I had a look for any leaks, can't find any obvious ones. I have a DT BPV so I don't think it's that, although it could be entirely possible mine is a dud?

What else good it be? I'm 4600ft above sea level, so boost won't be as high as normal to begin with.

I hit around 10 PSI and it stays there. I have a 16% SCP and a 1%CP with JCW belt.

Here is a video to explain what I'm talking about. Pull away was done in 2nd gear.

http://www.youtube.com/watch?v=87qunTSy9_Y

 

Start with the easy and most logical stuff first. If you have no codes, or other symptoms...check the rubber SC Couplers.

I had a brand new OEM set recently which were terrible....They are being made of thinner rubber ( I compared them to my original set mfg in 2002) The new OEM's ones seem to have less grab in my opinion due to their thickness. M7 and Alta make aftermarket ones. I had a set of used M7's kicking around, so they are on mine now. They are nice and beefy with plenty of meat to cinch the coupler clamps down.

-check the belt to see of maybe it needs to be replaced. Look for any shiny glazing indication of slippage. On our modded engines it is not unheard of to go through two belts a year if you are heavy footed.

- check all the connections for the boost guage. Make sure quick ties are used at all connections for the boost lines, esp at the T fitting.

- check the lower supercharger tube. Not easy to access. It has a lime green gasket which is not the best construction. The tube is also made from ABS plastic so it has a tendency overtime to become warped in the area of the gasket making an improper seal. Mine was toast after 90K miles I think. My dealer and MINI Mechanic are now replacing these things quite frequently as most 02/03's are getting to that sort of mileage now.

The pic below, red arrow shows where the tube hooks up.

 

Wow thanks for the in depth reply.

I can basically rule out the couplers, because they are brand new. I took off my Alta ones because they were a pain in the *** to get on, especially the drivers side.

The belt is also brand new with about 200 miles on and the whole hole on the tab is showing.

I will zip tips the connectors for the boost gauge. I have a feeling the gasket you mentioned by the supercharger. My car only has 45000 miles though. Is there a aluminum alternative for the plastic tube? Might as well change it while the car is apart. That plastic one has always been a bit flimsy to begin with.

 

You can also try two other techniques to find a vacuum or boost leak. One is take a length of hose, hold one end to your ear, and pass the other around the engine. A leak will have a hissing sound. The other is a smoke test through the air filter.

You may or may not have slight belt slippage adding to the issue. The stock belt is 1388mm in length. I have a 1374mm belt with my 15% pulley; I believe this is the JCW belt. Since you have a 16% supercharger pulley and a 1% crank pulley, you might need a slightly shorter belt. When you look at the tensioner shaft (going through the center of the tensioner spring), you should see 8-10mm sticking out, or roughly the entire first hole.

 

Don't rule out new intercooler couplers / bellows. They can still leak around the clamps. That happens frequently. Best solution is to grind down the clamps a bit. Just did mine last night. See this thread:

https://www.northamericanmotoring.co...s-sliding.html

 

I would make sure the belt is appropriate size for the pulley you are running too, that could be an issue, esp since you recently replaced it and you recently now have a problem with boost. I have a new tensioner and with a NAPA 535 belt and the tensioner spring pushes that belt so I have only -1/2 a hole showing.

M7 at one time made an all aluminum tube to replace this plastic monstrocity.......While it would seem to be a good upgrade structurally, could be once heated up the metal ones held the heat longer than the ABS plastic.

* if you examin 2nd photo above, you will see a tab on the left with a hole in it. That hole is supposed to be round. As you can see the old one was not round. After some time the plastic hole becomes elongated making a loose connection, so it's also a weak link of design along with the gasket.

Maybe if they came out with a tube made of both ABS plastic and metal at the stress points, that would be a home run.

 

The plastic SC duct should not cause a loss of boost, even if it fails completely. It's on the pre-boost side of the SC.

Slipping belt is certainly a possibility, as are the intercooler couplings and the bypass valve.

 

A trick to getting aftermarker IC couplers on is to soak them in hot slightly soapy water. Makes them much more pliable.

Also loosen up all of the IC bolts as this will allow more movement to help with the install.

 

Thanks for all the pointers guys, now to start the long tedious process of elimination. Man I hate this part!

That's very true!

 

Any update? Were you able to find the leak?

 

Unfortunately not. BMW has had my car for almost 3 weeks to install the xenon OEM retrofit. :(

I'll get to it as soon as I get it back and give an update