Boost Creep... What is it?

OrangeDot3083 · 05-11-2005, 02:14 AM

Ok I am really new to the turbo side of the house. I have no clue really what I am doing yet. Now I have done a search on boost creep and did not really turn too much up. Ok so I was not looking that hard... but could some one explain just what it is and what are the possible causes and cures for this problem. I have a completely stock STi. As soon as I get back from BFE I plan to take care of that problem with a intake and down pipe modification.

Huy · 05-11-2005, 02:25 AM

http://forums.nasioc.com/forums/showthread.php?t=477715

I found a link in one second with the search function!

**TRM** · 05-11-2005, 03:08 AM

Quote:

Originally Posted by Huy

http://forums.nasioc.com/forums/showthread.php?t=477715

I found a link in one second with the search function!

amazing isn't it?

OrangeDot3083 · 05-11-2005, 04:43 AM

Yeah... still deployed wont let me on that site its blocked.

05SilverSTI · 05-11-2005, 05:16 AM

from the link above:

With the countless threads about boost creep problems with turbobacks on the 2.5l STI, I think this thread should be helpful as a quick summary to those planning on moddifying their STI.

Q) What is boost creep?
A) Boost creep occurs when the wastegate is physically unable to bypass enough exhaust around the turbine on the turbo.

Q) Is boost creep harmful?
A) Yes, boost creep is one of the worst problems you can have with a turbo engine. Boost creep means that there is NO way for the boost pressure to be controlled. Boost pressures in excess of 20psi!!! have been recorded on STIs with TBE before the ECU cuts fuel.

Q) What causes boost creep?
A) Installing a turbo back exhaust whether aftermarket catted or not will in almost all cases cause boost creep to a certain extent.

Q) Are there any other options to prevent boost creep besides porting the wastegate?
A) Yes, Installation of an exhaust that either keeps the stock OEM muffler or one of the stock cats should not cause boost creep.

Q) How do I know if I have boost creep?
A) If you have a full TBE, then you probably have it. A boost gauge will tell you what pressure you are at as well. Fuel cut occurs when the ECU senses boost in excess of 17.5psi for 2-3s. Fuel cut in my experience is a very violent "stutter" from the engine that resembles extreme knock, followed by CEL.

Q) What is the overboost CEL?
A) (P0244) Wastegate malfunction

Q) Is there anything else I can do besides porting the wastegate to prevent the creeping....MBC, EBC, engine management etc?
A) This problem is isolated to the wastegate only. The wastegate is a mechanical system. There are no current workarounds or "fixes" besides this. The 2.5l just flows too much exhaust through the turbo once a turbo back has been added for the wastegate to control boost. If you think of it as a hierarchy, then it should make sense.

level 1) wastegate controls boost pressure
level 2) boost solenoid controls wastegate
level 3) MBC/EBC/ECU controls boost solenoid

Using this logic, if the problem resides on the 1st level, no matter what you do on top of it, you will still have the problem. Whatever (MBC, EBC, UTEC, ECUTEK) is controlling the wastegate CANNOT prevent boost creep if the WASTEGATE is UNABLE TO FLOW ENOUGH EXHAUST to prevent boost creep. A fuel cut defender will not eliminate the boost creep problem, but it will stop the fuel cut. Your boost will still creep up to 20psi, but the ECU won't be able to tell due to the altered signal from the FCD.

Q) My car seems to boost creep when it is cold out. Why is that?
A) Ambient temperature plays a huge role in how well your engine runs. In general, the cooler ambient temperature, the better your engine runs due to the laws of thermodynamics. The colder air causes your engine to make more HP (more work under the curve with lower temps), therefore more energetic exhaust gases, therefore your car is more prone to boost creep when it is cold out. If you live in an area that does not see colder temperatures (AZ for example) too often, then boost creep may never become a problem.

Q) I want to port my wastegate. What do I do?
A) Can you remove and install a turbo? If yes, there are a couple of options. You can send it to Deadbolt (www.deadboltspeed.com) for porting, have a local machine shop port it, or do it yourself with a "Dremmel like" tool.

OrangeDot3083 · 05-11-2005, 10:48 AM

thank you for posting that, it really helped.

05SilverSTI · 05-11-2005, 01:38 PM

no problem

Assami · 01-29-2007, 11:58 AM

Q) Are there any other options to prevent boost creep besides porting the wastegate?

what do you do on this !!!!

lackskill · 01-29-2007, 12:32 PM

Quote:

Originally Posted by Assami

Q) Are there any other options to prevent boost creep besides porting the wastegate?

what do you do on this !!!!

