Downpipe Thermal Wrap?
03-11-2003, 10:04 PM
#1
Registered User
Thread Starter
Join Date: Dec 2002
Location: Dallas Texas
Posts: 201
Car Info: 2003 WRX Blue
Downpipe Thermal Wrap?
I am about to install a PDE downpipe. I am trying to decide between cutting the heat shield to fit or putting some thermal wrap on. I wanted to find out which is better for keeping the heat out of the engine bay. If anyone has done the thermal wrap, I want to hear how you like it.
03-11-2003, 10:22 PM
#2
Registered User
Join Date: Nov 2002
Location: who wants to know?
Posts: 378
personally i would cut the heat shield and just use it. i have heard of the heat wrap trapping in moisture and causing exhaust pieces to rust. just what i have heard tho, anyone else heard this or have any info. what do you guys think about wrapping the intake?
03-12-2003, 09:29 AM
#3
Registered User
Join Date: Nov 2002
Location: Sacramento
Posts: 349
I don't have a wrapped down-pipe. I am getting ready to have my BPM wrapped up-pipe installed. Yes I have heard the horror stories about the wrap trapping the moisture and rusting the pipes.
I E-mailed another memeber from the "other" club about his experiences with the Thermo-tec wrap. He had both his up and down pipes wrapped and after a year or so he took the parts off (he didnt say why) and checked them out. He stated that there was no rust on them whatsover and claimed that since we are using Stainless Steel in up and down pipes then we are fine.
I bought the stuff and called the Thermo-tec information line person. He was very knowledgeable and had tons of information and he said basically the same stuff. It was that when some folks put the wrap on some headers (not made of stainless) then folks experienced these problems. He went on to say that the incidences that he heard about rusting were from many years ago.
I used the Graphite black thermo-tec wrap and am going to use the spray as well.
have fun
I E-mailed another memeber from the "other" club about his experiences with the Thermo-tec wrap. He had both his up and down pipes wrapped and after a year or so he took the parts off (he didnt say why) and checked them out. He stated that there was no rust on them whatsover and claimed that since we are using Stainless Steel in up and down pipes then we are fine.
I bought the stuff and called the Thermo-tec information line person. He was very knowledgeable and had tons of information and he said basically the same stuff. It was that when some folks put the wrap on some headers (not made of stainless) then folks experienced these problems. He went on to say that the incidences that he heard about rusting were from many years ago.
I used the Graphite black thermo-tec wrap and am going to use the spray as well.
have fun
03-12-2003, 11:11 AM
#4
Guest
Posts: n/a
You have a choice let the heat go in the engine bay or keep it in the exhaust system and turbo.
The turbos run red hot now any hotter and they will melt.
I have read post of people wrapping their exhaust and turbo. The result is cracked turbo housings.
I have drilled holes in my heat shield to keep my turbo as cool as possible. Cant remove them completly or things will start melting.
The turbos run red hot now any hotter and they will melt.
I have read post of people wrapping their exhaust and turbo. The result is cracked turbo housings.
I have drilled holes in my heat shield to keep my turbo as cool as possible. Cant remove them completly or things will start melting.
03-12-2003, 11:57 AM
#5
Admin v2.0
iTrader: (9)
Join Date: Nov 2002
Location: Alameda, CA, USA
Posts: 6,965
Car Info: 02 Black Legacy GT
Turbo's don't melt. 
I would do both. Wrap and heatsheild.
There is a possibility of cracking, but it barely happens. Mostly if you wrap the manifold, not the DP. The DP's don't get hot enough.
I am going to wrap the uppipe and the downpipe.
You want to keep the gases as hot as possible. The hotter the gas, the higher the velocity. Hense, better spool-up. Of couse, your engine bay temps will also drop.
I would do both. Wrap and heatsheild.
There is a possibility of cracking, but it barely happens. Mostly if you wrap the manifold, not the DP. The DP's don't get hot enough.
I am going to wrap the uppipe and the downpipe.
