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My dad and I were playing a game of cat-and-mouse today up and down the hills near Mount Rushmore his truck would run about 15 miles an hour faster up the hills and then I blow his doors off going down hills because his engine break is absolute garbage so he has to go slow down the hills where I can be at 65 miles an hour and hold it there going down. Do the 870s have crappy engine brakes or is something wrong I know he's tried to get it working better he's replaced the harnesses and everything else under the sun.

He has a 550 horse Cummins tune from 3 years ago I'm going to guess 2050 torque

And mine's from here 550/1950
Forgot to add I'm pretty sure his turbo isn't kicking in like the cm871 ones do but his actual engine retard is working fine just no turbo and he does still have his air powered turbo
They hold better than any ither engine I've ever driven by miles and should be exactly the same if not slightly better than the cm871's.

My cm870 will hold 80,000 at 45 mph (8th gear @ 1700 rpm) on a mile long 9% grade pushing 31+ psi. I may have to lightly pump the brakes twice to lower rpm's and give the engine a rest. But that's just me being kind to the engine. I imagine I don't have to pump the brakes at all.

If I'd go down to 7th or lower it'll hold whatever speed I desire as long as the RPM's are 1500 or higher.

Haven't you posted before that your dad has problems with boost pressure, the turbo or something of that nature? Who did the tune on his truck? Is it verified good?
the engine brake on the 2250's and 2350's is slightly stronger than the 870's were. Newer engines have a higher compression ratio.
It's stock cummins tune. Turbo is 1yr old. Air control module is 2 months. Overhauled w new head Jan '18
Are you positive that its the correct Cummins calibration for his exact engine ESN & CPL? Cummins shops have been well known to put in wrong or incompatible cals.
Insight should show me his current AV code for his program right? If we get near each other again I'll get it and his CPL number and post them for a check as I don't have a tune library to compare it to. I just know he took the computer off the truck and two Cummins and had them program it from 500 horse to 550.

He did just tell me on the phone that is engine brake rockers are spitting some oil and that he used to work good on the engine break with the turbo and then slowly declined to wear it only builds about 10 lb of boost when rolling down the hill were used to build 30.
When was the last time he checked his exhaust back pressure sensor? He may be experiencing a soot problem. The small stainless steel line that goes from the exhaust manifold to the exhaust pressure sensor housing clogs real easy overtime. Also the housing for the sensor fills with soot. guys will change the sensor and think everything is alright. But the problems are still there because everything from the exhaust manifold leading to the sensor is packed full of soot and the proper pressure can't reach the sensor or soot flakes off and flies up into the sensor blocking proper readings.

10 psi is way low. 22-30+ is more accurate. And it should go there relatively easy with a load on.
(06-25-2019 )Chamberpains Wrote: [ -> ]They hold better than any ither engine I've ever driven by miles and should be exactly the same if not slightly better than the cm871's.

My cm870 will hold 80,000 at 45 mph (8th gear @ 1700 rpm) on a mile long 9% grade pushing 31+ psi. I may have to lightly pump the brakes twice to lower rpm's and give the engine a rest. But that's just me being kind to the engine. I imagine I don't have to pump the brakes at all.

If I'd go down to 7th or lower it'll hold whatever speed I desire as long as the RPM's are 1500 or higher.

Haven't you posted before that your dad has problems with boost pressure, the turbo or something of that nature? Who did the tune on his truck? Is it verified good?

Totally agree on the 870, that exhaust brake was a beast. I have never owned another motor that could match it. Mine had the full three stages available.
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