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FWIW, Stainless is an excellent material for an exhaust system. Just like any other material, grade is important. Low grade material will not hold up well.

Mild steel is economical and easy to work with, but is inferior to stainless for the high temperature environment of a header. The usefull lifetime of a mild steel component will not be near that of a quality stainless piece in this application.

The experience with the stainless cracking was likely due to low grade material, or improper grade, but could also be due to a bad design not accounting for expansion/contraction or some other design flaw. If the design was at fault, you could have expected mild steel to have failed even sooner.

Price and workability are good reasons to use mild steel in place of stainless for a header. But strength and durability are not.
 

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Point taken.

But bare in mind that things like bolt holes also need to be enlarged to allow for expansion as well. Stainless has a higher rate of expansion than "mild" steel. So care has to be taken with stainless in that respect.

My only point is that when extreme heat cycles are involved, mild steel is an inferior material for durability when compared to a properly setup piece constructed of quality stainless steel. Mild steel is easier to work with and much cheaper to purchase, but those are it's only pros. Fatigue cracks to the point of total failure are to be expected when using mild steel in a pre-turbo environment that sees any real amount of power.

If I was doing it, I would use mild steel until it failed because I cannot easily weld stainless at home. But you can bet, that after making a set, round two would be for someone to take my prototype and produce a set made from 321 stainless for a durable solution.

Do you have any pictures of the failure with the stainless, or happen to know the grade used?

I understand your point completely, (you used it...it failed you in practice). That's completely understandable. I just think it would be good to understand if it was really the material at fault, or design.

Take Care
 

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I have to run stainless on my powerstroke. Any diesel engine making much power is likely going to have relatively high exhaust gas temperatures unless multiple chargers, nitrous oxide, or a very large single charger are used.

I had completely destroyed the OEM steel up-pipes 3 times before switching to 321 stainless.

Granted, the truck could use a larger charger, but my egt's pin the gauge at 1719 degrees before I get the truck out of 3rd gear at WOT. Heavily fueled diesel engines commonly run very high exhaust gas temperatures. 2000 degrees is not uncommon.

But the point is, mild steel is MUCH cheaper to buy. You can actually weld it with the stuff most of us have at home anyway, and it will be decently durable for most applications as long as the thickness is kept up high enough.

In the end, if you don't mind fabrication, you could probably build a set from mild steel, have it fail and build another set by the time you reached the price of a completed stainless piece.

Proffesional race teams don't use stainless exhaust components just because it sounds nice, looks cool and they've got money to burn. They got tired of trying to finish on no boost because the manifold broke in half 3/4 of the way through the race.

Mild steel will "Probably" work for "most" cases for a decent amount of time before failure. True enough.

Course quality stainless properly welded with a good design incorporating expansion/contraction will work in all cases for a good long time.

$0.02
 

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Yeah, they do. I don't like it because the pistons are not reliable at exhaust gas temperatures higher than 1250-1300 degrees. When towing in a steady-state environment I don't exceed 1200 degrees. But for a full power run up to top-end, you just can't get enough heat soak into the piston/valve/turbo material to actually kill it. The relatively "Thin-walled" OEM exhaust components on the other hand, couldn't take it. The pistons have oil cooling jets hitting the bottoms of them, and the valves relieve some heat through the guides and so on, but the exhaust work has no real way to relieve the heat other than through that radiated out into the engine bay.

Basically on a diesel engine with cooling jets and so forth setup for extended towing duty, a full power run for around 30 to 40 seconds just cannot get enough heat "soaked" in to damage the engine components.

But for the ability to run full power extended, air management is crutial. That's why I have to run two compounded chargers on this truck now. To keep the intake charge cool, and to get more o2 in those cylinders to cool this engine off.
 

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These were almost certainly not pistons with individual dedicated cooling jets spraying the undersides of them.

International explicitly specs the powerstroke to run durated continuous duty at pre-turbo exhaust gas temperatures of 1250 degrees.
 

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It really depends on the engine in question. On a ford 302 Gasser, then by all means YES. I would never consider running egts like that extended.

But the fact of the matter is, that most commercially available diesel engines intended for durated use include piston dome cooling jets from the factory.

International Navistar (the maker of my powerstroke) specifies a durated Pre-turbo egt maximum of 1250 degrees. This is straight from the maker of the engine with the assumed saftey factors in place. This is the temperature at which they feel the engine will still run to its intended service life at full power without injury to pistons, valves, seats and so on.

The 6BT is rated to over 1300 degrees egt durated by cummins.

These engines are designed to shed piston and valve heat and have cooling systems dedicated to those tasks.

You don't usually see piston failure in a powerstroke until you start towing down the interstate running 1350-1400+ degrees sustained. And even then, it's more of a slow wearing out process. You really need 1500-1700 sustained to actually blow a hole in a piston like a torch on one.

I think these light diesels are tougher than they might be given credit for right now.

