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Posted by Paul (in NY) on Tuesday, January 15, 2008 at 16:25:26 :
In Reply to: Re: 4bt/4bta physical differences? posted by wetcoast bruce on Tuesday, January 15, 2008 at 14:53:31 :
From the Cummins Shop manual
B3.9 & B 5.9 Series Engines
Section E
Engine Identification
General 4B engine Data
Compression Ratio on 4BT3.9 is 17.5:1
Compression Ratio on 4BTA3.9 is 16.5:1
There are two different after coolers available from Cummins for these engines.
One is CAC (Charge Air Cooled) The air cooler, like a radiator sits in front of the truck radiator and is plumbed with 3 inch lines from the engine to the CAC. You will find its nearly impossible to neatly run 3.0" lines from the engine past the radiator to the CAC. There simply is no room.
The second after cooler is a coolant cooled unit. This unit sits on top of the intake manifold opening. Engine coolant is run thru the cooler and the turbo charge air is routed into the WJAC (water jacket after cooler) and then directly into the engine. This After cooler requires special injector lines that run for and aft of the actual cooler. I use this after cooler on my diesel swaps as it fits real nice in a PW/M37 or WC.
The CAC is a more efficient after cooler, but difficult to use in our application of PW/M37/WC.
The injection pumps on 4BT and 4BTA are calibrated differently for fuel delivery. If your adding a after cooler to a 4BT among the other issues mentioned is a re-calibration of the Injector Pump at a Injector Repair shop. Then you know exactly what your feeding the engine.
Paul
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