Should i go back to 3" turboback?

[Jeff822]

Ok, heres the deal, i used to have a 3" turbo back apexi gt downpipe to a HKS high power catback, i went to a 2.5 inch turboback on the t-25 to help with boost creep, but i just got a evo3 b16g and all the supporting mods. do you think it will be safe for me to go back to my 3" turboback on the E3 b16g? i have an evo o2 housing also im going to put on.

 

[prplhz96]

I would go 3" and let that turbo breathe better

 

[kenamond]

With a 3" exhaust, you may be setting yourself up for creep with the evo3. It is apparently notorious for creep when combined with a more free flowing exhaust. If it's still off, you may do a bunch of research on the forum and find out how to (and if it is in fact necessary to) properly port the wastegate entrance on the inside of the turbine housing, wastegate flapper hole, and etc.

I saw plenty of threads with 3" exhaust + evo3 = creep problems, and DSM wiseman "OLDMAN" **always** suggested porting as a solution. You can also go with an external wastegate, but it depends on your downpipe/O2 housing setup as to which is cheaper and/or easier.

There is a tech article that addresses this issue, but it's too late for me to search It's titled something like "How to cure boost creep by porting".

 

[Jeff822]

Well, i have a evo gt exhaust manifold on right now and evo o2 housing that i still need to put on, and i got the turbo ported with a 34mm wastegate flapper if that would help.

 

[kenamond]

Depending on the port job, they may have just focused on improving flow into the turbine wheel but not out the wastegate. They probably just reamed out the wastegate and put in a larger flapper, but this won't improve flow from the turbine inlet around the corner and out through the wastegate.

Here is a before and after of what I did to my B28 based on what I read about creep. The exhaust gasses will have an easier time rounding the bend and getting out the wastegate than before. If they choose to go through the turbine instead, they'll creep up your boost. The B28 wastegate flapper is increased over the T25, and they reamed it out as well, but I didn't buy the ported option, so I don't know what it would've looked like.

 

[gsxpj6428]

it is up to u on the exhaust. i had a gsx with 2.5 greddy evo exhaust and car was dynoed at 355 hp. i have a new car now and am runiing a ported evo 3 16g and supporting mods with a custom 3inch exhuast. im going back to the 2.5, ive read all the tech articles on building up your car and if you are not planning on going over 400 whp, a 2.5 is recommended. plus 3inch sucks for daily driving in my opinion. hope it helps

 

[No_Skillz]

Don't restrict your exhaust to combat creep. That's basically giving up.

 

[Lordpaxin]

get necessary mods to run 20+ psi

so you are boosting creep level

 

[rjclagett]

My E3 creeped with 2.5" turboback. 3" woulda have been same if not worst I imagine.