And this isn't just something I read out of a book. I have seen tons, and tons, and tons of failures with these powerstrokes, from ring lands cracked by nitrous, domes cracked in half from cyinder pressure spikes, cylinder walls blown open into the water passages, rods horseshoed around until the wristpin hits the big end, entire blocks ripped in half dumping the crank through the oilpan, pistons with holes that look like you hit them with the torch, bent, broken and mangled rockers/pushrods/valves from piston:valve contact through drive/boost pressure, so many head gaskets failures from stock to copper, to multilayer, to o-ringed, to fire-ringed, yada yada yada.........

I know where these engines fail all too well, and 1200 degrees egt is a joke. It's actually still 50 degrees below the OEM spec, lol. And the B series cummins is actually rated even higher than that (stock).

I'm somewhat against the grain on the coatings, but my personal opinion is, if you have even a shred of efficiency in your turbo design, you do not need any coatings to survive. I've seen engines with some coated and some uncoated pistons (due to running out of time). It was in a pulling truck running OVER 2000 degrees egt and the pistons that cracked in half were the coated, lol. Not that the coating explicitly caused it, but in a situation like that you just can't help but laugh at coating parts.

The point is just that, coating is a worthless expense on one of these engines not exceeding 1300 or so sustained. Because the engine is probably OEM spec'ed to run that temp from the factory sustained, 24-7 anyway.
 

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I'll state it one more time, lol.

My 1250 degree max sustained exhaust gas temperature limit I use when towing is not opinion, or something I used a devining rod to arrive at.....

It is the exact specification given for my engine by International Navistar (the engine manufacturer)

This value was arrived upon based on the ability of the under-piston cooling jets to shed piston dome heat, the ability of the valveguides to shed heat and so on.

More than 1250 and they deem the heat to be a run-away and the engine's expected service life might be compromised.

As to the reason a short burst up to speed will not hurt your engine, it has to do with "Heat soak" for lack of a better term. It just physically takes time to heat up an given component. That's why intermittant temperatures can be much, much higher than steady-state temperatures.

Take a torch with a flame temperature easily hot enough to blow straight through a piston. Now take a pair of pliers and stick the piston in the flame and right back out. Would you honestly expect the piston to have a huge hole in it, lol.

It takes time. And usually long before you've gotten the actual piston dome temperatures high enough to hurt something on an short burst you're going so fast you're out of road anyway.

This is why steady-state towing is the only time egts are not something to mess with.

To put it in perspective, I am actually VERY conservative with my egts compared to nearly anyone making good power with a light diesel.
 

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I made it all up. Well kind of anyway. A case of beer and a Wigi board told me......

:eek:
 

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Haha. I didn't read it anywhere. Years back the 7.3 powerstroke (International Navistar T-444E) racing community wanted a concrete number for maximum sustained exhaust gas temperature.

We contacted the engineers themselves and they got back to us with 1250* pre-turbo for durated service. I do not know if they posted that figure in any literature since.

I also spend a good bit of time at the track and obviously the 5.9 is a hell of an engine, so it's everywhere. I remember being pissed years back when I learned that the sustained egt for the B series was higher than for the Powerstroke. I cannot conclusively remember if it was 1300 or 1350 so I went with 1300.

I can ask around to any number of the cummins performance shops near me and get a conclusive number. Jeff Garmon lives less than an hour from my house and I go there pretty often. There are numerous 700+rwhp fuel only 5.9's there. One is over 850rwhp fuel only and one of their trucks is over 1000rwhp.

I'm sure that he can tell me where pistons fail. Otherwise, I'm sure there is literature on both of these subjects with their respective engines somewhere.

I'll look for you. How bout that?
 

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Well I appologize then.

The biggest difference I see between that remark and myself is that I really do what I say and have seen nearly every possible way a powerstroke can break, because I've done it myself, or been a part of the analysis when it happened to another engine. I've held the broken parts in my hand knowing what the temps were and knowing what the live cylinder pressures were as graphed through the use of cylinder pressure testing equipment with respect to crankshaft degree. I know exactly what to expect with a given boost pressure and timing or any combination of the two, not through what I read somewhere or heard someone say, but through EXTENSIVE time consuming, and expensive testing on my own and others engines (engines that take around 8k on average to fix and over 20k in many instances). So taking known chances with engines with price tags like that is not what I do. Testing is one thing, but I need not do anymore exhaust gas temperature testing..... I KNOW where they fail, and how they will fail, and how long to expect them to live at a given temp and so on and so forth.....time and time again I KNOW this.

I KNOW where the stock rods will fracture. Not from word of mouth or something in a book, but from Live cylinder pressure testing and more broken bottom end components than you can imagine through the testing process.

Do you honestly think you could produce 482rwhp every day for years on an engine designed to make around 200rwhp if not for THOUROUGH testing and development? If my knowledge base was so horrably skewed, how could you expect my truck to tow what I tow even one time? Let alone the hundreds upon hundreds of trips that my truck has completed and still has better than average compression on all cylinders with an untouched OEM longblock.

