Love My 2006 Dynasty ISL-400 & Engine Brake / How About You?

[Gene Y]

6 minutes ago, Tom Cherry said:

FWIW….The history of the Black Mountain descent goes back to 1973/74.  I lived in Statesville, NC where 77 and 40 intersect.  I was building a plant in Eastern TN and drove up every Sunday night and back on Friday.  One Sunday or perhaps Saturday there was a horrific accident and I sat in traffic for many hours as there was no “massive communication” systems.  That is when the road was revised and more speed constraints added.  Maybe 5 years ago, I was chugging along going UP  and was close to the speed limit when I was passed by a car.  Maybe 5 MPH faster than posted.  Within a minute, it was pulled over by the SHP.  Not commenting but the limits are considered as the REAL LIMITS and most in state folks respect that.

if you read the history of the I77 Grade, it has a bloody past also.  

Not to be personal, but I looked up your home location and I would have thought that the I64 to I81 to I40 would have been the preferred route.  We go north and west from Raleigh and travel I 77 to Wyethville a lot as well as coming down I 77 one the way in and out as my BIL lives in Mocksville and we overnight there often.  

That eliminates the winding section from the TN border to Asheville and the maze or mess around it.

We have never driven I 81 between Knoxville and Virginia, but really enjoy it for the view.
 

 

Actually didn't consider I-81. Kinda developed a prejudice against it from traveling from home to Blacksburg when my son was in school there. Every time I drove it (years ago) there was heavy truck traffic in the section below Lexington (VA) where tractor trailers would pull into the left lane on an uphill grade to pass another then not have the power to complete the pass. This would slow traffic to a crawl and repeat over and over. Maybe there are more 3 lane sections where there are uphill grades now. Funny now I would be part of the slower group trying to make those grades!

I have developed the same prejudice against I-65 between Indianapolis and I-80/94 when traveling to visit the same son who now lives in Chicago. No grades but the truck speed is regulated to 10mph less than car speed, when the TT's go to pass each other it gets messy.

Anyway based on your recommendation I will give that route a shot.

Thanks again 

[Tom Cherry]

1 hour ago, Gene Y said:

Actually didn't consider I-81. Kinda developed a prejudice against it from traveling from home to Blacksburg when my son was in school there. Every time I drove it (years ago) there was heavy truck traffic in the section below Lexington (VA) where tractor trailers would pull into the left lane on an uphill grade to pass another then not have the power to complete the pass. This would slow traffic to a crawl and repeat over and over. Maybe there are more 3 lane sections where there are uphill grades now. Funny now I would be part of the slower group trying to make those grades!

I have developed the same prejudice against I-65 between Indianapolis and I-80/94 when traveling to visit the same son who now lives in Chicago. No grades but the truck speed is regulated to 10mph less than car speed, when the TT's go to pass each other it gets messy.

Anyway based on your recommendation I will give that route a shot.

Thanks again 

Thanks….hope it works for you….have fun in San Diego.  We spent (ZZZZ) New Year’s Eve there one time….slept and never got back up to go to Elephant Bar in hotel to celebrate.

We did do Disneyland  on another trip and that was great.  Moving around kept up awake.  We can now say we have done NYE on both US parks….

GOOD LUCK

[Marine Boy]

I have a 2006 Dynasty 42 with an ISL400.  I have the engine brake with a hi/low setting.  I am out west for the first time and always thought it was working correctly, but now doing grades over 5% I am not sure.  I don't seem to see a big difference if any when going from low to hi...  Going down a big grade the trans will downshift to the point where my RPM gets to hit 2500rpm, and at that point I use my service brakes....   How much difference should I see when switching to hi on the engine break and is there anyway to verify it is working?

 

[Ken Thompson]

My 2002 ISL 400 has the 2 stage jake brake. There isn’t a huge difference, but you can feel it. I never let my rpm’s goes to 2500. I add service brake at about 2200. Not sure, but 2500 seems too high. I’m sure Frank McElroy knows for sure.

[Dr4Film]

My Cummins ISL-400 in our Dynasty has a similar response depending on the speed. Anything over 54 mph the high setting is not head jerking like some people claim that it is. So when doing a significant grade like the Fancy Gap Grade on I-77, I make sure I am under 54 mph when I crest the grade or use the service brakes to get the coach down under 54 mph. Then I simply toggle between high and low the entire 6 miles all the way never having to touch the service brakes even once.

