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


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I have owned this 2006 Dynasty with a Cummins ISL-400 since last February and have driven it for over 6000 miles now which includes a trip from Salt Lake City Utah to Florida and then up to New Hampshire and back to Florida recently over a wide variety of terrain, etc.

I am very impressed with its power and performance especially the two-stage engine brake.

i have found that the engines "sweet spot" is around 54-55 mph where it is running at about 1420 rpm and in 6th gear. It will actually stay in 6th gear while dropping mph until it reaches about 53 where the Allsion will kick down to 5th gear. So now my normal highway travel speeds stay around 55-60 mph. Whereas, the Windsor with a Cummins ISC-350 had a sweet spot of 62 mph.

When running 55 on mostly level terrain as in South Carolina, Georgia and Florida I was getting over 9 mpg towing loaded coach and towing my car. That drops to about 7.5 when the terrain starts having rolling hills. Then when in mountainous terrain the mpg drops to just under 7 mpg. My previous Windsor would average between 8-9.5 mpg when driving the very same roads.

What has impressed me the most is the two-stage engine brake as compared to the PRXB Exhaust Brake in my previous Windsor. I leave the engine brake switch on all of the time and the Hi/Lo switch in the high position. If the High is too much, then I reach over and switch it to Low and then back to High when finished.

If anyone has driven on I-77 from I-81 down through Charlotte and Columbia SC you are very familiar with the Fancy Gap area which includes a 4.5% grade that is 7 miles long. Just before I crested the top of the grade, I made sure my speed was under 63 mph as that's where the engine brake really starts to perform well. Anything above that, not so much. Then for 7 miles I never had to touch the service brakes once. I simply toggled between the High & Low settings to control the speed of the coach keeping it between 55 & 60 mph.

It was a real pleasure descending that grade with the Dynasty versus the Windsor.

What have others with a Cummins ISL- 400 discovered while driving your coaches?

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I too have the Cummins ISL-400 and agree with your comments about the exhaust brake. I mostly use mine when I may need to stop quickly. It also saves on the brake pads. My sweet spot is about the same as yours however I am getting slightly better fuel mileage. I typically use the cruise control with the Allison in Economy mode so it shifts at a lower speed. I typically hit 6th gear at 57 then will set my cruise. Once done I will then back the cruise down to 55mph. I typically get 10.5 mpg just letting it coast along on the interstate. I reset the mileage at each tank fill-up so I can monitor the mileage per tank. We just came home from a trip where we left Florida and went to Pigeon Forge, Tennessee. Each tank fill-up was about the same at 10.5 mpg except our last fill-up in north Florida. Driving from north Florida to Sarasota we got 11 mpg. Simply put the ISL-400 is a beast and perhaps one of the best engines on the road.

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Hi Steve,

I am using the data from the SilverLeaf to obtain my mpg because both the generator and Aqua-Hot use diesel from the same tank. So, I have no way to calculate accurately how much gets used by those two devices versus just the engine using the number of gallons pumped divided by the miles driven.

My cruise control is non-functional right now. So, I can't use it. It will turn on, but the SET and RES buttons will not work to set the cruise control speed. Hopefully it is an easy fix by replacing the SM210 control box someday when they become readily available.

Had the same problem with the CC on the Windsor but could never find a new control box to install before it got sold.

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So i have tried to get MPG in my rig, by staying out of the turbo is where life is good. When im at 5 to 6psi i can motor right along at 55 to 58, however its funney once i dip into the 60 or better that psi starts to ramp up up pretty quick an there goes my mpg. Most of my driving is in and around the Sierras out west, yesterday i left reno an am at Klamath Falls, both me an the coach just happy as could be till Susanville, 5k+ ft and a two lane road🤦‍♂️ Mindya im not complaining, but i AWAYS laugh when someone asks me “so whats your fuel milage like”😂😂😂

I love this lifestyle of traveling, an the joy of being able to enjoy to do it WAY exceeds any pain at the pump!6A5D49C5-E3CF-4D17-934A-6D5B2C519692.thumb.jpeg.df8ac23f2306917a2314bd2051fcd7c9.jpeg3301E20A-FB83-4791-95EB-C4D5FD79D043.thumb.jpeg.3d0035af2ccc5c416d8ae3dcb18d402c.jpeg

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My experience is about the same except I normally run at about 62.  Running below 60 for me creates too much of a hazzard when on higher traffic routes like I-95.  With very light traffic 55-60 is fine but when folks are getting in a line to pass, I'll speed up a bit.

