Overboost Problem
Thread Starter
VIP Member
Joined: Nov 2004
Posts: 270
From: Japan, where the term "JDM" doesn't exist
Car Info: '94 WRX, '97 Forester S/Tb, '95 WRX-RA
Overboost Problem
A couple weeks ago, I helped my friend install an Apex'i intake. On the test run, the car would overboost from .08mpa (stock) spiking all the way to 1.4mpa in some instances. We rechecked the installation procedures in the manual, and we did everything right. We even reset the ECU, but that didn't help. Before the Apexi intake, he had only a cone filter installed. The Apexi intake replaces the filter and the plastic intake tube (after the MAF sensor) with an aluminum tube. Prior to this incident, his car ran fine. His only other significant mods are a turbo-back exhaust. A few days ago, he had a boost controller installed, but even with it turned to the lowest setting, the car still overboosts. It happens at around 6k RPM with the throttle floored, the boost hits 1.3 - 1.4, the car sputters and backfires and then the fuel cuts off the same way a speed limiter does. This is a real mystery. Why would a slightly "better" intake cause this? I have heard of intakes causing lean conditions, but never overboost conditions.
VIP Member
Joined: Apr 2003
Posts: 846
From: Orange County, CA
Car Info: 08 WRX - 401whp/408wtq
Originally Posted by Toiletbrush
A couple weeks ago, I helped my friend install an Apex'i intake. On the test run, the car would overboost from .08mpa (stock) spiking all the way to 1.4mpa in some instances. We rechecked the installation procedures in the manual, and we did everything right. We even reset the ECU, but that didn't help. Before the Apexi intake, he had only a cone filter installed. The Apexi intake replaces the filter and the plastic intake tube (after the MAF sensor) with an aluminum tube. Prior to this incident, his car ran fine. His only other significant mods are a turbo-back exhaust. A few days ago, he had a boost controller installed, but even with it turned to the lowest setting, the car still overboosts. It happens at around 6k RPM with the throttle floored, the boost hits 1.3 - 1.4, the car sputters and backfires and then the fuel cuts off the same way a speed limiter does. This is a real mystery. Why would a slightly "better" intake cause this? I have heard of intakes causing lean conditions, but never overboost conditions.
Thread Starter
VIP Member
Joined: Nov 2004
Posts: 270
From: Japan, where the term "JDM" doesn't exist
Car Info: '94 WRX, '97 Forester S/Tb, '95 WRX-RA
Please don't waste my time by posting some useless crap like that. Thanks.
I have an intake on my STi, and it runs fine. I have owned 3 WRX's to date, and they all ran great with aftermarket intakes. This is the first case like this that I have ever seen or heard of.
I have an intake on my STi, and it runs fine. I have owned 3 WRX's to date, and they all ran great with aftermarket intakes. This is the first case like this that I have ever seen or heard of.
Last edited by Toiletbrush; Jul 8, 2005 at 06:09 AM.
Registered User
Joined: Jul 2005
Posts: 40
Boost creep????
Sounds like a classic case of a boost creep to me.
Which downpipe is there? Bellmouth or divorsed? Stock turbo?
Stock turbo+3"TBE+CAI+BC=99%boost creep+EGT problem at WOT.
I am on my first suby but I went through a lot of research about turboing
CAI got to go....IMHO
Search try to search NASIOC for boost creep...
Good Luck
Which downpipe is there? Bellmouth or divorsed? Stock turbo?
Stock turbo+3"TBE+CAI+BC=99%boost creep+EGT problem at WOT.
I am on my first suby but I went through a lot of research about turboing
CAI got to go....IMHO
Search try to search NASIOC for boost creep...
Good Luck
Thread Starter
VIP Member
Joined: Nov 2004
Posts: 270
From: Japan, where the term "JDM" doesn't exist
Car Info: '94 WRX, '97 Forester S/Tb, '95 WRX-RA
Did the search, lot of good info! I guess I just needed a name to go with the problem.
