Boost problems

I have a 1979 Porsche 930 with GHL headers, K 27-7200 turbo, and an HKS boost controller. I haven't gotten my boost controller to control, it overboosts, so I turn it off and my stock .8 spring takes over. If you have advice with the controller let me know, but my most annoying problem is something else. With the controller off, the wastegate should perform as stock, and it does during certain times. I get .8 on the streets in cool weather, however when it's hot I get only .6-.7 bar. It's really annoying because I don't get the boost when I really want it, like at the track yesterday, or at the dyno. Do I need a wastegate rebuild? Thanks in advance

Keith
79 930

What HKS unit are you running?
I just installed a HKS EVC II and I'm in the process of working some of the bugs out.

I would first make sure you don't have any intake leaks. Make sure all Vacuume lines are secure and not leaking.

How do you have the three hoses connected?

I have had the HKS unit and had no troubles. Make sure the sensor and controller hoses are hooked up to the correct connections and that you went through the "learn" process so the controller unit will see the boost curve of the turbo and what the engine requirements are. The boost pressure is read from the intercooler on ours as we no longer have a pop-off valve. One of the settings on the HKS unit is for the overboost and I set ours to 1.25 bar for 8 seconds and have actually only used it once to test it and it worked fine. You may need a waste gate overhaul, especially if it is leaking or corroded from moisture. When I installed ours I talked to HKS and their tech support was very helpful to insure I had each line connected correctly and he knew Porsche systems well. Remember the Turbo owner's manual says to drive hard enough each time you drive to cause the waste gate to open and blow out moisture! Good luck.