Exhaust Manifold Inner Diameter For Gt3076 X 2

[TwinTurboM3]

I started building the turbo exhaust manifolds for my 2 x GT3076. Have two options:

48 mm piping or 58 mm piping can be used for the exhaust manifolds.

will 58 mm give more top end power and longer boost build up?

Mert

[Adriano]

Are you talking inside diameter, if so i wouldnt go for either of those sizes, what size are the valves/exhaust ports

[180bfj20det]

Im sure hes talking OD with a thickness of about 4mm if hes using steampipe bends (im assuming).

You want about an ID of about 36-40mm. If youre using 2x 3076, then I would go for 40mm. Use 40NB bends.

Just out of interest, what are the head mods? Whats your goal?

Sounds like a big hp setup

Are you talking inside diameter, if so i wouldnt go for either of those sizes, what size are the valves/exhaust ports

[djr81]

Im sure hes talking OD with a thickness of about 4mm if hes using steampipe bends (im assuming).

You want about an ID of about 36-40mm. If youre using 2x 3076, then I would go for 40mm. Use 40NB bends.

Just out of interest, what are the head mods? Whats your goal?

Sounds like a big hp setup

If by steam pipe you mean pipe to ANSI B36.10 then the two OD's are 48.3 & 60.3 which correspond to 40mm & 50mm nominal bore (1.5" & 2" for the old school). For standard weight pipe the ID's are then 40.9mm & 52.5mm, for extra strong they are 38.1mm & 49.2mm.

So if the choice is between the two get the smaller, ie 40NB. But that is still a big pipe....

For the pedants obviously bends are to ANSI B16.9 for the LR stuff & B16.28 for the SR gear.

[TwinTurboM3]

Head is BMW M3 3.2L 2005 model.

Head is ported and polished.

Intake valves are 36,5 mm (this is the + 1 mm valve)

Exhauts valves are 31,5 mm (this is the + 1 mm valve)

Dual springs, titanium retainers are in place.

288/280 cams are installed.

The engine has 3.2L capacity, and 2 x GT3076s.

What I have seen is that, my friend has a Supra with GT55 turbo. This is a huge turbo with 91 mm compressor wheel.

He has a full race brand exhaust manifold where all runners are 60 mm ,,

So they make over 1000 whp on my Dyno Dynamics and I really would like to know if someone has a technical explanation for the runner size.

[discopotato03]

Search FullRace Motorsport and talk to Geoff in his own Q/A section .

[TwinTurboM3]

Thank you very much.

Regards.

mert

[Adriano]

I seriously doubt your friends supra has 60mm i.d. exhaust runners, it would be impossible to make the manifold, and wouldnt work anywhere near as well as more appropriate sized runners.

[T04GTR]

58 are you serouse!!! same size as the port mate. thats lag city. 1.5"at the largest if its making 1400hp. if not 1.25" id.

[T04GTR]

you have to remember the exhast housing is the restriction. not the runner. so the quicker it gets there the less lag you will have with no sacrfice at top end.

[T04GTR]

id like to see a vernier mesuring that. those manifolds use 1.5" id thickwall stainless.

[T04GTR]

1.5 is 38mm. add the 6mm or 8mm (depending on what shedule) of combined wall thickness and its 44 or 46mm od.