set them on the "tight" side of the adjustment... Meaning it takes a fair amount of effort to slide the feeler gauge across the rocker. I've seen them where the cross bridge falls out from a loose setting, makes instant engine miss and lots of raw fuel white smoke.

Just curious..... what it all cost?
Well now youíve got my concern upÖ. Since the engine was sitting at around 67k and I always right there and having to swap parts and adjust some of the lash anyway, I checked everything. I made sure everything was at or adjusted to the nominal setting in QuickServe of 0.012Ē on the intake and 0.022Ē on the exhaust. Then I set the Jake lash at 0.090Ē per QuickServe and Jacobís install instructions. So, I certainly hope I donít have that issue. I was surprised at the allowable range for both I will say.

All told Iím in it about $1500 in parts. Heading to Cummins/Freightliner shortly for my ECM recalibration. I have a little sense they might just reflash and send me on my way, but Iím prepared for that to be $150 or soÖ Of course I did all the labor, probably 10 hours tops I would estimate, but that would be a big cost driver if you were having it done.
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Old 07-14-2022, 09:21 AM   #11
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Originally Posted by vito.a View Post
Great write up. Please let us know how it works?
Thanks! Finished the rest of the install last night and heading to Cummins/Freightliner shortly for my ECM reflash and can report back.
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Old 07-14-2022, 09:25 AM   #12
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Originally Posted by 153stars View Post
What happens to/with variable geometry turbo. Do they just disable the brake portion
Yes, normal driving the VGT will still function normally. After the reflash the ECM will no longer command the VGT closed, but instead will energize the engine brake circuit. I have to add additional wiring to the OEM harness at PIN 36 for multi-stage engine braking control. But PIN 36 currently receives the signal for my VGT brake, so my existing switch will give me some engine braking immediately after the ECM reflash.
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Old 07-14-2022, 09:28 AM   #13
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Originally Posted by 96 Wideglide View Post
Good for you !

I know all about how inadequate a VGT brake is on a heavy coach !!!!
Yes, I suppose if youíre accustomed to no auxiliary braking functions it might seem to provide good assistance. But, being very familiar with engine braking, Iím a career engineer (driving and pumping) at the FD, so driving engine brake equipped vehicles of similar size and weight is my job, it makes it quickly apparent the significant difference in capability.
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Old 07-14-2022, 09:37 AM   #14
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Originally Posted by shootist View Post
Did you figure out how it ties to your regular brakes, transmission and cruise control? The hi/lo switch is pretty simple. Just a break-out on the ecm wire. It is one coming from the ecm and splits to 2. 1 of those 2 runs to the hi lo switch and back. Watch your voltage, it's a long run. A relay in the rear may be in order.
In short, that is all coordinated via the ECM. I donít know yet on my ECM, but I know some have options for how the engine brake is activated. Mine currently targets second gear on the transmission when engaged, I will keep that the same. I will have my engine brake engage ďimmediatelyĒ versus demand after it sees an activation of the service brakes. I believe there is also an option to have it automatically engage while cruise control is active if it notes a speed greater than 5 MPH above the set speed.

Iím familiar with the ECM pin out for the engine brake control, itís just making the connections from my current on/off feed into the new multi-level switch. What baffles me is that the 490A Jacobís unit has three level braking control, the same as my fire engines do, but they only use two wires and two brake heads. So I must admit I have no idea how that is accomplished. One would assume lo/med/hi are 2, 4 and 6 cylinders active, but that doesnít seem possible with only two brake heads with a single wire to eachÖ
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