[disturbed1]

may have been covered before but curious to see if people out there have had any prob with their ssautochromoe or similar manifold cracking.. also what lengths have u taken to reduce the risk of 1 cracking suck as flexi pipes used in the downpipes or turbo/exhuats braces to support some of the weight.. i was told by 1 person to not support it and just let it move where it wants to when it warms up cause trying to restric the movemnt or 6 different length runners will cause additional stress on the welds -

anyway lets here what u guys running these manifolds have to say

 

[supra8795]

Well some say to get it jet hot coated to help it from cracking and some say that it doesnt help. I myself went ahead and got it coated because every little bit helps. Some people have braced it but i havent yet although i have thought bout doing it in the future. I also was told to put a flex setion in the down pipe and i did that also. Hope this helps.

Dustin

 

[suprra_girl]

k so who has ss autochrome manifolds on their cars and key word... running
has anyone had them crack yet?

i'm thinking... they're cheap enough, so i'm just gonna stick it on as it is.. and see what happens

 

[1988SupraDreams]

"And see what happens" I like your attitude :lol: Good Luck :bigthumb:

 

[suprra_girl]

well i have it on good authority that being a 6 cyl and top mount we shouldn't have too many issues..... i guess i'll find out lol

 

[tsuper92]

i put a flex section in my dp.i also welded a support bracket off the t4 flange.i have a stay that bolts from that to one of the motor mount bolt's.it's been on for almost 500 mile's with a few 45 minute drive's on the highway(egt's up at 600deg cel.)

 

[Krister]

Here's a brace that my mech did:

 

[MADSUPRA88]

I have one on the car as we speak, runs great. no crack no nothing, i didnt have to mod it up at all, because i though it was braced enough out of the factory, unless i was the only diff one, heres a pic chek around the welds, see those little tabs welded form the runner to the base. i thought that was good enough, and havnt had a problem yet. hope this helped good luck

by the way, i dont have a flex pipe er anything, juss a 90 degree pipe.

 

[harwewe1]

we just had to fix Jwcatto's cracked up HKS manifold. It had cracks all around the turbo flange and down two of the seams right under the flange. This is the 2nd HKS I've seen cracked but I've also had to have a Greddy fixed. I think all of the damn things whether they are expensive or cheap are made by the same damn Chinese company.

 

[MadMaxx]

This is the 2nd HKS I've seen cracked but I've also had to have a Greddy fixed. I think all of the damn things whether they are expensive or cheap are made by the same damn Chinese company.

HKS sources to Taiwan.

 

[bftsupra]

I have been running one for almost a year. I added a couple of 10mm rods from the main flange to the turbo flange just to help support the turbo. Works fine so far, doesn't mean it needed it but it sure didn't hurt anything.

 

[blackout_89t]

I added a brace on each side of the t4 flange that was welded onto the head flange. You can also see the horid discolouration of the steel.

 

[Suprawill1]

They are ALL prone to cracking especially if they are Stainless. SS is a hard steel which is susceptible to going brittle after repeated heat cycles, 304 or otherwise. Coating will deter some of the heat soaking but will not stop the effects of heat cycling. There are 3 things that are proven to further resist cracking, only one of which will pertain to the SS Autochrome.

1. Bracing (counters the forces of turbo & DP weight)

2. Thicker tubing with tube in flange welding (vs butting)

3. Milder steel (less susceptible to becoming brittle from heat cycling)

Mild steel with coating is the best way to go with a longer tubular style.
Cast is probably the better for the shorter style but even cast has been documented for cracking.

Bracing will not restrict the tubes from heat cycling natural movement. In fact not bracing promotes cracking from all that weight.

 

[driftedmk3]

i heard welding brace to the manifold helps and it support the weight of the turbo.

