3" exhaust really necessary for FI ? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Deep Six · 06-18-2013, 05:08 PM

Simple question: how much impact does the 3" exhaust provide for moderate power FI system versus the typical 2.5" ?

Tainen · 06-18-2013, 05:11 PM

Is it necessary? No. Will there be a difference? Yes. Largely depends on the design and output you will be at.

Tansey86 · 06-18-2013, 05:12 PM

Enough to make it worth going 3" if its your first time around buying exhaust for the car.

If you already have a 2.5" system stick with it until you hit about the 350rwhp mark.

For a turbo system, the exhaust closest to the turbo is where it matters most, the closer towards the exhaust tip you get, the less of a difference a larger diameter exhaust will make.

FeaR-S · 06-18-2013, 06:09 PM

you do realize that if you have a 3" down pipe 2.5" Mid and 3" exhaust the entire system will flow like a 2.5" system

Tansey86 · 06-18-2013, 08:15 PM

Quote:

Originally Posted by FeaR-S

you do realize that if you have a 3" down pipe 2.5" Mid and 3" exhaust the entire system will flow like a 2.5" system

The " A chain is only as strong as its weakest link " doesn't apply to exhaust in terms if diameter.

3" from the turbo that tapers to 2.5 at the frontpipe and remains that size to the end will perform better than full 2.5 from the turbo all the way back.

Its a matter of back pressure. JDL's car made 416rwhp at 16 with a 3" downpipe to 2.5 exhaust. He would of made less and spooled slower with a full 2.5" system.

Deep Six · 06-18-2013, 09:02 PM

My objective with forced induction is a heat manageable 275 whp that will stay reliable for 6-10 track weekends a year and some rotational daily driving in between. My orginal plan was leaning towards a turbo system sometime next year but something came up that may put a supercharger on it much sooner. I was planning to buy an ISIS catback because I love the sound and the price but if a 3" makes sense then I will probably by the Ultimate Racing version for the same reasons. There is still the possibility that the car will remain NA and I have heard all kinds of talk regarding compatabilty with a 3"exhaust. If the s/c deal moves forward then I am limited to just a catback for the time being. Meanwhile I have wheels, tires and suspension parts stacked up in my garage and guest bedroom waiting for me to get to it. I have only had one chance to get it on a track(Roebling) so far in stock form and although it wasn't exactly fast it was a blast till the tires cooked and it has lots of raw potential. Sucks though having to honk your horn to get another driver to lift a little after they point you by.

FR-S Matt · 06-18-2013, 09:33 PM

I'm going full 3" N/A for a while before I go turbo. I don't feel like replacing the entire exhaust for when I do go turbo later down the road. The sound I don't have an issue with as I will be keeping my front pipe catted, a beefy midpipe resonator and my Nameless offset axleback. The turbo will quiet things down later.

Deep Six · 06-22-2013, 12:00 PM

I made the same choice and ordered the Ultimate Racing 3" this week. I don't expect any downside if the car remains NA longer than I expect.

SubaSteve · 06-22-2013, 09:51 PM

I'm contemplating getting the new 3" perrin due to wanting fi after the warranty goes out (and I have a better job). I currently have motivs over/midpipe combo catted. Do I have anything to worry about running this for a while?

FR-S Matt · 06-22-2013, 10:24 PM

Quote:

Originally Posted by SubaSteve

I'm contemplating getting the new 3" perrin due to wanting fi after the warranty goes out (and I have a better job). I currently have motivs over/midpipe combo catted. Do I have anything to worry about running this for a while?

I don't see why not, although I'd probably recommend something more than the stock header when running a 3". I could be wrong though. I doubt you will see anything negative.

FT-86 SpeedFactory · 06-22-2013, 11:33 PM

3" is overkill plain and simple unless you're 500+ HP.

jamesm · 06-22-2013, 11:52 PM

I'm going to be picking up a 3" system soon, but for now I'm running the stock exhaust with my turbo. It's still fun as hell. I'm sure it'll be better with the 3", but I wouldn't say it's a prerequisite for boost. Even a 2.5" I'm sure would be fine for most reasonable boosted applications, and probably a bit quieter.

FTEIGHTSIX · 07-03-2013, 10:59 PM

Quote:

Originally Posted by FT-86 SpeedFactory

3" is overkill plain and simple unless you're 500+ HP.

This statement is based on what facts?

Have you ever felt the difference between a 2.5" and 3" exhaust on the same turbo car?

TURBOS LOVE TO BREATHE. FACT.

Tansey86 · 07-03-2013, 11:00 PM

Bigger the better on a turbo car. Open downpipe if you can swing it. SC/NA is different though.

06-18-2013, 05:08 PM	#1
Deep Six Senior Member Join Date: May 2013 Drives: 2013 FRS / 2013 427 Vert Location: Orlando Posts: 611 Thanks: 212 Thanked 328 Times in 197 Posts Mentioned: 5 Post(s) Tagged: 0 Thread(s)	3" exhaust really necessary for FI ? Simple question: how much impact does the 3" exhaust provide for moderate power FI system versus the typical 2.5" ? __________________ [SIGPIC][/SIGPIC] 2013 FR-S Asphalt BC Coils/Rev Works UEL header/HKS Front Pipe/Racing Brake BBK/Shorai LW Battery/ACT 6 Puck Clutch/FBM Radiator & Oil Pan/JR Oil Cooler/Jackson Racing High Boost C30/Rev Works Built Motor 2016 Audi TTS APR Tuned

