Making tubular exhaust manifold (for those who know!)

[kj16v]

No offence meant to anyone but could only people who know for sure answer this one.

I've been told that the exhaust ports on the 16V are 42.5mm diameter. The nearest size tube available is 1.5" and 1.75".

It's proving to be a real pain to get all the bends in 1.75" which would be about spot on including the wall thickness.

Would 1.5" work without causing too much restricion? It will be about 6 mm too small including the wall thickness

[BenR]

Use 1 3/4" tube of 20 gauge, that will give you a total dia of 42.6mm .

Its commonly available, and you can get it in any centre radius you want with U bends, J bends, 90 deg, 70 deg, 45 deg, 15 deg and straight.

Who are you using to source tube?

[kj16v]

I've been trawling through the Yellow Pages so far! None of ones I've tried can get 1 3/4" bends. The best one so far is a new company called Dynoflow.co.uk. He doesn't have any 1 3/4" though.

Can you reccommend any companies who would sell the correct diameter in straights and bends?

Much appreciated.

[northy]

u can buy pipe from demon tweets mate, and manifold flanges

[fasterthanjesus]

question.

if i were to buy the bits from demon tweeks, can anybody recommend anyone/anywhere to get the manifold engineered?

cheers

ftj

[BenR]

The stuff from DT is rubbish.

And as for buying the bits and have someone put it all together, i wouldnt bother. A good manifold is all about the sizing, step downs, lengths and cylinder pairing. Just slapping together something that fits is pretty useless unless you get extra lucky.

Where are you located in the country?

[northy]

never seen the pipes ben so i carnt comment.

I know blueflame can make nice manifolds.

[stan]

Get in touch with the lads from "american chopper"...they have loads!

[Anders]

There is quite a lot more to it than getting hold of some tubing, bending it and welding it all together...

the inlet and exhaust manifolds are critical to the whole engine performance...unless you have access to major tools such as fluid dynamic simulations, air flow benches and analysis calcs/spreadsheets then I wouldn't bother...

waste of time...yeah sounds great that you desinged and built your own manifold...but I guarentee performance will suffer as a result. If it was easy then we would all be doing it..

[Jonny1]

Unless you've got particular plans, and are able to exicute your self, I wouldnt bother. Buy a off the shelf item, they lack some finess but offer a resonable product for reasonable (ish.) gains.

I'm in process of makin a manifold myself. Material costs alone are quite expensive, and the labour involved in making a worthwhile job is extensive. Hence if you were to pay anyone for the trouble it's gunna cost you.

Materials cost for mine so far are as follows:

Laser cut Manifold Blank - £12
Laser cut Turbo up pipe flange - £8
Laser cut Turbo Down pipe flange - £6.50
20 x 1 1/2" 90 deg. Inconel Bends - £120

Alot of that's mate's rate's too!

If you wanted me to make it for example, I would want a couple of hundred quid atleast. Would be a propper bo job though mate! :D