Boost issues.

[Ozone302]

I bought my 92 talon tsi a few months ago 100% stock except for drilled rotors. It runs perfect and has ~80k on a stock rebuilt 6 bolt. Also has 10k on a rebuilt tranny and 10k on the clutch. Only things wrong is it needs new struts and has 1 broken exhaust mani stud. But anyways, I always went off the stock boost gauge when I first got it and it read ~12psi full boost. But since I got an aftermarket boost gauge, its pegged at 7psi which I'm told is waste gate pressure and stock is 12. It reaches full boost (7psi) at about 3000-3200rpms which is fine I'm told on a 14b. But I'm just wondering why it's only getting 7psi? There's no boost leaks at all. All hoses and lines are good. Has a literally brand new 1g bov with about 2k miles on it, recirculated. And I really don't think that broken exhaust mani stud is the issue because it spools up nice and fast. It just will not go over 7psi in any gear. Doesn't spike or anything, just pegs at 7 according to my aftermarket gauge and I've tried 2 different gauges and both said the same thing.

So what could be causing this? This is my first turbo car and I've learned a lot about it in the couple months I've owned it. I'm just at a loss and the car feels so sluggish compared to what it should feel like from having almost half of the boost it should be pumping out. The only thing I can think of would be maybe the BCS is bad and not raising the boost like it should which is only allowing wastegate pressure? Does this sound plausible? My Friend told me to just get an MBC because it will bypass the BCS anyways which sounds reasonable to me. Any help would be appreciated. Thanks

 

[zcoh2gdsm]

stock wastegate for a 14b is 9lbs. im running the same in my 2g. if your only hitting 7 you might have an exhaust leak from that broken stud.

 

[Ozone302]

Hmm I thought i read somewhere it was 7.. Either way, it's not hitting full boost. I bypassed the BCS today and ran the line straight from the waste gate to the j pipe and it's still at 7 so I guess that means my BCS isn't working because it's the same without it. Also spools quicker without it now . You're probably right about the stud maybe dropping it a couple psi but it spools nice still. I gotta work on getting a MBC now I guess and fix that stud. Thanks

 

[9SECAWD]

Find a boost controller and hook it up. Turn it up a pound or 2 and see if it will go up that way, i would think that a single broken exhaust stud would cause much of an issue.

 

[delta448]

My 2G FSM says the "supercharging pressure" should be between 6.4-14.7 psi. I would imagine the 1G FSM specs have a similar range, but I've not checked.

The BCS only increases boost beyond wastegate pressure under certain conditions.

An exhaust leak shouldn't limit you to 7psi on a 14b unless it's really bad. The more noticeable symptom of a pre-turbine exhaust leak would be slower spool up. At what rpm do you see that 7psi?

Fix the stud. Check for exhaust leaks, including the wastegate flapper. Get a boost controller.

 

[Ozone302]

Yeah I don't think the broken stud is doing much. You can hear the leak which just sounds like a tick but it's very small. The turbo spools up good. Reaches 7psi at about 3200. Wouldn't it be the BCS though because I bypassed it and it hits the same boost level now without it. There's no boost or exhaust leaks besides that stud which I'm probably not gonna mess with until I swap manifolds. I'll be getting an MBC here in a couple weeks. How do I check the flapper?

 

[Ozone302]

Also, would a turbo starting to go bad cause this? The guy I bought the car from said it was rebuilt prior to me buying the car but I don't trust people. I'm not saying I think it's bad, just wondering if that could be a cause of my problem? I've never owned a turbo car before this and don't really know what the turbo should sound like.. But it doesn't really whistle like other turbos I've heard. My turbo has kind of a low "wurrrrrrrr" sound, not the high pitched whistle you'd expect a turbo to make. Idk if maybe its just because it's at low boost or what.. I'm gonna pull off the intake tubing tomorrow and inspect it and check for shaft play.

 

[delta448]

That's about average for full spool from my experience, ideally it should be a little quicker but that's fairly normal on an old 14b.

Check the flapper by pulling the O2 housing off and making sure the flapper is sealed over the wastegate passage. Also make sure there's no big cracks visible in the turbine housing while you're in there. If you have a little air compressor or hand vac pump handy, you can also use your aftermarket boost gauge to see what pressure the wastegate actuator is opening the flapper at.

A simple MBC should net you better boost pressure as long as everything else checks out. You've already BLT'd I assume?

edit: That noise doesn't sound normal to me. I see a new turbo or a rebuild in your near future.

