Engine/Transmission (1998.5 - 2002) Back Pressure, Who needs it?

[RBallard]

I posed the question today to cummins, is there a minimum back pressure needed for the diesel engine? I know my gas rams did not like having little back pressure, my low-end torque suffered greatly! But what about the diesel? I have run it both with and with out the muffler and it seems to run better with the muffler although this may be a mind over matter thing. Does the truck seem to run better because the back pressure is there and not allowing the boost to drop as fast as I manually change my gears or does the back pressure actually help with torque. The most information Cummins gave me was "Cummins, Inc. is not in a position to advise the effects of removing Dodge exhaust system components, such as mufflers, pipes, silencer rings, etc. We have discussed exhaust system size with several Dodge customers and advised that Cummins recommends that exhaust restriction be limited to 4. 0 in-Hg and the chassis builders are expected to engineer their exhaust systems to this recommendation.



We have been told that going to a larger 3 1/2 or 4 inch exhaust or a 'mandrel bent' 3 inch exhaust will reduce restriction of the stock Dodge exhaust. Reducing restriction is fine and may make the engine perform even better, but it does not increase horsepower. "



So how about it folks, lend me your thoughts,



Bob Ballard

My web page

 

[Rob Thomas]

Bob,



The turbo on our engine's provide the back-pressure we need, I haven't a "muffler" on my truck since 3 days after I bought the truck new.



Later, Rob

 

[nickleinonen]

after the turbo, 0 backpressure or as close to it as possable is what you want. the only time you want backpressure on a turbo diesel is for the exhaust braking. even gas engines with turbos work best with as little backpressure as possable.

 

[Riflesmith]

The engine will have some backpressure no matter what exhaust system is on the truck due to the turbine.



The lower backpressure environment the turbine(any turbine) exhausts into, the more work it does. The amount of work any turbine, gas or steam driven does is determined by the enthalpy drop from turbine inlet to outlet. Enthalpy can be described by the pressure of a gas(exhaust) plus the temperature of the gas.

Temperature of the gas going through a turbine is every bit as important as pressure. Turbines squeeze work out of both temperature and pressure. The hotter the gas driving the turbine is(within limits), the more efficient it is.

 

[Diesel Freak]

Originally posted by Riflesmith

The engine will have some backpressure no matter what exhaust system is on the truck due to the turbine.



The lower backpressure environment the turbine(any turbine) exhausts into, the more work it does. The amount of work any turbine, gas or steam driven does is determined by the enthalpy drop from turbine inlet to outlet. Enthalpy can be described by the pressure of a gas(exhaust) plus the temperature of the gas.

Temperature of the gas going through a turbine is every bit as important as pressure. Turbines squeeze work out of both temperature and pressure. The hotter the gas driving the turbine is(within limits), the more efficient it is.

couldn't have said it better myself!