I use the Jake whenever I need to going down hill or to stop.  However, I don't leave it on all the time.  Whenever I take my foot off the throttle I want to coast and not waste energy by braking unless I need to.  Going down hill I'll let it run up to about 68 before turning on the Jake. 

On engines with a DPF, leaving the Jake on all the time is a bad practice when the Regen light comes on.  The Regen cycle will suspend every time the Jake brake activated.

Will use cruise on level ground but when in hilly terrain I turn the cruise off in order to anticipate grades increasing speed before the grade and slowing down when cresting.

Leaving the cruise and Jake brake always on in hilly terrain was a mileage killer for me.

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36 minutes ago, Frank McElroy said:

Leaving the cruise and Jake brake always on in hilly terrain was a mileage killer for me.

On my next trip back to New Hampshire in the spring I will leave the engine brake switch off unless I am traversing a grade to see if my mpg increases like you state. No cruise control yet until I replace the SM-210 control module.

I have found that anything 64 mph and over the engine brake has very little affect until the speed reaches 63 then the coach starts to slow down quickly as you can hear a definite change in the sound and the coach actually feels like I had used the service brakes.

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A foot switch works great for me. I keep the switch in HI for normal driving and if there is a need for panic stop, just slam both pedals. No mistakes leaving it ON when not needed. It works best with higher RPM. Doesn't your tranny downshift with it permanently ON?

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3 minutes ago, Ivan K said:

Doesn't your tranny downshift with it permanently ON?

Not as long as I have my foot on the fuel treadle even if it is lightly sitting there.

If I remove my foot completely that's when the Allison display changes to 2nd gear and the coach starts to reduce speed. I use the same procedure as I did with the Windsor and its Exhaust Brake. However, BIG differences obviously between the two.

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50 minutes ago, Dr4Film said:

On my next trip back to New Hampshire in the spring I will leave the engine brake switch off unless I am traversing a grade to see if my mpg increases like you state. No cruise control yet until I replace the SM-210 control module.

I have found that anything 64 mph and over the engine brake has very little affect until the speed reaches 63 then the coach starts to slow down quickly as you can hear a definite change in the sound and the coach actually feels like I had used the service brakes.

Richard, 

I've only taken one 2000 mile trip in my MH and I had the exhaust brake on the whole time.  I noticed that my cruise control would not work at all.  The light would come on in the switch, but "set" and "resume" had no effect at all.  

There is another very similar thread going on this forum right now and here is what I have learned:

1.  It is not advisable to leave the exhaust brake on full time, as Frank mentioned above, because it has some negative effect on the DPF.  I don't think that I have DP Filter on my engine, but you might.

2.  Your fuel economy may suffer by leaving it on 

3.  The exhaust brake and the cruise control cannot be used at the same time.  This is probably why I could not get my CC to work on my last trip.  Since you mentioned that you also tended to leave you e-brake on full time, maybe by leaving it off, your CC will work without having to replace your module.  

I'm hoping my CC will work when I leave the e-brake off and I hope yours does too!

Carey

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Most folks likely don't know this but on many of the newer Cummins engines there is an ECM option that Monaco rarely used.  It is a setting to allow the cruise control to interact with and automatically apply the engine brake when the coach speed exceeds the cruise set speed by a set amount. 

If the "Cruise Control and Engine Brake Interaction" feature is Enabled, you can set the speed above the cruise control set speed where the engine brake would activate and if a two stage engine brake the speed where the second stage would activate. 

On my coach, I enabled that feature and set the Low Jake brake to activate at +5 MPH  and High Jake to activate at +8 MPH above the cruise control set speed. 

So, if I have my cruise control set at my normal 62 MPH and I'm going down hill, once I get above 67 MPH, the low Jake brake would come on; if above 70 MPH, the high Jake would come on.  Then once the speed got to my set speed of 62 MPH, the cruise control would resume. 

I like it.  If other want it, you need a shop with the Cummins Insite software to make changes in the Features and Parameters settings of the ECM.

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I see signs when coming into most towns saying no engine brakes and hearing the noise some trucks make, I understand why.

However, I don't know if I have ever heard an RV engine brake before so do most RVs not make such a loud exhaust noise?

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Frank, the Jake brake / cruise control interface set up on your coach rocks. Mine requires the Jake to be off for CC to activate. I do like the smart cruise and Jake for reducing driver workload! As a first time MH owner there is so much to learn. Thanks to all on this forum for sharing their knowledge! 

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18 hours ago, Idoc57 said:

Richard, 

I've only taken one 2000 mile trip in my MH and I had the exhaust brake on the whole time.  I noticed that my cruise control would not work at all.  The light would come on in the switch, but "set" and "resume" had no effect at all.  

