Little back story. When I first got the car the boost would hit 17psi and hold that all the way to redline. I put a wideband and a boost controller on it a couple months later and it would hit and hold 22-23psi to redline. Then late last year I was at the track and I noticed it wouldn't go up past 17 no matter what I did with the boost controller. I figured the 8 wastegate were weak so early this year I had the radiator out so I took the arm off and turned it about. 1.5-2 turns and turned the boost controller down. Now it was at 17psi again so I turned it up and it went to 20 so I left it alone.

Last night at the track I turned it up a few clicks to see what it would do and it started spiking 25psi to a quick drop to 17psi then stayed to redline. Then the next pass I heard a pop and the boost dropped to 10psi so I let off thinking I sprung a leak. me and my friend sat in the pits looking for a good 30min at all the connections and lines and couldn't find anything. Said screw it I i'll look at it tomorrow. Well on the way home I got on it and it spikes to 20 and drops to 15psi right away and holds to redline. I'm going to do a boost leak this weekend but I'm wondering if the wastegate is just getting to weak now?

Car has 116k on it. Turbo I assume is original. Motor mods are eBay lower intercooler pipe, Greddy upper intercooler pipe, Trust elbow at throttle body, Bushur intake, bushur exhaust with the factory o2 housing and synaps bov in recirculation mode.

Last year my track time was 13.4@105 1.9x 60' and the best I could get last night was my second pass before I started having the boost spike issues and it was 13.3 at 104 with a 1.95 60' slipping the clutch hard off the 2 step. didn't have the 2 step last year either. also it was like 20 degree cooler yesterday than when I went last year.

 

What kinda boost controller is on there? Is it an EBC, or an MBC? Maybe I missed it. Who tunes it? Do you happen to know if the original 9.8 hsg is on there still, or has it been replaced with a 10.5?

 

The -20 F. difference in ambients can cause a 2-3# increase in peak boost if you are running an MBC. Also, up in the 20+ PSI boost range the factory O2 hsg combined with an unported turbine housing can cause sufficient exhsust backpressure that the bypass port is not able to bleed off enough exhaust flow. These factors (colder air temps and insufficient bypass and turbine exducer flow) may be causing the spike/creep issue. At least it's possible, huh?

 

woops its a grimmspeed mbc. no tune yet. stock turbo 9.8 i would assume. af's are solid 11.2 at any boost. yeah i understand the change in pressure do to temp but it doesnt explain the spike then huge drop in pressure when it never did this spike before.

 

Reread my response above, as I edited and added a few observations. Also, you need to get a tune.

 

Do a quickie preload and creep test by adjusting the MBC to its lowest boost setting and going for a WOT run in 4th gear. This will tell us actual spring pressure at the gate, and let us know if it is creeping at low boost setting, also it will help diagnose the health of your suspect 100K mile stock WGA.

 

ill turn the controller down all the way in the morning and test that way. its not creeping though. ive had creep in my vw and its not like this. it just spikes 20 then falls to 15 and stays at 15. doesnt creep back up. ive been wanting to get an o2 housing but getting the gf to not freak on me for buying one is a job of its own lol.

 

boost controller turned all the way down it holds 12 psi to redline. couldn't do a 4th gear pull though only 2nd gear.

 

10-12# spring pressure is pretty minimal. At the very least, if you don't want to cut the actuator rod right off the bat, just remove the backup nut located behind the turnbuckle on the threaded tip of the actuator rod and proceed to jam the turnbuckle down all the way til it bottoms on the ip of the actuator rod. Maybe this mod will get spring pressure up to 14-16#. If you want better spool you'll need to cut 3/8" (3 threads) off the threaded tip of the actuator rod though.