Boosting less now with mbc on j-pipe

[Black91TSiAWD]

Hey Ive had a mbc T'd into my intake mani to bov vac line, had it set to 11-12psi and ran it that way for the last 6 months. Heres the deal, I just switched it over to the j-pipe and now it only boosts 7-8 psi. Why would the boost decrease from switching it?

 

[oldman]

Hey Ive had a mbc T'd into my intake mani to bov vac line, had it set to 11-12psi and ran it that way for the last 6 months. Heres the deal, I just switched it over to the j-pipe and now it only boosts 7-8 psi. Why would the boost decrease from switching it?

This indicates that you have boost leaks, this is one of the many benefits of tapping off the compressor/J-pipe instead of the BOV line, allow me to explain.

1. Tapping off the BOV line. Your mbc/actuator is recieving pressure signal from the end of the intake tract, turbo works overtime until the intake tract reaches 12psi along with the boost leaks.

2. Tapping off the J-pipe. Your mbc/actuator is recieving pressure signal from the beginning of the intake tract where the effect of boost leaks is greatly reduced. Your wastegate opens earlier instead of allowing the turbo to over spin, your boost gauge now reads 7psi which imediately lead you to a boost leak test.

 

[Black91TSiAWD]

Hey thanks man, I was leaning towards boost leak myself. Looks like I have something to do after work tomorrow!

 

[oldman]

You're welcome, good luck.