3" to 2.5" exhaust help creep ?

[Dsmj89]

I couldn't find a direct anwer to my question so i'll ask here.
I've done quite a bit of reading on boost creep and didn't think of this until now.
I plan on getting a 16g, i currently have the stock o2 housing, 3" pr downpipe, and a 2.5" greddy cat-back that came with the car.
I plan on getting a 2.5" externally dumped o2 housing and re-do my exhaust, but i was wondering if maybe doing a full 2.5" from the downpipe back help the car from not boost creeping when i get the 16g ?
I don't plan on making more than 400hp so i doubt the 2.5" would be a restriction for my hp goals.
Thanks for any input.

 

[xxsupralvrxx]

to be truthful turbo cars hate back pressure so a 3" will help spool and more peak power...

 

[andy4g63]

^^^ That is true, BUT, Larger DP, than the rest of the exhaust system is allways a good thing. Exhaust gases, that come out of the turbo are extremely hot, so the volume is bigger at the DP, than the rest of the exhaust system. Plus in this configuration-3"-2.5" should keep the velosity UP. Theoretically you should be perfect. If you get a 3" DP now, there will be no need for upgrade later, in case something doesn't work.

 

[xxsupralvrxx]

yea but i have a 2.5 dp goin down to stock exhaust an its REALLY resritced u never wanna choke a turbo car but hey you can try it an always go bigger later

 

[pboglio]

The Greddy 60mm catback exhausts are restrictive. Switch to a 3" catback and you are going to notice the midrange and topend difference. Boost creep is different on everybody's setup. People make this big deal about it, its really no big deal unless you don't have enough injector and you lean out. My car with the boost turned down will hit 15 psi then slowly work its way up to 20 psi. There is no rule book that says a rising boost curve is bad, within reason. This is a hell of alot easier on parts then spiking to 30 psi in the midrange and dropping of at redline for instance. If your setup for it, boost creep is nothing to worry about and makes for a nice linear power curve.

 

[dylnwit]

People make this big deal about it, its really no big deal unless you don't have enough injector and you lean out. My car with the boost turned down will hit 15 psi then slowly work its way up to 20 psi. There is no rule book that says a rising boost curve is bad, within reason. This is a hell of alot easier on parts then spiking to 30 psi in the midrange and dropping of at redline for instance. If your setup for it, boost creep is nothing to worry about and makes for a nice linear power curve.

+1 on this, Tuning this way can also help grip issues, because the boost eases in instead of being suddenly there around 3000rpm. It also helps people (like me) who like to romp it from time to time on the street stay out of the higher boost going off of lights and such

 

[Dsmj89]

Thanks guys. Keep in thought my goal is mid to high 300 only.
I plan on running a walbro 255, 650cc's, and an safc2 to tune along with the turbo. Just thought maybe i wouldn't need a 3" for my hp goal, but like you said, the problem differs from car to car, and on a prepped car with supporting mods, shouldn't be a problem.
I guess i'll just run the rest from the downpipe back 3" and stay off high boost till i get the supporting mods.
Thanks again guys. If anyone else feels like chipping in their opinion on my idea feel free, i will be more than happy to hear it.

 

[rock1t]

Just another food for thought (or what I thought). On turbo cars, your turbo is your back pressure and everything after that doesn't matter(correct)? I understand the bigger pipe the more air can flow from the exhaust housing, but putting on an exhaust just catches the harmful gasses that are not supposed to be released into the air (thus emissions laws and greenhouse gasses).

Correct me if I am not correct.

 

[DSMunknown]

Justin (jusmx141) repeatedly hails the use of 2.5 inch piping instead of 3 inches on E316Gs and smaller. Or at the very least, a full 2.5 inch DP and a 3 inch catback. Not sure if I necessarily agree with him, but that's another matter.

 

[Dsmj89]

Justin (jusmx141) repeatedly hails the use of 2.5 inch piping instead of 3 inches on E316Gs and smaller. Or at the very least, a full 2.5 inch DP and a 3 inch catback. Not sure if I necessarily agree with him, but that's another matter.

That's the 16g guru. Was hoping to read that sometime. Thanks man.