How much back pressure can I run w/60# springs?

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My 4" BD brake is set at 20psi @ idle. It will go up to 40psi tops on a down hill with the engine revs at 2500. I have 60# springs throughout so my thinking is I should be able to adjust for a higher top pressure. Am I understanding this right? The 60# springs are good to 60psi or is that 60# of spring pressure.
I just want to adjust for max braking.

Larry

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1972 Chinook class C with 96/215 5spd, 4/5" exh, 4"BD, MagHytec, 85gal fuel, K&N RE0880, AutoMeter, 370's, BD gov kit, BD afc kit, 16cm, 16%btdc, yada-yada-yada
www.fostertruck.com/cummins

 

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LarryB,

I have my "elbow" style BD adjusted for 20lbs at idle. The manual says 20-25 with the sixty lb springs. I too max out at about 40lb of back pressure. Not sure what that 60lb spring rating signifies.

 

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60lbs. means that you can go up to 60lbs of back pressure without fear of floating the valves. Adjust your idle pressure to 25lbs & you'll see higher back pressure when in the retarding mode. You must remember that when BD, Pac, Jacobs, US Gear, etc. design these brakes for a maximum of 60 lbs they are taking into account Cummins recomendation of up to 3100rpm, so at 2500rpm you won't see maximum pressure. One of the highlights of the BD brake is you can set a higher idle back pressure to achieve higher retarding hp at lower rpm's.

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Piers, BD engine R&D

 

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Thanks Guys, I love this site.

So, I can turn up the pressure but must keep in mind that higher rpm means more pressure so keep an eye on the back pressure gauge and don't excede 60psi??

I have a solenoid valve connected to the e-brake that switches the boost gauge feed from the turbo pressure to the exhaust pressure when the brake comes on. This works great, good thing I bought the 60# "blower" gauge. That BD brake sure works great and is easy to adjust. I love tinkering with stuff like this.

Thanks Piers

[This message has been edited by LarryB (edited 01-05-2001). ]

 

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Inside the piston, that's used to pull the valve closed, there is a spring, as the pressure builds on the valve it compresses this spring, as the spring compresses it allows the valve to open more, bleeding off excess pressure. You should be able to raise your idle pressure to 25lbs to be able to achieve higher retarding hp in the lower rpm's, but not have to worry about over pressuring the system as it will bleed off the extra pressure automaticly.
Clear as mud? #ad


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Piers, BD engine R&D

 

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Except for your spelling, Piers #ad


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Real BOMBers never get speeding tickets. . just a lot of warnings!

 

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OK, that makes sense. It seems to top out about 40psi no matter how high the rpm. I guess that is where the brake spring lets off. looks like that is all I'm gonna get.

Unlessss... hmmmm, Is the spring adjustable?? #ad


You know how it is, we always gotta push till we find the edge. #ad
E-brake bombing, LOL

[This message has been edited by LarryB (edited 01-05-2001). ]