I recently purchased a 6776bb and Can't get the boost under 20 psi. I ordered the standard actuator but I'm wondering if i was sent a high boost instead. I've run a hose from compressor to actuator. Adjusted the rod both out and in but 20 is as low as it will go. Any help is appreciated.
Lowering boost
- Thread starter power6usa
- Start date
- Joined
- May 26, 2001
It is mandatory to port the wastegate hole on any P-trim turbine wheel equipped turbo on a stock motor with a Terry Houston style downpipe. Even more so on a car with heads and or a cam. The 6776 has a P-trim turbine wheel. This is true whether you have a standard spring actuator or a heavy duty spring actuator. Also, if you can pull the wastegate actuator arm significantly out of the can, then it is a standard spring actuator. If you can't pull it very far at all by hand, then it's probably a HD actuator. If your wastegate puck on your downpipe measures 1.30", then I would port the wastegate hole in the turbine housing out to 1.15" to 1.20". You want to have about 1/16" of an inch around the hole for the puck to seal. Meaning a 1/16" of a lip for the puck to seal against and you want this hole to be a straight as possible on the flat surface, and contoured nicely on the inside, not simply drill a hole and have sharp edges. Make a nice transition or blending contour on the inside of the hole. It is very important that you mark the position of your swing valve puck as to where it falls on your turbine housing before you start cutting the housing. If not, you could port the hole off center and the puck could miss the hole and you're spool up would be dead, not too mention no boost control. With the 3-bolt studs allowing a little play, and the downpipe bolts allowing a little play as well, you can start to see where this play can affect exactly where the puck falls over the hole. Some people have successfully ported the hole out while leaving the turbo installed and using a shop vac. I personally do not recommend this method because there is no real way to keep from getting particles and fine grinding dust from coating the turbine wheel. You need to mark the puck location on the turbine housing using some marking compound or some paint, remove the turbo, unbolt the turbine housing, properly scribe the puck position, then port the hole. Unless you install an external wastegate onto the crossover pipe, you will not have very good boost control, or in most cases, be able to run boost levels below 19psi. I had to have my housing ported on both of the 6776 turbos that I have run. Both on the journal bearing 6776S that I previously had, and on my current 6776RHP.
HTH
Patrick
HTH
Patrick
