No boost - Single turbo legacy

[Skiier]

Hi guys,

I just aquired a '96 gtb with a full v3 sti set up (photos to come, when it's clean😃) Has been recently rebuilt and seams to run very nice and tight except it's barely spooling up the turbo. I have been all through the vacuum lines and added hose clamps and checked to see that the waste gate was not jammed. Not currently throwing any CEL codes. Found that one of the hoses from the single turbo solenoid was not connected, so I looked up Rubens single turbo 2.0 thread to check plumbing and re plumbed the BBoD to match exactly what's in the photo. Still only boosting to 2-3psi. Checked for any leaks and can't find any except a small exhaust leak where the L headers join on the R side of engine bay. I know the exhaust leak is not helping but is not massive. Kind of head scratching now and wondering if anyone can help? If someone has a similar set up in ChCh that doesn't mind leading a hand that would be great🍺🍺🍺 all round. Cheers

[Rosssub]

Might have a sick turbo, the exhaust manifold leak definitely wont be helping though. Could be the BOV leaking, block it off completely to rule it out and see if it makes a difference.

A good way to check for boost leaks is to block the intake at the AFM then pump 10-15psi into the manifold with a compressor, any boost leaks will be obvious:

[Joker]

still has BBoD? thought they went west when you go single T, never been there otherwise not much help from me soz (guess some of the solenoids are still used yea?

[Skiier]

Thanks for the replys guys. The BBoD has been gutted and had the single turbo solenoid in place just using the plastic hose ports to keep it tidy looking. After further research into vacuum line plumbing im not convinced mine it set up right. I seam to have 'extra' hoses not being used from my intake manifold. I got a feeling when this was all re plumbed the guy set it up all ass backwards and the way it drives the wastegate actuator is just not letting it spool up. Will check BOV as well to be sure. Boost gauge has it barely gaining pressure. Ill take some photos tonight and see what you think. If someone with a v3/v4 set up is around chch that I could copy that would be ideal.

[Rosssub]

Try connecting a straight vac hose between the turbo and wastegate. Should give wastegate spring pressure of about 7.5psi and rules out a boost control problem.

[Skiier]

Will do cheers Ross. gotta love inheriting some ones mistakes in a new car, one thing at a time.. will post an update tonight

[Skiier]

Update: ran hose from waste gate actuator to turbo inlet as in picture above went for drive -still no boost. Removed bov and plugged hose test drove - still no boost checked bov and does not appear to be leaking. looked up v3/4 boost control diagram and re plumbed mine to suit, see pictures http://www.rs25.com/forums/f128/t157501-help-v4-sti-stock-boost-solenoid-setup.html . So starting to think it must be the exhaust leak? Seams weird that It would give me no positive manifold pressure? Did notice a bolt missing from ex housing to down pipe that would not help. Is there any other possible things going on?

[Guest]

If it doesnt make 7 psi with line as per ross's link you have other issues. Either exhaust leak pre turbo or wastegate actuators toast.

[Skiier]

Update:

Found that exhaust manifold was leaking at the start of up pipe. Replaced gasket with gen Subaru one ( so much better quality that the blown one)

At this point I though that would be it but still no boost.

Checked all other joins in manifold and exhaust ports and as far as I can tell by looking under there with car running that there is no other exhaust leaks. Looking at the headers it looks like the guy used exhaust goo can't see gasket ( might be hiding under goo), not ideal but as I said does not look to be leaking.

As mentioned before I have eliminated bov, and boost control issues as far as I can tell.

Starting to feel a bit stumped, is it possible that the turbo is toast and what would the signs be? (Apart from no boost) there is no smoke/ leaks from turbo and it sounds like it's spinning freely at idle.

Any suggestions would be appreciated, cheers

Skiier

[Rosssub]

Grab the wastegate actuator rod with pliers and force it open, then let it go. You should hear it slap shut. Then try the compressed air boost leak test described in the second post ^^^.

If all still tests ok, then it's probably time to whip the downpipe off and check the turbo out.

[Skiier]

after hearing a similar problem in a friends old GTB legacy removed mid section of manifold and stripped off heat shields to find this. It has a split in the flexi section that was leaking behind the shields that stopped me being able to see/feel it. this combined with leaking uppipe gasket and may FINALLY be boosting! (trying not to get too excited)

Incidentally if anyone in chch has a spare one of these lying around for a v3/v4 manifold that would be ideal!

[Guest]

Cut out the flexi and weld in a straight piece of pipe. May as well upgrade it if replacing it.

