951 MBC problem / lesson
12-23-2002, 09:32 AM
#1
Three Wheelin'
Thread Starter
951 MBC problem / lesson
I thought I would post this so other 951 owners can learn from a problem I had with my manual boost controller. After installing a MBC recently I started test driving my 951 to set the boost using the MBC. The first couple of runs went fine but after about the third adjustment of the MBC I found that the car was overboosting. Fortunately I was watching the boost very closely and backed off as soon as the boost went beyond 15 PSI so it didnt cause any problems. Then I found that even when I backed off the MBC to reduce boost again nothing happened ie it was still able to overboost.
It turns out that one of the plugs in the MBC had worked its way out so the MBC was venting the boost signal to atmosphere. I replaced the plug and then started driving again to set the boost and the same thing happened but to the other plug this time (there are two ports and two plugs on the turbonetics MBC). I guess it pays to check the tightness of those plugs as they come from the factory. Mine are now sealed properly and securely in place with some teflon tape. But I am amazed at how the second plug went from fully seated to blown out in as little as 30 minutes driving.
As a side note, the boost leak in the intake system did not cause any noticeable problems in how the car ran because my boost enhancer seems to have prevented a vacuum leak and the MAP system compensated for air lost through the MBC leak. It was nice to see that the turbo could still generate high boost even with the leak though.
PS My MBC is mounted in the engine bay so there was no hiss that might have been heard if the MBC had been located in the cabin.
It turns out that one of the plugs in the MBC had worked its way out so the MBC was venting the boost signal to atmosphere. I replaced the plug and then started driving again to set the boost and the same thing happened but to the other plug this time (there are two ports and two plugs on the turbonetics MBC). I guess it pays to check the tightness of those plugs as they come from the factory. Mine are now sealed properly and securely in place with some teflon tape. But I am amazed at how the second plug went from fully seated to blown out in as little as 30 minutes driving.
As a side note, the boost leak in the intake system did not cause any noticeable problems in how the car ran because my boost enhancer seems to have prevented a vacuum leak and the MAP system compensated for air lost through the MBC leak. It was nice to see that the turbo could still generate high boost even with the leak though.
PS My MBC is mounted in the engine bay so there was no hiss that might have been heard if the MBC had been located in the cabin.
12-23-2002, 11:57 AM
#3
Three Wheelin'
Thread Starter
[quote] Did I read that right? Your running a MBC and a boost enhancer? <hr></blockquote>
Yes I decided to run both, the LBE allows boost to build quickly to 10 PSI and once above 10 PSI the MBC restricts boost to what I set as the upper limit (presently 15 PSI while I run in the motor). This setup seems to work quite well.
Yes I decided to run both, the LBE allows boost to build quickly to 10 PSI and once above 10 PSI the MBC restricts boost to what I set as the upper limit (presently 15 PSI while I run in the motor). This setup seems to work quite well.
