little hole on mbc...purpose?

[gurmanator]

the little hole on the brass fitting on my mbc(hks)leaks air during test.what is the purpose of that hole?question #2...someone told me to put the mbc as close to the turbo as possible or can I put it in the cab so I dont have to keep getting out of the car all the time?

 

[FORMONTOYA]

the little hole on the brass fitting on my mbc(hks)leaks air during test.what is the purpose of that hole?question #2...someone told me to put the mbc as close to the turbo as possible or can I put it in the cab so I dont have to keep getting out of the car all the time?

1. The hole is to "leak" air. And most will instruct you not to rotate the hole from a certain point. The MBC is able to "raise" the boost by tricking the WG into thinking that you running less boost than you actually are. It does this by bleeding off pressure thus NOT allowing the WG to open as soon as it would otherwise. When doing a boost leak test you should remove the MBC from the mix before you start. I actually will test mine from the IC inlet as even with a new turbo the seals will most likely leak without oil pressure to help the seal properly.

2. The MBC should be as close as possible to avoid spikes in the signal. Kits are made by certain companies to get the adjustment inside the cabin. Hallman make one such unit for example.

 

[gurmanator]

1. The hole is to "leak" air. And most will instruct you not to rotate the hole from a certain point. The MBC is able to "raise" the boost by tricking the WG into thinking that you running less boost than you actually are. It does this by bleeding off pressure thus NOT allowing the WG to open as soon as it would otherwise. When doing a boost leak test you should remove the MBC from the mix before you start. I actually will test mine from the IC inlet as even with a new turbo the seals will most likely leak without oil pressure to help the seal properly.

2. The MBC should be as close as possible to avoid spikes in the signal. Kits are made by certain companies to get the adjustment inside the cabin. Hallman make one such unit for example.

I can run 12-15 pounds all day long but when I turn it to 18-20 it pulls like crazy in 1st gear only but when I grab 2nd I only get 5psi as for 3rd also,would the mbc have anything to do with that? any ideas?

 

[FORMONTOYA]

I can't really think of why it would act that way. Usually it gets hooked up back wards and you will have unlimited boost until you hit fuel cut or blow up the engine. I know on my Hallman it specifically instructs you to not rotate the hole in the barbed fitting from a certain point or it will not operate properly. Did you happen to rotate that fitting to where the hole is in a different location than it was when you got it?

Also this is going to be a stupid statement, but I'll say it anyway, turning clockwise or in NORMALLY raises boost, counterclockwise or out NORMALLY lowers boost. I know it seems elementary, but we sometimes forget things in our zeal to get things done, especially before we take a test spin.