 

[stacked1G]

first off the stock boost gauge is not accurate, so dont trust that,ever. meaning it may have always been at 7psi.

seems as if your spool time is about right, but id still fix your exhaust mani stud, and do a boost leak test. check your turbo for shaft play(both up and down, and in and out)

as far as the "sound" your explaining, i cant say anything without actually hearing it, you may just spell the sound or discribe it differently with words than it acutally sounds .

 

[Ozone302]

That's about average for full spool from my experience, ideally it should be a little quicker but that's fairly normal on an old 14b.

Check the flapper by pulling the O2 housing off and making sure the flapper is sealed over the wastegate passage. Also make sure there's no big cracks visible in the turbine housing while you're in there. If you have a little air compressor or hand vac pump handy, you can also use your aftermarket boost gauge to see what pressure the wastegate actuator is opening the flapper at.

A simple MBC should net you better boost pressure as long as everything else checks out. You've already BLT'd I assume?

edit: That noise doesn't sound normal to me. I see a new turbo or a rebuild in your near future.

Ok I'll check it all out tomorrow. What's blt'd? Yeah I don't think the turbo noise is normal either do I'm already assuming its probably the turbo on its way out. Thanks for your help though man I appreciate it. I'll post what I figure out after checking everything tomorrow. Gonna start checking classifieds and Craigslist for turbos tonight just in case .

 

[Ozone302]

first off the stock boost gauge is not accurate, so dont trust that,ever. meaning it may have always been at 7psi.

seems as if your spool time is about right, but id still fix your exhaust mani stud, and do a boost leak test. check your turbo for shaft play(both up and down, and in and out)

as far as the "sound" your explaining, i cant say anything without actually hearing it, you may just spell the sound or discribe it differently with words than it acutally sounds .

Well I said I used to go off the stock gauge till I got an aftermarket one and I'm sure it's always been at 7 but I used to think it was higher if that makes sense . I've already checked for boost leaks and there isn't any. I'm not worried about the stud because I'm sure the leak from it is almost negligible and isn't the main cause of my problem. gonna inspect the turbo tomorrow. Lol it's kinda hard to describe the sound and you can't hear it on video, I tried.

 

[delta448]

What's blt'd?

Boost Leak Tested

I've already checked for boost leaks and there isn't any.

What pressure did you test at and how long did it hold it?

I'm not worried about the stud because I'm sure the leak from it is almost negligible and isn't the main cause of my problem.

It still needs fixed. Once it starts leaking it can cause much bigger problems, like damage to the manifold or an engine bay fire.

 

[Ozone302]

Well, got a couple chipped impeller fins. Gonna start saving up for a 16g now.

 

[stacked1G]

Well, got a couple chipped impeller fins. Gonna start saving up for a 16g now.

you may just be better off grabbing a 14b cheap, or rebuild it. so u can take care of other mods that at this stage that will help more, like full exhaust, mani, intake, fuel etc.. then grab a 16g. but hey idk, maybe u wanna do it backwards.

i only say that because u wont be getting much of a gain if any at all having a 16g on stock exhaust,maybe just more lag.

 

[Ozone302]

you may just be better off grabbing a 14b cheap, or rebuild it. so u can take care of other mods that at this stage that will help more, like full exhaust, mani, intake, fuel etc.. then grab a 16g. but hey idk, maybe u wanna do it backwards.

i only say that because u wont be getting much of a gain if any at all having a 16g on stock exhaust,maybe just more lag.

Only reason I wanna go the 16g route from the get go is because I had planned on getting one down the road and 16g's are a dime a dozen where I live. I already found several on Craigslist for around $200 that aren't eBay junk. I only found 1 14b and it's $200 do I figure for the same price basically I can have a 16g ready to go. I just think that makes more sense money wise than spending money on rebuilding or buying a new 14b and eventually upgrading to a 16g anyways

 

[Ozone302]

I drove the talon last night. It drives so good.. I'm gonna be sad seeing it outta commission for a little while.. Every time I drive it, the turbo sounds different. I have never worked on dsm's before besides doing the brakes on this car. I'm actually excited to work on it and slap a new turbo on. Gonna keep driving it until I save up the money for the swap. This car is gonna be a little sleeper when I'm done with it. I still have the stock exhaust and everything so it will be fun with the extra power the 16g has on a stock car. Eventually gonna do exhaust and everything else but for now it's gonna be a 16g sleeper