You want to keep the gases as hot as possible. The hotter the gas, the higher the velocity. Hense, better spool-up. Of couse, your engine bay temps will also drop.
03-12-2003, 12:23 PM
#6
Guest
Posts: n/a
A fool would wrap the turbo or manifold they will get hot enough to crack on a turbo car.
The down pipe is not as critical for heat cracking. However the cooler the exhaust gas is after the turbo the less volume it has. It flows easier through the exhaust so less back preasure and more spoolup.
Yes turbos do melt. I have melted seals a few times.
The down pipe is not as critical for heat cracking. However the cooler the exhaust gas is after the turbo the less volume it has. It flows easier through the exhaust so less back preasure and more spoolup.
Yes turbos do melt. I have melted seals a few times.
03-12-2003, 04:33 PM
#7
Admin v2.0
iTrader: (9)
Join Date: Nov 2002
Location: Alameda, CA, USA
Posts: 6,965
Car Info: 02 Black Legacy GT
A fool?
No, a person who does his research and evalutes the advantages and disadvantages of both will wrap whatever he wants to wrap.
Turbo's don't melt. Seals do. So blades. But you said:
I am sure you referred to the exhaust housing, since you cannot see neither the seals or the blades.
The housing will not melt, unless you are talking TopFuel dragsters.
The greater the temperature, the higher the velocity. Thats why wrapping your manifold and uppipe is benefitial.
Wrapping downpipe will not give you any valuable performance gains, but it will keep engine bay temps lower.
You cannot wrap the turbo using conventional wrap. They sell "turbo" blankets which work great. But, for a turbo, I prefer a regular heatsheild.
The key to cracking and wrapping is thermodynamics of metal. The fact that the metal expands at high temps and shrinks at low temps can attribute to cracking. However, if your entire manifold is wrapped and doesn't have any air pockets, it will heat up and cool off evenly and gradually and not crack. If you wrap it poorly and cause portions of metal be exposed, it will crack since the exposed areas will cool much faster and shrink when the rest of the wrapped pipe will not do it fast enough to compensate.
Hotter exhaust gases will also reduce the emissions by activating the catalysis process in the cat faster. Hense all the wrap on the stock pipes.
Advantages of PROPER wrapped exhaust system are huge.
Disadvantage is potential cracking if not done right and fire hazard. If oil gets on the wrap, it will burn like a tourch. Not pretty.
No, a person who does his research and evalutes the advantages and disadvantages of both will wrap whatever he wants to wrap.
Turbo's don't melt. Seals do. So blades. But you said:
The turbos run red hot now any hotter and they will melt.
The housing will not melt, unless you are talking TopFuel dragsters.
The greater the temperature, the higher the velocity. Thats why wrapping your manifold and uppipe is benefitial.
Wrapping downpipe will not give you any valuable performance gains, but it will keep engine bay temps lower.
You cannot wrap the turbo using conventional wrap. They sell "turbo" blankets which work great. But, for a turbo, I prefer a regular heatsheild.
The key to cracking and wrapping is thermodynamics of metal. The fact that the metal expands at high temps and shrinks at low temps can attribute to cracking. However, if your entire manifold is wrapped and doesn't have any air pockets, it will heat up and cool off evenly and gradually and not crack. If you wrap it poorly and cause portions of metal be exposed, it will crack since the exposed areas will cool much faster and shrink when the rest of the wrapped pipe will not do it fast enough to compensate.
Hotter exhaust gases will also reduce the emissions by activating the catalysis process in the cat faster. Hense all the wrap on the stock pipes.
Advantages of PROPER wrapped exhaust system are huge.
Disadvantage is potential cracking if not done right and fire hazard. If oil gets on the wrap, it will burn like a tourch. Not pretty.
