Engine/Transmission (1998.5 - 2002) Header Hype --- Truth or Fiction?

[NoSeeUm]

Reading through the last issue of Diesel Power regarding the ATS multi-piece pulse exhaust manifold. This article is on page 122 titled Heatsink. Two comments really jumped out at me.

A crucial upgrade for all Cummins Engines

The EGT was as much as 100 degrees cooler

A 100F reduction in EGT seems huge for what in the article seems to describe a stock truck with a Banks (power elbow??? --> no clue) 4 inch exhaust system.



Truth or Fiction?



Thanks;

Jim

 

[SamBrown]

I am gonna go with truth. It has much better flow characteristics, more robust design that can handle expansion and contraction and will spool your turbo up to the mooon.

 

[chrleb1]

The reason i would say it is a must item, is because the stock manifolds shrink when they get hot. It's not quite a huge issue with the 24 valve, but the 12 valve trucks can have a huge problem if the manifolds shrink too much (snap a mounting ear off). When the stock 24 valve manifolds shrink, they tend to crack right in the center.

 

[KKlingbeil]

The reason i would say it is a must item, is because the stock manifolds shrink when they get hot.

After taking thermodynamics, im gonna have to say that this is not possible. Getting the manifold WAY hotter then it was designed for may expand it enough to crack it, or the more likely answer is that because it is WAY too hot then it cools too fast which will cause a crack, but getting something really hot does not cause it to shrink.

 

[Forrest Nearing]

so what causes them to shrink? because they DO shrink...



and I wouldn't call it Truth or Fiction... I'd call it marketing...

 

[Bob4x4]

After taking thermodynamics, im gonna have to say that this is not possible. Getting the manifold WAY hotter then it was designed for may expand it enough to crack it, or the more likely answer is that because it is WAY too hot then it cools too fast which will cause a crack, but getting something really hot does not cause it to shrink.

Maybe your profs told you that but out here in the real world... ... ... exhaust manifolds have been doing it for years. If you look through specialty tool catalogues you will see the spreader tools designed many years ago to allow shrunken SBC exhaust manifolds to be reused. The 12 valves have been a victim of this,breaking,bending bolts and in extreme cases breaking an ear off the head. I have a rodeo riders truck in my driveway right now that should have one, but those guys like to spend their money on different things... ... . hence a big ole weld :-laf



Bob

 

[tshort]

Put ATS man. on two diff. trucks, 95 and mine. Did notice reduction in boost, lower EGT's (around a little less than 100). And for the record both trucks manifolds shrunk.

Ryan

 

[BigEasy]

What we have here is a failure to communicate... they don't shrink when they get hot, they shrink over time, over thousands of heat cycles.

 

[NoSeeUm]

Put ATS man. on two diff. trucks, 95 and mine. Did notice reduction in boost, lower EGT's (around a little less than 100). And for the record both trucks manifolds shrunk.

Ryan

Thanks Ryan, now we are getting some where. I had heard that boost would drop also. I am not sure how much for me since I also have a cam. But the drop in boost seems like a pretty good indicator of the improved gas flow efficientcy.



Is the 100F drop across the board or just near WOT?



I am going to assume the "truth" is primarily WOT or close to it. I am interested more in steady state pulling conditions.



Jim

 

[NoSeeUm]

After taking thermodynamics, im gonna have to say that this is not possible. Getting the manifold WAY hotter then it was designed for may expand it enough to crack it, or the more likely answer is that because it is WAY too hot then it cools too fast which will cause a crack, but getting something really hot does not cause it to shrink.

Ask about cases where you force the metal into undergoing a crystallin structure formation change when its hot and then rapidly cool it. Or times when you heat it and then introduce contaminants like O2, H2 or C which tend to harden and or shrink metal components by migrating into the crystallin structure and changing its properties.



Few will disagree that the cracks are likely formed as the metal cools.



Jim

 

[Gary - K7GLD]

What we have here is a communication problem... they don't shrink when they get hot, they shrink over time, over thousands of heat cycles.

ABSOLUTELY!



Most matter EXPANDS when heated - and that goes for the metal in our manifolds as well! The issue is NOT what happens at the time the manifold is actually HOT - but what happens to the manifold over many hot/cold cycles.



And for the record, chances are MOST of the after market manifolds will do exactly the SAME over a period of time, regardless of brand - or hype...



Check out this currently running thread on ATS 3-piece manifold breakage if you need a bit of persuasion. :-laf



http://turbodieselregister.com/forums/showthread.php?t=167629



~

 

[tshort]

My EGT reduction doesn't seem to be but at WOT. Cruising hasn't changed, may be able to notice if I had a digital gauge with the ability to store temps.

