What's the proper way to use the jake brake

[Roysbigtoys]

Is it more effective to use the jake brake at low or high rpm? Which is better for the engine, low or high rpm?
My best employee tends to leave the jake switch most of the time. If he is shifting up and shifts fast enough the jake being on is not a problem. But there are times when I hear him leave a job site that I hear the jake come on between shifts....drives me crazy. It seems to me that this is not good or am I worrying for nothing?

[Rawze]

Some related info:

* I usually tell others that the jake should have a 30 seconds delay, and a minimum of at least a 5-second delay if u can't wait that 30 seconds for it. This is because I have seen an occasional ISX that has dropped a valve on cold days and jake set at 0 delay. Also happens on brand new engine sometimes. - Can you get away with it?-- Most of the time, Likely, but why risk a $36,0000 engine over it? - Not worth it just so that you can shift a bit faster.

* If you have 100% factory programming (emissions still in tact, etc), then the jake can easily handle up to 2400 RPM. If you have de-mandate programming (truck is deleted) and someone went in there and turned up the jake brake settings like a dumbarsse to try to make it stronger ... your prone to dropping a valve at high rpm. I see this mistake being made a whole lot when reviewing other peoples custom programs.

* I have seen (but it is fairly rare) where someone climbs a huge mountain, getting their truck and engine really hot because of heavy load and steep grade (like when climbing cabbage or 4th july, veil, Donner, etc.), and they are giving it all its got... Then crest the top of the mountain, its minus -15 or lower degrees-F outside, and they have zero delay jake ... That sudden inrush of super-cold air hits those very hot cylinders, and "boom", a cracked liner or valve. - Hence the recommendation of a 30-seconds delay for the jake.

Granted, all these situations are fairly rare to happen (except in the case of bad programming), but they should be at least known before someone decides to set their jake on 0 delay, thinking that it could never happen to them. I have mine set on 30-seconds. I haul 80,000 lbs over every one of the big mountains in the worst cold weather that has been seen. I just do not like knowing about the slight risks of having to rebuild my engine because I am impatient and want to shift faster. Besides that, I have yet to see an ISX that I could not speed-shift like a race-car (while test driving the truck only) with no jake turned on at all. - Just ask anyone who has been at my house and seen me do it while stress testing their truck.

This is just my own experiences, others may vary.

[JimT]

I have my engine brake set for a 2 or 3 second delay. lets me back out of the throttle or move my right foot around without the system engaging. I personally do not like the engine brake engaging when I shift, especially with 3 different levels, since it changes the shift timing. I guess if you only used one level and practiced power shifting then it would work, but since I own the equipment I no longer want to beat up my engine and transmission by hammering it. I also tend to be really light on the accelerator, so when i climb grades I'm in lower gears only pushing 10-15 psi boost, 22 psi max to maintain a speed/rpm. I actually use the engine brake to slow me down more than my foundation brakes. Coming up on 2 years since my rear brakes were replaced and they still have a long way to go. Front brakes have not been replaced in the 2 years I've owned the truck and they too have lots of life left.

As for protecting the engine, I always leave the engine brake off until the engine is up to full operating temp. I try to run it on the lowest setting for my present load that will control my speed. As for switching from heavy engine load to engine braking, I tend to roll out of the throttle as I'm cresting a hill and let the rpm's drop pretty low (with no engine load/boost) then let gravity speed me back up down the other side. By the time I need to engage the engine brake some time has passed for things to cool off.

As for a 30 second delay, I don't think I could work with that big of a gap. I'd probably be downshifting by the 10 second mark (or sooner) and the accelerator usage would reset the timer. Not to mention the rare times when you need the combined power of engine braking and foundation braking for a sudden deceleration. 30 seconds would be 15 seconds too long, in my opinion.

Recently I've also begun turning the engine brake off completely when I'm empty or bobtail, or really really light load. No sense putting wear on a system when it's not actually needed. When I was a young kid, constantly touching everything, my grandpa used to tell me that every switch can only be turned on/off so many times before it breaks. While he was mainly trying to get me to stop turning lights on/off, I found as an adult that it's very good advice for reducing maintenance intervals.