 

[adam pecush]

Quality 321 or 304L tubing welded with 347 consumable will not be susceptible to sensitization (intergranular corrosion) upon heat cycling and will not become brittle. A manifold made of this will retain its strength for quite some time, however, with inadequate bracing, all sorts of problems may develop. Thicker tubing is not the answer as the major problem seems to stem from the welds - an overmatched weld material(weld stronger than the base metal) would go a long way in reducing cracking.

You gotta be way more specific with "mild" steel. Many steels will be terrible as manifold steels. Off the top of my head, look to ASTM A335 for a list of steels. P9 or P5 would be solid choices for a manifold, as they are both highly weldable and have good creep resistance.

They are ALL prone to cracking especially if they are Stainless. SS is a hard steel which is susceptible to going brittle after repeated heat cycles, 304 or otherwise. Coating will deter some of the heat soaking but will not stop the effects of heat cycling. There are 3 things that are proven to further resist cracking, only one of which will pertain to the SS Autochrome.

1. Bracing (counters the forces of turbo & DP weight)

2. Thicker tubing with tube in flange welding (vs butting)

3. Milder steel (less susceptible to becoming brittle from heat cycling)

Mild steel with coating is the best way to go with a longer tubular style.
Cast is probably the better for the shorter style but even cast has been documented for cracking.

Bracing will not restrict the tubes from heat cycling natural movement. In fact not bracing promotes cracking from all that weight.

 

[Suprawill1]

Quality 321 or 304L tubing welded with 347 consumable will not be susceptible to sensitization (intergranular corrosion) upon heat cycling and will not become brittle. A manifold made of this will retain its strength for quite some time, however, with inadequate bracing, all sorts of problems may develop. Thicker tubing is not the answer as the major problem seems to stem from the welds - an overmatched weld material(weld stronger than the base metal) would go a long way in reducing cracking.

You gotta be way more specific with "mild" steel. Many steels will be terrible as manifold steels. Off the top of my head, look to ASTM A335 for a list of steels. P9 or P5 would be solid choices for a manifold, as they are both highly weldable and have good creep resistance.

Hi Adam,
Always good to hear someone elses 2C.
When I checked around to metal specialists and tubular manifold fabricators, coated mild steel is what they recomended. It was confirmed by more than 3 sources concerning the brittle nature of a hardened steel like the 321. Of course, it would take more heat cycles than 304 or other inferior choices.
I would be curious as to what problems you think would develop from inadequate bracing even on the 321 or 304L SS.
Also, I've seen where tubes and collectors have been compromised in opposed the the weld as far as cracking. It appears that both should be addressed.
Going with your recommendation of overmatched weld material, I would think that a thicker tubing would be prudent in that situation considering what we've both seen. Tests on the SS Autochrome came up with average or less thickness than what its competitors were offering.
As far as the mild steel, this is what the metalurgical specialists and tubular builders recommended. You seem to have the inside track pertaining to the type.
I personally am not as versed to be more specific in this matter so I would turn to your recommendation for the P9 or P5.

 

[adam pecush]

Hi Adam,
Always good to hear someone elses 2C.
When I checked around to metal specialists and tubular manifold fabricators, coated mild steel is what they recomended. It was confirmed by more than 3 sources concerning the brittle nature of a hardened steel like the 321. Of course, it would take more heat cycles than 304 or other inferior choices.
I would be curious as to what problems you think would develop from inadequate bracing even on the 321 or 304L SS.
Also, I've seen where tubes and collectors have been compromised in opposed the the weld as far as cracking. It appears that both should be addressed.
Going with your recommendation of overmatched weld material, I would think that a thicker tubing would be prudent in that situation considering what we've both seen. Tests on the SS Autochrome came up with average or less thickness than what its competitors were offering.
As far as the mild steel, this is what the metalurgical specialists and tubular builders recommended. You seem to have the inside track pertaining to the type.
I personally am not as versed to be more specific in this matter so I would turn to your recommendation for the P9 or P5.

