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Old 10-30-2003, 08:19 PM   #1
300blueballs
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Unhappy Turboback for an STi (Don't buy one *yet*) = horrible boost creep and fuel cut

Ahh... the aches and pains of modding. After reading so many rave reviews on what wonders a turboback system did for the vendor's and it's customer's cars I went out and got the Borla Hushback which I modified to fit the TSX DP and catback adaptor. I got out on the highway and went on a WOT test run. Readline came up MUCH faster than before and by the time I shifted to 5th at about 5600rpms *BAM* the car felt like it had stalled. The cruise controll light was blinking and check engine light was on. Thinking to myself (this sucks). After realizing the only thing it could've been was boost creep I went out on another WOT run and I was hitting about .115 mpa (16.7psi) in 1st 2nd and about .12 mpa (17.4 psi) in 3rd and fourth was about the same. 5th gear I hit maybe ~.132mpa (19.xxpsi)!! *Bam* another fuel cut in the midrange as soon as I shifted. I got on here and did some research and noone seems to have an actual fix for this. The wastegate can be ported but I am trying to keep my car under warranty. I'm pretty sure a ported out turbo would viod any warranty, if anything went wrong. People also use boost controllers but I heard they don't really help much in keeping boost down. Plus why would I want the computer to have no controll over the boost??? So then when I'm not paying attention I'll can overboost and break the bearings in the turbo? I don't get it... There has been very few threads on this and people still just rant and rave about how great their Turboback Exhaust is for their STi. I'm debating if I should switch back to stock because the boost creep issue is pretty bad ans will get worse with the colder weather. I can't go WOT for fear of overspinning the turbo or worse overboosting the engine. I'm probably going to go back to stock unless I can find a fix. Does anyone have any real insight on this? Any fixes?


Also: Doesn't anyone wonder why ANY the manufacturers didn't get or report issues of boost creep when selling their exhaust systems??

Ahhh....

( i know a TBE voids warranty at some dealerships, but my dealership will warranty my car except for the exhaust)
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Last edited by 300blueballs; 10-31-2003 at 02:23 AM.
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Old 10-30-2003, 08:49 PM   #2
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There has been several thread about this. So far the only reasonable fix that I have seen is to port the waste gate. The other fix was to use a FCD. Stopping fuel cut due to over boosting is not really a fix espcially if you can't control fueling for to the extra air you're getting. What kind of A/F are people seeing? I know people are getting more power due to the extra PSI. Is this causing a lean condition? Maybe it's not a problem since we're alread pig rich. I'm fairly certain that most SOA rep would probably deny warrenty work if they saw your after-market TBE espicially if you're hitting fuel cut due to overboosting.
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Old 10-30-2003, 09:00 PM   #3
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I'd like an answer as well. Will the Profec or SBC-id fix this with high boost set at 17psi? I got .13 MPa with a godspeed dp, greddy evo, and Blitz SUS. But, stock I would run .11 MPa.

Will the UTEC fix this when it becomes available?

BTW, I think the removal of a cat will void your warranty.
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Old 10-30-2003, 09:17 PM   #4
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FCD? What is that?

Stopping fuel cut is obviously not a fix, but that's what the ECU does as a safety net in order to protect the turbo/engine. I don't think running lean is as much of a problem as overspinning your turbo since it is running close to it's peak in stock form.

The person who helped me install the exhaust was an STi mechanic at my dealership. From his experience with the WRX's, exhausts had no effect on the warranty, other than the exhaust components and anything associated with that like O2 sensors. Again this depends on your dealership since it seems to vary. Besides if your car is in bad shape, an exhaust is one of those things you can remove and swap it back to stock before it's brought to the dealership.

The whole point is that people should be aware of this problem. I would have waited until there was a fix for this (redesigned downpipe/engine management?) if I had known about it.
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Old 10-30-2003, 09:28 PM   #5
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FCD = Fuel cut defender. There are several manufacturer. I beleave that they all require that you splice in to the ECU harness somewhere. This will at least stop the fuel cut from happening. I still say that porting the turbo so it can expell enought exhaust to keep the boost down is the better way to go. I'm certain that UTEC has the ability to move/remove the fuel cut. It will also allow you to control fueling. If this or some other form of this were already available, that would be ideal. I beleave that some people are going old school with the FCD and SAFC. There is also some doing the Greddy E-Manage for fuleing. I'm not sure if it can control fule cut though.
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Old 10-30-2003, 09:38 PM   #6
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There are no good solutions right now if you ask me. I'd take it off and wait. I think it's bs that "tuners" are selling exhausts for cars that can't adapt properly to the change. They should be warning customers. That being said, it doesn't surprise me that they aren't. Good Luck man.

-st
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Old 10-30-2003, 09:55 PM   #7
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I'm putting my stock catback on this weekend.

