C 15 descending hills question

Like he says keep your engine fan on it adds 40 to 50 retarding horsepower

 

Cat has never been known to have a strong jake. If you're used to the jake on an ISX you'd definitely be disappointed by the C15.

 

There are different model jakes for cat. Maybe you have one of the weak ones maybe it needs adjusted. Running a Jake at 2000 rpm on a cat is not a wise thing to do. A jake on a cat does better at holding around 16 to 1700 rpms. If Jake is working properly, find the gear that works with Minimum foot brake usage.

 

Amen.

I have the twin turbo. It's not the greatest either.

 

My dad went from a 475 MBN C15 to a 530 ISX (EGR only). Trucks were pretty much identical spec, only difference between the 2 being the rear axle ratio (4.33 with the Cat, 4.10 with the Cummins). He claimed he could come down the same hills a full gear higher with the ISX while being on the brakes even less.

 

The Detroits and isx's I've driven were much better jakes. I've got the same engine as OP. I don't know why his is single and mine is double turbo.

 

Because somebody built it back to a single turbo.

 

Having your overhead set correctly will help immensely also ....

 

Another thing, air filters. Seen that one cause weak jakes too. Plugged up air filters were limiting the boost with the jakes on. Dropped in 2 new ones and the boost came up a few PSI. Made a noticeable difference in hold-back according to the driver.

 

The way I read the OP initial post he said the signal doesn't hold it back as well as the compounds did. From that I would assume he was driving it when they swapped the turbos, and there is the problem. A big single just doesn't have the drive pressure of the compounds.