Stainless backgassing

[Mach1]

What are the consequences of not back gassing stainless?
Am I looking at exhaust lasting 10 yrs instead of 20? Any real world experience?

[racrguy]

[ame]http://www.youtube.com/watch?v=02U0H15_WEg[/ame]

[turbostang]

A lot of it depends on what the part is used for, if it's heat cycled a lot like exhaust - it should be backpurged to be done 'correctly'. I've done it both ways and haven't had any real problems either way. There's so few people willing to do turbo kits out of stainless because of material cost and labor cost - it's tougher to cut, it should have a back purge, and it's a LOT harder to form.

The guy in the video doesn't really say it, but notice he welded the backpurged part first and then the non-purged part? By the time he welded the non-purged part, the tubes were heat saturated REAL bad. This makes the 2nd half of that part like he's welding with 50-100% more heat - which makes that 'sugaring' in the inside a lot worse looking. In fact, I'd say he started on the purged part a little too hot. Maybe he did it for illustration purposes, idk.

There is an alternative to backpurging. It's not 100%, but it works pretty good. SolarFlux. It's a grey flour looking powder that you mix with methanol or HEET (that stuff you put in the gas tank!) of all things. You brush it on the inside of the tubes and weld them together, as that stuff burns away it makes a flux similar to what you'd see with an arc welder.

[Mach1]

A lot of it depends on what the part is used for, if it's heat cycled a lot like exhaust - it should be backpurged to be done 'correctly'. I've done it both ways and haven't had any real problems either way. There's so few people willing to do turbo kits out of stainless because of material cost and labor cost - it's tougher to cut, it should have a back purge, and it's a LOT harder to form.

The guy in the video doesn't really say it, but notice he welded the backpurged part first and then the non-purged part? By the time he welded the non-purged part, the tubes were heat saturated REAL bad. This makes the 2nd half of that part like he's welding with 50-100% more heat - which makes that 'sugaring' in the inside a lot worse looking. In fact, I'd say he started on the purged part a little too hot. Maybe he did it for illustration purposes, idk.

There is an alternative to backpurging. It's not 100%, but it works pretty good. SolarFlux. It's a grey flour looking powder that you mix with methanol or HEET (that stuff you put in the gas tank!) of all things. You brush it on the inside of the tubes and weld them together, as that stuff burns away it makes a flux similar to what you'd see with an arc welder.

I heard of a crazy trick the other day where a guy was suggesting masking tape on the back of the weld, when it catches on fire it burns up the oxygen around the weld, pretty wild.

[turbostang]

I heard of a crazy trick the other day where a guy was suggesting masking tape on the back of the weld, when it catches on fire it burns up the oxygen around the weld, pretty wild.

The only problem with that is that it stinks like hell, and It contaminates the weld - Have you ever tried to weld any where near masking tape? It burns REAL good..

[Mach1]

The only problem with that is that it stinks like hell, and It contaminates the weld - Have you ever tried to weld any where near masking tape? It burns REAL good..

I just tack xyz up, then pull off the tape, never usually close enough to burn it, yet!

[Matt]

Some guys use flux instead of backpurging

[Mach1]

Some guys use flux instead of backpurging

Did you purge the exhaust on Phil's ls1 240sx?

[Matt]

yes

[Matt]

Here's what I use

[one slow 5.0]

Here's what I use

Where did you pick those up at and how much?

[Matt]

I got them from a local guy when he closed down shop. Online pricing is about $250 or so. I don't remember who makes them off the top of my head. He hardly ever used them and didn't believe in back purging LMAO