There is another very similar thread going on this forum right now and here is what I have learned:

1.  It is not advisable to leave the exhaust brake on full time, as Frank mentioned above, because it has some negative effect on the DPF.  I don't think that I have DP Filter on my engine, but you might.

2.  Your fuel economy may suffer by leaving it on 

3.  The exhaust brake and the cruise control cannot be used at the same time.  This is probably why I could not get my CC to work on my last trip.  Since you mentioned that you also tended to leave you e-brake on full time, maybe by leaving it off, your CC will work without having to replace your module.  

I'm hoping my CC will work when I leave the e-brake off and I hope yours does too!

Carey

 

9 hours ago, det944 said:

Frank, the Jake brake / cruise control interface set up on your coach rocks. Mine requires the Jake to be off for CC to activate. I do like the smart cruise and Jake for reducing driver workload! As a first time MH owner there is so much to learn. Thanks to all on this forum for sharing their knowledge! 

Carey & Dan,

My previous Windsor has an Exhaust Brake, and the original owner had the ECM flashed so that the Cruise Control could be utilized while having the Exhaust brake Switch in the ON position. Not sure about the Dynasty with its Engine Brake as I am still in the troubleshooting mode with the VIP SM210 control module to see whether it has failed or whether something else is causing the problem.

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22 hours ago, Ray Davis said:

I see signs when coming into most towns saying no engine brakes and hearing the noise some trucks make, I understand why.

However, I don't know if I have ever heard an RV engine brake before so do most RVs not make such a loud exhaust noise?

Ray, if I'm not mistaken, I believe that the signs refer to "engine brakes" that are actually internal to the engine itself.  These are a form of compression release directly off the cylinders and they are extremely loud.  I think they vent directly to the atmoshpere rather than through the muffler as our exhaust brakes do.  I'm pretty sure that these loud engine brakes are similar to the hand/cable activated compression releases that we used to use on our dirt bikes back in the 70's.

Carey

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46 minutes ago, Idoc57 said:
23 hours ago, Ray Davis said:

 

Ray, if I'm not mistaken, I believe that the signs refer to "engine brakes" that are actually internal to the engine itself.

Right Carey, that's what I believe too.  These guys talking about their engine brakes are making me want one too, and that means trading coaches.  Moma D is not near as excited about engine brakes as I am, I just don't understand women. 😇

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My 2008 Holiday Rambler Scepter with the 400 will apply exhaust brake while cruise control is on and will resume speed when needed.

As far as High Low setting, I'll have to see if that is somewhere on the panel, I don't recall seeing it before.

I love my 400, sweet spot seems to be around 64 mph. 

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12 minutes ago, Matt Lavender said:

My 2008 Holiday Rambler Scepter with the 400 will apply exhaust brake while cruise control is on and will resume speed when needed.

As far as High Low setting, I'll have to see if that is somewhere on the panel, I don't recall seeing it before.

I love my 400, sweet spot seems to be around 64 mph. 

The Scepter and Camelot are twins in all mechanical and electrical and chassis and whatever….except the interiors, paint schemes and decals/logos are different.

Your Cruise and Exhaust brake interaction is the way it came from the factory and was “designed” that way.  SOME other models, up and down the food chain and also earlier and later do NOT, with the same ISL engine work that way.  Your experience and observations are correct.

The downside of that is that  going downhill and engaging the exhaust brake, if the speed gets below the set point, the cruise will apply power.  So if you set it at 60 and start down a bill that is 45, opps….too fast,  you have to tap the service brake to disengage….as well as turn on the exhaust brake.

In addition, when you hit resume at the bottom and the Exhaust Brake is ON, your fuel mileage will drop around 5-10% as the exhaust brake comes  on and off as the cruise cycles .”On and OFF” the accelerator to maintains speed and negates the advantage of using the cruise.

Finally, the Camelot/Scepter  did not have, as a standard or optional feature, the additional Jacobs or Jake Brake.  Occasionally Monaco MIGHT allow that as a custom feature or upgrade.  But a few months prior to the 2009 bankruptcy, they ran out of the ISL Camelot/Scepter engines and starting using up the surplus Dynasty engines.  It was an “ADD” to the MSRP and around $2,900.  That engine had the Jacobs brake in addition to the VGT exhaust brake,  I passed on a future build with that.  

IF you have the Jake Brake, there will be an additional switch on the driver’s left console, next to the RED Exhaust Brake switch, with a LO/HI switch and marked “Brake” or something like that.

Just clarifying this for folks…..