06-18-2013, 05:11 PM	#2
Tainen Senior Member Join Date: Nov 2011 Drives: First SWP BRZ-L Location: Washington Posts: 809 Thanks: 154 Thanked 350 Times in 174 Posts Mentioned: 11 Post(s) Tagged: 0 Thread(s)	Is it necessary? No. Will there be a difference? Yes. Largely depends on the design and output you will be at. __________________ First white BRZ in the country Limited SWP BRZ, 35% tint, clear bra, Nameless Performance downpipe, axelback, headers

06-18-2013, 05:12 PM	#3
Tansey86 Senior Member Join Date: Sep 2012 Drives: 2003 Subaru Outback Location: Long Island, NY Posts: 1,318 Thanks: 154 Thanked 529 Times in 300 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Enough to make it worth going 3" if its your first time around buying exhaust for the car. If you already have a 2.5" system stick with it until you hit about the 350rwhp mark. For a turbo system, the exhaust closest to the turbo is where it matters most, the closer towards the exhaust tip you get, the less of a difference a larger diameter exhaust will make. __________________ " I know a lot about cars, man. I can look at any car's headlights and tell you exactly which way it's coming. "

06-18-2013, 09:02 PM	#6
Deep Six Senior Member Join Date: May 2013 Drives: 2013 FRS / 2013 427 Vert Location: Orlando Posts: 611 Thanks: 212 Thanked 328 Times in 197 Posts Mentioned: 5 Post(s) Tagged: 0 Thread(s)	My objective with forced induction is a heat manageable 275 whp that will stay reliable for 6-10 track weekends a year and some rotational daily driving in between. My orginal plan was leaning towards a turbo system sometime next year but something came up that may put a supercharger on it much sooner. I was planning to buy an ISIS catback because I love the sound and the price but if a 3" makes sense then I will probably by the Ultimate Racing version for the same reasons. There is still the possibility that the car will remain NA and I have heard all kinds of talk regarding compatabilty with a 3"exhaust. If the s/c deal moves forward then I am limited to just a catback for the time being. Meanwhile I have wheels, tires and suspension parts stacked up in my garage and guest bedroom waiting for me to get to it. I have only had one chance to get it on a track(Roebling) so far in stock form and although it wasn't exactly fast it was a blast till the tires cooked and it has lots of raw potential. Sucks though having to honk your horn to get another driver to lift a little after they point you by. __________________ [SIGPIC][/SIGPIC] 2013 FR-S Asphalt BC Coils/Rev Works UEL header/HKS Front Pipe/Racing Brake BBK/Shorai LW Battery/ACT 6 Puck Clutch/FBM Radiator & Oil Pan/JR Oil Cooler/Jackson Racing High Boost C30/Rev Works Built Motor 2016 Audi TTS APR Tuned

06-22-2013, 12:00 PM	#8
Deep Six Senior Member Join Date: May 2013 Drives: 2013 FRS / 2013 427 Vert Location: Orlando Posts: 611 Thanks: 212 Thanked 328 Times in 197 Posts Mentioned: 5 Post(s) Tagged: 0 Thread(s)	I made the same choice and ordered the Ultimate Racing 3" this week. I don't expect any downside if the car remains NA longer than I expect. __________________ [SIGPIC][/SIGPIC] 2013 FR-S Asphalt BC Coils/Rev Works UEL header/HKS Front Pipe/Racing Brake BBK/Shorai LW Battery/ACT 6 Puck Clutch/FBM Radiator & Oil Pan/JR Oil Cooler/Jackson Racing High Boost C30/Rev Works Built Motor 2016 Audi TTS APR Tuned

06-18-2013, 06:09 PM	#4
FeaR-S Member Join Date: Apr 2013 Drives: Great White Location: ?? Posts: 69 Thanks: 0 Thanked 10 Times in 9 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	you do realize that if you have a 3" down pipe 2.5" Mid and 3" exhaust the entire system will flow like a 2.5" system

06-22-2013, 09:51 PM	#9
SubaSteve Captain Cocoa Join Date: Jul 2012 Drives: CBS BRZ MT Location: MD Posts: 597 Thanks: 32 Thanked 282 Times in 161 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	I'm contemplating getting the new 3" perrin due to wanting fi after the warranty goes out (and I have a better job). I currently have motivs over/midpipe combo catted. Do I have anything to worry about running this for a while?

06-22-2013, 11:33 PM	#11
FT-86 SpeedFactory Join Date: Jul 2012 Drives: 2013 Scion FR-S Location: Des Moines, IA Posts: 7,694 Thanks: 1,298 Thanked 3,579 Times in 1,253 Posts Mentioned: 341 Post(s) Tagged: 5 Thread(s)	3" is overkill plain and simple unless you're 500+ HP.

06-22-2013, 11:52 PM	#12
jamesm Banned Join Date: Mar 2013 Drives: 2013 FR-S Location: Orlando, FL Posts: 2,929 Thanks: 1,166 Thanked 2,293 Times in 1,180 Posts Mentioned: 313 Post(s) Tagged: 4 Thread(s)	I'm going to be picking up a 3" system soon, but for now I'm running the stock exhaust with my turbo. It's still fun as hell. I'm sure it'll be better with the 3", but I wouldn't say it's a prerequisite for boost. Even a 2.5" I'm sure would be fine for most reasonable boosted applications, and probably a bit quieter.

07-03-2013, 11:00 PM	#14
Tansey86 Senior Member Join Date: Sep 2012 Drives: 2003 Subaru Outback Location: Long Island, NY Posts: 1,318 Thanks: 154 Thanked 529 Times in 300 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Bigger the better on a turbo car. Open downpipe if you can swing it. SC/NA is different though. __________________ " I know a lot about cars, man. I can look at any car's headlights and tell you exactly which way it's coming. "

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