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Not sure if this should be here or not since we don't have and Exhaust forum  But I thought this had some good info that should be passed along. May also be good to put in the FAQ's as well.
The question was brought up on one of the TuboBuick boards I frequent for my 89 TTA (Buick Grand National powered for those that don't know). Anyway it was asked if anyone used header wrap, is it recomended or not.
Looks like not...
http://www.centuryperformance.com/heatwraps.asp
Just thought I'd pass it on for those that may be considering header wrap.
Last edited by scottd60; 01/08/06 03:01 AM.
Scott
2000 Contour SVT #1464
Mustang Dyno: 171.6hp/145.3lb
Dynojet Dyno: 171.1hp/148.9lb
1989 20th Anniversary Turbo T/A "Indy 500 Pace Car"
#1376 of 1550 All Original, 46k with a few mods 
2002 F150 SuperCrew
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i cant believe anything he said ujust because he does kno what he is talking about 1 minute he is talking about NASCAR engines whicvh rev to 10 max the he talk about drag racing which revs to 6500 big differnece.
then he is comparing melting points of mild steel and stainless steel which is a difference of about 700 degrees.
personally he does not know exactly what he is talking about. he is just using information that makes sense to him to prove his theory. no actialy tests were done.
IT IS JUST A THEORY.
2000 contour V6 ATX
BAT suspension kit, k&n filter, SVT TB, SVT UIM, SVT LIM, MSDS headers, MSDS Y-pipe, SVT dual exhaust, Custum burned ADC chip, 7000k HID's, 200 amp HO alt, custom gauges, and 17" rims
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Good information but you must remember that most are using stock motors and the temps are not going to run that high for these people. This is also for Naturally aspirated engines not turbos. I noticed what I believe is improved boost response when using header wrap vs without. I also didn't coat every inch, I did the majority of it to keep from roasting all my wiring, radiator fans and AC hoses. I run wrap from the collection point on my crossover pipe up to the turbo and back down based on the proximity to components.
Some people have been running wrapped headers a long time too. So I don't know what the right answer is, guess it depends on your goals. I'd prefer to run heat shields rather than wrap but I've no room in certain areas.
Did you know that under the stock y-pipe heat shield there is a foam or wrap injected next to the pipes? Yep, the whole pipe under the shielding is essentialy wrapped. Also, the precat champers on the stock manifolds are double walled which would spell death for any metal if breathing were the only issue at stake, especailly since that is only inches from the exhaust port.
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
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FYI. The stoc V6 exhaust manifolds are s/steel apart from the port flagne. The construction is an airgap clamshell design with external heat insulation under the heat shields. The stoc Y pipe also has heat insulation material under its heat shields and is all S/steel.The reason wrapping normal mild steel headers/pipes is a bad idea,because at elevated temps mild steel oxidises at a faster rate than s/steel. A combination of high temps and the amount of water in all exhausts causes rapid oxidisation from the inside of the pipes out....wrapping mild steel speeds thisup. In very bad cases a mild steel wrapped pipes will perforate from the inside out.On the manifolds and Y pipe I'm quite well up on the design and its materials because, apart from Ford, you know where I worked in GR. Bentler!!!!
-'96 SE MTX 3L
-'98 SVT 1,173 of 6,535
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metal-noob question: does mild-steel = aluminized?
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Originally posted by todras:
FYI. The stoc V6 exhaust manifolds are s/steel apart from the port flagne. The construction is an airgap clamshell design with external heat insulation under the heat shields. The stoc Y pipe also has heat insulation material under its heat shields and is all S/steel.The reason wrapping normal mild steel headers/pipes is a bad idea,because at elevated temps mild steel oxidises at a faster rate than s/steel. A combination of high temps and the amount of water in all exhausts causes rapid oxidisation from the inside of the pipes out....wrapping mild steel speeds thisup. In very bad cases a mild steel wrapped pipes will perforate from the inside out.On the manifolds and Y pipe I'm quite well up on the design and its materials because, apart from Ford, you know where I worked in GR. Bentler!!!!
More good information! So this is practical experience that shows stainless steel doesn't suffer from the same problems as mild steel.
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
See My Mods
'05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red
'06 Mazda5 Touring, 5spd,MTX, Black
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Originally posted by lizard:
i cant believe anything he said ujust because he does kno what he is talking about 1 minute he is talking about NASCAR engines whicvh rev to 10 max the he talk about drag racing which revs to 6500 big differnece.
then he is comparing melting points of mild steel and stainless steel which is a difference of about 700 degrees.
personally he does not know exactly what he is talking about. he is just using information that makes sense to him to prove his theory. no actialy tests were done.
IT IS JUST A THEORY.
 
Mark
2000 Black CSVT
3.0L Hybrid - 206fwhp & 195fwtq
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A large reason why it is beneficial is the decreased under hood temperatures and not the fact it helps retain heat energy in the exhaust gasses. This is the same reason the stock precats and Y-pipe are clamshell shielded. There is less heat transfer to the engine bay & oil pan.
That site was mainly for using coatings over wrap. There is no argument there because a quality coating is superior to a wrap in longevity of itself and the piece in question.
Now the durability of aluminized steel far surpasses what most people give it credit for. Metallurgy has come a long way. My headers are 4 years old. From the collectors back have been wrapped for over 3 of those years. My Y-pipe/down pipes have also been wrapped for 3+ years. First as a Y-pipe and then as part of my duals a year later. None show any significant degradation. Yes the headers have a basic ceramic coating. Yes I sprayed everything with Thermo-Tec when I did my 3L. (over 2 years ago now) I did not wrap the primaries for concerns of over stressing the metal.
