The quest for lower underhood temps!!

That spinning thing that makes all of the cool noises. OE and Aftermarket.

Moderators: Helpinators, Moderators

Post Reply
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

The quest for lower underhood temps!!

Post by boostjunkie »

Okay guys, in preparation for the coming warm months of summer I've purchased a DIY intercooler water spray kit and a couple of STi water sprayers in the hope of battling heat soak on the intercooler. I was also thinking it might be beneficial to heat wrap the exhaust manifold, uppipe, downpipe, and quite possibly, the turbo. A couple questions, though.

1. Positives
Turbo wrap - DEI markets a turbo wrap. Basically a baggie that ties around the exhaust turbine and made out of fiberglass. Not only will this lower the heat radiated from the turbine, but it will also keep the heat within the turbine making for better spool (according to Mr. Corky Bell, most of the power generated by the turbine to spin the compressor wheel is from HEAT, and not actual velocity of the exhaust gas - yes, I know the two are directly linked).

Exhaust manifold, uppipe, and downpipe wrap - Again, widely marketed to decrease underhood temps (some people advertise up to 70 degrees!!) and increase in heat retention in the exhaust stream. Better spool up as per the previous paragraph.

I noticed a while ago that when I'd go through the underbody car wash that my car would steam up ALOT. Wasn't sure if it was due to the turbo being hit with water or the exhaust manifolds. Either way, I didn't like the idea of a hot manifold or turbo being hit with water that might increase the chances of cracking the cast iron parts due to sharp changes in temps. I was thinking these wraps might help protect the parts from the elements as well.

2. Downsides
I've heard that these exhaust manifold wraps cause a retention in water around the exhaust piping which might cause for earlier degredation of the cast iron and stainless material. However, I was thinking that the heat shields are still on the stock header, so I could possibly wrap the heat shields with the material, preventing the actual ruining of the underlying exhaust manifold. Yes, this will have some effect on the heat retention inside the manifold, due to the wrap not being around the actual manifold, but it should still keep underhood temps lower.

Another thing I've found is a silicone spray that you spray on after installation of said kit. It's supposed to seal the wrap and protect against the elements. Does anyone know how effective this treatment is?

The turbo shielding - are there any detriments to keeping more heat in the exhaust turbine? Is there an increased propensity for cracking of the iron turbine?

Sorry for the long winded explanations but I'd like to have your thoughts on this subject. I've been reading alot about these ej22t's and what always comes up in discussion is the characteristic of these engines to run a little hot (it's a turbo engine - no surprise there), so anything I can do to lower those temps I'd want to do.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
DLC
Site Admin
Site Admin
Posts: 2775
Joined: Tue Oct 15, 2002 1:58 am
Location: Utah
Contact:

Post by DLC »

A simpler but more expensive solution to this is to get WRX headers with a coating on the inside and outside, like Jet. It not only keeps the heat inside, but apparently makes the going smoother for the gasses, so their velocity increases.

Same for the downpipe.

As for the turbo, one of those baggies probably does as good a job as anything.

Dave
Legacy Central
2001 Legacy Outback Wagon | 2005 OB XT LTD | 1997 Legacy Outback Limited | 1998 Legacy L Wagon | 2000 GT Limited | 93 Legacy Touring Wagon 5MT | 90 Legacy L+
IggDawg
Knowledgeable
Knowledgeable
Posts: 382
Joined: Mon Dec 16, 2002 12:00 pm
Location: Sterling, MA
Contact:

Post by IggDawg »

The chimney prolly does a lot of good. it keeps underhood temps down anyways. it might make the turbo a little cooler, but when you're idling, the tendancy will be for the heat fromteh turbo to go out the scoop instead of into the engine bay air.
IggDawg is cool.

