27 replies to this topic

[m0useYy]

Hi, I'm looking to buy this:

http://www.minispare...id=33488&title=

What would be the benefit of buying a stainless steel back box over the mild steel one provided in this kit?

And if the benefits are significant, do minispares sell this kit with a stainless back box?

Thanks!

[Mini 360]

Stainless means shiny shiny and you won't need to maintain its finish from rusting (well not as often anyway)

They do sound different, with stainless sounding more tinny to my ear.

[holmesy]

just sprayed my stage 1 exhaust and manifold in exhaust paint, the manifolds rust quickly but if treated then last forever

[Dan]

A stainless exhaust will last more or less forever, unless something hits it. A mild steel one could rust through in as little as 5 years. As above they do sound slightly different. You don't just want a stainless backbox but the whole thing. Mini Spares exhausts are available in stainless yes.

[R1minimagic]

Depends on the quality, SS can still rust quite quickly

[dklawson]

SS can still rust quite quickly

Really? What grade of stainless was that and/or whose kit was it?

[R1minimagic]

It is usually 409 grade used for exhausts, however difficult to tell just by looking at them. I have had several stainless exhausts over the years some last very well and others start rusting on the weld joints, end caps and link pipes quite quickly.

[dklawson]

I suspected the material would be 410. I'm not familiar with 409 but assume it would be similar. Rusting at the welds makes sense if the process wasn't well controlled. Thanks for the warning.

[holmesy]

the internals of the boxes will go before the actual pipes and boxes if they are kept well maintained, the coke will help the inside from rusting a little bit once its built up and for the outside just sand down and degrease with thinners then give a few coats of VHT paint which lasts ages

[Dan]

the internals of the boxes will go before the actual pipes and boxes if they are kept well maintained, the coke will help the inside from rusting a little bit once its built up

Not in my experience. The wet soot that builds up inside and all the other stuff in the exhaust, particularly oxides of nitrogen, is very acidic. Rather than protecting the metal, this etches its way through mild steel fairly quickly. Boxes fail from the bottom, or from the joint with the end cap as that's where the acid pools and collects.

Luckily I've never had a bad stainless exhaust myself though.

[Sprocket]

It is usually 409 grade used for exhausts, however difficult to tell just by looking at them. I have had several stainless exhausts over the years some last very well and others start rusting on the weld joints, end caps and link pipes quite quickly.

Most commonly available stainless exhausts are manufactured from 304 stainless. 304 'yellows' with heat and can start to rust as the carbon precipitates to the surface.

310 is more suitable for exhaust manifolds but it is more expencive. It has a higher carbon and chromium content than 304, allowing it to withstand higher temperatures than 304 or 321 yet still retain its oxidisation resistance. 321 is more desireble with similar properties to 304 and with the added titanium component it increases its strength at high temperatures. Both of these are used in the aerospace industry for piston engines. 321 is desireble with its added strength for turbo exhaust manifolds since the weight of the turbo usually hangs on the manifold itself.

Iconel is the 'ideal' material but is very expensive and difficult to work with. They use this in formula 1.

Edited by Sprocket, 06 April 2012 - 03:58 PM.

[mike.]

I'd go for stainless anyday. I bought my mild steel RC40 when cash was tight and now i'm gutted I didn't fork out the extra £70 for the stainless version.

[Ethel]

Water is a bi-product of burning hydrocarbons, like petrol, exhausts corrode from the inside too.

[R1minimagic]

Water is the main product of burning hydrocarbons! Along with CO2.

[mini-luke]

I'm sure Minispares say their RC40's have stainless internals regardless of being the stanless or mild version.