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3" Or 2.5" Full Exo System?

Started by IIIRpower, May 03 2005 05:09 AM

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#1 IIIRpower

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Posted 03 May 2005 - 05:09 AM

real quick q...
for 850turbo w/stock 15g @17psi,...would 2.5" racecat and muffler be better off or worse than 3" full exhaust system??
dont you need backpressure and whatnot,..like will the 3" cause the turbo to take more time to spool up vs 2.5"
just checking again before i hook the shizzle up on my car one way or the other.
any thoughts, opinions, and reviews would be greatly appreciated...
g

Edited by IIIRpower, 03 May 2005 - 05:10 AM.

1995 T5-R yellow
k&n l kumho ecsta supra 712s on titans l upsolute chip l ipd catback l clear side markers

1995 850turbo white
k&n l avon tech m550s on 17" pegs l speedtuning chip l koni adjustables l h&r springs l samco l hightech silicone l 10% tint l denso iridiums l thule roof rack l valentine 1

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#2 Overboost850

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Posted 03 May 2005 - 05:18 AM

no back pressure is best for the turbo to spool quickest. only the larger you go you can run into boost creep but I'm not sure if that is really a problem on the 15g.

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#3 JHEIII874T5M

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Posted 03 May 2005 - 05:58 AM

one thing i've always thought... the 15g's only 2.5" diameter. 16T is 2.75" diameter and 19T is 3.0" diameter. (size of exhaust outlet off turbo).

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#4 IIIRpower

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Posted 03 May 2005 - 12:33 PM

QUOTE(JHEIII850Turbo @ May 3 2005, 01:58 AM)

one thing i've always thought... the 15g's only 2.5" diameter. 16T is 2.75" diameter and 19T is 3.0" diameter. (size of exhaust outlet off turbo).

you got me!?!...dont they flare out the connection to either the down pipe size or CAT size?? if they're diff than say the 15g's 2.5"dia.

1995 T5-R yellow
k&n l kumho ecsta supra 712s on titans l upsolute chip l ipd catback l clear side markers

1995 850turbo white
k&n l avon tech m550s on 17" pegs l speedtuning chip l koni adjustables l h&r springs l samco l hightech silicone l 10% tint l denso iridiums l thule roof rack l valentine 1

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#5 Gregg

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Posted 03 May 2005 - 12:56 PM

If I Recall Correctly, 3" turbo-back exhaust, because of the reduced backpressure, will cause the turbo to spool up a little more slowly than with a 2.5" system (or other system with a little more backpressure). But this small amount of lag will be more than made up for in the higher flow characteristics at upper RPMs.

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#6 IIIRpower

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Posted 03 May 2005 - 12:59 PM

QUOTE(gmischenko @ May 3 2005, 08:56 AM)

If I Recall Correctly, 3" turbo-back exhaust, because of the reduced backpressure, will cause the turbo to spool up a little more slowly than with a 2.5" system (or other system with a little more backpressure). But this small amount of lag will be more than made up for in the higher flow characteristics at upper RPMs.

hey greg,..you trying a borla system??..got info from other greg on other post.
and yeah...the backpressure stuff is what i thought.

Edited by IIIRpower, 03 May 2005 - 12:59 PM.

1995 T5-R yellow
k&n l kumho ecsta supra 712s on titans l upsolute chip l ipd catback l clear side markers

1995 850turbo white
k&n l avon tech m550s on 17" pegs l speedtuning chip l koni adjustables l h&r springs l samco l hightech silicone l 10% tint l denso iridiums l thule roof rack l valentine 1

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#7 Gregg

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Posted 03 May 2005 - 01:06 PM

I already bought the Borla XR-1 Sportsman oval muffler (40943) but I don't have it installed yet. I am waiting to do a nice 3" cat-back system soon. I picked up the Borla as a recommendation from Rob @VMS.

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#8 Guest_DougK_*

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Posted 03 May 2005 - 01:32 PM

back pressure bad

your not goign to make more back pressure with an exhaust than the exhaust wheel on the turbo is already making

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#9 ToxicLemonade

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Posted 03 May 2005 - 01:55 PM

Go 3 inch.

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#10 Che'_Moderator

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Posted 03 May 2005 - 02:02 PM

Not even gonna bother but I run 12 on 2.5. Just something to think about. Also if you run a 3" system and do not get a chip built for 3" your actually gonna loose power.

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#11 IIIRpower

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Posted 03 May 2005 - 02:04 PM

QUOTE(ToxicLemonade @ May 3 2005, 09:55 AM)

Go 3 inch.

haha,..gotcha ryan...no more q's.

