Blow off Valve recommendations

**lynnbilodeau** · 12-23-2021, 11:17 PM

83 745i. Upgraded to a TCD manifold and turbo. Tuoma chip (so no cut off when boost gets too high!!!) Running a Tial wastegate with an 11 psi spring. Did a build thread on this back in 2012. M90 block with S38 head gasket. Runs really well.
Have never had boost issues. Always levels out at 11 psi.

Had a bit of a scare last night. Washed the car (did not wash engine compartment) and didn't feel like drying it at the car wash. Took it up to the interstate to dry it off before going home.
Put my foot in it in third gear heading up the on ramp, and it waaaay overboosted. Happened so fast I didn't even have time to let off the gas. Boost gauge pegged, something popped and I was stranded on the side of the road. I am guessing the waste gate stuck shut. Opened the hood and found the tube from the intercooler to the charge pipe had blown off. Also noticed the vac tube going from the magnetic valve to the waste gate was blown apart. I was able to cut the vac tube and re-attach. Also was able to put the pipe connection back together.

Obviously, I may need a new waste gate. I didn't put my foot in it last night to see if it is still over boosting. I think I need to put a blow off valve in line on the pipe from the intercooler to the charge pipe. Because I DON'T have the electronic cut off, I need something mechanical as a last resort. What are you guys using for a blow off valve?

Any help appreciated.

**lynnbilodeau** · 04-04-2022, 08:40 AM

Forgot about this post.

I bought a blow off valve on ebay. I plumbed it in line on the tube going from the intercooler to the charge pipe. I did not run a vacuum hose to it. Instead I modified it so that it would release air at 15 psi.
Had to make a fixture out of PVC and use a hand pump to dial it in.
I have not needed it yet, but feel better having protection for an overboost situation.