[Skiier]

good point. I though the flexible qualities might be needed to account for bumps and torque twist to maintain seal on gaskets? otherwise off to the welders...

[Guest]

Bumps and torque shouldnt flex the engine that the manifolds attached too if it does you have a funny engine lol. Its for heat expansion but people have been cutting them out for years with no dramas. Will need to bolt it in place when you weld it so flanges dont warp and it sits where it needs to.

[hijacka]

i should have one of those, or i could weld that one?

[Skiier]

that would be sweet, Ill PM ya

[Skiier]

Just went and saw Tony at RDL, diagnosis is turbo is most likely toast. Can get a rebuilt VF23 for $550 + gst. Wondering if anyone on here has a vf23/vf24 in good nick keen to part with? tempted to go for the rebuilt option for peace of mind...

[A_J_T]

Have a look through the Classifieds. There is a VF28 in there http://clubsub.org.nz/forum/showthread.php?46145-FS-VF28-turbo-AKL which would probably do the trick

What happened after fixing the above leaks ^

Edited May 4, 2015 by A_J_T

[Skiier]

Still no boost. even removed vac line from wastegate to see if it would free boost to test if turbo was working and won't build positive boost pressure. even with a small boost leak that should have given it something. Ended up ordering rebuilt VF23 for the 'do it once do it right' approach. going to swap turbos this weekend and will post update. Good learning curve this is :-) Feel a bit stupid for buying a car with a f**ked turbo but life goes on, hopefully faster!

Edit: spelling and content

Edited May 4, 2015 by Skiier

[Skiier]

Weekend update:

- Removed old VF24, bearings were worn and turbine becoming hard to spin.

- installed reconditioned VF23 with gen Subaru gaskets. Looks crisp!

on the install I removed the banjo bolt and cleaned out all the fittings, removed oil feed line and cleaned, replaced oil drain pipe then

tested for oil flow.

- replaced mid pipe on manifold with a good one with no leaks (cheers hijacka for the hook up) gen Subaru gaskets again.

- replumed the factory BOV recirc pipe and installed factory v4 sti BOV while I had intercooler and turbo off.

at this point I was expecting a totally new experience but alas i'm still chasing bugs. With the wastegate actuator plumbed direct to turbo outlet i figure i'm making 6-7 psi (hard to tell because the gauge in car is a peice of Sh*t) feels slow anyway but better than before.

I have a feeling I have a leak or something weird going on still as i cant get it to spool up any further. I have plumbed the boost solenoid to what appears correct any tried to see if that will let me boost more but no it wont. I tried to see if i could free boost it to test with WGA unplugged but didn't seam to make huge difference, I was being super paranoid and light footed though.

Further to my paranoia I whipped off down pipe to double check the turbine on the new unit was spinning freely and it was fine. Just wanted to make sure I had not done something stupid at 1am and ruined a new turbo! (:

while the intercooler was off I had a good look at all the fittings and it all seems ok and could not see anything split that looked like it would leak.

I know the compressed air trick would help me eliminate a few more things but I dont have one to play with.

If any one of you chch clubsub ninjas could donate some hands on problem solving that would be choice! Im at the stage of feeling like f*ck it and taking it to a garage as im needing it to be my daily soon. defeatist I know but I only have so much time to spend under the bonnet right now.

TL;DR - new turbo on but still not what it should be; HELP!

New VF23

[Rosssub]

7psi is right for wastegate spring pressure, (straight hose from turbo to WG).

Have you got a restrictor pill in the stock boost hoses? Guessing the V3 STI 3 port solenoid uses one.

[Percy]

I have a compressor if you want to try the leak test?

I fact I have an old Subaru air suspension compressor in a tool box you can borrow, has the advantage of running off 12v!

[Rosssub]

[Skiier]

Cheers for the replys crew. The diagrams you put up rosssub are the ones I copied from somewhere But I will double check plumbing in morning. Not sure if it still has restrictor on bottom pipe, is that essential? Percy I will take you up on that compressor I think, will send you a PM.

I do have some sort of restrictor pill in the line from the turbo housing looks roughly 2mm which as far as I can research is right?

Yah im hoping I have it narrowed down to a leak/boost control issue, was good to know that the turbo was indeed toasted. Is there any other tricks I should be applying? will post another update after rechecking plumbing/compressor test.

clubsub is awesome

[Skiier]

... quick question (prob belongs in stupid question thread) based on the above diagram I would not have the actuator and turbo outlet on a 'T' running to solenoid? I got a weird feeling im going to have an 'Ahah' moment tomorrow....