03-12-2003, 05:11 PM
#8
Jet-Hot 2K & Thermo-Tec wrapped
My TurboXS u/p & d/p are Jet-Hot 2000 coated & Thermo-Tec wrapped & have been installed since late October. I was just going to wrap the pipes, but was waiting to-o-o long for the UTEC so I had them Jet-Hot 2K coated. The pipes are coated inside & out. Even though their web site indicates substantial heat retention, the coating was not all that *I* expected .. and still had too much time on my hands, so I wrapped them also. I had some thoughts about effieciency and cooler engine bay temps, but mostly had too much time to think about it.
I used the black graphite stuff just as BlueGargantua did and spray sealed the wrap with the stuff from Thermo-tec.
*************************
I also called Thermo-tec & he highly recommended that the sealer be used to prevent oil soak and fire hazard as Imprezer mentioned. Our oil fill is on the other side of the engine ... but to be safe and all that is needed is one can which is cheap.
*************************
I also got the turbo blanket from Thermo-tec, but did not use it. I am running a VF34 so a little trimming of the stock turbo heat shield & it fit fine ... stuck with that because it looked better and I can always with little trouble remove it & put the blanket on.
Results; since Oct. I obviously haven't had any summer heat to swelter in, but have had plenty of spirited runs. After those runs you can put your hand on the d/p ... can't keep there tight, but you can hold it for a moment. Of course engine bay temps are way down. By August I will know a lot more.
I also just purchased an infrared thermometer & will be able to tell more about the temps when the weather becomes more moderate.
Lastly, the rumors about stainless "rusting" have some truth. However, it is not rust and it is not caused by trapped moisture. When stainless alloy such as T304 is subjected to high temp (>800 deg F) hydrocarbon gases, the carbon in the stainless is "leached" out. This is called carburization. The remaining material is weak & flakes away. Thus, a wrapped pipe will be much hotter than a "naked" pipe exposed to ambient temps. Unfortunately, I have no information on the rate that this occurs at the temps that are present in our exhausts.
I used the black graphite stuff just as BlueGargantua did and spray sealed the wrap with the stuff from Thermo-tec.
*************************
I also called Thermo-tec & he highly recommended that the sealer be used to prevent oil soak and fire hazard as Imprezer mentioned. Our oil fill is on the other side of the engine ... but to be safe and all that is needed is one can which is cheap.
*************************
I also got the turbo blanket from Thermo-tec, but did not use it. I am running a VF34 so a little trimming of the stock turbo heat shield & it fit fine ... stuck with that because it looked better and I can always with little trouble remove it & put the blanket on.
Results; since Oct. I obviously haven't had any summer heat to swelter in, but have had plenty of spirited runs. After those runs you can put your hand on the d/p ... can't keep there tight, but you can hold it for a moment. Of course engine bay temps are way down. By August I will know a lot more.
I also just purchased an infrared thermometer & will be able to tell more about the temps when the weather becomes more moderate.
Lastly, the rumors about stainless "rusting" have some truth. However, it is not rust and it is not caused by trapped moisture. When stainless alloy such as T304 is subjected to high temp (>800 deg F) hydrocarbon gases, the carbon in the stainless is "leached" out. This is called carburization. The remaining material is weak & flakes away. Thus, a wrapped pipe will be much hotter than a "naked" pipe exposed to ambient temps. Unfortunately, I have no information on the rate that this occurs at the temps that are present in our exhausts.
Last edited by PsiStar; 03-12-2003 at 05:23 PM.
03-13-2003, 06:54 AM
#9
Guest
Posts: n/a
If you insulate your turbo or manifold where does all the extra heat go? The seals and bearing and intake housing are now in (or connected to a ) well insulated oven. The water and oil will help cool a bit when running but you will still get hotter intake gas and now need a really long shut down time.
There was a long tread on this a number of years ago in the DSM form. Conclusion was wrapping turbos definitely caused cracking and premature failure from actual experience. There was no noticeable power advantage from wrapping a turbo.
There was definitely evidence that wrapping HEADERS on normally aspirated engine improved performance. It was found that even though hot gasses have more volume they will still flow better through hot headers. The theory is that cold pipes cause poor laminar flow. The cooling along the surface of the pipes cause turbulence reducing the even flow through the long headers.
