Ok, this is my first turbo build and i really dont know what to do, as far as downpipe size and exhaust size. One friend says," hell yeah go 3, why not" and the other is like, " dont do that its stupid" so i dont know what i should do .

I was seeing if any one could give me some insight to the pros and cons of a 2.5 downpipe to full 2.5 exhaust and the same for a 3 inch ?

I have ...

B18b
Skunk2 intake manifold
B16 TB bored to Itr specs
DSM 450's
BMC race log manifold
Greddy type rs BOV
Tial sport waste gate 38mm 6psi spring
Turboxs boost controller
Jonny Race car Frontmount intercooler with 2.25 inch intercooler piping
Gsr Tranny
Exedy Stage 1 organic clutch
8lb balanced flywheel
Obd2b-to-Obd1 conversion tuned on Uberdata


WE are looking to run 6psi and 12psi on a dual stage boost controller

Garrett T3To4e COMPRESSOR SPECS:flow: 53 lbs/min 678cfm.60 A/R HOUSING

60 TRIM WHEEL

TURBINE SPECS:.63 A/R HOUSINGSTAGE 3 WHEEL

All in a 99 si shell

All the feed back i can get would be greatly appreciated!

 

Some one help Please!!

 

from what i have read/done you wont need 3 inch for 12 psi. 2.5 should be good for 15ish depends on your power goals but almost everybody i know is running 2.5 including me.

 

i used a 2.5" and made 304whp at 14 psi. a bigger dp would be better but 2.5 will be fine for a stock ls.

 

The larger the downpipe the faster the turbo will spool. It's up to you, if you can fit 3" w/o many problems go with 3" if it's going to be one big headache to try to get 3" to fit go 2.5". Turbo's dont like exhaust, the bigger and the less the better. -Nick

 

thanx guys any one else

 

<--- Turbo EM1.

Do it right the first time. (3")

Im sure you could make acceptable power with the 2.5", but you will (eventually) limit your potential HP output if you start to upgrade your booooosterz.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbro &raquo;</TD></TR><TR><TD CLASS="quote">The larger the downpipe the faster the turbo will spool. It's up to you, if you can fit 3" w/o many problems go with 3" if it's going to be one big headache to try to get 3" to fit go 2.5". Turbo's dont like exhaust, the bigger and the less the better. -Nick
</TD></TR></TABLE>
i couldn't of sayd it better!

 

Listen:

i too have a turbo EM1. a 2.5" DP will get you to 300whp and thats about it. if you're plans are to stay below 300 then go with it. but if you think for one second you want to go beyond that, save yourself the trouble of buying two DPs and go with the 3" right off the bat.

its as simple as that sir.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr. Vapor &raquo;</TD></TR><TR><TD CLASS="quote">Listen:

i too have a turbo EM1. a 2.5" DP will get you to 300whp and thats about it. if you're plans are to stay below 300 then go with it. but if you think for one second you want to go beyond that, save yourself the trouble of buying two DPs and go with the 3" right off the bat.

its as simple as that sir. </TD></TR></TABLE>

Really? I have an EM1 with the B16 and am running 15 psi and I make 361 whp with a 2.5 in. DP. Just my experience.

 

what are your other specs...do you have the same turbo as he has listed?

 

Yep, except it's a 57 trim.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbro &raquo;</TD></TR><TR><TD CLASS="quote">The larger the downpipe the faster the turbo will spool. It's up to you, if you can fit 3" w/o many problems go with 3" if it's going to be one big headache to try to get 3" to fit go 2.5". Turbo's dont like exhaust, the bigger and the less the better. -Nick
</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dnbruut &raquo;</TD></TR><TR><TD CLASS="quote">
i couldn't of sayd it better!</TD></TR></TABLE>
x2

also if u want more power then 3" is the way to go

 

I have a 50 trim, pushing 340 HP...2.5 inch downpipe/3 inch exhaust.

 

I would go for 3" just because of the quicker spool. You can make alot of power on a 2.5" downpipe, but since you're getting one now, might as well go with the one that will support the most power.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr. Vapor &raquo;</TD></TR><TR><TD CLASS="quote">Listen:

i too have a turbo EM1. a 2.5" DP will get you to 300whp and thats about it. if you're plans are to stay below 300 then go with it. but if you think for one second you want to go beyond that, save yourself the trouble of buying two DPs and go with the 3" right off the bat.

its as simple as that sir. </TD></TR></TABLE>

That right there is total BS. I've seen people do over 600whp on a 2.5"dp.
https://honda-tech.com/zerothread?id=1382007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tactic$ &raquo;</TD></TR><TR><TD CLASS="quote">Do it right the first time. (3")</TD></TR></TABLE>

the bigger the better.

 

it all depends on how much space you have...

id WANT a 3" dp off the bat, but if i couldnt fit it b/c of a/c and what not, then id just go with a 2.5 flared to 3"...

thats what my friend did on the same turbo & motor and his doesnt take that long to spool..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EVIL Hx Coupe &raquo;</TD></TR><TR><TD CLASS="quote">I would go for 3" just because of the quicker spool. You can make alot of power on a 2.5" downpipe, but since you're getting one now, might as well go with the one that will support the most power.

That right there is total BS. I've seen people do over 600whp on a 2.5"dp.
https://honda-tech.com/zerothread?id=1382007</TD></TR></TABLE>

great, im not trying to start an e-thug fight you dude. i never said it wasnt possible, take a second to re-read my thread. im simply stating, and i think EVERYONE in this forum will agree INCLUDING yourself that, if you plan to make some GOOD WHP numbers right from the bat, and you're given the CHOICE at the beginning of a 2.5" or a 3" DP which would you choose?

most of us when we first built our motors opted for the 2.5" DP for one of several reasons: Money, convenience (say it was a friends and he gave it to you) or didnt have plans to make crazy #s right off the bat. i mean how often do we see a member saying "oh its i jsut want 280whp and thats it, its street driven" and then you see them come back a year later saying "ok, i wanna make 500whp"

ok im rambling, point is from the start of a build, which would you chose? sure you can make over 300whp, but its just not logical if you have the chance to go with a 3"

ok cool, yea im drunk lol..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr. Vapor &raquo;</TD></TR><TR><TD CLASS="quote">great, im not trying to start an e-thug fight you dude. i never said it wasnt possible, take a second to re-read my thread. im simply stating, and i think EVERYONE in this forum will agree INCLUDING yourself that, if you plan to make some GOOD WHP numbers right from the bat, and you're given the CHOICE at the beginning of a 2.5" or a 3" DP which would you choose?

most of us when we first built our motors opted for the 2.5" DP for one of several reasons: Money, convenience (say it was a friends and he gave it to you) or didnt have plans to make crazy #s right off the bat. i mean how often do we see a member saying "oh its i jsut want 280whp and thats it, its street driven" and then you see them come back a year later saying "ok, i wanna make 500whp"

ok im rambling, point is from the start of a build, which would you chose? sure you can make over 300whp, but its just not logical if you have the chance to go with a 3"

ok cool, yea im drunk lol..</TD></TR></TABLE>

Not trying to start an e-fight here either. I'm about to start drinking