ISL 2 Stage Brake.

[Redwing 77]

I have a 2006 Dutch Star with an ISL 400 with exhaust brake . Was wondering if it is possible to up grade to a 2 stage C Brake, and has anyone done this
or is it even cost worthy.

[smlranger]

Are you absolutely sure you only have an exhaust brake? It is my understanding that the ISL has the two stage engine compression brake. I have a 2007 ISL 425 and it has the two stage compression brake....no exhaust brake. Also, if you have the variable geometry turbo, it adds to engine braking by acting similar to an exhaust brake.

[Old Scout]

I too thought that ISLs only came with "Jake" brakes but continue to hear about some with exhaust brakes. Guess it might be possible to "upgrade" to a Jake but it would mean eliminating the existing exhaust brake system and modifying the top of the engine [valves/head/etc. ECM and wiring???] to the Jake configuration. Only guessing but would have to be very expensive??????

[Sky_Boss]

Originally Posted by smlranger

Are you absolutely sure you only have an exhaust brake? It is my understanding that the ISL has the two stage engine compression brake. I have a 2007 ISL 425 and it has the two stage compression brake....no exhaust brake. Also, if you have the variable geometry turbo, it adds to engine braking by acting similar to an exhaust brake.

I have the same 2006 model at the OP. It came with the single stage exhaust brake controlled by the VGT waste gate. Off the top of my head the max BHP at max power off RPM (2400 rpm) is about 330 BHP.

Don't see any feasible options to add engine braking. I suppose it could be done given enough time and money but it would seem more effective to upgrade to a new coach.

Not to twist this thread off too much but I've been told that the 3 stage brake systems use braking in the following order.

1. VGT.
2. VGT + 3 engine cylinders.
3. VGT + 6 engine cylinders.

I'm not so sure about 2 & 3 using the VGT and cylinders but that was what I was told. If anyone can confirm or correct that would be nice.

BTW...we are actively looking to upgrade our coach and the getting engine braking is one factor. While the exhaust brake gets the job done it is a little anemic at times especially in conjunction with cruise control and rolling hills. HOWEVER, our reasons to upgrade are far more related to floor plan, getting a 3rd AC and Oasis/all electric than the brake.

[Route 66]

The 2007 DSDP was the first year for the compression release "Jake Brake". 2 stage, 3 or 6 cylinders.

The 2006 models had an exhaust brake. All exhaust brakes are single stage.

It would be prohibitively expensive to convert as a new head, valve train and hydraulic plumbing is required.

Note that Jacobs Vehicle Systems (Jake) makes both exhaust brakes and compression release brakes, so it can be confusing when referring to a Jake brake.

https://www.jacobsvehiclesystems.com...xhaust-brakes/

https://www.jacobsvehiclesystems.com...elease-brakes/

[Harry B]

It is the coach manufacturer's choice if an exhaust brake or Cbrake (Jake) brake is installed.
I read a post sometime ago that to convert to a Cbrake costs about $ 11000. I have seen 450 isl engines yet with an exhaust brake

[Smitty77]

And the reality is with a mid size displacement engine, the jump in Braking Horsepower would probably be minimal...

I've never researched this, so it is a 'SWAG opinion by me', but I suspect the CAPS ERA ISL 2 Stage Jake Compression Braking Horse Power, is probably very close to the Variable Geometry Turbo era ISL with Exhaust Brake and the VGT also adding to the total Braking Horsepower. Would be very surprised if theirs more then a 10-15% variant between them...

(And if I cared enough, I would dig a bit deeper. But, looks like the DW is holding on to the galley in this coach for the years ahead... If my ISL ever needs replacement, I'll be lucky if she releases enough funds to cover a Briggs & Stratton engine! As, she could care less:(!)

Best to all,
Smitty

[Sky_Boss]

Originally Posted by Smitty77

And the reality is with a mid size displacement engine, the jump in Braking Horsepower would probably be minimal... ...

From my reading of the differences the difference is quite measurable.

