The turbo is a garrett t3 tbo357 from a 87 saab 900, internally gated. on a jdm b18bls pretty much stock internals.
-tried hooking it up stock at first with a hose from the compressor housing to the wastegate - 3psi
-next i tried my manual boost controller (t-ed into the hose and one line to bottome connection of the mbc, top fitting open) and i got no change any way i adjusted it
-to test it, i disconnected all the hoses from the wastegate and let it rip to 10psi no problem. than 15psi no problem.
does this mean the wastegate is good?? why does it open at 3psi with a hose and holds shut up and possibly over 15psi without being blown open? does anybody know about what psi they are blown open?
and i do have a wideband and moates tuning kit so i know i’m not running too rich or lean, don’t hear detonation or any noises at higher boosts, but i don’t hold it there cause there is no way of governing boost right now, just letting off when i want it to stop boosting. i really wanna get the gate working so i can feel the full potential. thanks in advance
im not 100% sure i understand what you’re asking but ill try to answer.
the reason why the wastegate does not open when the hose is not hooked up is because it doesnt sense any boost. when it is hooked up it should open at the stock boost setting. im assuming that 3psi is not enough boost for you? im not sure what type of boost controller you have so it is hard for me to tell you if you are installing it properly or not. hope this kind of helps.
ok, what i was trying to ask was why it’s only opening at 3si, shouldnt the stock wastegate open at more than that? at least 5 or 6? and why isn’t the boost controller working when t-ed in?
TeggeT:
having the hoses disconnected was just a test to see if the gate was being blown open at 3 psi which would have meant bad actuator, but it stays shut.
the boost controller is just a ebay manual controller. i had it t-ed in with my last setup and it worked great with no overboosting, now it won’t work t-ed in at all, still hits 3psi. so i hooked it up inline and it works but overboosts about 3-4psi and then drops.
any quick fixes for the overboosting?
i’m not a noob to turbos or anything, and i have done, and am still reasearching this issue. also i do have a 38mm external but i don’t wanna reinstall it cause it makes a black mess of my engine bay, and i’d have to make/get another downpipe. and thanks to all advice already given, and about to be given.
one of these. but im not using that t-block they provided, which 2 of the fittings are straigth through and the other one is restricted some, could that releive excess pressure somehow and help prevent overboost??
yes you are 100% correct, i meant boost SPIKE not creep, i feel so rediculously stupid. sorry for all the inconvenience, normally on top of shit like that to prevent harrassment but i’m a dead target now.
so i’ve screwed with it a bit and it’s still hitting 10psi than dropping to 5psi after about 2 seconds, i can get it to hit 5 and stay steady with only about 2-3 clicks of the controller, or just boost to hell with 1 click the other way.
the controller is set inline with the wastegate, line goes from turbo housing to bottom of mbc, and the top line on the mbc goes to the actuator. tried t-ing in the mbc again but this time hoses as short as possible (had it in the cabin last time it didn’t work), still 3psi. tried larger hoses, still no luck.
You had the mbc installed correctly by running it inline; why did you run it back as a “t”?
I personally can’t recall ever using a mbc/internal wg setup where there wasn’t some sort of spike or creep issue. Juanpac0 pretty much hit the nail on the head imo.
(If you were running a 38mm wg you really needed to run a dumptube to route the spent gas out the bay to avoid the “barbecue grill engine bay” look
If you’re having boost spike then it sounds like you have your MBC hooked up wrong on top of possibly having a boost leak or a faulty/weak wastegate. Basically what happens in this case is you build 10psi and at 10psi your wastegate can’t hold the pressure anymore and blows open.
This is how wastegates normally operate, but if you have an improperly “sized” one (for example, you have a 4psi wastegate and are trying to build 10psi with no MBC) then it would be an issue.
What I think your problem is is that you may have a low psi wastegate with a combination of having your MBC hooked up wrong, so it’s not doing its job and keeping the wastegate from opening.
BUT it could be a boost leak, make a boost leak tester just to be sure.
i’ll have to try out the leak tester soon. i only t-ed back in to test it out to see if it would work any better.also i’ve seen many boost controllers t-ed in which routes pressure away from the wastegate, making the turbo boost more till the wastegate sees its set psi. this worked with my external with no boost creep.
i don’t think the mbc is hooked up wrong cause then it would just block off the holes with the ball inside, and pressure would go beyond what i want, my friend just had his backwards and that was the result, no control at all. i’ll try switching it though.
i do however think that the wastegate is old/weak so i’m gonna make another dump tube for my external, i did have a nice dump tube but it unbolted and went bye bye.
ok, so i finally hooked up my external wastegate (xs power 38mm), and after a great day at 10psi, i realized the wastegate was sticking open a little, i could hear it (atmospheric), and it seems to lag just a little. so now i’ve tried numerous things - except changing the spring. manual boost controller was mounted inline.
checked spring rate by hooking the wastegate up normally with no controller. reads 5 psi
t-ed in the mbc, and ran the top bleader port back to the top of the wastegate like ive seen in picutes (the air being bled off helps keep the wastegate closed). maybe a little quieter, but not good enough for me, and there was no way to control the boost. even tried shutting the mbc and still boosted sky high.
than i tried t-ing into the line for the bov so that when i am off the throttle, the vacuum will suck the wastegate shut. seems to work better but still seems to be open a little.
noticed that the wastegate is cracked open a hair when i pull it off the car, once i pull it apart and put it back together it’s fine for a day or so…than it seems to stick. i do also notice a bunch of crap on the inside, looks like the paint is coming off the spring or something.
should i change the spring?? any other ideas??
oh and i just left the internal on for now, wired it shut so it won’t blow open, and i’m definately definately sure it’s closed all the way.