This has been driving me nuts.. im open for suggestions. Ive done a lot of reasearch but still no solid answers.. I have 17-18psi in 2,3,4th gear. and 21-22 in 5th. I dont want to over boost more than 20.. but then to do this.. i have to set 2,3,4th low to keep 5th at a constant 20.. And regardless of all this.. it ALWAYS tapers down 2-3 psi.. never hold.. its worsened after my exaust.. it spikes a little more.. and psi spools up a lot faster.. but still doesnt hold constants

Often when set between 17-20 i have 22,23 psi spikes for a second or so.. is this dangerous ? I dont want to set my boost any lower..

I have a TurboXS MBC...

Im thinking to fix this

Get a better BOV.. Like the MR one.. or Works tuning (designed just for Evo)

What kind of system..electronic boost controller.. or something else... would allow the computer to constantly adjust boost to keep it at one rate?? any idea's

 

that's normal. The stock ecu will let the boost tapper off by ~5000.. IMO, what your seeing is the ecu attempting to adapt to the MBC.

 

Some of the more expensive EBC's have gear specific settings. With my Greddy Profec B Spec-II, I set a limit feature slightly above what I want my boost set to. So to run 19 psi, I set the limit to 19.5psi, and when it hits that, it lowers my boost setting by 4%. This keeps my boost up to 19psi in the lower gears and keeps it from going too high in 4th and 5th.

 

No problems here holding 21psi on my Hallman MBC and stock BOV

 

you will see more boost at higher speeds in most cases because of the increased airflow over your intercooler. see if its fifth gear, or high 4th as well. it has nothing to do with gearing, i can tell you that much.

 

not so much the intercooler

its the amount of load on the engine

 

So how is it mine tapers and never stays constant.. it drives me nuts.. i wanna a controller that adjusts the boost to keep it constant...

 

more boost at higher gears because more load. Try fitting 5 people in ur Evo and redline to first gear. You'll boost steady 20 psi. Then Kick one person off ur car while driving and shift to second gear, u'll boost steady 20 psi. Now kick 2 people off ur car and shift to third, u'll boost 20 psi. Now keep ur last passenger in ur car and shift to fourth. You should be able to kick ur last passenger out of ur car at 5th gear and still boost to 20 psi.

 

If you want rock solid boost that doesn't change, get a Hallman MBC. What you're experiencing is your MBC not holding 100%, obviously.

- Jason

 

Ahh Horse A$$ Turbo XS MBC should be just as good.. I dunno what to do.. im gonna wait till Turbo Trix comes up to Dallas and have them take a look at it.. when i get my Utech Installed..

 

But if i spike at 23 for a second... should this be a concern?

 

I'm not sure if this is the only possible problem, but I have heard of some people stretching the rubber connectors on their intercooler piping after several boost spikes. Although I think those cases were spikes to 24-25 psi.