Internal Wastegate from hell

[Black99gst]

ok guys, i have been playing with a '97 GSX with a few kicks... well it has the EVOIII16g turbo on it, ported, and its externally dumped... well, boost control is fine, settings are fine, it holds boost just fine, no boost leaks, nothing like that... BUT! (you know its always something!) i dont really know how to explain whats going on and i tried to search... here goes. i hit WOT in 2nd to redline (20psi) wastegate open at about 2700rpm for full boost (perfect), shift into 3ed and return to WOT and the wastegate is still open for a very short period of time and builds boost VERY slowly(once it closes, boost shoots up to 20psi and it opens again) same thing in all gears if i shift from any RPM at full boost... how do i stop this? thanks

 

[tbonitz301]

Are you saying that your boost is pulsing?Do you have a logger?

 

[Black99gst]

no, i'm saying that it drives and boosts just fine, but when i shift gears, the boost drops (because the BOV opens as its ment to do) but the wastegate doesnt close! it drive fine with an open wastegate for a little then the wastegate closes, boost builds again, and then it opens again... the issue is when i shift gears from WOT, the wastegate doesnt close right away... everything else is fine with the car, and its running DSMlink. thanks

 

[Black99gst]

no one has any ideas?

 

[BoostedTalonTS]

double check that your boost controller is hooked up correctly... As a test, try running the WGA directly to a boost source to see if the problem still exists... THat way you can eliminate a sticking flapper or bad diaphram in the WGA. Do you have a vacuum pump?

 

[92awddsm]

Sounds as if you are running a homemade ball/spring type mbc without a bleed hole on the port to the wg. It builds pressure between the mbc and wg but cant realease without a bleed hole which holds the wg open until pressure bleeds off through the ball again. Make sense?

 

[Black99gst]

its a Turbo XS boost controller, i'll try running it w/o the boost controller tonight... thanks guys! i'll post results here if not tonight, tomorrow morning.

no, i do not have a vac pump

 

[toojung2die]

Sounds as if you are running a homemade ball/spring type mbc without a bleed hole on the port to the wg. It builds pressure between the mbc and wg but cant realease without a bleed hole which holds the wg open until pressure bleeds off through the ball again. Make sense?

I was thinking almost the same thing as I read this thread. It's also very possible that the MBC has a bleed hole to allow the wastegate to close but the hole may be slightly clogged or it may be too small in the first place if it's a home made job. Take the MBC apart and clean it. Run a fine wire through the bleed hole to make sure it's open. If the wastegate still closes too slow then enlarge the hole slightly.

 

[toojung2die]

its a Turbo XS boost controller

Turbo XS is a bleed-type boost controller. The instructions on their website tell you to cap off the boost signal nipple on the turbo compressor and 'T' into the BOV hose. I see two things wrong here. Bleed-type boost controllers are generally regarded as inferior to ball and spring boost controllers. Second, the boost signal coming from the turbo compressor side is preferred over tapping into the BOV hose.
http://www.dsmtuners.com/forums/art...237982-best-way-install-mbc.html#post50468083

 

[Black99gst]

the boost controller is hooked up right per that link... positive pressure from the J-Pipe, then the MBC, then the wastegate... its not tapped into the BOV line... i'm not new to this guys, this is just the first time i ever saw a problem like this, and since i am not "proven" because i would rather read then post... and i cant find anything on the topic, i'll post a thread here in the newb forums.

ok, so i ran the car w/o the MBC, i fed the tap in the j-pipe directly to the wastegate, and its perfect (accpet running 9psi is weak!) but everything functions exactly as it should.... since i bought the GSX as it sits, minus a few little things, their is no telling how old the MBC is, or how ofter it was cleaned or even how long its been on the car. i dont care much for the MBC, but this is the new DD... so what now? how do i clean this thing? i'll search around, if someone knows the answer on how to clean it or if their is another one i can pick up cheap that will function properly, please inform me!

thanks

 

[turboglenn]

EDIT: didn't read the last post, it's fixed

{RESOLVED]

 

[toojung2die]

the boost controller is hooked up right per that link...

...if there is another one i can pick up cheap that will function properly, please inform me!

I have the Joe P XZ. Reasonable price:
JoePMBC.com.. Performance Products for Turbo Cars.

Build it yourself. I made one of these and it works every bit as well as well as the Joe P but since I spent $ I kept the Joe P on my car:
http://www.geocities.com/chmwatson/FAQs/mbc.html

You'll find inexpensive ball and spring boost controllers on eBay. The design is so simple it's almost fool-proof. Take your pick.
You know what? I'm feeling generous so if you PM me I'll send you my homemade ball and spring MBC for free. I'm pretty sure I know where I put it

 

[Black99gst]

pm'ed!

I cant like, clean the one i got? i mean this thing is pretty nice looking, i took it appart last night, and its a ball and spring boost controller for sure... just i dont know why its not working properly... sure sucked driving to work this morning knowing i could only push 9psi... the thing felt about as powerful as a SOHC honda civic...

 

[Black99gst]

RESOLVED:

Issue was in fact the bleed valve on the MBC. special thanks to tooJung2die for the replacemnet Boost controler!

thanks to all for your help!