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

[Rikadoo]

Since i adapted my pac brake system to include a foot switch (which it never had before) i can say driving has gotten simpler an safer as i never have to take my hands off the wheel. In my pick up it has a clutch so i dont know if that adds to the simplicity of using my left foot while driving but it just feels better behind the wheel. Before if the switch was on during downhill manuvers there would be times i would lift on the accelerator to let it drift an i would have to switch off the brake or else it would start the whole brake sequence when i didnt want it. So the dance of switch on / switch off seemed a distraction from the act of driving. Most of my driving is done in the Sierras, which may be different in other locals that have longer downhill runs that would possably make it better to have a switch, i remember years ago in the Rockies there downhills were steeper for longer periods.

[Ken Thompson]

Out here in the NW we have big hills as well, but also would like to be able to let it coast in certain situations. It’s wired just to the switch right now, but I may add the foot switch

[MHRookie]

Can anyone tell me if you are NOT moving & park brake off and you push your pedal does the transmission selector still change to “2”?

I had a no working issue and found wire off post on head (it worked), then had some smartwheel issues.  Haven’t driven coach yet but was wondering if above question will verify Jake function or if I need to take it for a spin.

[Dr4Film]

If you are at a stop light not moving with the brake pedal pushed, the transmission indicator should be at 1 not 2 in (D)rive unless you are in (N)eutral, then it should read 0.

Not sure what you mean by "push your pedal", what pedal are you referring to?

[MHRookie]

43 minutes ago, Dr4Film said:

If you are at a stop light not moving with the brake pedal pushed, the transmission indicator should be at 1 not 2 in (D)rive unless you are in (N)eutral, then it should read 0.

Not sure what you mean by "push your pedal", what pedal are you referring to?

I’m troubleshooting the jake brake pedal (I’m in a parking lot).  If not moving and brake off with transmission in drive… if you push the jake pedal does the tranny selector switch to “2”?.

I’m wondering if it can be verified tested by NOT driving it.  It’s not that big a deal if I have to road test just curious if I don’t have to.

[Dr4Film]

Sorry, I don't have a Jake Brake pedal, only the brake pedal.

Can't help!

[Jdw12345]

I think you have to be above 15mph for the Jake to actuate, I don’t have a Jake pedal but I do believe you have to be rolling, I believe you’ll have to go for a test ride.

[MHRookie]

12 minutes ago, Jdw12345 said:

I think you have to be above 15mph for the Jake to actuate, I don’t have a Jake pedal but I do believe you have to be rolling, I believe you’ll have to go for a test ride.

Thanks JDW… 

[Gene Y]

On 10/19/2022 at 7:20 AM, Dr4Film said:

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?

 

Curious where that grade is. Is it on 77 or 81.

[Ivan K]

1 hour ago, MHRookie said:

Can anyone tell me if you are NOT moving & park brake off and you push your pedal does the transmission selector still change to “2”?

I had a no working issue and found wire off post on head (it worked), then had some smartwheel issues.  Haven’t driven coach yet but was wondering if above question will verify Jake function or if I need to take it for a spin.

I just tested it with the ISM, don't see why it would be different. My shifter displays max selected gear, not a current gear so if I shift into D, it normally shows a '6'. While stationary, it does not show the preprogrammed gear (in my case 4) as it normally would do while driving, so it would appear that you can not test it like that. And that's even with my ECM programmed to allow Jake all the way to 0 MPH.

"Engine Brake Delay Time","0.0",s
"Engine Brake Minimum Vehicle Speed","0",mph

[Frank McElroy]

Some trans gear selectors will display both the highest forward gear and the gear the transmission actually is in.

So, when you press on the Jake brake pedal, the highest forward gear is 2 as it was programmed that way when it left the factory.  If you are driving down a grade the display likely will show 66 before you press the Jake pedal.  After you turn press the Jake it will show 26, then as you slow so that the engine will not over rev, it will down shift and will show 25, then 24 then 23 then 22 and when it can shift to 21, the Jake brake will release.  That's at about 10 mph.  So when stopped, and you press the Jake pedal it will likely show 21.

