| Author | Message | ||
| Lin (66.159.223.29)
Rating: |
I want to put an exhaust brake on my HD 478 Toroflow. Does anyone know if it can take the 35 pounds of back pressure required? | ||
| Tom Caffrey (Pvcces) (64.114.233.126)
Rating: N/A |
Lin, the only thing that I know about that engine is it it touchy about lugging. It will make head gaskets leak in an instant if you let the loaded RPM fall to around 1000 or lower. Why should one of these engines have trouble with that kind of back pressure? They are designed to work on the firing stroke up around 1500 psi, I believe. Good luck! Tom Caffrey PD4106-2576 Suncatcher | ||
| Gary Carter (68.27.249.214) Rating: N/A |
Exhaust brakes require heavier exhaust valve springs to keep them form floating | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Gary, I wonder if that is actually true. If you think about it, when an exhaust brake is engaged, there's about 20psi in the exhaust manifold (at least that's what mine does), maybe 30psi at most. This will be pushing against the bottom of the exhaust valve adding to the pressure trying to open it, true, but the surface area of a valve isn't many square inches- a 2" diameter valve is what, 3 square inches, so even 30psi would only put 90 pounds on it, and valve springs are loaded well over a hundred pounds in most big diesels. So say it did float the valves... that would only happen as the pressure got way up there, and then the valve would open, relieve some of that pressure, and close again. I can't see that it would adversely affect an engine when it was being used as a retarder (ie you're not asking it to make horsepower at that point) and it would, at worst, only limit the amount of pressure thus retarding action. It's doubtful that the valve could be lifted high enough to strike a piston- if 90 psi were to lift a valve it would only be a few thousandths at most and the pressure would go right down again... so unless I'm missing something big here, I can't see where any harm could occur except you may not get as much retarding action as you expect if the valves float. I didn't change a thing in my engine and my exhaust brake works fine at 20psi.... That said, I'll qualify myself by admitting that I'm not a seasoned diesel mechanic, so I may have a lesson coming...??? Cheers Gary |
