Exhaust material, GTI owners, your opinions?

[Guy_H]

Ladies & Gent's,

Need your assistance on the final steps for our Polo 6R exhaust - materials & cost.

We have traditionally only offered hand finished stainless steel, we are working with a new manufacturer who can offer awesome quality with a choice of materials.

Who would like to see an aluminised steel version available & save $400 - $500 over a traditional Stainless steel version?

Aluminised steel lasts a long time, probably in street use, longer than the vehicle itself - the system will still have full stainless mufflers & tailpipes.

It is possible that we can offer both materials, but initially in batch quantities, we will only offer one material.

Expected pricing:

Aluminised full turbo back system, 200 cell metal cat, stainless mufflers & twin walled 75mm tailpipe tips. $1995 incl GST

Stainless full turbo back system, 200 cell metal cat, stainless mufflers & twin walled 75mm tailpipe tips. $2450 incl GST

[gavs]

ALuminised steel all the way. We build (through a separate company arm) aluminsied steel fuel tanks and for the cost saving over stainless, it makes you wonder why people still insist on stainless. The other benefits include:

Less suceceptable to stress cracks
Easier to weld (for those not good with a tig)
Better heat disipation (less heavy metal in the alloying)
Less brittle when hot

On a side note, what is (other than strength) the benefit of going to twin-walled?

[Guy_H]

ALuminised steel all the way. We build (through a separate company arm) aluminsied steel fuel tanks and for the cost saving over stainless, it makes you wonder why people still insist on stainless. The other benefits include:

Less suceceptable to stress cracks
Easier to weld (for those not good with a tig)
Better heat disipation (less heavy metal in the alloying)
Less brittle when hot

On a side note, what is (other than strength) the benefit of going to twin-walled?

Thanks Gav's - awesome feedback!

the twin wall is the exhaust tips - they look nicer & you can clean the inner lip as well. I'll try to post a couple of pics of the tips. We are very happy to get it out at this price considering the complexity of the heat shields. I have already seen the results of no heat shields & its not pretty.

[RoknRob]

Would there be a difference in weight?

If the aluminised stuff is cheaper AND lighter, and will likely last as long... it seems it would be a no-brainer...

[Guy_H]

Good question Rob, I don't think there would be much in it weight wise, I'll try to find out.

The market I understand has been driven to stainless steel over the past couple of decades due to the early 80's (and earlier) use of mild steel & harsh winter salt.

You standard Polo uses aluminised steel pipes & stainless mufflers anyway!

[gavs]

Good question Rob, I don't think there would be much in it weight wise, I'll try to find out.

The market I understand has been driven to stainless steel over the past couple of decades due to the early 80's (and earlier) use of mild steel & harsh winter salt.

You standard Polo uses aluminised steel pipes & stainless mufflers anyway!

Yeah, exactly. While stainless is stronger than regular mild steel, it's also less forgiving and has a much closer yeild:failure ratio. When stainless yeilds, it will generally fail pretty closely, especially with un-intentional heat treatment, such as in an exhaust.

[RoknRob]

I'm surprised you don't think it would be much lighter. Obviously, I know very little on the topic...

Is it because the parts ate small and light to begin with? Or is it because of the process? What is meant by aluminized steel anyway?

On another note, while winter salt may not be a consideration here, what about the salt from our coastal habitat?

[gavs]

Coastal Salt isn't an issue, while the air is more laden with salt it is not to the same extent as the european roads in Winter. I have been over there when they are salting the roads and it is litterally like an old, wheely bin garbage truck laying down a mix of rock salt and fine gravel. Imagine constantly driving though beach water and sand for 3 months and that's what it's like. We just don't get those conditions here.

Aluminised steel is a somewhat "New" alloy in that the constituants aren't alloyed together but the aluminium (not Aluminum, stupid americans, can't even correctly spell an element!) is fused, similar to a plating to the outside of the steel. It's a better, more stable and more environmentally friendly to zinc plating or galvanising. You would be more likely to see a weight saving advantage toward the alunminised steel but it wouldn't be really worth considering....

[Guy_H]

Will try to weigh an OE system vs ours when we next do an install.

[Bug_racer]

no option for titanium ?

[kaanage]

I'd love to see the price of a titanium exhaust!!!

For the non-technically minded, aluminized steel is like galvanising except for using aluminum rather than zinc as the coating (or alcad aluminum with mild steel being covered by raw aluminum instead of the body metal being an alloyed aluminum) - it's nothing like an alloy.

The fatigue properties of stainless may be better up near the turbo outlet where the operating temperature is high (this is where titanium really shines) but welds can be brittle and crack from vibration (although the welds will be as corrosion resistant as the rest of the sheet while this will not be the case with an aluminized steel fabrication). The other advantage of stainless steel is that scratches won't affect the corrosion resistance while aluminized steel will rust if the the scratch is deep enough to go through the aluminum cladding (something for the slammed crowd to consider).

Tensile strength of mild/aluminized vs stainless steel isn't very different (assuming both have been cold worked to a similar degree) but mild/aluminized steel is much easier to work with.

stupid americans, can't even correctly spell an element

What's wrong? We use the terms "sway bars" and "shock absorbers" so why not aluminum (and gasoline and tires)

[gavs]

What's wrong? We use the terms "sway bars" and "shock absorbers" so why not aluminum (and gasoline and tires)

Yes, but they are technical descriptions, not an atomic element that can only be that specific element, rumour has it according to my old chemisty lecturer that the reason they spell it differently is because it was so hard for them to proncounce that when someone said "Aluminum", they could not relate it to the true "Aluminium" spelling. Don't know how true that was, but I like it, it sounds feasible enough, especially considering whatching a doco in Queen last night, an ex journo from Rolling Stone said that Queen wasn't overley successful with their album "Jazz" in the US because the public couldn't understand that just because an album is called Jaz, there is no Jazz music on it, or the fact a band with 4 men could be called "Queen"

Technically it's classified by manufacturers as an alloyed material due to the aluminium having to be fused into the steel somewhat as the aluminium doesn't bond very well to the steel, unlike Zinc plating, e-coat, nitriding etc. Splitting hairs here though

Guy, I think you have had your question answered

[kaanage]

Eutectic mixture at the interface?

But it was the original name given to the element and it's shorter and we love US terminology here (add color to the list above)
World Wide Words: Aluminium versus aluminum

[Guy_H]

The Americans can't pronounce "Soldering" either

[RoknRob]

So will the system be clad inside AND out with alumin(i)um?

We may not get 3 months of harsh exposure to salt, gavs, but wouldn't continuous exposure at low levels add up? Just playing Devil's Advocate - is there a definitive study on the subject?

BTW, count me in as someone who is happy to teach his kids that both spellings are correct, depending on where you are. Just like I am happy to be called Roberto in Spain. It can be chips or it can be fries. It can be tomato or it can be tomato.

Can't we all just get along?