exhaust brake hard on valves?

[BSkinner]

I had a truck driver tell me today that idling with the Jacob's e-brake on was hard on the valves. I've spent a lot of time reading TDR and other groups and this is the first time I've heard of this. "Old truckers tale", or what?



Bob

 

[jvmoore]

It's all in the user

I have a BD exhaust brake on my 95 2500 CTD with a 5 spd and have logged over 160,000 miles on it. After having it installed I had the valves run every 25,000 miles. I have yet to have any trouble and I had a jacobs installed on my 03 before I took delivery. The short period that the exhaust brake is engaged is not going to harm a cummins!

 

[Jeff Clark]

It does have some effect on the valve springs. The older trucks came with 30lb exhaust valve springs and those wanting to run an exhaust brake were advised to upgrade to 60lb. Newer trucks all come with the heavier springs.

 

[jvmoore]

60 lb springs

I guess I should have said that that was one thing I had done when the BD brake was installed on the 95.

 

[jelag]

Well the trucker that gave you the information is sure full of it..... Don't know what it is... . but he's wrong in this case... .



On the early trucks... Cummins used a lighter exhaust valve spring in the engines going into the pickups... . the 60lb springs we put into those early 1st gen trucks were actually Cummins springs for the same engine used in HD applications...



When the exhaust brake closes... it backs the pressure up into the exhaust manifold and against the head of the valve... . To improve the efficiency of the exhaust brake..... heavier springs were installed.....



And the ability to retard... . is the piston coming up on the exhaust stroke... usually free travel... . but now with the exhaust valve open and the exhaust brake on... . the pressure that was in the exhaust manifold is now in the combustion chamber... . so the piston is moving up against pressure..... and this is the ability the engine has to absorb energy.....



When we install a PacBake exhaust brake we know its been factory tested and set up for maximum back pressure..... this will give you the highest available retarding HP... after all... the retarding HP figures come from simple physics... ... .



Does the retarding generate heat... . the simple answer is yes..... retarding HP... . for it to function based on physics... . this energy is turned to heat... . can the engine handle it... sure it can... . after all there is no heavy combustion going on when this is happening... .



Hope I've offered an answer that is understood... if you have any additional questions please post them.....



OH BTW... . there is a lot of guff about one brake being better than the others..... ask your vendor theses questions..... Do you have in house engineering... and build all parts in house... . Do you have full CAD and FEI software and mechanical engineers on staff... and remember... . retarding HP is a factor of RPM, and back pressure..... any given engine no matter what brake is installed... . at the same back pressure and rpm will have the same retarding HP... .



Jim

 

[bmoeller]

Originally posted by jelag

Well the trucker that gave you the information is sure full of it..... Don't know what it is... . but he's wrong in this case... .

I think the exhaust brake would be easier on the valves than a compression brake. A solenoid on those brakes, open the exhaust valve before the fuel is injected, turning the engine into a big air compessor (hence the cool sound ). The exhaust brake doesn't move the valve, so less wear on the valves and guides/seats/springs.