[Dr4Film]

4 hours ago, Gene Y said:

 

Curious where that grade is. Is it on 77 or 81.

It is on I-77 southbound. It pretty much finishes jyst before the state line into North Carolina.

[Gene Y]

Thanks for that info, I had considered that route to get to 40 West from Eastern Va.,   I think I have reconsidered!

[beemerman]

I just wanted to clarify the difference in engine brakes on the ISL400 engines. The PacBrake and Jake brake are actually compression brakes and an exhaust brake is just as it sounds.  A compression brake uses the energy it takes for the piston to compress the air in the cylinder to slow the engine.  The jake head then opens the exhaust valve and releases the pressure before it can force the piston back down in the cylinder, that is why they are louder than an exhaust brake.  An exhaust brake simply closes off the exhaust and slows the air flow through the engine.  The exhaust brake is not as efficient as a compression brake.  The compression brake is actually an extra mechanical device that sets on top of the valve train so it can control when the the exhaust valves open for braking.

One other thing that I feel should be mentioned is the recommended RPM limit for the ISL400 is 2,200.  Both types of engine brakes put out more braking horsepower as the RPM rises.  My Dynasty with the ISL400 will put out about 16 lbs of manifold pressure with the Jake brake on HI at 2,000rpm.

As the Maintenance Mgr for a trucking company for 47 years I thought I would pass along some knowledge gained along the way.

Happy travels.

[Tom Cherry]

12 hours ago, Gene Y said:

Thanks for that info, I had considered that route to get to 40 West from Eastern Va.,   I think I have reconsidered!

I have the "VGT" Brake or the "Jake WANNABE".  It is NOT a compression brake like you, I think, have.

If you have ever gone down I40 E or the Black Mountain descent and had no issues, then the I77 is much easier.

The Black Mountain is a drop of 1361 Ft in 4.8 miles

The I77 is closer to 1300 ft in 6.2 miles.  

I have driven 177 many times coming back from the midwest.  That grade is "NOT A BLACK MOUNTAIN".  You take it easy and let your exhaust brake do the job. I never, maybe a tap or two, used my brakes on Black Mountain and I have done that more times than I can remember since the 70's....and In my old Gasser Winnie and at least 10 times in the Camelot....

I don't even recall doing a double take or thinking about the I77 grade.  I DO remember it because it takes a little TLC to climb...but coming down....safely....NADA

That's my experience....so you can think it over.....
 

[Ken Thompson]

1 hour ago, beemerman said:

I just wanted to clarify the difference in engine brakes on the ISL400 engines. The PacBrake and Jake brake are actually compression brakes and an exhaust brake is just as it sounds.  A compression brake uses the energy it takes for the piston to compress the air in the cylinder to slow the engine.  The jake head then opens the exhaust valve and releases the pressure before it can force the piston back down in the cylinder, that is why they are louder than an exhaust brake.  An exhaust brake simply closes off the exhaust and slows the air flow through the engine.  The exhaust brake is not as efficient as a compression brake.  The compression brake is actually an extra mechanical device that sets on top of the valve train so it can control when the the exhaust valves open for braking.

One other thing that I feel should be mentioned is the recommended RPM limit for the ISL400 is 2,200.  Both types of engine brakes put out more braking horsepower as the RPM rises.  My Dynasty with the ISL400 will put out about 16 lbs of manifold pressure with the Jake brake on HI at 2,000rpm.

As the Maintenance Mgr for a trucking company for 47 years I thought I would pass along some knowledge gained along the way.

Happy travels.

Are you saying the maximum rpm for the I SL 400 under power and compression is 2200 RPM? I read it Cummins post that say the engine can turn upwards of 2600 RPMs. I would never run my net high, but that’s what I have read. I usually keep mine under 2300 RPMs under compression.

