Big E

I just finished replacing all the vacuum lines and eliminating the venturi deal under the manifold a few weeks ago. As I planned to put in an Accuboost, but the boost gauge hadn't come in yet, I kept the cycling valve but moved it from under the manifold so I wouldn't have to go under there again.

I got the boost gauge (Autometer Phantom, fyi) hooked up yesterday afternoon, and nothing seems right. It's only reading about 10" at idle and on decel, but the boost levels are way too high. I can hit 15psi w/ less than half-throttle in 3rd gear. The turbo/chips/wg are all stock. I'm trying to forget the brief period where I floored it and the needle swung up around 20, my eyes bugged out, and then I lifted off completely.

Maybe the cycling valve is shot now, vibration or something from it's new location (pretty much just laying near the headlight - yes, that's a lot of extra hose) ? But I didn't think the computer would let it get anywhere near as high as I'm seeing. I guess I could just put in the Accuboost now and adjust it so it maxes at 12 (is that right for stock?), but the vac reading has me confused as well. It seems to be idling fine.

Of course, I'm supposed to take the car on a ~1000 mile drive on Monday.

Somebody, help, please!

951Porschiste

During the summer I replaced all the hoses under the intake manifold. The picture shows one of the original hoses to the CV. Notice the tear in the hose. Since I have replaced that hose, I now have better vacuum and less boost. No more neck-snapping acceleration when I floor it. My theory is that the CV was not functionning properly before which made the wastegate open later and allowing a lot more boost. Now that it is properly connected, the wastegate opens sooner allowing less boost buildup.
You may have a leak to the CV preventing the wastegate from opening sooner.

tconn

I could be wrong but I thought the limiting factor for max boost was the wastegate. If you have the stock wastegate with no shims then it should open at 12-13psi even if the CV isn't working
correctly.

theedge

The wastegates on our cars are backwards... When part of the stock boost control system fails, the wastegate "fails" closed, and wont open. The norm is that it will fail open, thus you can no boost, but you can limp home without too much danger or damage.

I think thats what I read in another post...

MHT

sounds like your boost/vac. gauge is not calibrated properly, if the car was running like c--p I could understand 10" at idle but it should still make vacuum on decel. If you are unable to fix it before your trip, you can still drive the car, just avoid full throttle runs. Are you sure that the hoses to and from the CV are hooked up right? As Brian said, no boost to the wastegate and it won't open. Is your fact. boost gauge still connected? What does it say?
Good luck

Big E

Well, I'm still puzzled on the vacuum part, but I got rid of my ridiculous cycling valve setup (musta been 12 feet of hose in there) and put in the Accuboost, and now at least the boost side seems fine. Max boost I saw on the first drive was 10psi, and it held it there rock solid with my foot planted, so that seems good to go with a little adjustment.

What theedge says about the WG failing closed if some other boost control fails would fit what seemed to be going on previously.

As far as I can remember, the stock gauge has always showed about 0.4 at idle, which is a little under 12 in. Hg. if I did my conversions right, so that seems not to have changed much. But still is way low compared to what others seem to read. In a semi-stroke of genius, I used red vac lines and black wire ties so I can see pretty quickly if any of the small vac lines have come off, and they all seem fine.