So you may get bit better flow too if you wrap a turbo system but since it is physically connected to the intake system that is much more sensitive to heat soak you will be worse off.
Engine bay temperatures have nothing to do with performance. I would be more concered with keeping your intake manifold cool. So dumping exhaust heat into it through the turbo housing is not good.
If you are still concerned wire your rad fan to a switch and keep it running. It will keep your engine bay a lot cooler.
There was a long tread on this a number of years ago in the DSM form. Conclusion was wrapping turbos definitely caused cracking and premature failure from actual experience. There was no noticeable power advantage from wrapping a turbo.
There was definitely evidence that wrapping HEADERS on normally aspirated engine improved performance. It was found that even though hot gasses have more volume they will still flow better through hot headers. The theory is that cold pipes cause poor laminar flow. The cooling along the surface of the pipes cause turbulence reducing the even flow through the long headers.
So you may get bit better flow too if you wrap a turbo system but since it is physically connected to the intake system that is much more sensitive to heat soak you will be worse off.
Engine bay temperatures have nothing to do with performance. I would be more concered with keeping your intake manifold cool. So dumping exhaust heat into it through the turbo housing is not good.
If you are still concerned wire your rad fan to a switch and keep it running. It will keep your engine bay a lot cooler.
03-13-2003, 07:45 AM
#10
If the exhaust system (including possibly turbo) is wrapped the retained energy flows through the turbo. Thi result is more of that "free" exhaust energy that the turbo is tapping into to begin with. The energy that the turbo extracts cools the gases. PV=RnT; thermodynamics.
It has been mentioned and measured many times in the discussions about cold air intakes having no effect because the WRX is intercooled.
What does affect the intake system is the intercooler getting heat soaked. Keeping the engine bay temps down is a secondary benefit. Unless you are at the drag strip & have the opportunity to water/ice down the intercooler. But, that is a little difficlut for a normal drive.
Therefore, engine bay temps definitely affect performance especially in city traffic in the summer and the intake temps are *almost* irrelavant. Searches in the forums will help this, but basically the turbo & down pipe heat "chimney" up through the intercooler & out the scoop.
Several have experimented with various fans within the engine bay. Conclusions when measurements are made (as opposed to just opinion) are that even additional fans (that fit) without an outside air supply cannot flow enough to make any difference. The radiator fans do not help. A search here & at nasioc could help.
Like the stories of "rusted" stainless steel, there is some fact in the cracked turbo housings. Those stories too, are from "a number of years ago". Alloys are improved. Designs are improved. Admittedly I do not *know* for certain about the stock turbo nor any aftermarket turbo of *current* manufacture. However, in 2 years of lurking & reading forums & discussing with a few in the business ... I have found *no* reports of cracked turbo housings of these current designs. Also, never provided are links to those DSM threads that describe the design of *that* system.
It is difficult to find real facts in forums. But, one thing for sure whether the individual is at fault or not, if they have a problem they will usually raise holy h---- typically blaming Subaru. I have not seen anything like that re; tubos.
Lastly, if you are going to play, be prepared to pay. If the gamble of a cracked turbo housing is a major concern, don't wrap. Of what can go wrong I considered it minor cause for concern. Most likely the real issue will be blown clutch, tranny, or engine with the after market HP increases.
It has been mentioned and measured many times in the discussions about cold air intakes having no effect because the WRX is intercooled.
What does affect the intake system is the intercooler getting heat soaked. Keeping the engine bay temps down is a secondary benefit. Unless you are at the drag strip & have the opportunity to water/ice down the intercooler. But, that is a little difficlut for a normal drive.
Therefore, engine bay temps definitely affect performance especially in city traffic in the summer and the intake temps are *almost* irrelavant. Searches in the forums will help this, but basically the turbo & down pipe heat "chimney" up through the intercooler & out the scoop.
Several have experimented with various fans within the engine bay. Conclusions when measurements are made (as opposed to just opinion) are that even additional fans (that fit) without an outside air supply cannot flow enough to make any difference. The radiator fans do not help. A search here & at nasioc could help.