[Frank McElroy]

1 hour ago, Ken Thompson said:

My 2002 ISL 400 has the 2 stage jake brake. There isn’t a huge difference, but you can feel it. I never let my rpm’s goes to 2500. I add service brake at about 2200. Not sure, but 2500 seems too high. I’m sure Frank McElroy knows for sure.

Anything above 2700 is considered engine abuse and the engine ECM is programmed not to exceed it.  The engine ECM won't let the transmission downshift if the engine would exceed 2,700 RPM.

I've checked my engine report and my max engine RPM since birth was 2,648 RPM. 

In order to achieve effective engine braking the road speed must be low enough for the transmission to downshift and NOT exceed 2,700 engine RPM.  Depending on grade and road speed, you might need to slow down enough for the engine brake to be effective.  If your speed is below say 40 MPH, you should absolutely feel a difference between high and low Jake.  If you don't, then high Jake might not be working.

[Marine Boy]

33 minutes ago, Frank McElroy said:

Anything above 2700 is considered engine abuse and the engine ECM is programmed not to exceed it.  The engine ECM won't let the transmission downshift if the engine would exceed 2,700 RPM.

I've checked my engine report and my max engine RPM since birth was 2,648 RPM. 

In order to achieve effective engine braking the road speed must be low enough for the transmission to downshift and NOT exceed 2,700 engine RPM.  Depending on grade and road speed, you might need to slow down enough for the engine brake to be effective.  If your speed is below say 40 MPH, you should absolutely feel a difference between high and low Jake.  If you don't, then high Jake might not be working.

Thanks Everyone.  I think I have an issue.  On 5-7% grades, starting below 40mph, I have to keep using my vehicle brakes to keep for going above 2500rpm.  I will get another test tomorrow starting in Salt Lake City finishing in Moab, UT.

[Tom Cherry]

13 hours ago, Marine Boy said:

Thanks Everyone.  I think I have an issue.  On 5-7% grades, starting below 40mph, I have to keep using my vehicle brakes to keep for going above 2500rpm.  I will get another test tomorrow starting in Salt Lake City finishing in Moab, UT.

That is absolutely OK.  From a practical standpoint....I tested the "VGT" (don't have a Jake) on the Eisenhower pass west of Denver.  I stopped and put the tranny is ONE and turned on the VGT (Exhaust).  Then, I realized...maybe let the Allison be held in 2.  That lasted for a while...and finally, the ECM and the Allison TCM (brain) said...ENOUGH...we need to upshift despite your well intentioned belt and suspenders....and it did.

Seriously, when you get ready to descend, I choose to have an override and maybe use 2nd or 3rd.  but, I keep my foot off the accelerator and only accelerate enough to get going and then back off as gravity takes over.  If my speed gets faster, then I downshift the Allison. 

On major descents....especially longer ones, you are going to have to tap or apply and let off....NEVER RIDE the service brakes.  It HELPS to have TOAD Braking as well.  OR, even unhook and let someone gear down and follow you.

Frank is the expert...but Allison told me, in general, and I have watch the Tach, but it is not digital, that 2600 is the recommended DO NOT EXCEED in Deceleration number.  I don't doubt Frank's 2700, but the tech said that was HIS recommended range...

AND a word of caution.  When you start to climb...do NOT keep the engine in "FLOAT" as it is at the ECM's governed or max POWER (accelerating or driving) RPM.  Back off maybe 100 - 200 RPM.  That puts less strain on the tranny...and that was an Allison recommendation... Pulling off for a few minutes if traffic is backed up behind you (like going in from the West entrance to Sequoia) is also a good thing and courteous...

It is HARD to try to break the Cummins as the Allison and the ECM will not let you...

[Frank McElroy]

Using 2600 as a max guideline for an ISL is OK but not really necessary.  My point is that the engine ECM will not allow the transmission to downshift if the RPM would be above 2700.  Above 2700, the engine computer will start recording the amount of time that the engine is operated 2700-2800, 2800-2900, and above 2900 RPM ranges.  RPM above 2700 for more than a second is considered engine abuse and will be recorded.  Rarely would an engine with an automatic transmission get into the range of recording RPM engine abuse.  It's more of an issue with standard shift transmission.