I did a bit of research before putting my TBE on. I thought that the boost creep was more prevelant in cars that had an aftermarket intake as well.

I left mine stock and crossed my fingers.

BUT, like you, i'm overboosting.
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Old 10-30-2003, 10:32 PM   #8
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As everyone has said this is a known problem with turboback exhausts, the gases flow more freely and there won't be a fix until engine management is available to correct the readings from the sensors.
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Old 10-30-2003, 11:51 PM   #9
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FWIW

Using EBC (HKS EZ) boost is rock solid.

The factory boost controller is not upto the job.

Buy a good EBC- problem solved

300blueballs
Maybe later you will put on a bigger turbo and complain that no one told you that 30psi and 30deg advance on 91 octane would cause your motor to go boom.
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Old 10-31-2003, 12:29 AM   #10
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Quote:
Originally posted by Wombat North

300blueballs
Maybe later you will put on a bigger turbo and complain that no one told you that 30psi and 30deg advance on 91 octane would cause your motor to go boom.
That's a dumb thing to say right there. I am not a moron so don't treat me like one. I knew perfectly well that there was elevated boost levels after a TBE but I did not expect it to be ~4psi higher than stock and rising until the ECU cut the fuel. For example (I am not picking on TSX in any way, but they have dyno results posted):

"The TXS STI's boost curve is healthier than specified by Subaru with a peak boost value of 15.6 psi stock and 15.8 psi with the addition of the TXS RFL-TI Exhaust System."

So I heard people had some overboost issues on the forums but noone was really complaining about it and as my concrete info I looked at many manufacturer websites besides TSX which mentioned nothing about the stock wastegate not being able to cope with the extra flow. I thought to myself that .2psi higher than stock is no big deal (I was looking forward to higher boost levels ~1psi), but I did not expect not to be able to go WOT after putting a TBE on (getting 4psi higher than stock - until fuel cut). As a reference I used to boost .1mpa (14.5 psi) stock.

I am not complaining just for the sake of complaining. I am trying to make people aware of this and rather have them wait to get a TBE until there is a solution, if there isn't one. I love the exhaust, just looking for a way to stop it from overboosting SO MUCH.

Last edited by 300blueballs; 10-31-2003 at 12:46 AM.
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Old 10-31-2003, 12:35 AM   #11
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Wombat-

(I know it's hard for you to refrain from putting others down ) but can you share what setup you have and if you have tried the TBE with/without the boost controller? Did it effectively keep the boost down? What boost levels are you getting with it (EBC on/off)? Have you hit the fuel cut with/without the EBC? I'll try anything as long as it works.
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Old 10-31-2003, 01:08 AM   #12
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Old 10-31-2003, 02:02 AM   #13
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I would not go to the extreme and recommend not to buy a TBE. A TBE is a very good mod, but its very unfortunate that the stock VF39 wastegate is a poor design. There are ways to combat boost creep and they have been redundantly discussed for months. I don't know if you heard the old saying, If you wanna play, you gotta pay!

Personally, I have a full TBE, MBC and intake, but I went back to the stock DP and just running a catback with no other mods. I did this due to the boost creep problems. I feel that its not heathy for the stock VF39 to be taking that kind of abuse. Once engine management is out, it might be worthwhile, but until then, i'm staying safe. Like mentioned in another thread, we'll probably be seeing a lot of blown stock VF39's from people overboosting.
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Old 10-31-2003, 02:23 AM   #14
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is this boost creep and fuel cut problem happening to everyone with a TBE or to just some of u?

so porting the wastegate is basically the only fix available now right? how much does that cost and what are the drawbacks of doin that?
also where do i get that done?

i just want to prepeare 'coz i have a tbe on the way and i want to be able to deal with this problem immediately.
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Old 10-31-2003, 02:33 AM   #15
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Quote:
Originally posted by JikJak
is this boost creep and fuel cut problem happening to everyone with a TBE or to just some of u?

so porting the wastegate is basically the only fix available now right? how much does that cost and what are the drawbacks of doin that?
also where do i get that done?

i just want to prepeare 'coz i have a tbe on the way and i want to be able to deal with this problem immediately.
Happens to everyone running a free-flowing TBE with factory boost controller. Can be capped to a certain extent with a MBC or EBC. Wastegate porting is about the only real solution, but that is a irreversable modification; the only drawback. Again, this is all done at your own risk right now until engine mgt is available and more R&D with the new 2.5L. There is a vendor on this forum that does porting called Deadbolt Enterprise. He did quite a few VF39's and had satisfactory results. I think he charges $195 for the service.
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Old 10-31-2003, 02:40 AM   #16
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Thanks STi Dreams, I hadn't seen a couple of those threads in my search. So I guess there is a possibility that the ECU can be remapped to activate the wastegate at lower boost. People on previous posts say the wastegate starts to open at 7psi. I wonder if a changed wastegate actuator map would be enough or it's just that a fully open wategate is not efficient enough to deal with lower backpressure. Once we know that, we can determine if Engine Management will be a cure.