Just my 2 cents...

[Chamberpains]

I can say I've used 0.4 second delay for 500,000 miles with zero problems. I can't stand having the jake bark between shifts. I've found the jakes set 0.2 and shorter allow that to happen. I don't let the boost go above 28 maybe 29 psi or over 1800 rpm while jaking and I absolutely don't use them until the engine is up to full operating temp. I also don't ever pull a hill at more than 3/4 throttle and I strive for no more than 1/2 and keep the rpm's above 1400. Thats for fuel mileage and also to keep the heat from building on the engine. I found that the jakes are damn near useless under 1300.

A full second delay would drive me nuts let alone the 30 seconds delay Rawze recommends. Thats a half mile of travel at 60 mph before the jakes kick in. That kind of delay in the Appalachians would have the service brakes smoking in no time. I use my jakes to slow the truck over the brakes always. Unless I'm on really icy roads.

I've noticed all the trucks I've hooked insite to have had anywhere from 0.3 to 0.8 second deley set and that's fleet calibrations and a few O/O's that never messed with the factory settings.

Wouldn't the delay in the jakes not even be a thing to consider? At 1800 rpms a full 1 second delay would mean the engine completed 30 full rotations. Shouldn't that be more than enough time for the engine to settle if there is that much weakness in the valve springs and valve/rocker clearances? I would think that a properly adjusted overhead and a well engineered engine would never have a problem with a valve hanging long enough to contact the piston. I can see the case for the sudden freezing cold air intake cracking a liner. But thats a simple solution of just keeping your jakes off at the crest of the hill and then manually turning the switch on after an appropriate delay.

[Magard]

I set mine at .7 delay

[Roysbigtoys]

How do you change or check your delay? I will change my original questions slightly, is the jake brake more effective at low or high rpm? Does low rpm or high rpm jake braking put more strain on the engine?
Thanks

[Rawze]

the higher the rpm, the more negative horsepower it produces. I run mine up and do not get on the brakes until it gets to 1900+.

[marek4792]

my x15 performance in the 3rd stage will produce close to 32-33lbs of boost stock around 1500rpm and creep back down as the rpm goes up, put zero delay in and I do not prefer it especially when I forget to turn it off when I upshift or downshift even when holding the accelerator slightly, will be turning the delay back to one second. The 2nd stage jake is also stupidly strong at just around 20-25ish psi of boost. I'm almost afraid to use the third stage starting down the hill and start in the first or 2nd stage and gradually bring it up to 3rd stage especially when it's colder out.
My CM870 had zero delay and it was all right but then again turbolag and lower compression comes to play with them.

[Chamberpains]

Cummins Insite is the program you use change the engine brake delay. Its under features and parameters.

Just like Rawze said, the higher the RPM the harder the jakes hold you back. On my CM870, fully loaded grossed out at 80,000# set on 3rd stage jake, it would hold me back at 55 mph 1800 rpms on a 8-9% grade without touching the brakes. Cummins has by far the best engine brake in the world. I went from changing brakes once a year with my Detroit 60 series to maybe 1 time in 3 years with my Cummin ISX. And that was more do to cracked brake lining and scored drums from crappy after market brakes and dirty roads.

As far as damage to the engine... there should be none through normal operating RPM's. Ever.

As far as letting it run up in the 2000+ rpm range to hold you back. That might be the range where Rawze is worried about a valve hanging while hard jaking. Up in those rpm's that would be a lot of speed mixed with high PSI. I could see that potentially be a recipe for disaster. But on occasion I've downshift early (usually by mistake) and had the RPM's rocket up to 2100 under full load and was unable to correct it because of the terrain and Absolutely nothing ill happened. In fact the damn thing slammed the jakes on so hard it tugged me forward in the seat. And that engine had a million plus miles on it.