Catless downpipe, ported turbo wastegate, enginement managment, boost creep question
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Catless downpipe, ported turbo wastegate, enginement managment, boost creep question
Hey guys, sorry for the long title, thought it would make those searching for these subject easiers. I know I've been searching for hours on this subject so I thought I'd give some information and ask mine in the same thread. And this is part local question too. (My question is at the bottom for those who wanna just skip down there) Oh, and a search tip, always filter by most number of replies and usually search titles only first, then the body.
So I'm looking into getting an exhaust system because many people will agree that the exhaust will give you great gains for the money. A downpipe and uppipe would give you very good gains (not so much uppipe for the STi because they come stock without a cat in them). I also read that a catback won't give you as much of a gain if you mate them to stock downpipe/uppipe so basically a downpipe for a STi will give you good performance. So I find a nice used catless downpipe. New ones for catless range from 200-250 and catted for 300+, and uppipe is around 200 (gruppe-s). I'm about to buy it, but I want to research on the installation process and find a trail of problems.
A few issues I came up with are boost creep, fuel cut off, and CEL pertaining the fuel cutoff on 4th-5th gear WOT. Most of these are related to one thing, the wastegate.
The installation of a catless downpipe causes more air to run through the turbo because the vaccum is bigger. As many of you know, boost creep is when there is too much air/exhaust gas going into the turbo and the wastegate not being able to handle all the air so it can't bypass it and cause the turbo to overboost (?). This happens especially in the 2.5L engines because more air goes in the turbo. To solve the problem, many suggested getting engine management like the Cobb AP, and at first I was thinking I wanted a cheap mod to get good gains, and an AP would cost like 600 dollars. I was disappointed to find out that a simple mod like the downpipe would cause so many problems since exhaust parts are everyone's first mods. But I find out that the engine management will only fix part of the problem, not the true cause. Because of the fuel cut, the car will throw a CEL which is unpleasant. The car will run at higher than stock psi boost up to 20 psi for some people.
To fix the problem, all you need is a ported wastegate. A ported wastegate is basically opening up/smoothing the hole that the gas goes through, but you have to port it at a certain spot, shown here..
http://forums.nasioc.com/forums/show...ht=boost+creep
Many have reported no more boost creep after porting the turbo's wastegate hole which hopefully only cost 50-100 dollars.
So my question is, who in the bay area offer such service? and how much? Thanks for your time.
PS. You can send your turbo to deadbolt to get this done but I thought doing it locally would be much better.
Also a 3 inch downpipe will fit into a stock STi 2.5' catback but you have to use 2 gaskets but might still get leaks. (Just some stuff I came across while searching)
Also, feel free to correct any misleading or wrong information as I'm only putting it together through my searches and add anything you like!
So I'm looking into getting an exhaust system because many people will agree that the exhaust will give you great gains for the money. A downpipe and uppipe would give you very good gains (not so much uppipe for the STi because they come stock without a cat in them). I also read that a catback won't give you as much of a gain if you mate them to stock downpipe/uppipe so basically a downpipe for a STi will give you good performance. So I find a nice used catless downpipe. New ones for catless range from 200-250 and catted for 300+, and uppipe is around 200 (gruppe-s). I'm about to buy it, but I want to research on the installation process and find a trail of problems.
A few issues I came up with are boost creep, fuel cut off, and CEL pertaining the fuel cutoff on 4th-5th gear WOT. Most of these are related to one thing, the wastegate.
The installation of a catless downpipe causes more air to run through the turbo because the vaccum is bigger. As many of you know, boost creep is when there is too much air/exhaust gas going into the turbo and the wastegate not being able to handle all the air so it can't bypass it and cause the turbo to overboost (?). This happens especially in the 2.5L engines because more air goes in the turbo. To solve the problem, many suggested getting engine management like the Cobb AP, and at first I was thinking I wanted a cheap mod to get good gains, and an AP would cost like 600 dollars. I was disappointed to find out that a simple mod like the downpipe would cause so many problems since exhaust parts are everyone's first mods. But I find out that the engine management will only fix part of the problem, not the true cause. Because of the fuel cut, the car will throw a CEL which is unpleasant. The car will run at higher than stock psi boost up to 20 psi for some people.
To fix the problem, all you need is a ported wastegate. A ported wastegate is basically opening up/smoothing the hole that the gas goes through, but you have to port it at a certain spot, shown here..
http://forums.nasioc.com/forums/show...ht=boost+creep
Many have reported no more boost creep after porting the turbo's wastegate hole which hopefully only cost 50-100 dollars.
So my question is, who in the bay area offer such service? and how much? Thanks for your time.
