I've come to terms with the fact my stock cast exhaust mani is going to be a real bottleneck at my goal power levels so I'm going to need to get the TIG plant rocking. Is there a formula to work out what diameter tube would be best suited for a specific application, or is there a general rule of thumb on xxx power requires xx tube?

Also, before I get the elbows ordered through work, is there a company that people use themselves for their elbows?

Ta muchly!

 

There's a guy on here called 'crazycage' who fabricates manifolds. He might be happy to advise you on the elbows etc.

 

How much power are you making ?

It's easy for people to think bigger is better with turbo manifolds....and often it very much is not the case.

 

400bhp give or take a few, possibly more in the future if I go aftermarket management.

I got a price through work for 38.1mm 90 and 45degree elbows for about Ł3 a piece.

 

Not saying a better manifold wont help things, but surely it cant be any real restriction at that level, and it's bound to help any turbo spool well ?

 

People have ran them at over 500, but with enormous boost levels, even at 300whp you can get a good 20-30bhp from going tubular.

I'm also running a Holset + external gate so it'd be much easier than modding the cast item for it!

Valid point though

 

What engine , turbo ie t3 t4 etc , car is it and your right on any app if a tubular manifold is speced properly it will add bhp and torque.

Cheers Paul

 

B230 Redblock, 8v Volvo lump. HY35w Holset, in a 940 Turbo.

Would 38mm/1 1/2" be okay?

 

I compromised and knew the 4wd fannymold would be restrictive and the 2wd absolutely fine but if I was staying with a cast item (I can't afford hand build / bespoke Icconel jobbies) I guessed the next best route was what had already been tried and tested. I went for a WRC fannymold as it was proven and "off the shelf" albeit expensive it's not bespoke money. That was my logic / compromise. It also gives gain in torque too and that wins races lol.

 

I personally use 1/1/2 pipe if your moving turbo away from the head ie over gearbox etc to keep exhaust gas speed up and 1/ 1/2 tube is good for 500 bhp .
If your running turbo on short runners ie next to the cylinder head like cosworth then I would move up to 1/ 3/4 , this would be good for 600bhp .
The main aspect is really trying to get all the runners the same length which is a lot easier than it sounds with nice radius curves and try to get as least welded joints as possible as for every weld you've got one more area where a crack can occur.
Material is the next major factor , I use 304 and never had any problems on turbo car running 500 +bhp but if you can afford it use 316 stainless

Hope this helps

Cheers Paul

 

Or just buy one of these

 

Or just buy one of these

 

Excellent thank you Paul, most helpful!

Not sure what use that would be for a Volvo engine..

 

I wouldn't bother buying 45° elbows mate

 

Not necessarily compatible with Sch 10 type tubing, but seen this at Autosport earlier in the year.
Very nice product for assisting with making tubular manifolds from a kit setup

http://www.profusioncustoms.com/icen...deling-system/

 

Do you not tend to use them mate?

Dead link

 

It worked last night !!! lol

US seller

 

Those clamps would be a godsend!

 

It does look like a brilliant system, Profusion Customs had it all on display at Autosport last year.

 

No mate I just cut 90° in half and get 2x 45° for the price of one