External WG.

azndc5er · 01-29-2007, 12:36 PM

Q) Are there any other options to prevent boost creep besides porting the wastegate?
A) Yes, Installation of an exhaust that either keeps the stock OEM muffler or one of the stock cats should not cause boost creep.

I had no idea. Maybe I'll just do a stealthback in the future...

iamadam1122 · 01-31-2007, 04:25 PM

so with a TBE, a tune with say, a utec wont cure the boost creep?

lackskill · 02-01-2007, 05:55 AM

Quote:

Originally Posted by iamadam1122

so with a TBE, a tune with say, a utec wont cure the boost creep?

Boost creep is NOT, i repeat NOT, tunable.

Boost Spike vs. Boost Creep the real deal

Boost spike is a tuning issue, boost creep is a mechanical issue.

STI23 · 02-01-2007, 07:30 AM

Why would anyone mess with TBEs if boost creep is that common and dangerous to your car?

lackskill · 02-01-2007, 07:50 AM

Quote:

Originally Posted by STI23

Why would anyone mess with TBEs if boost creep is that common and dangerous to your car?

FWIW I have a non catted DP and no EM and have no boost creep or boost spike issues. Some people have issues, some people don't. I dont think boost creep is really all that common. Boost spike is pretty common but is often called boost creep. There has been a great deal of misrepresenting boost creep. I dont know of any cases (though I am sure they do exist) of boost creep where someones motor let go. If anyone has better info please correct me.

WXRTSI · 02-01-2007, 08:18 AM

Also, keep in mind that boost creep is only a true concern (mostly true in this case) when the tempuature outside is very cold during the winter time. When you go for a spirited drive in 5th gear on the highway in 30 degree weather, just keep an eye on the boost gauge. I have a dp but the factory catback and muffler, so it has been no concern of mine so far.

05-11-2005, 02:14 AM	#1
OrangeDot3083 Professional STI Racer Car: 04 Subaru WRX STi Fav Mod: Track days!!!!! Location: Vacaville Ca/Columbus Oh Posts: 846 Join Date: May 2005 Trader Rating: (2)	Boost Creep... What is it? Ok I am really new to the turbo side of the house. I have no clue really what I am doing yet. Now I have done a search on boost creep and did not really turn too much up. Ok so I was not looking that hard... but could some one explain just what it is and what are the possible causes and cures for this problem. I have a completely stock STi. As soon as I get back from BFE I plan to take care of that problem with a intake and down pipe modification. This ad is not endorsed by this member. Please register or login to hide this ad.

02-01-2007, 08:18 AM	#15
WXRTSI Grassroots STI Racer Car: Blue, 06 STI Fav Mod: Accessport Location: NC Posts: 586 Join Date: Aug 2006 Trader Rating: (3)	Also, keep in mind that boost creep is only a true concern (mostly true in this case) when the tempuature outside is very cold during the winter time. When you go for a spirited drive in 5th gear on the highway in 30 degree weather, just keep an eye on the boost gauge. I have a dp but the factory catback and muffler, so it has been no concern of mine so far. This ad is not endorsed by this member. Please register or login to hide this ad.

05-11-2005, 02:25 AM	#2
Huy The Next Petter Solberg Car: 2005 CGM WRX STi Fav Mod: Mod? Why never.. Location: Perth, Australia Posts: 962 Join Date: Dec 2004 Trader Rating: (0)	http://forums.nasioc.com/forums/showthread.php?t=477715 I found a link in one second with the search function!

05-11-2005, 04:43 AM	#4
OrangeDot3083 Professional STI Racer Car: 04 Subaru WRX STi Fav Mod: Track days!!!!! Location: Vacaville Ca/Columbus Oh Posts: 846 Join Date: May 2005 Trader Rating: (2)	Yeah... still deployed wont let me on that site its blocked.