PS. You can send your turbo to deadbolt to get this done but I thought doing it locally would be much better.
Also a 3 inch downpipe will fit into a stock STi 2.5' catback but you have to use 2 gaskets but might still get leaks. (Just some stuff I came across while searching)
Also, feel free to correct any misleading or wrong information as I'm only putting it together through my searches and add anything you like!
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Joined: Aug 2006
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From: North Bay Area
Car Info: 2004 STi
Not really sure if you can send the turbo to deadbolt, i dont really see why not, but if your looking for someplace local to you to do it, try calling Garaged Performance in Napa, friend of mine owns the shop, he should take good care of you. His name is Brian 707-255-7419 and he can give you several options to get rid of boost creep, one being porting your turbo for you
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Crucial Racing also does porting and they are local.
As far as your actual questions... True boost creep cannot be resolved with tuning, but that being said, very few cars out there experience true boost creep. Most of the reports of boost creep come from people running the stock ECU. This occures because the ECU is not programmed correctly for the higher flowing downpipe. With such a downpipe, wastegate duty cycles must be reduced significantly from the stock levels to keep boost levels in the apropriate range. The stock ECU tries to run stock WGDC's and ends up overboosting and hitting fuel cut. About 90% of cars experiencing this can easily be fixed with a tune. The last 10% are the ones that experience true, mechanical boost creep. This occures when there is no WGDC low enough to keep boost from climbing. This means that the wastegate cannot physically flow enough to keep the turbo from overspinning. The only real solution in this case is to have the wastegate ported. Some people have found that a catted downpipe reduces this as well because the cat adds a bit of backpressure after the turbo, giving it less tendancy to spool.
Thanks
As far as your actual questions... True boost creep cannot be resolved with tuning, but that being said, very few cars out there experience true boost creep. Most of the reports of boost creep come from people running the stock ECU. This occures because the ECU is not programmed correctly for the higher flowing downpipe. With such a downpipe, wastegate duty cycles must be reduced significantly from the stock levels to keep boost levels in the apropriate range. The stock ECU tries to run stock WGDC's and ends up overboosting and hitting fuel cut. About 90% of cars experiencing this can easily be fixed with a tune. The last 10% are the ones that experience true, mechanical boost creep. This occures when there is no WGDC low enough to keep boost from climbing. This means that the wastegate cannot physically flow enough to keep the turbo from overspinning. The only real solution in this case is to have the wastegate ported. Some people have found that a catted downpipe reduces this as well because the cat adds a bit of backpressure after the turbo, giving it less tendancy to spool.
Thanks
Thread Starter
Registered User
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From: Davis and San Francisco
Car Info: 2005 STi Silver
Hey thanks Ed and Projek for the reponse. I guess even with searching I still got it wrong. The thing with this downpipe issue for me is basically I THOUGHT a downpipe, being so cheap used, will be a great first mod, but if I have to get a tune which cost so much more than a downpipe, like 6 times more, I'll have to resolve to modding when I'm a bit older.
A few questions, if the stock ECU can't do it's job, what's the minimal engine management needed to fix it?
Still trying to learn but is a reflashed off the shelf ECU is just buying a map that is already programmed for the same type of mods I'd put in it?
Custom Tuned ECU is the same, using the stock ECU and changing the settings but the tuner runs tests and play with the settings to get it right..?
And piggy-back and standalone are more advance where one uses some of the stock ECU while the latter doesn't at all.
And wow, Cobb AP is 600 dollars? a map/tune is 200 per?
A few questions, if the stock ECU can't do it's job, what's the minimal engine management needed to fix it?
Still trying to learn but is a reflashed off the shelf ECU is just buying a map that is already programmed for the same type of mods I'd put in it?
Custom Tuned ECU is the same, using the stock ECU and changing the settings but the tuner runs tests and play with the settings to get it right..?
And piggy-back and standalone are more advance where one uses some of the stock ECU while the latter doesn't at all.
And wow, Cobb AP is 600 dollars? a map/tune is 200 per?
get an MBC.
Well, some people are running open source ECU reflashing (whch, as the name implies, is free) , don't know how well that's going. How about you call up Ed to ask all the questions? He'll set you straight.
Well, some people are running open source ECU reflashing (whch, as the name implies, is free) , don't know how well that's going. How about you call up Ed to ask all the questions? He'll set you straight.
Thread Starter
Registered User
iTrader: (7)
Joined: Sep 2003
Posts: 2,295
From: Davis and San Francisco
Car Info: 2005 STi Silver
Thanks Verc, I'm just really disappointed that such a cheap mod would end up costing so much, but an open source ECU sounds very good, i'll research more on that.
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