Jump to content

Boost control questions

Recommended Posts

'05 LGT 5MT, basic stage 2, 89K miles, in Denver. It was hitting about 15 PSI on the OTS tune. I'm going through an e-tune, and the last revision, the first off the base map, showed 14 PSI. I assumed we were working up to 16.5 PSI in steps, but apparently not. The tuner expressed concern that if I don't hit the boost target on the next revision, I need to either upgrade to a 3-port boost controller or check the wastegate flapper to make sure it's not offset and not blocking the hole entirely.

So my questions are:

1. Is checking the flapper just a matter of pulling the DP? I had it off recently and my very brief inspection didn't notice anything awry, but I don't kid myself that I would necessarily have caught a problem. Any tips on what to look for?

2. I know nothing about boost controllers. How can a different controller help me to reach boost levels I'm currently not?


Link to comment
Share on other sites

The 3-port boost controller is a different type of boost control system that gets rid of the restrictor pill and controls the wastegate directly. Since there is no bleed, the wastegate stays closed until commanded by the ECU. Your custom tune would use lower wastegate duty cycle values to reach a given level of boost.


There could be some mechanical reason the wastegate is not closing fully. You can visually check it by pulling the DP. The shaft that operates the wastegate can stick or bind. You can hook a vacuum pump up to the wastegate actuator (e.g. Mityvac). Gradually increase vacuum and release several times to see if the actuator is operating through its full range and the wastegate is closing as it should.


Another possible cause is a leak in the hoses controlling the wastegate.


It might be you are losing boost pressure through a leak in the intercooler plumbing somewhere.

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...

Important Information

Terms of Use