Evans Dash Air Nightmare
I'm a newbie to the RV world and would love some help dealing with a problem with the Evans Tempcon dash AC. The coach is a 2001 Monaco Knight on a Roadmaster chassis. I bought this RV knowing the d...
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Many diesel engines were equipped with a small vacuum pump driven off the belt to provide vacuum for accessories. I suspect that some manufacturers may have also used electrically operated vacuum pumps and if you are trying to retrofit a vacuum pump to a system that didn't come with one that is probably the simplest approach.
Diesel engines won't provide a reliable vacuum source whether turbocharged or naturally aspirated because they don't have a throttle plate so there is very little air restriction on the intake side and thus no significant manifold vacuum. This is the same reason that diesel engines not equipped with some sort of exhaust brake provide very little engine braking compared to a gas engine which develops its engine braking by forcing the engine to pull air through a nearly closed throttle plate. With large diesels, a "Jake brake" discharges the compressed air at the top of the compression stroke to provide excellent braking while lighter duty/small diesels use some sort of exhaust restrictor to provide engine braking often in the form of variable exhaust vanes in newer turbo diesel engines.
Some of the newer DPF equipped diesels have a throttle plate to help heat the system during regen but this isn't intended to provide a reliable source of vacuum or engine braking.
Diesel engines won't provide a reliable vacuum source whether turbocharged or naturally aspirated because they don't have a throttle plate so there is very little air restriction on the intake side and thus no significant manifold vacuum. This is the same reason that diesel engines not equipped with some sort of exhaust brake provide very little engine braking compared to a gas engine which develops its engine braking by forcing the engine to pull air through a nearly closed throttle plate. With large diesels, a "Jake brake" discharges the compressed air at the top of the compression stroke to provide excellent braking while lighter duty/small diesels use some sort of exhaust restrictor to provide engine braking often in the form of variable exhaust vanes in newer turbo diesel engines.
Some of the newer DPF equipped diesels have a throttle plate to help heat the system during regen but this isn't intended to provide a reliable source of vacuum or engine braking.
