Quote:
Originally Posted by Baker
Are the non-aftercooled engines any more "fortified" against heat than a aftercooled one(6BT vs 6BTA). Or is the turbo bigger on the aftercooled ones and/or do the generate more boost causing more heat? I guess the real question is right up to the aftercooler and is everything the same after the aftercooler?....the only difference being a cooler air charge and hence more power....
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Both are true.
The 6BTA has a much more robust cooling system to deal with the heat rejection. As a rule of thumb, if burning diesel makes 1 btu of heat, 1/3 goes into rotational energy, 1/3 out the exhaust and 1/3 out in the cooling system. So if a 6BT produces X btu/hr out of the exhaust or cooling system, the 6BTA will produce 370/210= 1.76*X
The turbocharger produces much more boost than the non aftercooled 6BT engine to have enough air to let you inject more fuel to make more hp.
So at a maximum boost of about 30 psi, the air in a 6BTA gets up to 500 deg F or so at wot. The aftercooler drops that down to maybe 100. With no aftercooler and 500 deg intake air, the engine's egt will go crazy and melt pistons and valves.
David