[Tom Cherry]

4 minutes ago, Ken Thompson said:

Are you saying the maximum rpm for the I SL 400 under power and compression is 2200 RPM? I read it Cummins post that say the engine can turn upwards of 2600 RPMs. I would never run my net high, but that’s what I have read. I usually keep mine under 2300 RPMs under compression.

Your engine may have DIFFERENT limitations....but for the 2009 ISL (memory....but close and watching the tachometer), when I downshift going up a grade, I think MY OVEREV under compression is around 2200.  I can see it "float" or hover around that RPM so I then upshift to get the next higher gear.  As I pointed out, I do the Black Mountain run and typically, I climb it around 45....there are some spots where I have to go down to keep momentum up and then when it has a mid grade level, I upshift because it will exceed the 2200 if I left it there...

As to the DECOMPRESSION or Braking....the stock VGT Turbo brake will upshift if you push it over 2600.  I had to descend the Isenhower passs (I70? which is right west of Denver).  I started in 1 and kept it there....and it kept upshifting....even though I had it set to hold in 1....with the Exhaust brake on.  I used the service brakes to tap and slow down....but never heated them up.

SO....my rule is similar to yours....I upshift when it breaks 2000 or so....and then I really let the OverRev protector do the upshifting when descending a grade.  If you have the Luxury of choosing your max RPM, then that is great....but on some of the grades outwest...you have to trust the ECM and Allison to do the shifting.  In order to keep the 24/2500 range, I would have had to stay on my service brakes and that would have caused issues...

 

[Ken Thompson]

Thanks for the info Tom

[beemerman]

I double checked my self and went to Cummins Quick Serve website.  This is a direct quote from that site.

"Engine brakes can be operated continuously at engine speeds below 2300 rpm. Engine brakes can be operated intermittently at engine speeds between 2300 and 2600 rpm. Do not exceed 2600 rpm under any circumstances.  Engine damage can occur."

My information was incorrect by 100 rpm in my mind, but I have always leaned to the more conservative view point for longevity. 

Guess that is what happens when I share my "vast knowledge."

Sorry for the inaccurate information.

Happy travels

[isptbart]

On 10/21/2022 at 11:03 AM, 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. 

Matt & others - at 64 mph what RPM's are you running on a fairly level/flat road?

Thanks! Bart from VA

[Tom Cherry]

6 minutes ago, isptbart said:

Matt & others - at 64 mph what RPM's are you running on a fairly level/flat road?

Thanks! Bart from VA

Bart, you do realize that your Scepter like my Camelot has a different rear differential ratio that the same year Dynasty.  So, unless you are comparing a Scepter/Camelot to another, the information will look incorrect.

For example.  A 2008 Dynasty with the same ISL that you and I have will shift from 5 to 6 around 57 MPH.  Mine shifts on a medium throttle acceleration around 61/62 MPH.  If I set my cruise to 62 and stay on level ground, I usually pull 1500 or so (memory) RPM.  

In addition, the upshift is the same regardless of the mode,,,,normal (performance) or economy.  But, if I leave it in the economy mode, the downshift back to 5 is based on a lower speed….I have seen mine drop down to 57 and not downshift.  If I have disengaged the cruise, I can baby or soft pedal the accelerator and keep it from downshifting to 5 and then gradually get it back to 62, the set point,  but, if I hit resume, it downshifts and accelerates faster.

If anyone answers your question, you need to ask them for the rear end ratio.  That is in their Sales Brochure as well as yours….I checked….we both have 4.30:1 and the Dynasty is a 4.68:1…

The gearing lower (as in it takes more engine revs) per mile for the Dynasty than ours.  So, when they Dynasty hits 57 or so, that is the peak torque….of 1200 Ft Lbs @ 1300 RPM.  That 1300 RPM is when the shifts are set up to be.

But, comparing speeds and RPM is only possible when you know the rear end ratio.  Tires and the same….

