If i keep my Sti exhaust all stock i wont get boost creep??? if so let me know and i want more horse power so i might put in a down pipe soon and a cold air will i get boost creep please get back to me or should i do my waste gate thanks mike
email me @msjp64@aol.com

 

Hello everyone,

I have been very busy the last month. Just had a birthday on Cinco de Mayo as well.

silverfox - since the dealer is in tampa, cold temps are related to boost creep so he probably doesn't get adverse effects. I'd guess he'll notice minor boost creeping during the coldest months down there, but it probably won't be severe enough to get fuel cut. I don't know how cold it gets in Tampa.

whoosh - Just to correct you, the wastegate is in the exhaust side of the turbo..., but I know what you meant. Well this has been done by a variety of people. From a porting of the whole exhaust side there are some minor performance gains, (~100-150rpm better spool, minor hp gains 5-10) there is still the possibility of increasing your chances of getting creep. Think of it like this.. air follows the path of least resistance. So if you make the exhaust side smoother, the air will have a tendency to go through the turbine when the wastegate is open.
There have been some with boost creep with a ported wastegate and turbo, so vendors have responded to this by making a larger flapper so they can open up the wastegate even more. One thing to watch out for is that they do not over port the wastegate to a point where the wastegate actuator maps in the ECU are useless. Then you may get things like lowered boost. They have just started to do this so I'd wait and see what others say and see if they're not having any drivability problems.

Personally, just a simple wastegate port is what I'd recommend. It's easier, works, and you'll be able to put ANY turboback on your STi.

msjp - a wastegate port will not increase performance on the STi with a stock turobback. You're in CT so you will more than likely get creep with a GOOD aftermarket turboback especially during the winter months. With a wastegate port you will not have to worry about boost creep which results in fuel cut for many people living in cooler seasonal climates. This way you can mod away w/o fear. You can go catless, throw on the biggest, most effective turboback and enjoy your 25-30whp gains. I'm e-mailing you.

Enjoy

 

Hi to everybody.

I'm French and have a 2004 STI, 2 liter engine here with an IHI VF35

I just installed an Invidia 3 inches and was more than aware of boost creep problems so I got my turbo designed for this (bigger wastegate hole). The problem is now that I don't get enough pressure even with an AVCR boost controller.

In fact the exhaust gaz are now pushing more on the flapper and the wastegate open it too early, causing leaks. Then we need to get the actuator a bit harder. The problem is that on the VF35 we can't adjust the wastegate ! Any solution on this apart from cutting the actuator arm and make it a bit smaller ?

Thanks for the answer,

Franck

 

Franck - People who generally get problems not getting enough boost usually have had their wastegates overported from what I've seen. If you enlarge the hole too much right out to the edge of the flapper, you will not get a tight seal and will always bleed boost off aven if the wastegate is closed. There is a slight bit of play with the flapper as well so you have to account for that. The ECU can compensate for the enlarged diameter hole (to a certain extent) and adjust the wastegate actuator accordingly as long as there is not an overport job.

If this is the case with you, I would try to find a larger diameter flapper and place it on there instead of the old one.

Oh, and I am too not familiar with the Euro STi's but I thought boost creep was not a problem for you guys with the vf35 with the addition of a turboback?

Suboobaru - What I go by generally is to take out 60-70% of the material out to the edge of the wastegate flapper seal. I also port the area beneath the hole at an angle to smooth out the airflow. Hope this helps.

 

Thank you blueballs

In fact I didn't enlarge too much the hole but i also get rid of the 90° bend at the entry so exhaust gaz can go to the flapper more easily. Perhaps this explain why.

But tonight I made an adjustable actuator arm and got back my pressure by reducing its length by around 5 millimeters.

Euro STI's have also a lot of problem of boost creep. With my Invidia it was around 1.4 bars @ 5600 rpm ! Now, with the modified turbo I got back to a more reasonable 1 bar @ 6500 rpm.

Here are two pics : before and after

 

And here is the bend that has been modfied also :

 

Good advice, Wingless!


Franck - Guess you didn't need my help after all. Your port looks good... just slightly slightly slightly larger than what I would do. You did grind beneath the hole at an angle which is just as important. I see you also ground the opening coming from the uppipe. Guess you have a larger diameter aftermarket downpipe, correct?

Adjustable wastegate actuator arms are a good way to adjust the positioning of the wastegate. Alot of the DSM guys do this when adjusting their boost / fix wastegate issues.

Did you weld bolt/screw type adjuster onto the arm?

 

Dang that is very cheap for installation. To bad i live in Colorado or I will go to you guys for all of the install. Hehe

 

This is a dead issue now that we have engine management....


No hacking my turbo up...

 

Currrently, I have a BOV, CAI, and HKS downpipe. The last two have not been installed yet. In relation to this thread, how would installing these affect the performance of my '04 STi? The car is stock, and I plan to keep the stock exhaust on. Would I still need to get the WG ported? Also, I was considering getting the Helix uppipe/downpipe combo, instead of the HKS, same question(s). For now, I just want to add some bolt ons without having to do too much like reprogram ECU/reflash, or do porting work. These questions might sound redundant or stupid, but I'm still new to this. Please advise. Thanks