VSR 6 branch Exhaust Manifold - is it made of stainless steel?

[matth76 1]

Hi

Is the VSR 6 branch Exhaust Manifold made of stainless steel or is it made of cast iron?

Are there any good quality aftermarket free flowing 6 branch exhaust manifolds (for a golf/corrado vr6) that are made of cast iron as opposed to thinner and weaker stainless steel?

Cheers

[Slim 0]

The VSR is an inlet manifold.

[francisjonno 2]

I've never heard of a cast iron 6 branch mainfold but if you don't like the idea of a stainless mainfold, Ashley Exhausts do a mild steel 6 branch http://www.ashleyexhausts.co.uk/product_info.php?cPath=5205_1163_1240_1274&products_id=1411117 that'll be stronger than a stainless one (race cars tend to use mild steel)

As slim said the VSR is a variable inlet manifold and its made of cast alloy.

Hope this helps

[matth76 1]

Thanks for your replies. I've already got a stainless steel exhaust manifold. Was just curious if there were any after market 6 branches made of the same material as the stock one, which is very strong due to it being cast iron, and also transfers heat better than steel.

Would be more of a future mod (but only IF my current one does crack in a couple of years - which I've heard they are prone to). Hopefully it will be fine though.

How long have people been running stainless steel ones on here? Mine wasn't cheap at £350 and is supposed to be good quality but then anything can happen.

It does seem to be more free flowing than my stock exhaust manifold. I still have the stock air filter. But I should be getting a BMC next month to get a bit more air into the engine. I think the exhaust manifold has actually reduced the back pressure quite a bit (along with my high flow cat and system). Without an uprated air filter can this cause a flat spot in low revs?

[francisjonno 2]

Main problem with Stainless manifolds is that they're more brittle (well, less flexible really) than mild steel and obviously less strong than original cast iron manifolds.

Most good quality stainless manifolds will last fine as long as your engine mounts are in good condition - it's excessive engine movement that snaps the welds. Fitting uprated engine mounts e.g. from Vibratec or VF, is highly recommendend by all when fitting a stainless manifold.

To help with heat transfer and reduce under bonnet temperatures most get their 6 branch manifolds wrapped (there are a few threads about this)

I shouldn't expect having the free flow exhaust without an uprated air-filter would cause a flat spot - i'm not an expert, but the engine management should compensate for any changes. Having said that the BMC should balance your free flow exhaust allowing the management to increase power, and hopefully help clear any flat spots (that may be present on the standard car)

[Buzzark 0]

Having an exhaust on without upgrating the inlet won't cause a flatspot but the exhaust will show up a flatspot more.

Stainless steel is actually a lot stronger than mild steel and more difficult to weld, which is where the problem lies. Better welds on stainless are done on a TIG welder and should make the joins stronger than the surrounding pipes. These will pretty much never break.

If yours cracks, it can always be welded again by a decent welder, it's a 5 mins job.

The original is cast iron because it's much cheaper to make than a tubular manifold and it's heat transfer capabilities are a downside, better to keep the heat in the exhaust. Your cat will be more efficient that way.

[matth76 1]

Thanks for your replies. So it's the welds that normally break if not done correctly. I didn't know that. How can I tell if my welds on the stainless manifold were done on a tig welder... will they show up as a different colour as I know mine looks a purply darker colour around the welds.

[FishWick 21]

It's the quality of the joins where the tubes meet the head mounting flanges that's critical, that's where they fracture through excessive engine movement, but if you've got decent mounts and a good flexi joint, don't worry.

Yes stainless is stronger than mild steel but it's also heavier. To counter that, stainless wall thickness can be thinner but it's very intolerant of metal fatigue....so get those vibratech mounts on!

Iron is a better conductor of heat that stainless and it's the heat stored in the iron that 'pulls' spent gases out of the cylinders, so it's critical you replicate this with good quality lagging on the tubular manifold. If the stainless is allowed to run too cool, the scavenging effects of the manifold can be affected.

Stainless will discolour with age and heat, don't worry about it.