[dangdude]

Car is 2007 335i, Dinan 3 software, with Dinan intake, big intercooler, silicone inlets, AR catless downpipes. Stock CP and DVs.

It pulls very hard but I have a choo choo train surge and hiss at WOT. ShShSshSshSsssh Sssssh Ssssh. The choo choo train slows as the RPMs go up. The car surges with extra power at the same frequency. I'm guessing frequency starts at 6x/second at 3k rpm and goes to 2x/sec at 5k rpm.

Is this failed DVs?

Can I test this by removing the vacuum lines from one or both DVs and seeing if the surge & sound goes away? I don't think so since without boost there won't be any hissing anyway... maybe I can find "the" failed DV if that's what this is.

Thanks!

[dangdude]

Originally Posted by thelightning

Boost leak. Perform a smoke test at a local garage to find the leak.

Thank you, you were right. I built the boost leak kit and found leaks where my stock DV hoses connect to aluminum fittings to attach to the VRSF silicone inlet hoses. I sealed the leaks with sealant tape before reclamping.

Please, I now have questions about the boost leak test.

I don't have a pressure gauge installed but am at maybe 10 psi according to my compressor regulator.

I get air leaking out of the inlet hose end of the PCV valve hose. The PCV hose is connected to the valve cover, but is disconnected from the inlet hose, and the inlet hose is plugged. I also get air escaping from the vertical pipe that I believe comes from an electric vacuum pump (?) to run the turbo actuator valves and power steering booster. I suppose it's coming from the vacuum lines running to the turbo valves. I can reconnect that pipe to the power steering booster but should I really pressurize what is designed to see vacuum?

If I plug both those leaks with fingers, everything is silent.

I am also happy to now drop the FMIC and pressurize from the "hot side" if that's the correct procedure now.