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Kraftday Kraftday is offline
Scottsdale Arizona USA
 
Join Date: Mar 2010
Location: Scottsdale, Arizona USA
Posts: 415
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diaphragm regulators acts as a damper

Interesting read on the experiments and the zeitgeist of the BOV / diaphragm regulators. I've had the notion the diaphragm regulators acts as a damper so removing generally causes crisper on / off throttle response. But when removed for whatever reasoning, different, non original configurations are there to factor..

Some other factors worth mentioning are effects of the mass of the flywheel / clutch assembly, intermediate volumes and catalyst / muffler systems, etc. I view it as a drivability and safely component of the emissions control, as a system.

Having machined and sold thousands of billet repro boost control valves over the past 12 years, I've had some time to question designs and argue with the correct way to use these.. Now, I generally believe following the engineering examples set by the constructors. So what did Porsche / Bosch do on the 965-or motorsports? Bosch really designed an engineering marvel with the original 930 system..but with emissions constraints. Now later or Motorsport / Bosch commits to recirculation type valve design ("Over-run cut-off valves"). Some reasons being emissions which not many care about or noise levels or not wasting metered air. The most important reason is reducing boost surge, thus protecting the turbocharger! Now if you wanted to stick with venting to atmosphere this will be louder but also because they are metal where as Bosch re-circulating type valves are a polyamide and thus quieter.

Some time ago (around 1999), ZucZ Performance had a “Long Neck” conversion package which consisted of a billet 3D machined adapter and updated to the 965 cut off valve. It was a slick, expensive package with some ugly machine work on the adapter but they worked (with the diaphragm regulator needed) and were sold to Performance Products / Automotion at the time. Unfortunately, not much empirical testing or feedback was there with just that part only replaced.. so never knew if it was worth it.
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Old 12-21-2011, 06:34 PM
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