I have about a dozen engine reports from forum members that I saved over the years.  Out of curiosity, I looked at the maximum engine RPM data.  None showed RPM above 2700 lasting more than a second.  However, of the dozen engine report I scanned, max RPM data ranged from 2689 up to 2737 RPM.  Those that did exceed 2700 were for a very short amount of time (less then a second) and not recorded under the engine abuse history report.  As it turned out, my engine had 2689 and Bill G (RIP) had 2737.  (And now we know why he used the name Hotrod.)  Tom Cherry, in case you're wondering, the max for your engine was 2718, Scotty Hutto- yours was 2705 RPM.

[Pudgy Camper]

Sorry to revive this older thread, but after reading the wealth of info here, I figured it was the perfect place to ask a few questions and try to better understand how my engine brake works. I love my engine brake and I think it's one of the best features about owning my coach, but I'm unsure if it's operating correctly.

I've only been on a few trips in my (new to me) 04 Windsor with the 400 ISL. During the last trip a couple weeks ago in the mountains of AZ, I tried to pay close attention to how my engine brake was operating. Like others have mentioned, I only feel a slight (if any) difference between the hi and low setting. After really paying attention on the long descents coming off the Mogollon Rim down to Phoenix, this is how my EB behaved.

When approaching the descent at about 62mph, engine brake switch in the ON position, hi/low switch in what I think is LOW - the coach descended the mountain perfectly and held about 55mph for most of the descent. Once speed drops to around 43/44mph the engine brake engages what seems to be another stage, drastically slowing the coach down almost too much and forcing me to accelerate a little to maintain speed in some places. 

I tried the hi/low switch in the other position in what I think is HI and noticed maybe a little more braking power but nothing crazy, and performs the same when I get to that 43/44 mph, really slowing the coach down.

So my question is...... is this how these engine brakes operate? Or is my hi/low switch not working properly? Is the braking power I feel at 43 mph the second stage (high)? From my research the LOW stage should be engaging 2 cylinders of braking and HI engages all 6. From my experience it feels like all 6 are engaging automatically at the 43/44mph range. 

Just trying to get a good understanding of how this thing should be operating, and if it's not working right I'd like to fix it, being that we do a lot of mountain travel. 

Thanks for any input!

 

[Jdw12345]

Sounds like what you are experiencing is the transmission down shifting around 42/43 MPH and that would account for what seems to be more engine breaking. Imo.

[Dr4Film]

Your engine brake in high position is using all 6 cylinders. In low is using 3 of the 6 cylinders.

The reason you feel a large difference when your coach reaches 43-44 mph is that your Allison is downshifting as your speed reduces.

Have you determined your speed shift points both up and down? That would give you a better understanding of your Allison and how it interacts with your engine and engine brake.

I always have the Hi/Low Switch in the High position and only move it to the Low position if needed.

When descending a moderate grade, if the High position is slowing the coach too much I switch over to the low position, then toggle back and forth between the two until we reach the bottom. Seldom do I ever have to touch the service brakes unless I need to come to a complete stop.

My engine brake is not head jerking at higher speeds but I do feel a difference between the high and low positions.

You will need to play with it to understand at what speeds it performs the best for your coaches weight and whatever you may be towing.

[Pudgy Camper]

19 hours ago, Jdw12345 said:

Sounds like what you are experiencing is the transmission down shifting around 42/43 MPH and that would account for what seems to be more engine breaking. Imo.

 

19 hours ago, Dr4Film said:

Your engine brake in high position is using all 6 cylinders. In low is using 3 of the 6 cylinders.

The reason you feel a large difference when your coach reaches 43-44 mph is that your Allison is downshifting as your speed reduces.

Have you determined your speed shift points both up and down? That would give you a better understanding of your Allison and how it interacts with your engine and engine brake.

I always have the Hi/Low Switch in the High position and only move it to the Low position if needed.

When descending a moderate grade, if the High position is slowing the coach too much I switch over to the low position, then toggle back and forth between the two until we reach the bottom. Seldom do I ever have to touch the service brakes unless I need to come to a complete stop.

My engine brake is not head jerking at higher speeds but I do feel a difference between the high and low positions.

You will need to play with it to understand at what speeds it performs the best for your coaches weight and whatever you may be towing.

Thanks guys, that makes perfect sense that it's the trans down shifting giving me that extra braking. Don't know why I never thought of that, I just assumed it was another stage of engine braking. I'll play with the hi/low switch on the next drive too.

I learn something new every time I drive my coach, I guess I need to go on more trips!

[96 EVO]

Higher RPM's, higher braking power.

Works for both compression brakes, and exhaust brakes!