1977 911 Turbo Boost Problems

Hi,

i just rebuilt a 77 911 turbo, and am having boost problems. I am trying to run about 1.2 bar for now, and the car runs great. However, the turbo will not exceed 5lbs of boost, it keeps shutting the boost off and on, trying to keep it at a static 5lbs. I think the problem is vacuum related, but im not positive. This is driving me crazy, i need to get this car tested and running right before i store it for the winter. Any help would be most appreciative. Thanks

another variable, the wastegate is leaking a little bit of oil. i REALLY doubt this is the cause of the problem. but who knows, but its not my highest concern right now

wow! thats whole lot of boost to run!!! I am nervous running 1 bar in my 77 turbo, (no intercooler) as for your problem did you check that the wastegate spring is not bound up??
Good luck on solving your problem.....Bobster

I would take the wastegate apart check for a bound spring and clean it up and reinstall. It's a simple assembley sometimes moisture build up will effect the unit and it just needs to be cleaned up.

I agree with Bob on the 1.2bar, I wont go above 1.0 in my 89 with an intercooler. I have read that at 1.2 bar you need to eliminate predetonation of the fuel mixture....You can do this using a highly effecient intercooler combined with octane booster or a fuel enrichment system.

Just a thought

i plan on running higher octane, but yes i think cleaning the wastegate might do it, but it feels more like a vacuum problem, like maybe the lines are rotted, and possibly letting air out through small cracks, fooling the turbo, and not giving enough air.