Engine backpressure is usually related to boost pressure. There is a math ratio for calculating how much engine backpressure is being created for a certain leel of boost.
At idle, it should be very low, however I think the sensor that read backpressure is calibrated for 14.7psi at sea level. Which means, even with the engine OFF, it will still read 14.7 psi.
So, when that check it at the dealership what are they looking for...a reading at idle, or at a certain throttle position, or what. I have the software to "read" the truck, just trying to find out the specs.
well, at idle, it should read 14.7psi of backpressure at sea-level because thats how much atmosphere is pushing against the sensor.
The only way to get an accurate reading is to LUG THE MOTOR. Our trucks dont make boost unless you lug them down and get the fuel rolling. You can "rev" it in park all day and not make any boost.
I've read the 6.0's dont have a backpressure butterfly like the 7.3's do. They get away with this by having the variable vane turbo. They can effectively cut off the flow by changing the vanes and create whatever they need. This is coupled with the torqshift tranny to create an exhaust brake.
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