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Hey all, has anyone ever done a vacuum rework with one of the vacuum blocks like this one?
I am wondering how you did it, which lines you put into it, where the main line came from, Can I tap a big engine vacuum port into one of my block off plates?
I'd say it depends on what you are trying to do with it. If you are running an aftermarket ECU or a racecar that would need it, go ahead. If your car is stock or mostly stock, I wouldn't touch it. If you are trying to keep the stock features, it would be more to your benefit to learn and restore the original vacuum system. With the Turbo II's, not all the lines are under vacuum at the same time. Some don't go under vacuum ever, and just see neutral air or boost.
Yes you can add ports to the block off plates. I added a vacuum nipple to restore a thru-hole port that was blocked when I eliminated my air pump, EGR, and all that. Photo here. This is where the S5 MAP sensor is supposed to read pressure from. I located and drilled the hole and put a small countersink on the back side of the plate, where the little tab is. I then press fit a small length of metal tubing and peened the tubing on the back side into the countersink to set it.
I was going to to the rework in my street car, emissions deleted and all that stuff. The new turbo would be putting out 16lbs of boost, scared of blowing off a line. Really the only vacuum lines I think there belong to the brake booster, primary injector air bleed, and the fpr.
Im sure the brake booster line could be routed into the block, wherever it comes from could be the main
What about the primary air bleed, suppose its best to keep that where it is considering its on the throttle body.
Im worried about the fpr. The nipple on the lim doesnt have a barb, what stops it from popping off?
should I have the little guys on the trottle body clamped down?
It would be a good idea to replace your vacuum lines with fresh ones. The old rubber ones get set and lose their elasticity, making them easy to blow of if you disturb them. If you get some replacement silicone vacuum hoses in the appropriate sizes, that would be a more substantial upgrade.
-The brake booster port on the UIM is fine as it is. You want that port to be as big as it can to reset the brake booster quickly.
-The purpose of the air bleeds, primary and secondary, is to keep measured air (post AFM air) moving past the injectors under idle and low throttle conditions to keep fuel mixing with air instead of just wetting against the inside of the intake manifold. The idle air adjust screw on the BAC does add extra idle air in addition to these two vacuum lines, but doesnt pass air directly past the injector nozzles. Note that the source for all of these lines is upstream of the throttle plates, ensuring that there is always positive pressure to feed air around the throttle body and into the intake next to the fuel injector nozzle.
-The vacuum lines are held onto the nipple by friction. As far as lines popping off, if you upgrade your vacuum lines as stated above, they should have a tight enough grip to keep them on at high pressures. I pressure tested my intake manifold with an air compressor and got about 30-35psi without having any issues of popping lines off. If you want to add clamps to the small vacuum lines for peace of mind, or you test and have issues with lines popping off, you can add some small spring clamps to the lines. Spring clamps can be easily set and removed with needle nose pliers, and a whole pack of them can be bought for a couple bucks. If you are pressure testing your intake manifold, be sure to disconnect your MAP sensor, so you don't damage it by too-high pressure.
02-04-24, 09:30 PM