-IggDawg

1994 Barcelona Red SVX LSi.
1990 CRX Si (for sale)

I know a little about Subarus.
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

Post by boostjunkie »

DLC wrote:A simpler but more expensive solution to this is to get WRX headers with a coating on the inside and outside, like Jet. Same for the downpipe.
I was thinking about the jet hot coating, but I didn't want to be without exhaust components for too long. It would get pretty costly buying more parts just to get the coating which is why I thought about the wrap.
The chimney prolly does a lot of good. it keeps underhood temps down anyways. it might make the turbo a little cooler, but when you're idling, the tendancy will be for the heat fromteh turbo to go out the scoop instead of into the engine bay air.
The chimney? Are you talking about the hoodscoop? The problem with this is that the heat will go out of the hoodscoop, but it will also heatsoak the intercooler in the process. I was hoping to lower underhood temps and prevent heatsoak.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
IggDawg
Knowledgeable
Knowledgeable
Posts: 382
Joined: Mon Dec 16, 2002 12:00 pm
Location: Sterling, MA
Contact:

Post by IggDawg »

I'm thinking of the kind of setup where there's a plate that separates the turbo vent from the IC opening like on a WRX.
IggDawg is cool.

-IggDawg

1994 Barcelona Red SVX LSi.
1990 CRX Si (for sale)

I know a little about Subarus.
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

Post by boostjunkie »

Hmmmmm . . . *gears turning*
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
Aaron's ej22t
Second Gear
Posts: 266
Joined: Wed Oct 16, 2002 6:57 am
Location: North Bend, Wa

Post by Aaron's ej22t »

I wouldn't wrap the header or turbo. i would just wrap the uppipe and downpipe. along with doing the water sprayer on your tmic. :o
92 Legacy Turbo \ 5MT \ Silver
LegacyT
Fourth Gear
Posts: 1220
Joined: Mon Oct 21, 2002 9:53 pm
Location: Ottawa, Ontario, Canada, Now Sioux Lookout

Post by LegacyT »

The WRC cars have ceramic coating and insulation wrapping on their exhausts. Could be some good stuff if you look into it.

Mark,
1991 Turbo Sedan, Aspen White 5MT, Sold RIP
1994 Turbo Sedan, Crimson Pearl 5MT, from British Columbia-no rust!
Legacy777
Site Admin
Site Admin
Posts: 27884
Joined: Tue Oct 15, 2002 11:37 am
Location: Houston, Tx
Contact:

Post by Legacy777 »

Couple things.

I'd too suggest the coating method. Yes it is more costly....but it's the best solution.

The stock manifold actually retains heat the best...compared to aftermarket jobbers.

I'd keep stock manifold.....get yourself some aftermarket up-pipes & down pipes....have them coated or heat wrap. A fiberglass type heat wrap shouldn't retain water against the piping......plus any water will evaporate with the heat.

Now on something you posted......
Turbo wrap - DEI markets a turbo wrap. Basically a baggie that ties around the exhaust turbine and made out of fiberglass. Not only will this lower the heat radiated from the turbine, but it will also keep the heat within the turbine making for better spool (according to Mr. Corky Bell, most of the power generated by the turbine to spin the compressor wheel is from HEAT, and not actual velocity of the exhaust gas - yes, I know the two are directly linked).
This is a very touchy issue.....because depending on how you look at it...and who you talk to.....you're going to get different opinions.

I was in a class last april for fundamentals of engines & compressors....granted this was based mainly for the large natural gas engines we use to compress gas and such. The basic principles are the same.

Myself, 3 other engineers, and the teacher had this discussion about turbos, and what "actually" powers them.

To bore you the long drawn out tid-bits. The guy teaching the course asked their turbo guru that went to kansas state, which by the way is the leading university in the nation, if not the world for turbomachinery research. Anyway......What actually moves the turbine is a volumetrix expansion of exhaust gasses. The law used to explain this is boyle's law.

The basics of boyle's law is: If the amount and the temperature of a gas remain constant, the pressure exerted by the gas varies inversely as the volume. That's the book definition. Here's a basic formula P is proportional to 1/V Where P is pressure and V is volume.

So, in a turbo application. You have exhaust gasses that are entering the turbine housing on the outer side and undergo an expansion of volume. Which according to Boyle's law states that pressure will decrease.

Temperature is a factor in this as well. If we look at this equations PV=k Where P is pressure, V is volume, and k is a constant that includes the number of molecules and Temperature.

Number of molecules should remain constant, however temp will not.


I am sorta butchering things here....and rather then me explain it incorrectly, I'll just sum up the info that was told to me.

The velocity of the gas has more to do in driving the turbine the temp does. With the velocity and volume issues brought up by boyle's law.....temperature is more a measure of the efficiency of the turbo rather then a driving factor.

