Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Some interesting info on Header Wrap

That's a decent & even slightly informative post Terry but on the material front you completely skipped any real world information in favor of theories and conjecture. You state it just like most others that do not grasp the strength of the materials involved. Your statements are right along the same lines as your out right statement the stock rods will not last because there are PM forged and thus will shatter like glass. You never gave any actual information and data to prove your point just like in your latest post (or most of your posts actually) and spout off a few technical terms and expect everyone to just blindly follow you. (then when they didn't you left ala Dom???) Well just like history has repeatedly proven many times is the past your unproven theories are normally incorrect logic and thinking. Your current allusion that mild steel will fail rapidly has to have some actual credence to it. Your use of the term rapidly would make people think days or months when in actuality it is several years. More proof of real world data and individual testing denouncing conjecture, hearsay, and cliff note theory.

I would be impressed if you actually used proof & hard data instead of empty threats, name calling, and just basic theory formulation. Words without proof are merely just words regardless of a piece of paper. Also because I know this is going to come up. When did you get your degree? How out of date is it now? Students now days are talking your degree in just their first two years of school. (US students) I bet the math you took is taught in junior high or high school now. Times change. Technology changes. There is a high percentage of people with engineering experience on this site and you think you are the only one that can state anything that has any technical knowledge in it. Well you are sorely mistaken and often wrong.
[/end of get of your high horse rant]

tell us how you realy feel

I'm sure my time at Benteler gave me a lot of info & it wasn't that long ago, all those materials are still in current use. What is your problem Demon??!!!

Low carbon steels have an oxidation resistance of around 500>800 deg F,ferritic s/steels run 1500>1700 deg F, austenitics run from 1500>2000 deg F...what else would you like to know about the construction and material in the stoc exhaust manifold...all the info is from the company that made them, Benteler. Any info you want on stainless steels re: elongation(%), yield strength @ 1600 deg F(in psi), thermanal expansion rate, benifits etc , just ask away!..my data is from Armco Adavanced Materials, Allegheny Ludlum Steel Co,T he American Iron & Steel Institute. FWIW!

For the 'masses'...attached! Normal carbon steel are crap for modern engines with high feed gas temps and cats....lets add exhaust manifolds, hydroforming, stainless steels etc to the MTX debate at SZ 06...eh!

Those are all high chromium and chromium nickel based stainless steels, not basic mild steel.

I don't know that we really can do any debate of hydroforming since none of us knows enough about it right? We also can't get that kind of part from the aftermarket so I'm guess the primary choices will be single walled stainless or mild steel, with mild steel being the predominate form of material we will use.
So are we all in trouble? I don't think so. I mean it won't last forever but it ought to be sufficient for most peoples purposes.

The big problem with mild steel is the diffusivity of the material at the grain boundaries causes cracking at elevated temperatures. Stainless also suffers with this but it has a higher service temp. It is a time-temperature based problem with some concern due to the atmosphere that the metal is subjected to.
I don't think we have enough information with our applications to honestly say what the lifespan of a mild steel part is without actual testing.

However, some speculation RE: MSDS headers; they have ceramic coating on the inside, this isolates the steel from the gasses you have flowing in the exhaust stream depending upon thickness and porrosity of the layer. Therefore the risk of failure is probably from intergranular diffusion, not really from oxidation. The diffusion of carbon and other alloying elements to the grain boundaries will make the mild steel brittle along those grain boundaries and softer in the middle of the grains where the carbon used to be, and likely to crack under stress. How long will be dependent upon the amount of time that the temperature stays AT or above the diffusivity point, or 2/3 the melting point of the material. Keep the amount of time at or above this point to a short period and the material ought to last quite a while. Eventually they will crack but based on what I've seen of temps in a production (non-race) car I would guess it would be in terms of years as long as they are coated internally; even though todays engines run higher temps than in years past. Of course no wrapping will let the heat conduct to the air easier and keep it cooler therefore will last longer.

...the point I'm making is that the stoc V6 system is made of better quality material than most all aftermarket parts. It was made that way for a reason re: cats, feed gas temps, under hood temps etc. I'd suggest that the data of aftermarket parts materials be compaired to the stoc parts before we all go gung ho on the old BS that aftemarket must always be better than stoc, which, in a lot of cases, is incorrect re: material specs. I further doubt than most aftermarket parts go thru the same durability testing, quality checks etc as the OEM parts have done. Buy what you wish but don't keep kidding yourself that aftermarket is always better.

...even with high grade stainless steels, operations are performed between each stage of working /forming the material. Example, most tubes are supplied pre-annealed. After they are say bent they are annealed again before say hydroforming. This maintains the workability of the material and prevents cracks and splits. Most steels work harden,incl low carbon mild steels. Adding these heat treating steps goes a long way to improve the durability of the final product and we know even welding with localised heat causes the material to become brittle in the area of the weld. This is all basic stuff used when forming and
working materials and is the same now as it was years ago. Many other factors come into play in a fabbed manifold such as 'weld draw', this is the amount of distortion on an assy caused by the heat and the 'order' in which it is welded together. A good company will carry out weld draw testing to establish the 'best order' the welds should be done to say, reduce deformation of flatness on the port flange, again this is all basic engineering practice and has been around for years....Don't get upset, I'm just trying to
improve your know-how....

Todras is channeling, again.

No, I'm not upset at all. I agree about the materials part being high quality on OEM. I used the OEM stainless manifolds as a basis for my last set of turbo pipes. I also highly doubt that any of these small header companies did ANY research into weld draw, hardness testing, or even annealing though that last would be easy enough with a high temp furnace. They probably do all their product evolution/redesign through analysis of failed returns.

I just felt it was important to point out some of the conditions that the parts we are buying would be subjected to and that I don't think the average buyer is going to wear them out too quickly even with header wrap, though they need to be aware of the problems associated with wrapping mild steel, and most especially for those in the winter areas where salt on teh roads will get tied up into the header wrap and sit there rotting out the pipes under the higher temps.

I'd read everything about header wrap before I wrapped my headers but I did it anyway.

Of course I swaintech'd my headers first and then wrapped them on top of that... and even with what people claim is about the best header wrap you can get the wrap is still blazing hot after a short period of running... nothing's keeping those 1600 deg temps in I guess.. silly turbo cars.

And just to bring up powdered metal rods.. I did some work for a company that makes a ton of powdered metal rods and they were starting production for an aftermarket company for 350 chevy's I think in the 600-800 hp range. Saying powdered metal rods are junk is just silly.. they can control the metalurgy so closely I can imagine powdered metal being the way to go.

OK.. enough rambling off topic.. nobody listens to me anyway.