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jeff

New Member

• Jun 17, 2012

• #1

Hi all ,


I need to make a new exhaust for my hybrid , it has a 3.9 efi,

it has hedman tubilare headers , what size is best 3" or 2.5"

can do it in either , just not sure if 3" is too big?

thanks

 

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dirtydiscov8

New Member

• Jun 18, 2012

• #2

I've got headman headers on a 3.9 and mine must be about 2.5 inch. 3" is for scoobaru impretza's isn't is?

 

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jeff

New Member

• Jun 18, 2012

• #3

dirtydiscov8 said:

I've got headman headers on a 3.9 and mine must be about 2.5 inch. 3" is for scoobaru impretza's isn't is?

Click to expand...

yeah have 3" on my impreza (2.5" is fine upto 400bhp)

so i take it 2.5" will be fine for 3.9 v8

 

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POAH

New Member

• Jun 18, 2012

• #4

2.5 is more than enough for the 3.9

 

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jeff

New Member

• Jun 18, 2012

• #5

so no advantage for going 3" ?

, just i'm biulfding the exhasut myslef and its no more work to biuld it in 3"

 

discool

Well-Known Member

• Jun 19, 2012

• #6

Mass of air that the engine breathes in + mass of fuel = mass of exhaust gases.
So unless you are increasing the fuel/air intake then the standard 2-1/2 inch size is ok.

 

Diesel Do

Well-Known Member

• Jun 19, 2012

• #7

Go too big and you may lose too much back pressure and make it run badly. I'd go 2.5 to be safe

 

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POAH

New Member

• Jun 19, 2012

• #8

jeff. said:

so no advantage for going 3" ?

, just i'm biulfding the exhasut myslef and its no more work to biuld it in 3"

Click to expand...

none what so ever