Quote Originally Posted by jhop View Post
I have this same confusion about factory routing vs aftermarket cc routing. I understand the concern with the factory routing of putting "dirty" air back into the intake and turbo, but my real question is with the amount of vacuum. The factory obviously feels that the intake manifold is sufficient for unboosted vacuum and that the driver side turbo provides sufficient vacuum during boost. Why do the aftermarket kits say you need both turbos for vacuum? Is this a "more is better" philosophy? If I installed an RX kit w/ CS separator and routed it per the instructions with the exception of not drilling the PS turbo tube, but instead, only used the DS turbo tube for WOT vacuum, would this work? Obviously I'm wanting to limit irreversible modifications... Another question... could you tie the two "dirty" ports on both sides together with a "T" and run them to the catch can as normal?
This is exactly how I have mine plumbed. I think I was one of the pioneers of the idea of only using the driver side turbo for boosted vacuum. This was discussed several years ago on another forum and UPR Joe jumped all over the idea when I brought it up. I have always been plumbed this way with drilling into the filtered side of the airbox as the clean air source. It seems to work very well for me. There have been discussions that drilling both turbos might actually provide too much vacuum under boost and pull unnecessary oil out, but I'm not convinced of this. I still get a little misting in my airbox under a lot of boost, and I think the second turbo source might actually help reduce this. Initially I was just using a breather filter on the clean side, but it misted on the engine cover which I didn't like. You could run a can in line on the clean side to maybe help some of the misting, but you definitely need the clean side to flow both ways as you need clean air in when not in boost. The misting I get back through the airbox is negligible and doesn't coat anything in the intake tube. When you are in boost, the dirty side PCV closes. You are already pressurized and air is being pushed back out, thus no need for another air source in like when in vacuum.