A surprising find...
#16
I agree with someone else, that you can get different grades of stainless steel that are magnetic.
Of course, if a magnet will stick to it, then it will rust (regardless of whether or not it's stainless steel).
Later, Steve
Of course, if a magnet will stick to it, then it will rust (regardless of whether or not it's stainless steel).
Later, Steve
Last edited by Steve Jarvis; 10-11-2011 at 11:21 AM.
#17
Magnets will stick to most common grades of stainless (sergical grade 304 for sure). Thinner tubing has less steel concentrated in the area that the magnet is touching. The greater the thickness the more likely a strong magnet will stick to stainless.
#18
without getting complicated, and Im no expert at this, the rule of thumb is that if a magnet sticks to metal , like on a exhaust part, its not stainless... I checked OEM exhaust flange and it does not stick.. nor rust... thus I would only assume high end after market exhausts would do at least the same ...
__________________
2001 996TT 3.6L and stock ECU
9.66 seconds @ 147.76 mph 1/4 mile click to view
160 mph @ 9.77 seconds in 1/4 mile click to view
50% OFF ON PORSCHE ECU TUNING BLACK FRIDAY SPECIAL
2001 996TT 3.6L and stock ECU
9.66 seconds @ 147.76 mph 1/4 mile click to view
160 mph @ 9.77 seconds in 1/4 mile click to view
50% OFF ON PORSCHE ECU TUNING BLACK FRIDAY SPECIAL
#20
I was curious so I did some reading. 400 series stainless is ferretic (magnetic) and the 300 series is austenitic (not magnetic). Both are not supposed to rust though. So either way those flanges are a no no. Dis-similar metals also promote corrosion. Aircraft have the issues fairly often. It bothers me to see a vendor that deals with mods with such a prestigious marque of car providing a product that they are selling under the assumption of it "what you pay for". If were the owner I would post the maker of the exhaust. I get aggrevated with the assumption that because we own porsches we should get charged a ridiculous rate whether the quality is good or not.
#21
I was curious so I did some reading. 400 series stainless is ferretic (magnetic) and the 300 series is austenitic (not magnetic). Both are not supposed to rust though. So either way those flanges are a no no. Dis-similar metals also promote corrosion. Aircraft have the issues fairly often. It bothers me to see a vendor that deals with mods with such a prestigious marque of car providing a product that they are selling under the assumption of it "what you pay for". If were the owner I would post the maker of the exhaust. I get aggrevated with the assumption that because we own porsches we should get charged a ridiculous rate whether the quality is good or not.
__________________
2001 996TT 3.6L and stock ECU
9.66 seconds @ 147.76 mph 1/4 mile click to view
160 mph @ 9.77 seconds in 1/4 mile click to view
50% OFF ON PORSCHE ECU TUNING BLACK FRIDAY SPECIAL
2001 996TT 3.6L and stock ECU
9.66 seconds @ 147.76 mph 1/4 mile click to view
160 mph @ 9.77 seconds in 1/4 mile click to view
50% OFF ON PORSCHE ECU TUNING BLACK FRIDAY SPECIAL
#22
I was always under the impression that mild steel flanges were used because they are less likely to crack and/or warp.
The exhaust manifold flange on my evo was mild steel and I never had any issues even after driving it through a winter. Didn't look all that pretty, but held up great.
The exhaust manifold flange on my evo was mild steel and I never had any issues even after driving it through a winter. Didn't look all that pretty, but held up great.
#24
LOL the last two sets that were on clients car leaked from the small little hex screws... plus the cheap plastic fitting on top leaks too... even if you screw it tight... odd...
__________________
2001 996TT 3.6L and stock ECU
9.66 seconds @ 147.76 mph 1/4 mile click to view
160 mph @ 9.77 seconds in 1/4 mile click to view
50% OFF ON PORSCHE ECU TUNING BLACK FRIDAY SPECIAL
2001 996TT 3.6L and stock ECU
9.66 seconds @ 147.76 mph 1/4 mile click to view
160 mph @ 9.77 seconds in 1/4 mile click to view
50% OFF ON PORSCHE ECU TUNING BLACK FRIDAY SPECIAL
Last edited by markski@markskituning; 10-11-2011 at 03:09 PM.
