3" dp/exh boost creep?

[96atawd]

Hello again 'Tuners. I have some questions regarding 3" downpipe and catback on a 2g. I'll start off by saying I will most likely be running the stock t25 for a good while, untill I can afford and find a bigt28, in which my goal would be to hit around 300whp. I have read that a 3" dp and catback will cause boost creep which doesn't sound fun to me at all. Would a bigt28 with 3" dp/cat/catback experience boost creep? Would I "NEED" 3" exhaust to hopefully hit the 300whp mark, or would a 2.5" dp/2.5"catback be able to hit the 300whp mark? If not, would a 2.5" o2 housing+2.5" downpipe with 3" cat+3" catback allow me to hit the 300whp mark without boost creep? I kind of don't want a "huge" o2 housing and 3"dp/catback, and was just wondering if a 2.5" o2 housing, 2.5" downpipe, 3" highflow cat plus 3" catback would be good, without boost creep?

Thanks 'Tuners!

 

[FIBA M - EC17PSE]

At 300 whp a 2.5" is more then enough, but will you want more later? Thats the question!!! To save some money in the future get a 2.5" dp and a 3" cat or test pipe back, thats what I am doing when I rebuild mine and its cheaper to upgrade a dp then the whole system,

As to boost creep you will still get it on a big t28 unless its boost is turned up a bit more, why do you want a t28? Hopefully someone with more boost creep info will chime in

 

[96atawd]

So even with a 3" catback, the 2.5" dp will correct the boost creep? Meaning its just the downpipe size that creates creep, not the catback size?

 

[Joethefallen23]

If you plan on keeping your cat, you are MUCH less likely to have creeping problems on any moderately sized turbo. I had a 3in "muffler shop" exhaust on the car with a HF cat when I bought it. No issues. Bought an SRS exhaust with a Megan downpipe and even the t25 had a bit of creep. Forget about when I moved up to a small 16g. It was creeping like crazy. Porting the o2 and turbine housing took care of it.

*edit* Terrible day.

 

[FIBA M - EC17PSE]

So even with a 3" catback, the 2.5" dp will correct the boost creep? Meaning its just the downpipe size that creates creep, not the catback size?

yes that is correct. the 2.5" is push it out faster then the 3" will so there for not cause any issues. even if its just 2.5" down under the oil pan then 3" from there i think that is still safe to do,

 

[WhiteVoid]

If you plan on keeping your cat, you are MUCH less likely to have creeping problems on any moderately sized turbo. I had a 3in "muffler shop" exhaust on the car with a HF cat when I bought it. No issues. Bought an SRS exhaust with a Megan downpipe and even the t25 had a bit of creep. Forget about when I moved up to a small 16g. It was creeping like crazy. Porting the o2 and turbine housing took care of it.

The higher the boost you run the less possible it is to creep. If your turbo creeps to 18psi, run 18 psi(obviously if capable) and it shouldn't creep. At the point the wastegate is able to keep up.

Not to thread jack, but did you have any fitment issues with the SRS/Megan combination? I'm thinking of running that same set up and it would be nice to know.

 

[Mark4g63t]

JOE "The higher the boost you run the less possible it is to creep. If your turbo creeps to 18psi, run 18 psi(obviously if capable) and it shouldn't creep. At the point the wastegate is able to keep up."

This is incorrect information. If he were to turn the boost up to 18psi with creep, it would just go to 18psi then creep from there into the 20+ range. NOT GOOD! Do not do that!
It is basically a risk you take when going with a bigger exhaust. I had a 3" on my 16g and it crept while my buddy had a 3" on his t25 with no creep. You're either going to have to go with the 2.5" exhaust for back pressure or external wastegate/ excessive porting on the stock o2 housing. Boost creep is not fun. I fought it for many many many months.

SRS and Megan will go just fine together.

 

[eDeclpse92]

Boost creep is when there isn't enough exhaust bypassing the turbine therefore causing your boost to rise. Your focus should be more on your wastegaste. A 2.5' exhaust would be fine for 300hp by the way. And most of your backpressure in turbo cars come from the turbine itself.

I'm assuming your turbo has an internal wastegate with a small flapper and hole. If you don't want boost creep, then you will need to make that hole bigger and get an external wastegate. I learned this from expericane. I have a 14b and it boost creeped like crazy becasue I was trying to run 20 psi and the exhaust couldn't bypass the turbine quick enough. I have a 3" downpipe that leads through a resinator and thats it. I also have an electric cut out which is before the resinator and it still crept. I got a tial 38mm wastegate and vented it to atmosphere. My car holds 20 psi beatifully in all gears!

The wastegate is what you should be looking at for boost creep issues. If you get an external now, you'll be set for more power if you want it. All you have to do it change out a spring. Hope this helps!

edit: Your back pressure comes from the turbine itself. You don't have a N/A car so you don't need to worry about backpressure.

 

[Joethefallen23]

JOE "The higher the boost you run the less possible it is to creep. If your turbo creeps to 18psi, run 18 psi(obviously if capable) and it shouldn't creep. At the point the wastegate is able to keep up."

