i have a 2.25" exhaust right now. I am planning on getting the greddy kit for my sohc soon and running low boost for a while. Will the 2.25" be big enough for this low boost application or should i go 2.5"? What kind of gains would i seen in going from 2.25" to 2.5" on stock 5.5psi?

 

I would like to know this too. I run 8 psi on 2.25.

 

Read this!!

https://honda-tech.com/zerothread?id=414433

 

so how big of a gain do you think i would expect from going up to 2.5 or even 3

 

Thank you. :adding it to my notepad:

 

your probably going to experience a better spool time. the less back pressure present is better for a turbo'd vehicle...hence the ideal size would be a 3", but I chose a 2.5" because I'm not going to deal with the noise. The turbo will supress the noise dramatically, but i want nerely all the noise controlled. a 500-1000rpm decrease in spool time is something i'll forfeit to have a sound piece of mind and the police not hassling me.

 

Going from 2.25 to 2.5 will not a small difference, but going from 2.25 to 3.0 could make a substantial difference depending on the amount of boost you run.

 

well i'm only planning on probably running 6-8psi for a while on the t25 in the greddy kit. Do you think it would be worth it to up my exhaust diameter or just keep what i got for a while. Right now i'm just using 2.25" mandrel bent exhaust.

 

If you plan on being turbo for a while and you have the spare change for a 3" exhaust I would go with that. Just remember that if you ever take your turbo off and go N/A again your car is going to lag with the 3" , so save your current exhaust for a later day.