My friend said that most stuff is 304 and that 321 is marine quality.

 

Okay, I was worried about heat. I'm sure 304 will be okay but it sounds like I shouldn't coat it. Turbo Tech uses 304 on their manifolds too. I guess 321 costs twice as much.

Found a little about the two metals here:

http://www.brownmetals.com/techinfo/....asp?Alloy=321

Type 321 is a stabilized stainless steel which offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range from 800 to 1500° F (427 to 816° C). Type 321 is stabilized against chromium carbide formation by the addition of titanium.
While Type 321 continues to be employed for prolonged service in th4e 800 to 1500° F (427 to 816° C) temperature range, Type 304L has supplanted this stabilized grade for applications involving only welding or short time heating.

Type 321 stainless steel s also advantageous for high temperature service because of its good mechanical properties. Type 321 stainless steel offers higher creep and stress rupture properties than Type 304 and, particularly, Type 304L which might also be considered for exposures where sensitization and intergranular corrosion are concerns. This results in higher elevated temperature allowable stresses for this stabilized alloy for ASME Boiler and pressure Vessel Code applications. The Type 321 alloy has a maximum use temperature of 1500°F (816° C) for code applications like Type 304, whereas Type 304L is limited to 800° F (426° C).

<small>[ February 05, 2003, 02:22 PM: Message edited by: rodent ]</small>

 

Have LOTS of money to spend on piping and mandrel bends for a 321 setup. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> It might be cheaper to buy a mandrel bender. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

The 304 seems to be right at half the price of 321. I say get the 304 and coat it. Did turboengineering give any reasons for being against that? Somebody might know but, isn't the surface of 304 stainless prone to flaking in extreme conditions(turbo manifold heat cycling)?

321 better last forever though for the price. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

John

 

TEC basically said 304 is not the best material to be used for a turbo system. It might have problems over time. The jet hot coating will make it much hotter for the 304 stainless.

After reading some more on the net, it seams that 304 is OK for most exhaust applications but is not the ideal stainless for turbo applications. The problem with 304 is that it allows carbon precipitation at elevated temperatures, 800 degrees F to 1600 degrees F, right in the range of an exhaust system. Carbon precipitation is the movement of carbon to join with the chromium in the stainless, this causes the stainless to become more susceptible to corrosion and over time become brittle and form cracks in the headers. Turbo Tech said they had this problem but now they don't (using 304). <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

I don't want to pay for a turbo system where down the road it will start to crack.

 

what kind does turbotech use? that hasnt been mentioned so far but talking to rob on the ls1m kit he was telling me that the stainless in the new kit in the pipe and in the weld is superior to the tt kit.

is there a stanless thats worse than 304?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MIGHTYMOUSE:
<strong> what kind does turbotech use? that hasnt been mentioned so far but talking to rob on the ls1m kit he was telling me that the stainless in the new kit in the pipe and in the weld is superior to the tt kit.

is there a stanless thats worse than 304? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Turbo Tech uses 304. The lowest grade looks to be 304L.

http://www.sppusa.com/reference/white_paper/wp_ss.html

<small>[ February 05, 2003, 03:17 PM: Message edited by: rodent ]</small>

 

I was talking to Turbo Engineering (www.turboengineering.com) and they suggested running 321 Stainless for a proper Turbo setup. They were totally against Jet-Hot coating the 304 where the 321 you could. I'd like to Jet-Hot coat the manifold/downpipe to reduce under hood temps.

I noticed 304 is used for the LS1M kit where CAS runs both (321 for manifold, 304 downpipe).

Any thoughts on this?

 

Build as many of the hotparts as you can out of 321. It will last alot longer, and stand up to the heat vs 304. I would limit your 304 stainless to the downpipe, and possibly the crossover if you are doing a single kit. Price means nothing when it starts to come apart down the road!

Chris

 

321 is optimum. If you can afford it, use it.

I am using 304. Ive seen people use STEEL headers at length with no problems. I figured the 304 would last me long enough. And given it is cheaper, even if I totally rebuilt my system 5 years down the road, I would still have gotten my money out of it.

So far, my headers have held up just fine. I dont have a real lengthy run time on them yet though so cant really make a good desicion based on that.

Good luck.