This is incorrect information. If he were to turn the boost up to 18psi with creep, it would just go to 18psi then creep from there into the 20+ range. NOT GOOD! Do not do that!
It is basically a risk you take when going with a bigger exhaust. I had a 3" on my 16g and it crept while my buddy had a 3" on his t25 with no creep. You're either going to have to go with the 2.5" exhaust for back pressure or external wastegate/ excessive porting on the stock o2 housing. Boost creep is not fun. I fought it for many many many months.

SRS and Megan will go just fine together.

Lol re-reading that, it was my mistake. Raising combats boost spikes not creep. I'm having that kind of day.

Megan DP and SRS mate up fine. Megan's 2 piece downpipe for the GSX necks back down to 2.5" at the catback flange. It also has a slip fit connection for the two pipes. It's prone to leaking. I welded in a straight pipe "cat" for inspection purchases and chopped off the 2.5" exit in favor of going for full 3". Not a bad setup. I paid $450 total to my door for the DP and SRS. Sounds great too!

 

[Alex Brunner]

From what I have been told, your O2 housing and wastegate are most important for creep.

 

[2gmitsueclipse]

When I had a FP Big t28, I ran a megan downpipe with a Buschur cat back exhaust. I cut the downpipe where it narrows for the flange. I cut a piece of pipe and used good quality slip clamps to mate the exhaust together. I also ported out the o2 housing with good success. I also had removed the BCS restrictor and rewired the fuel pump. When boosting, I would spike at 16, then settle to about 13-14. I did not experience boost creep anywhere near what I did when I ran an evo III 16g.

 

[96atawd]

So it seems the 2.5" o2/dp and 3" catback is the way to go? Would that make it "easier" to hit 300whp than 2.5" the whole way?

 

[FIBA M - EC17PSE]

So it seems the 2.5" o2/dp and 3" catback is the way to go? Would that make it "easier" to hit 300whp than 2.5" the whole way?

it will not have any difference in making the 300whp you want, not on our cars anyway and certainly not noticeable.

ive just bought my pipe today and i am going 2.5" to 3" straight through pipe with removable muffler! but i would not see a difference in power with a 3" so thats whay i am going this route and i have room to upgrade when my power does.

if your really not going to want more after 300hp then just go with the 2.5" all the way as you might beable to get a brand that goes stock route and goes over the rear axle where as the 3" is a very tight fit and tends to go under it.

up to you though you have our inputs so what ever you think is best for you and your future plans of the car

 

[96atawd]

I'd love to make 350 crank horsepower or at least 300 wheel hp as I am almost positive that going from a good amount less than 200whp to 300whp would make me plenty happy for a very long time. I was just wondering if it would be harder to hit 300Whp with 2.5" all the way or if it'd be easier with a 2.5"o2/dp + 3" catback.

 

[FIBA M - EC17PSE]

its not going to be hard or restrict you in any way even if you hit 400 or maybe 450 it still wont restrict you so a 2.5 is plenty enough

 

[Pipnorcali]

I run a t28 with full 3" not cat and don't have any boost creep issues but my wastegate is ported.

 

[andrew k]

the garrets are better about boost creep the then the mhi's. it has to do with the waist gate opening. the flapper on an mhi turbo doesn't move as far as a garret does. the actuator rod opens almost fully on a t25 where as it only opens about halfway on a 16g 14b etc. i have a 3in exhaust turbo back gutted cat. the 14b i run creeps to about 20 psi with my setup. it doesnt affect me tho personally because i have my boost controller set at 22 psi. the 14b is too small to maintain anymore boost regardless. at the high rpms it actually falls off... but it sure does have a mid range hit.. running it the way i am.

 

[Efalcon]

Question. I was going to get a dp. How soon after should I get a tune? I have the cat and everything after. The dp is stock.

Also I wanted clarification that the dp is just pipe doesn't matter what brand?

 

[99ECLIPSEGSXDSM]

T28s usually don't get boost creep. Like stated the hotsides better for preventing boost creep. You can run a dp without a tune at all but you won't be getting the full potential if the exhaust until you tune for it. That's why some people tell you to get link first so you can always max out the potential of your set up. A pipe is a pipe and your really just paying for the name when it comes to one

 

[JustinH]

Not to thread steal.. I have a 98 GSX automatic I've been told of two turbos It could have, I was going to run full 3" Megan racing turbo back with an o2 sensor extender. will that or how high of a chance is there that ill get boost leak?

 

[ryztriumph]

Not to thread steal.. I have a 98 GSX automatic I've been told of two turbos It could have, I was going to run full 3" Megan racing turbo back with an o2 sensor extender. will that or how high of a chance is there that ill get boost leak?

What are you actually trying to say here? I don't understand. Type your situation one sentence at a time.

 

[JustinH]

What are you actually trying to say here? I don't understand. Type your situation one sentence at a time.

I was wanting to know if full 3inch exhaust on an automatic will cause boost creep

 

[Bud92gsx]

I was wanting to know if full 3inch exhaust on an automatic will cause boost creep

Auto does not change the fact that your going from 2.25 to 3 inches..So yes bost creep would still be an issue with a non modified wg or ported turbine housing.

 

[JustinH]

But with auto's the wastegate doesn't open fully like it does manuals

 

[JusMX141]

But with auto's the wastegate doesn't open fully like it does manuals

Explain how 15psi on an automatic is different than 15psi on a manual in a way which would completely modify the way boost is controlled by the wastegate.