Jake Brake

TennesseeCRD · **Joined:** Mon Jan 11, 2010 11:01 am **Posts:** 181

Would our CRD's benefit from a jake brake (especially in our towing rigs)? Does anyone make one?

warp2diesel · **Posted:** Thu Feb 18, 2010 11:04 pm

TennesseeCRD wrote:

Would our CRD's benefit from a jake brake (especially in our towing rigs)? Does anyone make one?

Our Variable Vane Turbo kinda acts like a Jake Brake when we let off the accelerator.
One thing I don't do any more is use cruse control when I go up or down a steep grade when I am towing. The cruse control logic and how it communicates with the ECM and TCM is set up for gassers, not our CRDs. Going up a steep grade towing, the cruse down shifts too soon and revs the engine too high driving up the EGT very high. Going down a steep grade towing, it downshifts trying to slow the rig down and over revs the engine. When the engine revs too high the Variable Vane Turbo no longer acts like a kind of Jake Brake and makes the rig want to run away worst.

US Gear makes Jake Brakes for light Diesel Trucks and Motor Homes, they don't list one for our CRDs. The D-Celerator EXB-2500 (2 1/2" Exhaust) is listed at $1,295 for only use on lock up torque converters, I would not use the D-Celerator with the cruse engaged with our cruse control logic.
GDE has made comments not favorable regarding Jake Brakes, I suspect it some how effects their tune.
I would get another opinion if you don't have their tune.

DrHolliday · **Joined:** Fri Oct 30, 2009 7:19 pm **Posts:** 11

You can't get a true jake brake b/c the motor was not designed to have one. I'm assuming your reffering to an exhaust brake. IMO it will do nothing b/c I don't think there is a way to keep the TC locked. (TC needs to be locked to take advantage of the brake).

With the VVT turbo you can make it work like an exhaust brake, I have my Duramax tuned like this for towing and it works VERY well. But when towing with it it will keep the TC locked while decelerating until about 17 mph.

I'm not sure if GDE will do custom tunes beyond his mileage tune and high power tune, but from reading up on the changes he makes it sounds like it is possible to do.

As for the comments about downshifting while climbing causing EGT's to climb, I have a hard time buying it. I don't have an EGT guage in the wife's jeep, but when I tow with the Dmax its the oposite. When climbing hills loaded EGT's will start to climb, Bump it down a gear and they cool off some, if they continue to climb bump it down another gear and it cools off more. I know its apples to oranges, but they both work the same way being a turbo charged diesel engine with a VVT turbo.

Just my .02

BVCRD · **Posted:** Fri Feb 19, 2010 11:04 am

I'm not a rocket scientist, but it seems to me that higher rpm's equals higher exhaust temps. And no, the VM Motori engine (aka boat motor) was not intended for a Jacob brake.

warp2diesel · **Posted:** Fri Feb 19, 2010 4:53 pm

DrHolliday wrote:

As for the comments about downshifting while climbing causing EGT's to climb, I have a hard time buying it. I don't have an EGT guage in the wife's jeep, but when I tow with the Dmax its the oposite. When climbing hills loaded EGT's will start to climb, Bump it down a gear and they cool off some, if they continue to climb bump it down another gear and it cools off more. I know its apples to oranges, but they both work the same way being a turbo charged diesel engine with a VVT turbo.

Just my .02

I DO HAVE an EGT, BOOST, and TRANS-TEMP gauges, what I reported is what I got towing. Your EGT readings with your Duramax/Allison are not what I observed with my CRD. I will speculate your Duramax with an Allison should have an automatic designed for a diesel. Our CRDs have an automatic designed for gassers. If our CRDs had an automatic designed for a diesel, we would get readings similar to yours.

oddball · **Posted:** Fri Feb 19, 2010 5:34 pm

BVCRD wrote:

I'm not a rocket scientist, but it seems to me that higher rpm's equals higher exhaust temps.

You would be correct.

Off topic, sort-of - You know what's really fun, hitting the jake (3 stage) in one of my Peterbilt's (600 HP Cat's) and scaring the bejezus out of people! :ROTFL:

Big Montana · **Posted:** Fri Feb 19, 2010 6:10 pm

oddball wrote:

BVCRD wrote:

I'm not a rocket scientist, but it seems to me that higher rpm's equals higher exhaust temps.

You would be correct.

Off topic, sort-of - You know what's really fun, hitting the jake (3 stage) in one of my Peterbilt's (600 HP Cat's) and scaring the bejezus out of people! :ROTFL:

not nice.

oddball · **Posted:** Fri Feb 19, 2010 7:07 pm

I didn't say it was nice. I said it was fun, as in funny. :jester:

DrHolliday · **Joined:** Fri Oct 30, 2009 7:19 pm **Posts:** 11

BVCRD wrote:

I'm not a rocket scientist, but it seems to me that higher rpm's equals higher exhaust temps. And no, the VM Motori engine (aka boat motor) was not intended for a Jacob brake.

The higher RPM's relating to lower EGT's has to do with boost and the turbo's MAP. When your at highway speeds pulling your generally at a low RPM. Bumping down a gear revs the motor up and builds more boost creating more airflow to lower EGT's. Knowing that these motors weren't designed for pulling, they may be overloaded and the only way to drop EGT's is to raise RPM's and slow down.

I wish they had custom tuning software for these jeeps like they do for GM vehicles. I'd love to play with the tuning in the jeep to get a little better MPG's and see what else I can play with as far as making the turbo work as a brake.

danoid · **Posted:** Mon Feb 22, 2010 2:07 pm

The transmission wouldn't like an exhaust brake much either. Planetary gearsets create thrust along their axis when transmitting torque. There are thrust bearings set up to carry this and distribute the force properly to places that can support it. Large torques in the other direction lead to large thrust forces in the wrong direction also. The thrust bearings and snap rings need to be designed for such use.

ac5501 · **Posted:** Mon Feb 22, 2010 2:39 pm

What, the stock muffler on the CRD is not enough of a "jake brake" for you

BVCRD · **Posted:** Mon Feb 22, 2010 2:42 pm

ac5501 wrote:

What, the stock muffler on the CRD is not enough of a "jake brake" for you

Actually, it probably is. Out here, my 5 speed auto Mustang GT is a runaway going down passes. The CRD jogs down under control allowing me to save brakes. Rarely do I have to step out of overdrive.

CRD Joe · **Posted:** Mon Feb 22, 2010 4:51 pm

Exhaust brakes require a manual transmission dont they?

warp2diesel · **Posted:** Mon Feb 22, 2010 7:19 pm

CRD Joe wrote:

Exhaust brakes require a manual transmission dont they?

Lock up Torque Converters that stay locked up will work. Don't know if the stock or euro Chrysler torque converters would work, maybe a Suncoast would.
The big problem we have is out Auto Trans is not like the Diesel Pickups with the right logic that would lock the torque converter going down a steep grade in 4th or 5th. Instead it has gasser logic, that kicks it down into third and revs the engine up to at least 3500 RPM, if you tow in cruse. I have learned to not use cruse on steep grades and use my foot to help keep it in a gear that works when towing. The only time I use cruse towing is on a flat roads.

onthehunt · **Posted:** Tue Feb 23, 2010 2:59 pm

Please tell what your hauling that you need a E-brake?
The only thing good to come out of the new emission laws is the muffler design. They can't be modified or removed so some dumb booty can get his jollies listening to his Jake Brake.

Jake Brake

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