Basically with inadequate bracing on any manifold, you are allowing the metal to be experienced to a considerable amount of stress, both cyclic and uni-directional. For long term service life, problems such as fatigue cracking and creep damage will likely occur (also alloy-dependant).

You mentioned the brittleness of 321 as compared to non-stainless alloy steel. As a matter of fact, stainless steels such as 321 and 304 do not perform any worse than their alloy counterparts (they aren't actually hardened, they have an austenitic structure which is responsible for their mechanical properties); A P12 steel (1 Cr - 0.5 Mo) has a UTS of 415 MPa, a yield strength of 220 MPa and a min. elongation of 30% (in 50mm) Comparitavely, a TP321H (18Cr - 10Ni - ~0.5Ti) stainless tube has a UTS of 515 MPa, a yield strength of 205 MPa, and a min. elongation of 35%. These materials have quite similar properties, with the 321 having considerably better high temperature characteristics.

As for tube thickness, there is no doubt that a maximum thickness should be adhered to - if it is in fact the tube itself that fails, the tube is either a) completely unacceptable metallurgically speaking, or b) the wrong tube for the application. With quality tubes, overmatched welds, and adequate bracing, there is no reason for a manifold to fail, no matter what steel it is made of (within reason that is)

All of the tubing I am referring to is from ASTM standards A213 and A335 (Standard specs for Seamless boiler, superheater and heat exchanger tubes and Standard spec for ferritic alloy steel pipe for high temp service, respectively)

If anyone has a cracked manifold which they have junked, I wouldn't mind having a look at some of the sections to get an idea of what caused the failure.

 

[BrokenSupra]

best way to have it not crack is not to buy one

 

[Suprawill1]

Basically with inadequate bracing on any manifold, you are allowing the metal to be experienced to a considerable amount of stress, both cyclic and uni-directional. For long term service life, problems such as fatigue cracking and creep damage will likely occur (also alloy-dependant).

You mentioned the brittleness of 321 as compared to non-stainless alloy steel. As a matter of fact, stainless steels such as 321 and 304 do not perform any worse than their alloy counterparts (they aren't actually hardened, they have an austenitic structure which is responsible for their mechanical properties); A P12 steel (1 Cr - 0.5 Mo) has a UTS of 415 MPa, a yield strength of 220 MPa and a min. elongation of 30% (in 50mm) Comparitavely, a TP321H (18Cr - 10Ni - ~0.5Ti) stainless tube has a UTS of 515 MPa, a yield strength of 205 MPa, and a min. elongation of 35%. These materials have quite similar properties, with the 321 having considerably better high temperature characteristics.

As for tube thickness, there is no doubt that a maximum thickness should be adhered to - if it is in fact the tube itself that fails, the tube is either a) completely unacceptable metallurgically speaking, or b) the wrong tube for the application. With quality tubes, overmatched welds, and adequate bracing, there is no reason for a manifold to fail, no matter what steel it is made of (within reason that is)

All of the tubing I am referring to is from ASTM standards A213 and A335 (Standard specs for Seamless boiler, superheater and heat exchanger tubes and Standard spec for ferritic alloy steel pipe for high temp service, respectively)

If anyone has a cracked manifold which they have junked, I wouldn't mind having a look at some of the sections to get an idea of what caused the failure.

It's uncanny that the more metallurgical techs you talk to, the more conflicting answers you get. I guess it's all trial and error from there.
I'm sure, in a perfect setup with your metallurgical experience and the perfect engineering for the MKIII, the right manifold could be had for over 2K.
So, in conclusion, the only answer to prevention of cracking on the SS Autochrome would be bracing. Correct?


Out of the 4 cracks that I've seen, I only know one of the owners personally and he did not junk his. It was repaired. It was a cast HK$ longrunner.

 

[Suprawill1]

best way to have it not crack is not to buy one

Isn't that a little like saying, if a Supra is going to eventually break down then don't buy it?