Holed Exhaust System

[MD]

Ever wondered why the exhaust system on your 116 or 105 seems to rust out a lot sooner than the system on a modern Alfa? No, it is not the Russian steel theory. There is a bit of science behind it.

Actually it all starts with sulphur.

Our fuels contain sulphur and exhaust emissions pass sulphur laden gases out via the system. Depending on the temperature of the gases along the exhaust path, at some point along the chain these gases reach a "dew point" and deposit sulphuric acid in the internals of the mild steel pipework and mufflers. Typically around the over the axle area. This is why mild steel exhaust systems usually rust out the rear exhaust part of the system first.

So what about the new cars?

A by product of the Clean Air pursuit from legislators and manufacturers has been to incinerate the products of unburnt or partially burnt gases before they leave the exhaust pipe. This is being done by the uses of a catalytic converter in the main and by the use of insulated pipe wraps to keep the gases as hot as possible so that any residue of sulphur has a "dew point" beyond the exhaust system. Effectively there is far less impact of the sulphur on the exhaust system as there is very little of it to do the damage.

Solution for 105/116 cars

When is a solution never about how deep your pockets are? This is no exception. We can't do much about the sulphur in the fuel so the answer lies in materials resistant to it.

If you want to install a lifetime exhaust system on your classic machine, the system should be made of stainless steel. Type 304 will do but 316 is better. This should include all the flanges and mufflers. The key thing about the mufflers is that the internal baffles in the mufflers must be stainless as well. They are not always so as manufacturers try to be price competitive and use mild steel baffles thereby compromising everything- something to be wary of.

So there you go. Problem you have been losing sleep over has just been solved. Cheers, MD

[TEE Z2]

I had an Alfasud in the 1980's. The only thing that rusted faster than the body was the rear muffler. I was young and broke and I bought an Ansa rear muffler as a luxury performance upgrade. It lasted 11 months.

[MD]

Not quite the same issue but it does centre around the exhaust systems ....
At one stage I thought it a good idea to minimise the heat under the bonnet and do an insulation wrap around my cast iron headers. BIG MISTAKE. Yes, there was a heat reduction but there was also a not so welcome crack in the cast iron headers.

For modified cars that are prepared for racing there are often problems trying to reduce heat, especially radiant heat onto hydraulic systems, fuel systems, intakes etc. It's tempting to insulation wrap the headers but in my case, I have found that to do so simply accelerates their corrosion if they are made of mild steel. Never used stainless in this application so I cannot say.

My solution has generally been heat deflectors where possible instead of wraps. No experience with turbo set ups so I cannot comment. I use superchargers.