Tubular manifold runner size

[MarkTurbo]

I'm planning on making a T4 twinscroll manifold up for my car soon and i was looking at this merge collector as it would save a hell of a lot of time fabricating one. Just wondering what sort of bhp 1.5" runners will support as i haven't got a clue and that seems to be the only size available!

http://www.treadstoneperformance.com/product.phtml?p=2623&prodname=Twin+Scroll+Merge+Collector%2C+304+Stainless+Steel

 

[Fast Guy]

Any use.
http://www.wallaceracing.com/header_length.php

 

[MarkTurbo]

Thanks, it probably is useful but i was stuck after exhaust valve diameter

 

[splmum]

If you are using standard cams you need the following

exhaust valve opening = 4 degrees
exhaust valve duration = 248 degrees
exhaust valve centreline = 120 degrees
Peak RPM = you choose (say 7,200)
Volumetric efficiency = 0.60 (Brake specific something - forgot - used for turbo engines, NA is 0.50)

Hope this helps

 

[Makaveli_se7en]

VE is more likely to be around 90%.

 

[Fast Guy]

(Brake specific something - forgot - used for turbo engines, NA is 0.50)

Brake specific fuel consumption?

 

[The Doc]

Measure your exhaust port and calculate the cross sectional area, now make sure whatever tube you use has the same or larger csa, as you need to keep gas velocity up as well.

 

[MarkTurbo]

Thanks everyone.

Reading up on manifolds a bit more earlier i want to try and keep the runners as small as i can get away with to spool the turbo as fast as possible. I'm not too worried if i lose a little bit of top end power as spool is more important for what i use my car for.

My aim is to have more than double the bhp of a standard car with stock spool or better!

 

[Fast Guy]

Have you got a borg warner? I hear they help with that.

 

[MarkTurbo]

Not yet ;-) Just waiting until i've got enough spare cash to buy everything in one go, turbo/manifold flanges/elbows/v bands etc etc

 

[RO_SUNNY]

48.3 mm's with an 3mm wall for powers from 400 BHP and 44 mm with an 3mm wall for up to 400 BHP.