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Discussion Starter · #1 ·
I remeber reading somewhere on here someone had a VF34 with the HKS Downpipe and something about the backpressure was messing with the wastegate, and they had to switch to a Helix downpipe. I tried a search and could not find the thread.
 

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That was probably me. In the last few months It's been braught to my attention that the downpipe wasn't the problem.

peace
 

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damn ebrot, when did you become a mod? Congrats..... Anyways, it's nice to say that bellmouth and divorced wastegates are nice, but some turbos with certain setups will boost creep no matter what downpipe you have. The vf34 is one of those turbos. I would suggest to keep a high flow cat and or 2.5 inch exhaust after the downpipe instead of 3 inch catless if you're gonna get a vf34. This is all just my opinion.....

peace
 

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hippy78 said:
damn ebrot, when did you become a mod?
peace
musta been after the 9,400 mark. ;)
 

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Discussion Starter · #6 ·
hippy78 said:
damn ebrot, when did you become a mod? Congrats..... Anyways, it's nice to say that bellmouth and divorced wastegates are nice, but some turbos with certain setups will boost creep no matter what downpipe you have. The vf34 is one of those turbos. I would suggest to keep a high flow cat and or 2.5 inch exhaust after the downpipe instead of 3 inch catless if you're gonna get a vf34. This is all just my opinion.....

peace
I now have the HKS dp and HKS hipower exhaust (no cats)
You suggest putting some restriction back in?
 

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If you're having boost creep issues and need to fix them, adding restriction to the exhaust flow isn't going to make you any happier. You need to port the wastegate a little bit. That'll solve your problem.
 

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Hey, just cause you have a turboback, that doesn't mean you have no cats(still one in the uppipe). Like I was explaining b4, the problem only occurs with certain turbos, so if you're still running the stock turbo, I don't think you have to worry about it.

Also, I don't agree with the porting to solve boost creep, cause it doesn't. Saying that porting is the answer is rediculous. If a car creeps to 21psi in fourth, porting the wastegate might get you down to 18psi. This is not a solution, because being able to hold the boost at 18psi isn't actually controlling the boost. If that was the solution, you could just bump the boost upto 21 and say you have no creep:). If you could hold the boost at 12psi 14psi 16psi and 18psi, that's boost control, and that will not happen by poritng the wastegate no matter how much you port it. It would be much more possible with a high flow cat after the turbo(imo).............

peace
 

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Discussion Starter · #9 ·
I've read here the VF34 will do this, I have/will have: VF34 Turbo, Sti injectors, Cobb reflash, Vishnu Up-pipe, HKS downpipe, HKS Cat back exhaust. What do I need to change?
 

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Wait....are you having these issues or are you just worried that they might start?
 

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hippy78 said:
Also, I don't agree with the porting to solve boost creep, cause it doesn't. Saying that porting is the answer is rediculous. If a car creeps to 21psi in fourth, porting the wastegate might get you down to 18psi. This is not a solution, because being able to hold the boost at 18psi isn't actually controlling the boost. If that was the solution, you could just bump the boost upto 21 and say you have no creep:). If you could hold the boost at 12psi 14psi 16psi and 18psi, that's boost control, and that will not happen by poritng the wastegate no matter how much you port it. It would be much more possible with a high flow cat after the turbo(imo).............

peace
And as usual, I think you're on drugs.

There are multiple people on this board who have eliminated boost creep by porting the wastegate of a VF34. Adding a kitten is a bandaid for a larger problem.

The issue here is pressure. If the wastegate port can't flow enough exhaust, the exhaust gasses find it easier to flow through the turbo than through the wastegate. Since more exhaust energy is spinning the turbine, boost keeps rising.

If you want an efficient solution to this problem, adding backpressure to the turbine is the wrong thing to do. I mean seriously now... When have you ever heard anyone recommend ADDING backpressure to a turbocharged engine?? You want to eliminate as much backpressure as possible so the turbo can work as efficiently as possible.

The solution then is to increase the flow capability of the wastegate port, not decrease the flow capability of the turbo.

That is all.
 

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I'd like to see one of them hold 14psi of boost to redline in fourth(or even 16)........
Explain to me exactly why someone would want to run their car to redline under partial throttle. Do you really do that?? Most people that I know who hit redline do it under full throttle. Do you have some kind of weird slow map that you run to achieve low boost? Kinda defeats the purpose of a VF34, doesn't it...

Time for a Buick? :rolleyes:
 

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There are multiple people on this board who have eliminated boost creep by porting the wastegate of a VF34. Adding a kitten is a bandaid for a larger problem.
I'd like to see one of them hold 14psi of boost to redline in fourth(or even 16)........

The issue here is pressure. If the wastegate port can't flow enough exhaust, the exhaust gasses find it easier to flow through the turbo than through the wastegate. Since more exhaust energy is spinning the turbine, boost keeps rising.[/quote

See, the issue here is pressure:). Not enough exhaust gasses going through the wastegate is actually the result of the turbine wheel being small, and having such little backpressure, not the other way around. The turbine on a vf34 is small, and it has pretty good efficiency, so with all the exhaust gasses goin, it wants to spin. Since the turbine is so small, the wastegate will have to work more for it to lower boost compared to a turbo like a vf22 because it takes more gasses to move that wheel on the vf22. With such little resistance on the backside of the trubo, the exhaust gasses just wanna go through the wheel. If there was a cat after the turbo, the wheel wouldn't want to spin as much, and the exhaust gasses would wanna go through the wastegate more.

