Originally Posted by
nty1234
Hi all, Trying to finish my speed density tune and smooth everything out with my new turbo install. I have a 7675 single with a 44MM wastegate recirculating into the downpipe. Using a GFB 3 boost controller, with minimum duty cycle the boost is very stable, in the log posted below I have the duty cycle ramped up to 60%. The boost becomes extremely unstable and oscillates very bad. I'm aware of the 2x spring rate rule but starting with a base pressure of 5 pounds and having it oscillate from 6.5 all the way down to 4psi and back up to 6.5? seems like this could be something with the wastegate or solenoid or even the controller? The tune is a little rich, I've since leaned it out and smoothed the VE table. I should note the tune is on complete speed density with the upgraded OS from hptuners and the maf disabled. Not really sure what else to try at this point, I routed the wastegate lines a little different as per a forum I read with GFB's response and that had the turbo spool up very quickly hitting my boost cutoff with no control over it whatsoever. Thanks to anyone who can help.