Blow-Off Valves are NOT so much for preserving boost between shifts, are they are for venting excess pressure and preventing hyperbaric surge in th intake tract.
I don't believe our trucks have a "throttle body" with a butterfly valve like the typical gasser does. In a gasoline turbocharged vehicle, when the throttle body closes, there is NO WHERE for the high boost pressure to go -- and the turbo is still spinning and compressing the intake tract for some fraction of a few seconds. It's this increase in pressure that causes a momentary overboost condition, and shocks the turbo.
BOV's are opened by vacuum on the manifold-side of the throttle body. I don't think our trucks ever reach a true vacuum condition because there's still some boost off-throttle. The BOV may never open up to do it's job in a diesel application.
Greg
'87 944 Turbo <url>http://www.rints.com/hammond/turbo.html</url>
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Y2K Dodge Cummins QC 2500 SLT Laramie 4x4 Long Bed, 4. 10/Auto, Forest Green/Driftwood, 265x75R16 Michelin LTX, 6 speaker CD, Camper/Tow/Plow Packages, Westin Black Nerfs, Mopar bedliner, Ultra bright diamondplate toolbox, K&N Filtercharger. Autometer EGT and Boost gauges with 2-gauge pillar coming soon!
http://www.rints.com/hammond for photos!
I don't believe our trucks have a "throttle body" with a butterfly valve like the typical gasser does. In a gasoline turbocharged vehicle, when the throttle body closes, there is NO WHERE for the high boost pressure to go -- and the turbo is still spinning and compressing the intake tract for some fraction of a few seconds. It's this increase in pressure that causes a momentary overboost condition, and shocks the turbo.
BOV's are opened by vacuum on the manifold-side of the throttle body. I don't think our trucks ever reach a true vacuum condition because there's still some boost off-throttle. The BOV may never open up to do it's job in a diesel application.
Greg
'87 944 Turbo <url>http://www.rints.com/hammond/turbo.html</url>
------------------
Y2K Dodge Cummins QC 2500 SLT Laramie 4x4 Long Bed, 4. 10/Auto, Forest Green/Driftwood, 265x75R16 Michelin LTX, 6 speaker CD, Camper/Tow/Plow Packages, Westin Black Nerfs, Mopar bedliner, Ultra bright diamondplate toolbox, K&N Filtercharger. Autometer EGT and Boost gauges with 2-gauge pillar coming soon!
http://www.rints.com/hammond for photos!