dsm- i definately agree with you. Those blown vf39 threads really made me realize how potentially dangerous this can be. This is why I'm reluctant to install a EBC, MBC, or HPBC to try and keep boost levels down. Even with a BC boost levels are still above normal ~17psi. Plus some say that the boost can still vary depending on environmental conditions with a BC. Like someone said in a previous thread, a ported wastegate is like a "bandaid", not a true fix, neither is the BC. The safer route for me is to have the ECU cut the fuel, IMO. For now I will place the snorkus back in the car, put away the perrin panel filter and not do any WOT runs until there is some controlled testing done and the jury is out on the best fix for this.

Oh, I also edited the title of the post changed it to read "(dont buy one *yet*)" which is what I meant to say.

Last edited by 300blueballs; 10-31-2003 at 03:08 AM.
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Old 10-31-2003, 03:10 AM   #17
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i guess porting the wastegate will void the warranty. so it being irreversible makes it a drawback?
can the dealer tell if it is ported?
is there a website for deadbolt enterprise?


as far as boost controllers are concerned they help the fuel cut and cel problem but they can cause a more serious problem by damaging the turbo due to overboost?

and for the fcd, that eliminates the fuel cut but still causes overboost which can hurt the turbo as well?

lastly, software/programming is supposed to solve this probelm but there is non available yet right?

sorry for all the q's but im just trying to get a better understanding to all of this.
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Old 10-31-2003, 06:28 AM   #18
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Hoping the tuners log on to this thread...

Want to know if the UTEC will fix this when it becomes available as well as what the tuners recommend MBC, EBC, (brand)?
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Old 10-31-2003, 07:33 AM   #19
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Quote:
can the dealer tell if it is ported?
i dont think a dealer would know unless they really looked close...i think its one of those things that can be overlooked...althought i think deadbolt paints the exhaust housing..that might give it away
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Old 10-31-2003, 08:01 AM   #20
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Quote:
Originally posted by JikJak
i guess porting the wastegate will void the warranty. so it being irreversible makes it a drawback?
can the dealer tell if it is ported?
is there a website for deadbolt enterprise?


as far as boost controllers are concerned they help the fuel cut and cel problem but they can cause a more serious problem by damaging the turbo due to overboost?

and for the fcd, that eliminates the fuel cut but still causes overboost which can hurt the turbo as well?

lastly, software/programming is supposed to solve this probelm but there is non available yet right?

sorry for all the q's but im just trying to get a better understanding to all of this.
they can tell if its ported if they take it off and look inside. chances are, even if they do look inside, theyre not going to think something is different.

sorry, forgot the website...do a search for username deadbolt.

boost controllers (well...the txs hpbc at least) will let you change the way your car makes boost. you can adjust it so that you make boost earlier...or you can make it so you make boost later. you can make more boost...or you can make less. its up to you, and i believe it adds a level of security when you have a tbe.

fcd is dangerous. i refuse to put that on my car instead of an mbc without upgraded fuel/fuel management.

the only thing out there so far is vishnu's xede. turboxs's utec and cobbs accessecu should be coming out by years end.
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Old 10-31-2003, 09:42 AM   #21
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www.deadboltspeed.com

Is Jerry's website. He does great work!

Dan
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Old 10-31-2003, 10:34 AM   #22
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the $195 port and polish includes the wastegate porting?
or is that a sti exclusive port that excludes the 'MONSTER' port/polish job?
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Old 10-31-2003, 11:01 AM   #23
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Maybe for now you should try a stealthback system instead. I have one from TXS. Power gain is still very noticeable and it's pretty smooth. No boost creep!
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Old 10-31-2003, 12:07 PM   #24
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Quote:
Originally posted by lobelsteve
Hoping the tuners log on to this thread...
Yea, me too. This is one of those things that can be answered by a number of things: An efficiency map for the Vf-39 and some sort of testing of the efficiency of the wastegate when fully open. If I knew how to test for these thing and had the equipment, I'd be doing it as we speak. I wonder if the XEDE addresses this issue in their programming? Maybe by increasing the amount the wastegate opens starting at a lower boost level?

Calling all tuners: Vishnu, TXS, Cobb... where are you?
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Old 10-31-2003, 12:27 PM   #25
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Hmm, well mine had no issues for some strange reason.

Anyhoo why are you acting like 18psi is a *BAD* thing. That is exactly where the turbo WANTS to run. In fact if you kick it upto 18psi in the lower rpm band it can hold it to redline where as 16.5-17psi still drops to 13.5. Just get a FCD and have fun. The ECU will start to run super rich at those levels so you are safe. We had to pull ALOT of fuel out to get to 11.0:1 - 11.7:1 range
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