The important part is that you can touch the wrap even after spirited driving. Regardless of the extra stress on the metal the fact that exhaust heat is not entering the oil pan and engine bay are worth it to me. I will let everyone know when I have to build another set of down pipes.
2000 SVT #674
13.47 @ 102 - All Motor!
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Quote:
Engineers, Metallurgists, and other experts out there will state that there is no way that the material can fail because it can withstand, and it was designed to withstand, the internal temperatures of exhaust gases. TRUE! But, when the header is not allowed to cool so as to dissipate those extreme temperatures that the wrap is controlling, you have now developed a heat absorption that compares to thermal friction which will will continue to gain in temperature beyond the normal exhaust gas temperatures (EGT's). This is the same as with most any insulation.
The EGTs stay the same but the properties of the header material changes in a way of amplifying the temperatures because of the insulation. This action goes against normal laws of thermal dynamics, but this effect is fact, and you have to pull the ears off most engineers before they believe you. This is the trouble with plenty of education, but NO "common sense"!
Insulation will cause a header material to reach temperatures higher than the exhaust gas it�s exposed to? Maybe if its sees significant frictional heating from the exhaust flow, but how big an effect is that?
"properties of the header material changes in a way of amplifying the temperatures because of the insulation"
Amplifying the temperature? WTF?
To use his terms:
This is the trouble with no education, an ignorant man stringing together technical sounding terms without any real understanding of thermodynamics. Throw in a little crude humor; make fun of the professionals and half the fools out there will buy it.
99 Tropic Green SVT, Tan Leather, 20K miles, "Nice Twin" (factory stock).
99 Tropic Green SVT, Tan Leather, 28K miles, "Evil Twin" (Turbo AER 3L and more in progress)
96 Red LX, Opal Grey Leather 2.5L, ATX, 22K miles
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Originally posted by DemonSVT:
A large reason why it is beneficial is the decreased under hood temperatures and not the fact it helps retain heat energy in the exhaust gasses. This is the same reason the stock precats and Y-pipe are clamshell shielded. There is less heat transfer to the engine bay & oil pan.
That site was mainly for using coatings over wrap. There is no argument there because a quality coating is superior to a wrap in longevity of itself and the piece in question.
Now the durability of aluminized steel far surpasses what most people give it credit for. Metallurgy has come a long way. My headers are 4 years old. From the collectors back have been wrapped for over 3 of those years. My Y-pipe/down pipes have also been wrapped for 3+ years. First as a Y-pipe and then as part of my duals a year later. None show any significant degradation. Yes the headers have a basic ceramic coating. Yes I sprayed everything with Thermo-Tec when I did my 3L. (over 2 years ago now) I did not wrap the primaries for concerns of over stressing the metal.
The important part is that you can touch the wrap even after spirited driving. Regardless of the extra stress on the metal the fact that exhaust heat is not entering the oil pan and engine bay are worth it to me. I will let everyone know when I have to build another set of down pipes.
Airgap manifolds,be they clamshell or hydroformed, are done for two reasons...the main one is to retain the temp of the exhaust feed gas to the cats,this reduces heat loss and 'light off time' of the cat. A spin off is better /lower outer manifold skin temps. On airgap hydroformed down pipes noise reduction is another spin off. The 'inner' liner is usually around 2/3rd the thickness of the outer and of a higher rated s/steel.On some applications re the 'Benchmarc'(TM) cat developed by Benteler(heat retaning cat) the airgap is a sealed vac unit for insulation and heat retention in the cat for rapid light off,we also used 'Aerogel' in the vac space(liquid smoke) as an insulator.Look up the 'Benchmarc' cat ,very interesting project I worked on while at Benteler with
Dr Biel.
....if you understand what the pre-cats/'light off' cats do Re INCREASE the feed gas temps from the manifold to feed the main underbody cat for 1)Reduced cold start light off times 2)Reduce the chance of the main cat 'dropping out' Re reduced feed gas temps which cause the main cat to stop working at low speeds. This tells you that one of the hottest areas in the exhaust 'feed gas' temps is in the 'Y'
pipe.Changing the Y pipe from stoc to an off road 'MILD STEEL' type with stoc exhaust manifold with the cats still in place,is asking for trouble with the mild steel exposed to elevated gas temps which will cause it to oxidise at a rapid rate. The materials chosen for the V6 manifolds and Y pipe were very well chosen to retain feed gas temps to the cats and give longevity in service re rate of oxidising etc....The S/Steels used in this system are very expensive Vs 'mild steel'...
...for headers etc, is another area where 'eggspurts' mess up. There are TWO type of heat coatings. One type
INSULATES the component to RETAIN heat, the second helps CONDUCT heat OUT of the component(do YOU know which type you have on your headers???LOL). The insulation type would be fine on say a stainless steel pipe in a turbo system where the heat of the exhaust needs to be retained within the pipe for added power, but NOT with a mild steel pipe as this will increase the rate of oxidisation of the material. Conducting more heat OUT of the pipe poses the question of added heat to the surrounding components. The 'best' would be tube hydroformed s/steel headers with an air gap and thin liner tube. These have been made as we designed many proto sets at Benteler BUT the cost to hydroform such designs is VERY costly and anyone who knows materials
and hydroform technology will confirm this. Hydroform
tooling, presses, dies etc are VERY expensive and 'blowing tubes' to give a uniform air gap between the inner and outer tube is a design 'art', of which very few engineers or mfg's fully understand. Benteler has always been at the front in hydroforming, to the point where they design and build their own hydroform presses(in Germany!),which range from 500 to 1000 tons. Been there done that!!!!!!
-'96 SE MTX 3L
-'98 SVT 1,173 of 6,535
-'05 Mazda 6s, loaded, g/f's ride
-Need a 96-00 manual on CD? PM or email me
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