 

Honestly, I would worry a lot more about the care taken during the welding of the manifolds than I would about the material.

And I'm not sure that I would coat either one.

 

With the right thermal expansion allowances (stainless expands a lot), slots in header flanges and and allowable expansion in the exhuast system cracking will be reduced. Also do complete welds on the inside of the tubes (pressure boundary), and partial welds on the outside will help a lot. Also dont hang or support the turbo only from the headers, fabricate brackets that will carry the majority of the weight, but still allow movement.

The 300 series stuff is all pretty good, and 304 is diffently cheaper. We use the 304L in everything we make because of the low carbon content.

Gary

 

If I were building headers for a turbocharged application with sustained high temperatures in an enclosed application I would use 321 period!

If the application were not sustained nor enclosed I may or may not use 304 instead for cost reasons.

Both 304 and 321 have excellent resistance to thermal conductivity and therefore typically don't require a coating or wrap to keep heat in. In fact keeping heat from escaping may cause scaling to occur under extreme conditions (both sustained extreme heat and enclosed conditions). Scaling can cause portions of the metal to flake causing these particles to impact the turbocharger fins causing destruction of the part.

For maximum longevity I would also use 321. I have no idea though as to the lifecycle of 321 versus 304. It all depends on the heat and the stresses placed on the parts. A relative of mine who happened to be responsible for stress testing aircraft materials for the military gave me some formulas to figure out stress failures due to heat of stainless. Unfortunately this was done over a few beers and for the life of me I can't recall them...LOL... If I see him again I'll keep notes. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Well anyway...that's my 2 cents on the subject.

 

Cost wise 321 is approx 15-20% more in cost. If you buy in bulk you would be suprised how much of a discount you will get at places. (this is what I did) The 321 is very good (inconel even better but chaaaaaaaaaaachingggggggg$$) I personally feel that 304 will do the job that most all of us are going to be using this tubing for. Reason i say this is that most are not pushing the turbos hard really (12 psi is just getting warmed up imo) When my turbo and engine builder got together and were talking about 25-30 psi that is when I was really glad I got alot of 321 tubing <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
<a href="http://groups.msn.com/Zturbo/partsforsale.msnw?action=ShowPhoto&PhotoID=320" target="_blank">My 321 tubing <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> </a>

If you are going to spend the money to build a top of the shelf turbo system the cost factor from 304-321 is not much at all. When you factor in that a good set of wastegates cost $500+ a piece.

As for jet hot coating the 304 tubing i don't think I would even bother. I had my tt system coated when i had it and most flaked off, had it sent back and did the same. After talking to them they really don't have a coating that can take the heat. The only coating that i feel can take the heat is swain coatings high temp coating. Now it is ugly as all get out but works.

Steven

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by rodent:
<strong> I was talking to Turbo Engineering (www.turboengineering.com) and they suggested running 321 Stainless for a proper Turbo setup. They were totally against Jet-Hot coating the 304 where the 321 you could. I'd like to Jet-Hot coat the manifold/downpipe to reduce under hood temps.

I noticed 304 is used for the LS1M kit where CAS runs both (321 for manifold, 304 downpipe).

Any thoughts on this? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The main difference in application between 304 and 321 is the temperature range at which they are designed to be used in service. At ~1600F, a header constructed from 304 begins to diffuse carbon from itself. If you're running high EGTs in the 1600+ range, the 304 will begin to significantly weeken itself to the point that your header will begin to crack or just fall apart all together. If you're building a high horsepower race car that is going to see high EGTs, then 321 is the way to go. A prime example of this is Kent Rudbeck's Rosewood Buick. Kent was going through two sets of headers made from 304 in a season due to the ellevated EGTs he runs at (1800F +). After 3-4 months the headers would be so delapitated that trying to weld all of the cracks was self defeating. 304 also does not have the high temperature corrosion resistance that 321 has.

If you have a lower horsepower application that doesn't see daily use, 304 would work.

If you have a lower horeepower application that you drive daily, 304 is going to crack in a turbo application though adding expansion joints to reduce the thermal fatiguge expansion helps alleviate some of the tendenacy to crack.

If cost is no concern, 321 is the way to go.

<small>[ February 08, 2003, 03:03 PM: Message edited by: Tony DeQuick ]</small>