Need Help...Underboosting after upgrade
 

My modifications on my 2005 evo 8 mr are TBE and cone filter.
I purchased an AP and installed the stg 2 along with the vacuum lines cobb supplied me with which have a different seconday restrictor pill.

Car was running good stock peaking at 1.3 bar and then dropping off.

After installing the stg 2, i am only reaching 1.2 bar, so i am underboosting. I should be at 1.5 bar with the stg 2 map. I uninstalled the map and went back to stock and still am only reaching 1.2 bar with the cobb vacuum line.

Should I return to the stock vacuum line and remove the secondary restrictor pill from it? But wouldn't that cause the car to underboost even worse?

What is causing this? Any ideas..i checked for boost leak and there are none. The only thing i can think of is adjusting the wga springload and shortening it. However, i have not heard of anyone else having to do this. Also, does anyone have a link to how to adjust the nut on the wga properly?

Let me know any ideas of how to correct this. THANKS!!

bump..looking to get some help quick..thanks again!!

also something to add..i am currently using the oem boost control solenoid

would a mbc solve this problem? i was told it wasn't needed and that only the vacuum line needed to be replaced

bump

i replaced the stock vacuum line without the secondary restrictor pill and now i am boosting 1.5 bar, but only in 3rd gear and up. i uninstalled the AP and was still boosting the same. So my concern is, is the AP even controlling the boost like it should?

would a MBC help this?

You should get 3 port EBCS, liek one from Perrin. That should help with your boosting issues. I also have a custom Map for my IX that might work for you, Its their stage 2 tune for 93+octane but works great. Check out their site for details on the map. PM me if you want to know more information.

You have several options, but the boost pills are there to help you hit boost targets. The AP is indeed controlling boost, but you have to mechanically alter the system to hit higher targets exactly how you have done. That said, a 3-port EBCS is a good mod, but it will require custom tuning. Another option, the MBC, is a great way to control boost on the 4G63, it works rather well on these cars, but you will have to experiment to make sure it is setup right.

One last note, you will not hit peak boost in all gears, you should hit it in 3rd gear and up depending on load etc.

i understand the load changes throughout gears. the problem was that with the map installed and pill removed i was underboosting below the stock boost level in gears 1-2 and then hitting well over stock boost level in upper gears. the oem solenoid just wasnt doing the job.

a hallman mbc solved the problem. it is peaking and holding boost throughout the gear. i just have to adjust the mbc to accomodate for the load change in upper gears.

Glad that you were able to find a solution to your problem, boost leaks are a pain, but congrats on getting it taken care of.