23 hours ago, Ray Davis said:

Right Carey, that's what I believe too.  These guys talking about their engine brakes are making me want one too, and that means trading coaches.  Moma D is not near as excited about engine brakes as I am, I just don't understand women. 😇

For Clairty….

The later models….maybe in the 04/05 timeframe had Cummins Engines with the VGT or the Turbo Exhaust Brake.  There are pictures here and on Yahoo of,how,that works.  My Camelot ISL has only that feature.

On the higher food chain Dynasty and above, those same ISL engines came with a Jacobs “head compression” Brake as a standard feature.  The VGT and the Jacob work interactively…..  Frank McElroy is our expert and may have or can explain for the inquisitive folks.

NOW the PacBrake was also used on older models prior to Cummins, and Monaco, switching to the integrated VGT a turbo with exhaust brake.

I am not an expert on the “deceleration” differences or effectiveness between an add on “Exhaust Brake” and the Cummins VGT….except to say I have driven 65K with my standard VGT ISL and only “wished” I had the additional “Jacobs” “head” brake feature a few times.  That includes many trips down Black Mountain in NC and countless passes and such out west including the Eisenhower I70 pass just west of Denver….as well as getting in and out of the KOA West CG in Denver…..a thrill ride unknown to the masses.  I also did the west bound section of Highway 12 in Utah that is a real “trip”.  However, I did have my Mountain West grade book and planned my routes not to include their “fools will take these roads” “STARRED” ones….and I never smoked or came close to heating up my brakes.

There are those that are more well versed and they can chime in and correct, but the above is what I know from reading, discussions with Cummins and hands on experience.

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Thanks Tom.

And yes, heading down a hill and all of a sudden coach starts to accelerate, will wake you up real quick.

I typically always drive with the exhaust brake off and switch it off and on as needed.

Thanks for all the insight. It's good to know about the Camelot, I learned that on this site I believe.

 

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On 10/19/2022 at 10:58 AM, Dr4Film said:

On my next trip back to New Hampshire in the spring I will leave the engine brake switch off unless I am traversing a grade to see if my mpg increases like you state. No cruise control yet until I replace the SM-210 control module.

I have found that anything 64 mph and over the engine brake has very little affect until the speed reaches 63 then the coach starts to slow down quickly as you can hear a definite change in the sound and the coach actually feels like I had used the service brakes.

Richard….

I will only SPECULATE on this.  If you have an abrupt downshift using the Exhaust Brake and I know you have the Jacobs then I would offer a comment.

Over the years, my VGT worked great and when it was applied it downshifted the Allison.  Now, I use mine like Frank does and as a supplement and have never kept it on full time.  And YES, it will, based a couple bouts of “stupidity” cut into your fuel mileage with the cruise and exhaust brake BOTH ON.

However, I had my Allison serviced and the shop let too much fluid drain out.  Allison says the correct way is to immediately install the filter and pan and such.  They let mine drain and then added the 19 quarts (memory) that Allison says.  I checked the level using the key pad….level and warmed up….tranny same temp as engine. It showed 3 quarts low.  Allison said do NOT believe that.  OK, I added maybe 1.5 quarts….in one pint increments.  

i drove it about 15 K and that was a lot of grades out west.  It sat in storage for a year as I was laid up with a broken leg.  Then COVID and we backed off.  This spring, I noticed it was down shifting abruptly.  Checked the level.  OL OK or OK OL….but, curious, I put in a pint of Transynd,  slight improvement,  another pint….better.  Each time I tested and drove it and the oil level, per the shifter test was OK OL.  I quit on the 3rd pint.  I have been up and down grades and and also used it in suburban traffic.  The pad says OL OK ….

Just passing this along.  You might have an issue….and that is how I solved mine and did not exceed the OL HIGH sensor…

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25 minutes ago, Dr4Film said:

Tom,

I am gathering from some members posts here that there Monaco coaches with ISL-400 engines that have only an Exhaust Brake and not a 2-stage Engine brake?

Is that correct?

The short answer is yes, that is correct. 

On the ISL400 you could have an exhaust Pac Brake or a two stage Jake Brake.  I'm not sure if there is an ISL400 with VGT braking.  Maybe someone will chime in if they have a VGT electronic actuator on an ISL400. 

Then with the ISL425 (CM2150) with DPF you likely have a VGT (Variable Geometry Turbo) brake that basically closes off about 90+% of the exhaust opening or you could have a VGT + a two stage Jake brake.

Also, the first generation (CM554) ISL engines did not have roller cam lifters like the later generation ISL engines (CM850 and CM2150).

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