M51, Alloy v Plastic manifold?

Datatek · Oct 10, 2012

Looked closely at the turbo pipes while I have it all in bits and decided it would be a good idea to replace them. The question is, I have an alloy manifold that I could use to replace the plastic one, any thoughts on whether it would be a good idea before I order the pipes as the one to the manifold is different?
I would have thought that the alloy one would aid charge cooling, but what do I know?
I have run with the EGR disabled for a while which makes bugger all difference.
I have all the bits from my spares dog to do away with the VAC pump as well as the EGR so it would look like a non EGR engine. No problem here with the MOT I'm told if it looks standard.
Yes I have done a search.

Chrisfrain2007 · Oct 10, 2012

Can't see there being a whole lot difference my self, bUt the plastic one was later so BMW must of had good reason.............. or plastics cheaper

Grit Valve · Oct 10, 2012

Aluminium goes Porous over time , wieght and plastic internally smoother better flow but in saying that these factors are minimal , if changing you will have too drill and tap in new studs for cylinders 1 and 2

Datatek · Oct 10, 2012

defender300td1 said:
Aluminium goes Porous over time , wieght and plastic internally smoother better flow but in saying that these factors are minimal , if changing you will have too drill and tap in new studs for cylinders 1 and 2

The first 3 cylinders have the stud holes drilled and threaded for both manifolds on my 96 and my 2000, the last 3 are the same for both.

Grit Valve · Oct 10, 2012

Datatek said:
The first 3 cylinders have the stud holes drilled and threaded for both manifolds on my 96 and my 2000, the last 3 are the same for both.

It's been swapped at some time then

Datatek · Oct 10, 2012

defender300td1 said:
It's been swapped at some time then

All the ones I have seen are the same, drilled for both manifold types, too expensive to make different head versions I would think as the plastic manifold did not appear on all makes that use the engine.

Clarky130 · Oct 10, 2012

Would've thought a plastic manifold would keep charge cooler when subjected to a high-temp environment... Ally conducts heat alot better than plastic.

Datatek · Oct 10, 2012

Clarky130 said:
Would've thought a plastic manifold would keep charge cooler when subjected to a high-temp environment... Ally conducts heat alot better than plastic.

Unless the charge air is hotter than the under bonnet ambient when I would have thought it would cool the charge air better than plastic which is a good insulator

Clarky130 · Oct 10, 2012

Datatek said:
Unless the charge air is hotter than the under bonnet ambient when I would have thought it would cool the charge air better than plastic which is a good insulator

Yes, there is that... depends which way your heat gradient is running.... the manifold will generally be hotter than underbonnet ambient, though, as it'll conduct heat from the head...

Datatek · Oct 10, 2012

Clarky130 said:
Yes, there is that... depends which way your heat gradient is running.... the manifold will generally be hotter than underbonnet ambient, though, as it'll conduct heat from the head...

I had not thought of that and the gaskets provide little insulation

Grit Valve · Oct 10, 2012

Datatek said:
All the ones I have seen are the same, drilled for both manifold types, too expensive to make different head versions I would think as the plastic manifold did not appear on all makes that use the engine.

It might just be all the ones have been swapped at some time I say this as when I had an engine swap I have plastic type 1999 when fitting a 93 BMW the studs had to be drilled the two manifolds are Opposite after all why drill studs for something that hasn't come out yet after all time is money

mcapinha · Oct 10, 2012

If it ain't broken...

wammers · Oct 10, 2012

The plastic manifold is simply much cheaper to produce than the alloy one. Plus it's thermal advantages makes producing alloy ones a no brainer.

M51, Alloy v Plastic manifold?

Datatek

Well-Known Member

Chrisfrain2007

Active Member

Grit Valve

2000 4.6 Vouge

Datatek

Well-Known Member

Grit Valve

2000 4.6 Vouge

Datatek

Well-Known Member

Clarky130

New Member

Datatek

Well-Known Member

Clarky130

New Member

Datatek

Well-Known Member

Grit Valve

2000 4.6 Vouge

mcapinha

Active Member

wammers

No longer with us, RIP

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