Anyways, he (the friend) has a power FC on order and a very good tune shop that is going to set it all up for him. He got his HKS header in yesterday, and I know I will be getting a call in an hour or so asking for my assistance in installing it. Too bad I will have to tell him "NO!". It will just make the problem worse, no doubt. In the mean time, I will advise that the he swap the Apexi intake back to the Blitz one he had on before and drive nice until his FC comes in. This is still very very strange. As mentioned before, I have owned 3 WRXs, and all of them have had an HKS SPF intake with a HKS 3" TB Exhaust on the stock WRX TD05, and this has never happened to me. In fact, with my STi, (prior 2 were just WRXs) I was holding of on installing the SPF on this car (great thing with GC8's... almost all parts are transferrable), but when I did, it was like I freed up power that was just waiting to be used. It just went better with the bigger turbo and injectors I guess. Well, not all cars take modifications the same way. Will post more after his FC tune is finished.
Anyways, he (the friend) has a power FC on order and a very good tune shop that is going to set it all up for him. He got his HKS header in yesterday, and I know I will be getting a call in an hour or so asking for my assistance in installing it. Too bad I will have to tell him "NO!". It will just make the problem worse, no doubt. In the mean time, I will advise that the he swap the Apexi intake back to the Blitz one he had on before and drive nice until his FC comes in. This is still very very strange. As mentioned before, I have owned 3 WRXs, and all of them have had an HKS SPF intake with a HKS 3" TB Exhaust on the stock WRX TD05, and this has never happened to me. In fact, with my STi, (prior 2 were just WRXs) I was holding of on installing the SPF on this car (great thing with GC8's... almost all parts are transferrable), but when I did, it was like I freed up power that was just waiting to be used. It just went better with the bigger turbo and injectors I guess. Well, not all cars take modifications the same way. Will post more after his FC tune is finished.
VIP Member
Joined: Apr 2003
Posts: 846
From: Orange County, CA
Car Info: 08 WRX - 401whp/408wtq
Originally Posted by Toiletbrush
Did the search, lot of good info! I guess I just needed a name to go with the problem.
Anyways, he (the friend) has a power FC on order and a very good tune shop that is going to set it all up for him. He got his HKS header in yesterday, and I know I will be getting a call in an hour or so asking for my assistance in installing it. Too bad I will have to tell him "NO!". It will just make the problem worse, no doubt. In the mean time, I will advise that the he swap the Apexi intake back to the Blitz one he had on before and drive nice until his FC comes in. This is still very very strange. As mentioned before, I have owned 3 WRXs, and all of them have had an HKS SPF intake with a HKS 3" TB Exhaust on the stock WRX TD05, and this has never happened to me. In fact, with my STi, (prior 2 were just WRXs) I was holding of on installing the SPF on this car (great thing with GC8's... almost all parts are transferrable), but when I did, it was like I freed up power that was just waiting to be used. It just went better with the bigger turbo and injectors I guess. Well, not all cars take modifications the same way. Will post more after his FC tune is finished.
Anyways, he (the friend) has a power FC on order and a very good tune shop that is going to set it all up for him. He got his HKS header in yesterday, and I know I will be getting a call in an hour or so asking for my assistance in installing it. Too bad I will have to tell him "NO!". It will just make the problem worse, no doubt. In the mean time, I will advise that the he swap the Apexi intake back to the Blitz one he had on before and drive nice until his FC comes in. This is still very very strange. As mentioned before, I have owned 3 WRXs, and all of them have had an HKS SPF intake with a HKS 3" TB Exhaust on the stock WRX TD05, and this has never happened to me. In fact, with my STi, (prior 2 were just WRXs) I was holding of on installing the SPF on this car (great thing with GC8's... almost all parts are transferrable), but when I did, it was like I freed up power that was just waiting to be used. It just went better with the bigger turbo and injectors I guess. Well, not all cars take modifications the same way. Will post more after his FC tune is finished.
Registered User
Joined: Jul 2005
Posts: 6
Originally Posted by Toiletbrush
As mentioned before, I have owned 3 WRXs, and all of them have had an HKS SPF intake with a HKS 3" TB Exhaust on the stock WRX TD05, and this has never happened to me.
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