[ColonelSanders]

My 335d has been tuned for a couple months now and I've realized the amount of black smoke is way more than normal. OBD reports a max boost of around 29-30lbs. I get smoke anytime over 2/3 throttle, and a large continuous cloud at WOT.

The car:
-2011 335d, 120k miles.
-BPC stage II, stainless downpipe+exhaust, forge boost hose.

Notes so far:
-swapped the pairs of pressure converters and switchover valves, no change
-inspected turbo-intercooler-intake connections, all appear fine.
-No codes either through carly, or at the dealer
-replaced a lot (but not all) vacuum lines, and tested actuators. (sound fine)

What should I do next?

There is evidence of CBU looking down the throttle body. Could that be enough to restrict airflow this much?

[Persian Whisperjet]

Turbo about to crap the bed?

[BB_cuda]

Look for evidence of boost leak. I see that you have installed a Forge hose. Double check that the connections to intercooler are correct. Also, check further downstream at charge pipe to throttle body as there is an o-ring there. I had a bad cloud thing similar when inlet to intercooler red hose popped off and I got a limp mode. I installed new green o-ring and insured full insertion of hose into intercooler and problem disappeared. Good Luck.

[lnxguy]

Boost leak would be my guess as well. Usually something simple. Check your air filter as well.

[ColonelSanders]

I'd agree it sounds like a boost leak.

looks like i'll replace items 2,3,13,14 in the diagram? might as well do them all while i have it apart right?

edit:new air filter as of a few weeks ago, no change

[Torqu3]

Originally Posted by ColonelSanders

I'd agree it sounds like a boost leak.

looks like i'll replace items 2,3,13,14 in the diagram? might as well do them all while i have it apart right?

edit:new air filter as of a few weeks ago, no change

That's exactly where I would start since it's the cheapest and easiest fix. Your peak boost numbers are too low so I'd put my money on a boost leak.

[ColonelSanders]

Got everything apart last night. Replaced both gaskets on the charge air pipe, and the one on the intercooler side of the boost hose. It does not appear I have gasket #2 on my car, is that normal with the forge boost pipe? Anyone have a picture of what that gasket is supposed to go to?

One of the connections (picture) is all beat up, I cleaned up a couple rough edges, but it seems to be all functional still.

Didn't seem to notice a difference this morning, but i'll wait for more data to confirm.

[Mark M]

Just as an observer on here it seems like people have more trouble with the forge boost pipe than benefits.

On mine I'm using the upgraded OE pipe with yozh's tip of doubling up the seals where it mates to the turbo. Working well with no issues. But it did take some muscle and persistence installing.

[Chief Orman]

Originally Posted by BB_cuda

Look for evidence of boost leak. I see that you have installed a Forge hose. Double check that the connections to intercooler are correct. Also, check further downstream at charge pipe to throttle body as there is an o-ring there. I had a bad cloud thing similar when inlet to intercooler red hose popped off and I got a limp mode. I installed new green o-ring and insured full insertion of hose into intercooler and problem disappeared. Good Luck.

Is there a recommended heavy duty hose clamp and beefed up O-ring to use with the Forge pipe? I seem to remember this from one of threads.

[Hoooper]

I don't know about a beefed up o ring but the clamps should be replaced with t bolt clamps.

[ColonelSanders]

agreed to the T bolt clamps. one of the hose clamps didnt even go back on quite right.

Is that a 3" pipe I need to buy for?

[BB_cuda]

Originally Posted by Chief Orman

Is there a recommended heavy duty hose clamp and beefed up O-ring to use with the Forge pipe? I seem to remember this from one of threads.

Sorry, Chief. I just now came back to this thread. I didn't mean for you to be left hanging. Hooper chimed in better than I could have anyway. My memory was that the Forge uses the same OEM seals we already have but that it has a much better fitting on the top end to connect the hose up with.

[Hoooper]

Originally Posted by BB_cuda

Sorry, Chief. I just now came back to this thread. I didn't mean for you to be left hanging. Hooper chimed in better than I could have anyway. My memory was that the Forge uses the same OEM seals we already have but that it has a much better fitting on the top end to connect the hose up with.

Yeah the top fitting is a little improved, the bottom is no better. On my car the forge hose isnt quite long enough which seems to be an issue a lot of people have so getting really good clamps is important.

I think these are what I used on the hose HPS 76mm - 84mm Stainless Steel T-Bolt Clamp for 2-3/4" Hose

[BB_cuda]

Hooper, did you mean to include a link?

[Hoooper]

No that was the info I found from an old email. I think they are on Amazon too?

[ColonelSanders]

exactly the ones I was looking at:
https://www.amazon.com/HPS-SSTC-76-8.../dp/B0058W7X0A

anything to avoid one extra round of disassembly

well i'll update when two of these go on...

[BB_cuda]

Thanks, Hooper and Colonel 👍

[Yozh]

Boost leaks could also come on the output side of the intercooler, ASV mating areas to boost hose and to EGR or race pipe and same to manifold. Also swirl flaps or block off plates. Check all. For the vacuum system, you need to assure the whole system is tight.

[ColonelSanders]

Seems better with new clamps in, but no data yet. I should point out these are probably one size too large. Cranking them all the way tight is still loose enough to move them (barely) by hand. Trying these soon:
http://a.co/hxxTBb4

[Hoooper]

Strange. I stopped tightening mine for fear of crushing the hose ends.

[Thecastle]

Just to actually give a little help, there are boost leak testers out there. Where you pressurize the intake tract and check for leakdown. I've used them on other cars, boost leaks can be hard to find. http://turboboostleaktesters.com/. I also recommend a spray bottle with soapy water to spray all the fittings and look for bubbles. This method is pretty full proof. Also be careful when you pressurize the system to say 30psi, there is a lot of force contained in the fittings if they blow. If its a bad leak you'll be able to hear it.

[335stoner]

Originally Posted by Hoooper

Strange. I stopped tightening mine for fear of crushing the hose ends.

that is because you are a quitter!! jk