Again I was told that things are extremely more complicated then this, but I still would like to know. I need to go try and talk with the turbo guru with that company. Because I'm not real satisfied with the explanation myself.

So if I do go...and I get a better explanation.....I will share.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

Post by boostjunkie »

Ah yes, good ol PV=nRT (I still remember some of my college physics stuff). That's the equation I was thinking about when I was tying the two (temp and velocity) together, since temperature of the gas is directly proportional to velocity, as well.

At any rate, I'm gonna be buying a wrx heat shield off of someone in the nasioc boards. People are using them with their vf22, 30, 35's, with a little cutting work, so it should fit my turbo as well.

I'll prolly end up wrapping the other components once things start warming up around here.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
kelley
Vendor
Vendor
Posts: 484
Joined: Thu Oct 17, 2002 3:02 am
Location: portland, oregon.

Post by kelley »

boostjunkie, did you ever install an egt guage to see what temperatures your engine was seeing.
I have been running 15 psi for a little while now and ai have yet to see egt's higher than 1200 with lots of time in boost. usually around 800.
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

Post by boostjunkie »

Hehe, yeah I should get around to that EGT thing, huh . . . :lol:

I'm willing to bet that the increased fuel in the system is keeping my egts down . . . but I'll never know until I see it for real. I'd just like to make my setup as bulletproof as I can.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
kelley
Vendor
Vendor
Posts: 484
Joined: Thu Oct 17, 2002 3:02 am
Location: portland, oregon.

Post by kelley »

what have you upgraded in your fuel system?
why do you feal your temps are too high? does your temp guage run high at all? or are you just trying to be cautious?
I am puting in some rc 850cc injectors pretty soon.
then I'l be running at least 20 psi. hoefully I'll have my tranny by then as well.
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

Post by boostjunkie »

I've just upgraded the pump to a 255lph unit. Overkill, really. I'd like to run some 440cc injectors as I don't think I'll be needing THAT much fuel (I"m only expecting to run up to 18psi total).

I'm not seeing anything that would make me think my temps are too high. But I do have this TMIC that's not TOO TOO big, sitting right above my turbo with no real hoodscoop, so I'd like to keep the engine bay temps as low as possible to prevent heatsoak. It really has nothing to do with egts.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
EJ20impreza
In Neutral
Posts: 22
Joined: Tue Oct 15, 2002 4:11 pm
Location: harford county, MD, USA
Contact:

Post by EJ20impreza »

I have my turbo rapped with DEI stuff, without the spray you were talking about, and it keeps the underhood temps very low. I can actually put my hand on the rap around the turbo without getting burnt. The "kit" i bought came with header rap also, but it is not anywhere near as much as we would need to completely rap our headers.

the only problem is, im worried that the turbo temp may be too hot and the bearings might be too hot. I just hope the coolant and oil lines are doing their jobs.

noah
95 Impreza L - EJ20 swap
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

Post by boostjunkie »

Hey Noah, are you still going to the yard tomorrow? If it starts snowing too much, I'm most likely not going to work and I'll have some time to . . . well, not work :twisted:

I'd still like to meet up to take a look at your setup, so let me know if you'd possibly like to meet up tomorrow.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
EJ20impreza
In Neutral
Posts: 22
Joined: Tue Oct 15, 2002 4:11 pm
Location: harford county, MD, USA
Contact:

Post by EJ20impreza »

Definately I want to go tomorrow, give me a call if can get off work (email me if i forgot to give you my number)... I was thinking of going around 1 or so.

You dont happen to have a picture of your boost solenoid do ya? Im not exactly sure what it looks like... its just a two port unit bolted to the passenger strut tower, right?

thanks
95 Impreza L - EJ20 swap
boostjunkie
Knowledgeable
Knowledgeable
Posts: 1770
Joined: Mon Dec 16, 2002 3:20 pm
Location: Owings Mills, MD
Contact:

Post by boostjunkie »

Sure, I'll e-mail ya right after this post:)

The boost solenoid is a cylindrical looking piece with two vaccuum hose attachments on it. I thnk it's brown, if I'm not mistaken.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

[url=http://www.angelfire.com/md3/91turbolegacy/images/Summer_Car_Wash3.jpg]2000 Celica GT-S[/url]
Post Reply