Copper heats faster and is immune to corrosion (in the case we are interested in water gas). Stainless steel ditto but heats slower
You mean to put a copper pipe inside the exhaust pipe? What diameter? How to weld it at the junction with the steel of the exhaust pipe? (I am not a welder
The copper for a diesel engine passes but not for a gasoline engine .. this does not live lives ..
It is a copper tube that drives the exhaust gases into my boiler on the Chevrolet the duration is less than a year the copper becomes all hardened and finished by casing.
Well in agreement with Laurent that the preheating tube must be in the exhaust outside it is complicated to make contat to get the heat (it must be welded and in addition isolated, while inside not Of problem besides the restriction that this causes to the exhaust, as it is a definitive job to take good materials, one is not interested to return in the exhaust pipe.
In copper, insert in an exhaust tand that there is water in drop or suspension no problem but if you operate dry it is too hot on a gasoline engine, I prefer the stainless steel despite its inetie thermal..
To weld copper with steel or stainless steel, it is necessary to use brass brass, or to make mechanical joints with collar turned down. But welding is preferable ..
For spraying either an injection like Pitmix or a small carburetor that spits into a stainless steel tube in the exhaust as I do. Either as Michel GV. Or drip into the heated tube.
Andre