1995 T5-R yellow
k&n l kumho ecsta supra 712s on titans l upsolute chip l ipd catback l clear side markers

1995 850turbo white
k&n l avon tech m550s on 17" pegs l speedtuning chip l koni adjustables l h&r springs l samco l hightech silicone l 10% tint l denso iridiums l thule roof rack l valentine 1

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#12 ToxicLemonade

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Posted 03 May 2005 - 02:07 PM

QUOTE(Volvospeed Admin @ May 3 2005, 02:02 PM)

Not even gonna bother but I run 12 on 2.5. Just something to think about. Also if you run a 3" system and do not get a chip built for 3" your actually gonna loose power.

true, but you have to account for the mod bug, which will soon make him crave more power, which will result in a need for a chip.

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#13 IIIRpower

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Posted 03 May 2005 - 02:09 PM

QUOTE(ToxicLemonade @ May 3 2005, 10:07 AM)

true, but you have to account for the mod bug, which will soon make him crave more power, which will result in a need for a chip.

mod bug already hooked me up with a ST chip...thus must get exhaust out of system faster!

1995 T5-R yellow
k&n l kumho ecsta supra 712s on titans l upsolute chip l ipd catback l clear side markers

1995 850turbo white
k&n l avon tech m550s on 17" pegs l speedtuning chip l koni adjustables l h&r springs l samco l hightech silicone l 10% tint l denso iridiums l thule roof rack l valentine 1

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#14 ToxicLemonade

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Posted 03 May 2005 - 02:12 PM

QUOTE(IIIRpower @ May 3 2005, 02:09 PM)

mod bug already hooked me up with a ST chip...thus must get exhaust out of system faster!

see i knew it. happened to me the same way.

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#15 Che'_Moderator

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Posted 03 May 2005 - 02:15 PM

QUOTE(IIIRpower @ May 3 2005, 08:09 AM)

mod bug already hooked me up with a ST chip...thus must get exhaust out of system faster!

Well if you go 3" you will need to have the chip remapped. I really dont think the exhaust is the weak link here guys.

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#16 IIIRpower

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Posted 03 May 2005 - 02:22 PM

QUOTE(Volvospeed Admin @ May 3 2005, 10:15 AM)

Well if you go 3" you will need to have the chip remapped. I really dont think the exhaust is the weak link here guys.

i know i know...turbo and d p yadda yadda = weaklinks

1995 T5-R yellow
k&n l kumho ecsta supra 712s on titans l upsolute chip l ipd catback l clear side markers

1995 850turbo white
k&n l avon tech m550s on 17" pegs l speedtuning chip l koni adjustables l h&r springs l samco l hightech silicone l 10% tint l denso iridiums l thule roof rack l valentine 1

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#17 ToxicLemonade

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Posted 03 May 2005 - 02:24 PM

QUOTE(IIIRpower @ May 3 2005, 02:22 PM)

i know i know...turbo and d p yadda yadda = weaklinks

well just get a 3inch down pipe and exhaust. Then worry about a remap when you do a larger turbo. i guess i could benefit from a remap of my ST chip becuase i have a full 3 inch exhaust and down pipe, but im upgrading the turbo so its prolly a waste of money and time to do so.

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#18 Che'_Moderator

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Posted 03 May 2005 - 02:31 PM

QUOTE(IIIRpower @ May 3 2005, 08:22 AM)

i know i know...turbo and d p yadda yadda = weaklinks

Was thinking more like head and block but ok

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#19 GShyneDM

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Posted 03 May 2005 - 02:58 PM

QUOTE(Volvospeed Admin @ May 3 2005, 02:02 PM)

Not even gonna bother but I run 12 on 2.5. Just something to think about. Also if you run a 3" system and do not get a chip built for 3" your actually gonna loose power.

Interesting...

So lets say I keep the stock 2.5 down pipe...and install a Higher flow Cat, and a better flowing 2.5 exhaust...

Most chip manufacturers just recommend a catback... no one necessarily says to change the down pipe

not in their map?

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#20 StansMan

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Posted 03 May 2005 - 06:17 PM

QUOTE(Volvospeed Admin @ May 3 2005, 10:15 AM)

Well if you go 3" you will need to have the chip remapped. I really dont think the exhaust is the weak link here guys.

Haven't people said the speedtuning chips run rich to begin with? If this is the case, wouldn't a higher flow exhaust help? I'm no expert on engine mapping here so correct me if i'm wrong.