#25
VAGscum has it right. The 300-series (austenitic) stainless steels contain Cr and Ni, and are non-magnetic. The 400-series (ferritic) stainless steels contain Cr, but no Ni, and are magnetic. The 400-series alloys transform around 700C (dull red) to austenite, accompanied by a fairly large volume change. That would make them a very poor choice for an exhaust flange. Probably the flange Markski found was just plain steel.
The 300-series alloys are susceptible to corrosion when welded. There are lower carbon grades 304-L and 321-L that were developed to eliminate this problem. I believe that the cost is almost the same for the lower carbon grades. Might be worthwhile to switch.
Jon
The 300-series alloys are susceptible to corrosion when welded. There are lower carbon grades 304-L and 321-L that were developed to eliminate this problem. I believe that the cost is almost the same for the lower carbon grades. Might be worthwhile to switch.
Jon
#26
Yep... amazing indeed eh?!?! I used them on my car back in 2002 and then pulled the plug on ever selling those darn things. The nipples are a big POS too and leak/break.
#27
If you want a Shock, go and get the wife best Stainless Steel cutlery and put a Magnet on it. You will find it sticks to it. That's food grade SS
ps the OEM muffler is supposed to be SS but when I took mine off there were patches of corrosion just starting to blister.
ps the OEM muffler is supposed to be SS but when I took mine off there were patches of corrosion just starting to blister.
#28
Its funny, non ss flanges get a bad rep but in reality a proper low carbon mild steel flange in many ways is better.
-Mild steel expands at almost 1/3 of a lower rate then ss. This puts less stress on welds, and fasteners under extreme conditions.
-It retains less heat under operation as well as durning the fabrications process.
-Mild steel is MUCH easier to cut flat again if you need to.
-Is cheaper (not that cost of flanges is really a concern at this level).
When we build a header/turbo manifold for a car that high egt will defiantly come into play, we exclusively use mild.
Basically the only downside I can see is corrosion.... but its not like many of these cars are driven in the snow/salt belt.
We give our customers the option of ss when building custom parts but generally recommend mild(flanges only).
For what its worth, the headers I build for my own Cayman had mild steel flanges.
-Mild steel expands at almost 1/3 of a lower rate then ss. This puts less stress on welds, and fasteners under extreme conditions.
-It retains less heat under operation as well as durning the fabrications process.
-Mild steel is MUCH easier to cut flat again if you need to.
-Is cheaper (not that cost of flanges is really a concern at this level).
When we build a header/turbo manifold for a car that high egt will defiantly come into play, we exclusively use mild.
Basically the only downside I can see is corrosion.... but its not like many of these cars are driven in the snow/salt belt.
We give our customers the option of ss when building custom parts but generally recommend mild(flanges only).
For what its worth, the headers I build for my own Cayman had mild steel flanges.
#29
I was curious so I did some reading. 400 series stainless is ferretic (magnetic) and the 300 series is austenitic (not magnetic). Both are not supposed to rust though. So either way those flanges are a no no. Dis-similar metals also promote corrosion. Aircraft have the issues fairly often. It bothers me to see a vendor that deals with mods with such a prestigious marque of car providing a product that they are selling under the assumption of it "what you pay for". If were the owner I would post the maker of the exhaust. I get aggrevated with the assumption that because we own porsches we should get charged a ridiculous rate whether the quality is good or not.
#30
I just wanted to point out that not all are equal... some are poorly made.. others use cheap connections and leak, and the rest are probably made in underdeveloped countries... I get hit up by prospective clients often saying why mine is more money vs this one or that one... I just wanted to point out that it comes down to details.. and this is one of them... Ironically that exhaust has the best cats on the market..
"I know any good welder would know to use 309 instead of 308 on stainless to steel. No? "
I am not an expert with metalurgy or welding so I wouldn't know what 309 or 308 stainless is much less their attributes in this application. I am sure somebody like Markski or another fabber could answer this. I would expect that if they were going to use a particular metal type if would be best to use nothing but that metal type so that the weld joints are not weakened by the dis-similar metals. But I wouldn't be suprised if a good welder has trick to make it work.