The problem is not that the vf34 is made incorrectly, cause it works fine on sti's WITH CATS AFTER THE TURBO. The wastegate hole on a vf34 is as big as the divided pipe on a perrin or bosal downpipe, so if you have these, porting the wastegate probably won't help at all! The problem is with our setups. Porting the wastegate will help the problem not be so pronounced(if you only want to be able to hold your max boost and not anything below, that's cool), but it will not fix the problem. With a cat after the downpipe, you will have MUCH MORE control over boost. I could just be on drugs, so someone tell me if I'm wrong.

peace
 

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hippy78 said:
Not enough exhaust gasses going through the wastegate is actually the result of the turbine wheel being small, and having such little backpressure, not the other way around. The turbine on a vf34 is small, and it has pretty good efficiency, so with all the exhaust gasses goin, it wants to spin. Since the turbine is so small, the wastegate will have to work more for it to lower boost compared to a turbo like a vf22 because it takes more gasses to move that wheel on the vf22. With such little resistance on the backside of the trubo, the exhaust gasses just wanna go through the wheel. If there was a cat after the turbo, the wheel wouldn't want to spin as much, and the exhaust gasses would wanna go through the wastegate more.


Are you living in some alternate universe?

A- wastegate gasses pass through the cat just like the turbine gasses. Adding a cat adds backpressure to both.

B- a smaller turbine wheel in a smaller turbine housing has MORE backpressure than a bigger wheel in a bigger housing.

C- the entire point of a wastegate is to create a path of least resistance for the exhaust gases. When it's closed, all the gases must go through the turbine. When it opens the gases are diverted around the turbine. If the wastegate cannot flow enough to divert enough gas away from the turbine, you get boost creep.

The problem is not that the vf34 is made incorrectly, cause it works fine on sti's WITH CATS AFTER THE TURBO. The wastegate hole on a vf34 is as big as the divided pipe on a perrin or bosal downpipe, so if you have these, porting the wastegate probably won't help at all! The problem is with our setups. Porting the wastegate will help the problem not be so pronounced(if you only want to be able to hold your max boost and not anything below, that's cool), but it will not fix the problem. With a cat after the downpipe, you will have MUCH MORE control over boost. I could just be on drugs, so someone tell me if I'm wrong.
Well I certainly hope it's not the turbo design. I'll agree with you on that one. And that being said, adding a cat will probably eliminate the boost creep.

But once again, you're not fixing the problem. Pace put the situation in perspective like this:

dammit... my car keeps pulling to the left at high speeds... i figure I'll fit an airbrake to the passenger front fender to keep it tracking straight
So, like I said...You're on drugs.
 

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I was editing that last post when you replied:). I said 14psi of boost, I said nothing about partial throttle. When tuning a car, people like to hold the boost at 10psi then 12psi then 14psi then 16psi then 18psi or whatever, to be able to get the a/f ratios right in different load situations:). Some peole only run their max boost when at the track, or whatever.

I have my car setup, so that you can hold it at 18psi by pushing the throttle all the way, and have it ramp down to 12psi at 60%(where it crosses over). Some people like to be able to choose how much boost they hold til redline(like me). If you can't lower your boost below your max boost, then are you really controlling the boost? Also, having a high flow cat after the turbo, or running lower then 18psi of boost does NOT defeat the purpose of having a vf34:)....

When have you ever heard anyone recommend ADDING backpressure to a turbocharged engine??
now.....

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I'm going to stop now, as I feel that I've already made my case.
 

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If you're having boost creep issues and need to fix them, adding restriction to the exhaust flow isn't going to make you any happier. You need to port the wastegate a little bit. That'll solve your problem.
Are you sure about this? Have you ever tried it? On another note, the links above have very little good info on the subject(imo). Just cause everyone ports their wastegates.....blah. I guess what I say doesn't matter cause I'm not knowledgeable? I said what I said because I have had a vf34 and tried many different ways to fight boost creep. I was trying to save people time, money, heartache, and possibly damage. After talking to many many other people with the same problem, people without the problem and the same turbo, and trying different ways to fix it, the above is the conclusion I've come to. I'm sorry if you don't agree. The stuff above is just my opinion, but maybe you guys should listen to someone who actually has some experience with the subject.

The vf34 was made to work with more restriction on the other side of the turbo(like on the sti). If it was ment to work the way people with boost creep use it, it would have come with either a huge wastegate, or none(for external). This is all just my opinion too:).

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hippy78 said:
On another note, the links above have very little good info on the subject(imo).
The first link practically walks you through the process of correcting the problem, step by step. :rolleyes:

It's your prerogative if you wish to remain ignorant on the subject, but perhaps you should refrain from spreading misinformation.

Perhaps we should listen to people with experience. Hundreds, if not thousands of turbo owners have encountered boost creep and addressed it by wastegate porting or going external.

-Pace
 
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