05-11-2005, 05:16 AM	#5
05SilverSTI Spec C Club Car: 05 silver/silver STI Location: S.I NY / Boulder CO Posts: 1,537 Join Date: Sep 2004 Trader Rating: (0)	from the link above: With the countless threads about boost creep problems with turbobacks on the 2.5l STI, I think this thread should be helpful as a quick summary to those planning on moddifying their STI. Q) What is boost creep? A) Boost creep occurs when the wastegate is physically unable to bypass enough exhaust around the turbine on the turbo. Q) Is boost creep harmful? A) Yes, boost creep is one of the worst problems you can have with a turbo engine. Boost creep means that there is NO way for the boost pressure to be controlled. Boost pressures in excess of 20psi!!! have been recorded on STIs with TBE before the ECU cuts fuel. Q) What causes boost creep? A) Installing a turbo back exhaust whether aftermarket catted or not will in almost all cases cause boost creep to a certain extent. Q) Are there any other options to prevent boost creep besides porting the wastegate? A) Yes, Installation of an exhaust that either keeps the stock OEM muffler or one of the stock cats should not cause boost creep. Q) How do I know if I have boost creep? A) If you have a full TBE, then you probably have it. A boost gauge will tell you what pressure you are at as well. Fuel cut occurs when the ECU senses boost in excess of 17.5psi for 2-3s. Fuel cut in my experience is a very violent "stutter" from the engine that resembles extreme knock, followed by CEL. Q) What is the overboost CEL? A) (P0244) Wastegate malfunction Q) Is there anything else I can do besides porting the wastegate to prevent the creeping....MBC, EBC, engine management etc? A) This problem is isolated to the wastegate only. The wastegate is a mechanical system. There are no current workarounds or "fixes" besides this. The 2.5l just flows too much exhaust through the turbo once a turbo back has been added for the wastegate to control boost. If you think of it as a hierarchy, then it should make sense. level 1) wastegate controls boost pressure level 2) boost solenoid controls wastegate level 3) MBC/EBC/ECU controls boost solenoid Using this logic, if the problem resides on the 1st level, no matter what you do on top of it, you will still have the problem. Whatever (MBC, EBC, UTEC, ECUTEK) is controlling the wastegate CANNOT prevent boost creep if the WASTEGATE is UNABLE TO FLOW ENOUGH EXHAUST to prevent boost creep. A fuel cut defender will not eliminate the boost creep problem, but it will stop the fuel cut. Your boost will still creep up to 20psi, but the ECU won't be able to tell due to the altered signal from the FCD. Q) My car seems to boost creep when it is cold out. Why is that? A) Ambient temperature plays a huge role in how well your engine runs. In general, the cooler ambient temperature, the better your engine runs due to the laws of thermodynamics. The colder air causes your engine to make more HP (more work under the curve with lower temps), therefore more energetic exhaust gases, therefore your car is more prone to boost creep when it is cold out. If you live in an area that does not see colder temperatures (AZ for example) too often, then boost creep may never become a problem. Q) I want to port my wastegate. What do I do? A) Can you remove and install a turbo? If yes, there are a couple of options. You can send it to Deadbolt (www.deadboltspeed.com) for porting, have a local machine shop port it, or do it yourself with a "Dremmel like" tool.

05-11-2005, 10:48 AM	#6
OrangeDot3083 Professional STI Racer Car: 04 Subaru WRX STi Fav Mod: Track days!!!!! Location: Vacaville Ca/Columbus Oh Posts: 846 Join Date: May 2005 Trader Rating: (2)	thank you for posting that, it really helped.

05-11-2005, 01:38 PM	#7
05SilverSTI Spec C Club Car: 05 silver/silver STI Location: S.I NY / Boulder CO Posts: 1,537 Join Date: Sep 2004 Trader Rating: (0)	no problem

01-29-2007, 11:58 AM	#8
Assami Junior STI Driver Car: 05 STI 2.0L 6speed JDM Location: Saudi Arabia Posts: 94 Join Date: Oct 2006 Trader Rating: (0)	Q) Are there any other options to prevent boost creep besides porting the wastegate? what do you do on this !!!!

01-29-2007, 12:36 PM	#10
azndc5er Junior STI Driver Car: 04 STi Location: Buffalo, NY Posts: 169 Join Date: Apr 2006 Trader Rating: (0)	Q) Are there any other options to prevent boost creep besides porting the wastegate? A) Yes, Installation of an exhaust that either keeps the stock OEM muffler or one of the stock cats should not cause boost creep. I had no idea. Maybe I'll just do a stealthback in the future...

01-31-2007, 04:25 PM	#11
iamadam1122 Junior STI Driver Car: 06 WRB STi Fav Mod: Cusco Zero2R Location: Florida Posts: 170 Join Date: Jun 2006 Trader Rating: (1)	so with a TBE, a tune with say, a utec wont cure the boost creep?

02-01-2007, 07:30 AM	#13
STI23 STI Driver Car: 07 SWP STI Fav Mod: Strength Shoes Location: Los Angeles, Oklahoma Posts: 255 Join Date: Jan 2007 Trader Rating: (2)	Why would anyone mess with TBEs if boost creep is that common and dangerous to your car?