CHACATA":2jfzugoy said:
A line plumbed in the intake side of the turbo would generate enough vacuum to operate the modulator and allow tha trans to shift by herself i think.
Doubtful. I’ll admit that I’m no expert on how much vacuum a trans needs to shift properly, but the suction (i.e.vacuum) on a compressor’s inlet is very little compared to that generated behind closed throttle blades (where most vacuum sources are).
I’d go with a canister/check valve setup.
My Spirit R/T had a “vacuum†source on the suction side of the turbo for control of the AC vent damper. The thing would flap all over the place under boost because the vacuum generated was inadequate.
I would try an intake plenum vacuum source (i.e. behind the throttle blades) with a check valve. If need be, you can put a good sealing junkyard vacuum canister after the check valve to supply vacuum while you’re under boost. That’s what my Syclone has from the factory for the AC controls and cruise. It works great.
I think non-turbo 1990's S10s, S15s, Jimmys, Blazers etc also have them as well for WOT vacuum. It looks like a black plastic ball with a single vacuum nipple. I think they are under the battery tray.
And as stated earlier, factory turbo cars usually just have a check valve on the brake booster. It’s plumbed straight from the intake plenum. If you think about it, unless you’re trying to brake boost the car, you’re probably under vacuum conditions (i.e. throttle close) when you’re braking so everything works great.
Hope this helps.