Ryan

 

[paulb]

I am going to assume the "truth" is primarily WOT or close to it. I am interested more in steady state pulling conditions.



Jim

I thought your steady start pulling condition WAS WOT!?! :-laf



I don't have an EGT problem, but I wondered the same thing when I saw the article.



Paul

 

[chrleb1]

After taking thermodynamics, im gonna have to say that this is not possible. Getting the manifold WAY hotter then it was designed for may expand it enough to crack it, or the more likely answer is that because it is WAY too hot then it cools too fast which will cause a crack, but getting something really hot does not cause it to shrink.

Thermo may have taught you something like that, but if you take a metals class then you will learn that certain elements can move and leave. What happens is that the stock manifolds a high silicone cast iron (cheap) and when it gets up to a certain temperature, the silicone starts to leave the iron. So it now has small voids and the iron fills in. This is shrinking. If you start with a low silicone cast iron (higher cost), you have a lot less shrinkage.



I'd have to disagree on the fact that the temperature has nothing to do with it. My manifold seemed to shrink at a lot fast rate than when it was stock. Usually 1000* - 1150* is when the silicone starts to leave the cast iron.

 

[Bob4x4]

And for the record, chances are MOST of the after market manifolds will do exactly the SAME over a period of time, regardless of brand - or hype...



Check out this currently running thread on ATS 3-piece manifold breakage if you need a bit of persuasion. :-laf



http://turbodieselregister.com/forums/showthread.php?t=167629



~

The after market manifolds are multi-piece construction to allow for the expansion and contraction with much less risk. The heavy haulers are the ones I see most often with cracking... ... ..... my 94 has seen many pyro buried short trips with no ill effects showing yet,and a good number of 1200 degree towing hours with the ATS (ceramic coating looks the same as it did 8-9 years ago. )



Bob

 

[BigEasy]

Thermo may have taught you something like that, but if you take a metals class then you will learn that certain elements can move and leave. What happens is that the stock manifolds a high silicone cast iron (cheap) and when it gets up to a certain temperature, the silicone starts to leave the iron. So it now has small voids and the iron fills in. This is shrinking. If you start with a low silicone cast iron (higher cost), you have a lot less shrinkage.



I'd have to disagree on the fact that the temperature has nothing to do with it. My manifold seemed to shrink at a lot fast rate than when it was stock. Usually 1000* - 1150* is when the silicone starts to leave the cast iron.

You mean silicon right? Or do you have fake boobs in your cast iron?

 

[chrleb1]

well... you know those late night that you are working around the manifold and with no light... ... Yeah, silicon. I sell silicone, just a little typo. There are a lot of production facilities around here and they use food grade silicone for lubrication on the product... ... . So anyways, it comes from writing quotes.

 

[NoSeeUm]

ABSOLUTELY!



Most matter EXPANDS when heated - and that goes for the metal in our manifolds as well! The issue is NOT what happens at the time the manifold is actually HOT - but what happens to the manifold over many hot/cold cycles.



And for the record, chances are MOST of the after market manifolds will do exactly the SAME over a period of time, regardless of brand - or hype...



Check out this currently running thread on ATS 3-piece manifold breakage if you need a bit of persuasion. :-laf



http://turbodieselregister.com/forums/showthread.php?t=167629



~

Yeah Gary, I read that thread also and evidently they do crack under extreme low frequency stress. But those guys are pulling sleds and in the process pretty much ignoring the pyro. I am more concerned about towing.



As a side note, why is it common for the OEM 12v'ers to crack and the 24v'ers not to crack. Did they change the metal composition used in the header?

I thought your steady start pulling condition WAS WOT!?!

LOL OH Wait, Grrrrrrrr.....



For some reason I am trying not to break this truck too bad. At least until I can get it paid for.



Jim

 

[Diesel Freak]

Thermo may have taught you something like that, but if you take a metals class then you will learn that certain elements can move and leave. What happens is that the stock manifolds a high silicone cast iron (cheap) and when it gets up to a certain temperature, the silicone starts to leave the iron. So it now has small voids and the iron fills in. This is shrinking. If you start with a low silicone cast iron (higher cost), you have a lot less shrinkage.



I'd have to disagree on the fact that the temperature has nothing to do with it. My manifold seemed to shrink at a lot fast rate than when it was stock. Usually 1000* - 1150* is when the silicone starts to leave the cast iron.

Exactly!!!

 

[Yo Hoot]

They even make special jacking tools for re-installing cast iron exhaust manifolds. You put them between the pipes to spread the manifold so th ebolt holes line up.