If you actually knew anything about the powerstroke you would quickly realize that the temperatures that I run sustained are VERY conservative as is my general approach to engine building. My truck is a daily driver and as such has to be 100% dependable. Only a couple months ago I drove this truck from Atlanta Ga to Niagara Falls Ny to pic up the little 4BT that I'm working on now. About 11 hours into the trip up and at about 1:00 am somewhere in the middle of nowhere Pennsylvania, I ran across a chevy 350 powered S-10 that was not going to be happy until he blew me off the road. So probably over 700 miles from home in the middle of nowhere at 1 am I had enough confidence in my engine to go full boost all the way through 3rd, into 4th, all the way through 4th, into 5th and finally around 125 or so I pulled past him and put 5 lengths on him before lifting. (I however, in no way promote street racing)

While many people actually trailer vehicles to the track, producing power even to, or slightly higher than this truck, I drive and tow other vehicles to the track with it. That speaks volumes about the amount of faith I have in my setup.

That faith was earned through years, and years of testing and testing with the unavoidable failure here and there. It is not blind foolishness, I assure you.

Other than the realm of the dependable daily driver, I am CONSTANTLY around and a part of competition diesels. Wether drag racing or sled pulling. I have personally worked on vehicles ranging in power from mid 400's to over 1200hp. I spend a good bit of time at the dyno tuning and verifying what works and what does not, independent of however it might "feel".


I would appreciate it if some could refrain from the constant attempt at completely discrediting me with respect to light diesel performance.

And I appologize for my tone. I'll try and work on that.
 

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The 1250* info was actually directly from International Navistar's engine division. It was over a Chat program years ago powered by "Icechat" and through the channel "Ford-diesel-chat" of of "The Diesel Stop" server. I guess you would also not believe that Gale Banks also made a personal appearance in that same chat room would you?

And that although for the B series cummins engines I have not the same level of personal experience, but have garnered through long-time relationships with those who have forgotten more about those engines than you will ever know, that the maximum sustained egt is 1300.

So I guess you have "equivalent" experience with your 4BT as do I with the powerstroke? You have personally built and run over 20 sets of different injectors? You have run dual injection pumps? You have done extensive live cylinder pressure testing under full load and full boost? You have tried multiple types of head sealing "gaskets" and found what you like? You have completely re-designed both fuel and oil circuits from the ground up?

Many I am more than sure have much, much more than equivalent experience with the B series compared to mine with the powerstroke........you however, I know for a fact, are not one.

All of your "knowledge" over your engine is what you have heard from others as your engine is actually bone stock. Congradulations on the wealth of experience that must have bestowed upon you. If that counts as "experience" with a 4BT, then I more than likely have more than you, lol. My Case forklift is 4BT powered and I assure you I have more hours running it than you have driving your truck in one year. Nearly every Lull/Skytrack used to have the B3.9 before they went to the 4.5 I believe. I drive one nearly every day.

I have "run" many, many more 4BT's than you in reality.

Being that my truck is a diesel, and it came stock with ~200rwhp which was sufficient for most driving empty, but was not enough for actual work duty out of a 1 Ton truck when actually towing something other than a bassboat, do I actually have to feel what less than 100rwhp does in order to know it's a complete turd in an equivelant vehicle?



confused
 

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I just re-read this entire thread from start to finish just to try and see where it all fell apart, and to see where I apparently started the "problems".

I would honestly urge anyone feeling as though I have been unsympathetic and childish to re-read my posts from the begining (there are not that many) and actually take the time to read them and see where my target was.

Then notice that my tone only changed to one of frustration and sarcasm after having what I stated "called" out more than once.

If you wonder why one could get frustrated, imagine having actually had a chat room conversation with the men that actually built the engine in question only to have someone write this about your actual account of the event after your having contributed that information in the hopes that it might further someone else's understanding of just exactly what egt's mean, how to interpret them and when coatings should be considered.



(Mcinfantry Quotes me)
Quote:
Originally Posted by Charles View Post
We contacted the engineers themselves and they got back to us with 1250* pre-turbo for durated service. I do not know if they posted that figure in any literature since.
Quote:

(Mcinfantry then writes)
who is "we"? if you (you would actually be part of 'we") contacted "the engineers" then you should have received some type of document outlining the claim. you arent going to tell me "they said on the phone" i hope! and you say you dont know if has been psted "since" implies you have a copy.

so you dont have any data, charts, engeneer specs to back up what you have been posting as fact. i AM NOT ATTACKING YOU. i only think you should not argue your opinion as "facts". the average diesel turbo user feels 1200 is the safe range. you keep posting the opinion you have read and heard that 1300 is what cummins rates it for, and trying to post it as fact. the peoblem is this would be an expensive lesson for a guy to come here and follow your advice, imo.

if cummins believes that 1300 is continuous rated then there WILL BE A WRITTEN DOCUMENT stating such, provided by cummins. since they have to warranty the "fact" that 1300 is acceptable.

im patiently waiting.



Does that not spit in my face? The "I AM NOT ATTACKING YOU" is akin to simply ending the sentence, you are a lousy good for nothing piece of shit, with "No offense".

Just read my posts in the thread from the begining and I do not see how I can be seen in a bad light.

Thanks,

Charlie
 
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