The Jake Exhaust brake on a 400 ISL produces about 320 BHP. A true Jake Brake (engine) actually produces a bit over 100% of the engine rating. I can't seem to find my "fact sheet" but I will keep looking. 25% more BHP is pretty significant.

[Old Scout]

I don't own a 2-stage "jake" so don't really have any idea what I am about to say but never stopped me before [smile]: 1- my 2003 Alpine was one of the first 400ISLs put in our brand of coach--ironically, my chassis was wired for an exhaust brake so I only have one-stage brake [high]--which is pretty harsh; 2- fellow owners with 2-stage jakes see a significant difference between stages; 3- overall impact of the jake is driven to some degree by MPH and RPMs you are turning when jake is employed--mine won't kick in fully until MPH is below 65--ECM won't let Cummins over-rev; and 4 -perhaps most important, Jake/ECM/Allison can be programmed to default to a select gear on the tranny [eg 3rd, 4th or 5th] when jake is employed--significant impact. So need to consider all these parameters when discussing "jakes" or exhaust brakes.
PS--my experience is that some/many early 400ISLs came with an exhaust brake vs "jake."
PSS-Don't know about the impact of a VGT but just normal engine compression back pressure on the Cummins can modestly slow the coach.

[Mr_D]

Originally Posted by Sky_Boss

From my reading of the differences the difference is quite measurable.

The Jake Exhaust brake on a 400 ISL produces about 320 BHP. A true Jake Brake (engine) actually produces a bit over 100% of the engine rating. I can't seem to find my "fact sheet" but I will keep looking. 25% more BHP is pretty significant.

My ISX is rated for 650 hp, but Cummins says the VGT and engine brake can produce "up to 600 hp braking", which is the same braking rating as the 600 hp ISX.

[Smitty77]

https://quickserve.cummins.com/info/..._nondodge.html


ABOVE. That I can see, does not distinguish between CAPS vs VGT era ISL's.

https://cumminsengines.com/powerspec-isl-engine-brake

ABOVE. Just more general info on Jake Compression brake. I believe this is newer VGT engine related, as some of the features an options mentioned were not available to my CAPS ISL.

https://www.jacobsvehiclesystems.com...xhaust-brakes/

ABOVE: General info from Jacob's. Toggle between the Exhaust and the Compression to get more overview info. (And note, I do not believe they comment on VGT's added back pressure resulting in higher Braking HP(?) - But it does.)

=====

And I did shoot from the hip about not expecting a significant difference between Compression and Jake Braking Horsepower values, again, in regards to the mid size block 8.9L ISL.

I can say that I feel a difference between Low/High, especially in my target RPM range 2200-2400 range. (The higher the RPM, the higher the Braking HP.) It is very minimal, not going to toss you against your seat belt restraints! (Now, you from Low to High on a BIG BLOCK CAT, Cummins Detroit - and the displacement (SIZE DOES MATTER) will have a more dramatic feel from the driver's seat.)

And finally, the Braking HP's (Exhaust or Compression, whether or not with VGT assistance.) impact in one coach, can for sure be different then another coach. (Say the Braking HP is 200HP. A coach that weight 43K lbs, will not be effective as much as a coach weighting 34K lbs. (45' vs 34').

OP - another SWAG here from me. $8K - 15K range of costs to convert. Probably closer to the $15k mark, and that's assuming other computer mod's are not required between the Allison and the Cummins brains too... Really not costs effective expenditures of funds!

$.02!

Best to all,
Smitty

[Route 66]

The high setting on my 2 stage engine brake was so effective, I usually had to switch back and forth from high to low as high would slow me down too much.

[Route 66]

A bit of trivia.

Clessie Cummins who founded Cummins engines was later forced out of the company and then invented the engine compression brake.

He offered it to Cummins, but they declined.

He then sold it to Jacobs of Jacobs drill chuck fame.

[Koop]

Originally Posted by Route 66

The high setting on my 2 stage engine brake was so effective, I usually had to switch back and forth from high to low as high would slow me down too much.

I toggle between high and low settings on our ISL 400 to hold the desired speed on downgrades.