 

 

[Matt Lavender]

1 hour ago, isptbart said:

Matt & others - at 64 mph what RPM's are you running on a fairly level/flat road?

Thanks! Bart from VA

I think around 1600 rpm

[isptbart]

3 hours ago, Tom Cherry said:

Bart, you do realize that your Scepter like my Camelot has a different rear differential ratio that the same year Dynasty.  So, unless you are comparing a Scepter/Camelot to another, the information will look incorrect.

For example.  A 2008 Dynasty with the same ISL that you and I have will shift from 5 to 6 around 57 MPH.  Mine shifts on a medium throttle acceleration around 61/62 MPH.  If I set my cruise to 62 and stay on level ground, I usually pull 1500 or so (memory) RPM.  

In addition, the upshift is the same regardless of the mode,,,,normal (performance) or economy.  But, if I leave it in the economy mode, the downshift back to 5 is based on a lower speed….I have seen mine drop down to 57 and not downshift.  If I have disengaged the cruise, I can baby or soft pedal the accelerator and keep it from downshifting to 5 and then gradually get it back to 62, the set point,  but, if I hit resume, it downshifts and accelerates faster.

If anyone answers your question, you need to ask them for the rear end ratio.  That is in their Sales Brochure as well as yours….I checked….we both have 4.30:1 and the Dynasty is a 4.68:1…

The gearing lower (as in it takes more engine revs) per mile for the Dynasty than ours.  So, when they Dynasty hits 57 or so, that is the peak torque….of 1200 Ft Lbs @ 1300 RPM.  That 1300 RPM is when the shifts are set up to be.

But, comparing speeds and RPM is only possible when you know the rear end ratio.  Tires and the same….

 

 

Tom - yes, very good point! Like yourself, mine shifts into 6th gear in the 60 mph range. Likewise, mpg ranges are not only affected by speed. but by the rear end ratios, so generic questions about fuel efficiency are only accurate when compared with same ratio rear axle ratios. I really hadn't given thought to that in the past.

Many thanks Tom!

Bart from VA

3 hours ago, Matt Lavender said:

I think around 1600 rpm

Thanks Matt! As Tom Cherry pointed out, we have different axle gear ratios so really not a direct comparison as i was assuming.

Bart from VA.

[Gene Y]

13 hours ago, Tom Cherry said:

I have the "VGT" Brake or the "Jake WANNABE".  It is NOT a compression brake like you, I think, have.

If you have ever gone down I40 E or the Black Mountain descent and had no issues, then the I77 is much easier.

The Black Mountain is a drop of 1361 Ft in 4.8 miles

The I77 is closer to 1300 ft in 6.2 miles.  

I have driven 177 many times coming back from the midwest.  That grade is "NOT A BLACK MOUNTAIN".  You take it easy and let your exhaust brake do the job. I never, maybe a tap or two, used my brakes on Black Mountain and I have done that more times than I can remember since the 70's....and In my old Gasser Winnie and at least 10 times in the Camelot....

I don't even recall doing a double take or thinking about the I77 grade.  I DO remember it because it takes a little TLC to climb...but coming down....safely....NADA

That's my experience....so you can think it over.....
 

Thanks for your information, that is exactly why I was considering the I-77 route. On our way back from Albuquerque Balloon Fiesta we stayed on I-40 East thru the mountains to I-85 North. Although I had no problem navigating that route I didn't appreciate the reduced speeds coming down the East side. So we are heading West again for New Years 2024 and were thinking about taking I-64 West to I-77 South then picking up I-40 West

[Tom Cherry]

8 hours ago, Gene Y said:

Thanks for your information, that is exactly why I was considering the I-77 route. On our way back from Albuquerque Balloon Fiesta we stayed on I-40 East thru the mountains to I-85 North. Although I had no problem navigating that route I didn't appreciate the reduced speeds coming down the East side. So we are heading West again for New Years 2024 and were thinking about taking I-64 West to I-77 South then picking up I-40 West

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.