Like the stories of "rusted" stainless steel, there is some fact in the cracked turbo housings. Those stories too, are from "a number of years ago". Alloys are improved. Designs are improved. Admittedly I do not *know* for certain about the stock turbo nor any aftermarket turbo of *current* manufacture. However, in 2 years of lurking & reading forums & discussing with a few in the business ... I have found *no* reports of cracked turbo housings of these current designs. Also, never provided are links to those DSM threads that describe the design of *that* system.
It is difficult to find real facts in forums. But, one thing for sure whether the individual is at fault or not, if they have a problem they will usually raise holy h---- typically blaming Subaru. I have not seen anything like that re; tubos.
Lastly, if you are going to play, be prepared to pay. If the gamble of a cracked turbo housing is a major concern, don't wrap. Of what can go wrong I considered it minor cause for concern. Most likely the real issue will be blown clutch, tranny, or engine with the after market HP increases.
Last edited by PsiStar; 03-14-2003 at 08:06 PM.
03-13-2003, 09:11 AM
#11
Admin v2.0
iTrader: (9)
Join Date: Nov 2002
Location: Alameda, CA, USA
Posts: 6,965
Car Info: 02 Black Legacy GT
Engine bay temps have a lot to do with performance. You have your TMIC sitting there so it will soak all the heat as will all my FMIC pipes. Then, there is your intake manifold, TB and finally inatke. All those parts will be hot and your intake temps will go up and reduce the density of your charge and reduce performance.
03-13-2003, 09:17 AM
#12
Guest
Posts: n/a
I see your point now. A definate design disadvantage with a Subaru.
Your goal is the same as mine to keep heat out of the intake.
With a front mount turbo and intercooler I do it by keeping the outside air flowing to the turbo and manifold to keep it as cool as possible.
With the Subaru the biggest problem is the heat getting up into the intercooler so with out any cooling air flow insulation is importaint. (Now I understand why water spray in the STi)
I am surprised to hear that the fans or cold air intake don't help. I drop my underhood temperature 20 degrees in city traffic with my fans running. I also get 10 degree difference when using a cool air intake and its taking longer to heat soak.
I still think if you can get rid of the heat (not in the engin compartment) keeping the exhaust and trubo as cool as possible is the way to go. You loose very little energy in the cooling of the manifold and most of the time there is more then enough as it is being dumped by the waste gate any way.
Sorry if I am Subaru illiterate. My goal is to puchace one in the short future so I am getting a head start on learning how to improve it.
Your goal is the same as mine to keep heat out of the intake.
With a front mount turbo and intercooler I do it by keeping the outside air flowing to the turbo and manifold to keep it as cool as possible.
With the Subaru the biggest problem is the heat getting up into the intercooler so with out any cooling air flow insulation is importaint. (Now I understand why water spray in the STi)
I am surprised to hear that the fans or cold air intake don't help. I drop my underhood temperature 20 degrees in city traffic with my fans running. I also get 10 degree difference when using a cool air intake and its taking longer to heat soak.
I still think if you can get rid of the heat (not in the engin compartment) keeping the exhaust and trubo as cool as possible is the way to go. You loose very little energy in the cooling of the manifold and most of the time there is more then enough as it is being dumped by the waste gate any way.
Sorry if I am Subaru illiterate. My goal is to puchace one in the short future so I am getting a head start on learning how to improve it.
03-14-2003, 04:43 AM
#14
Guest
Posts: n/a
FWIW on the WRC car that I looked at it had manifold, and upipe wrapped as well as a turbo blanket and the first part of the downpipe wrapped maybe 5 or six inches. If cracking is a problem you would see it there because they are running very agressive anti-lag so you have a lot of heat. One thing that I have not seen a lot of people do is put the reflective sleaves (they are thermal insulating as well as keepin away heat soak) on their Fuel rail aeroquip hoses as well as oil cooler lines. Just an observaton but here is another area that we could all pay attention to.