Hotter In Engine Bay Than Before - Corolland: the Toyota Corolla Forums

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My oem exhaust manifold had a crack in it so I replaced everything from that manifold back, and decided to opt for a stainless steel racing header (4-2-1), hi flow cat, and catback exhaust/muffler.

However, since replacing the exhaust it seems hotter under the hood that it did oem. In fact the strut bar and intake pipe are pretty darn hot when I check them immediately after driving at normal temp. I could have sworn I followed the directions on the exhaust wrap to a "T" when I wrapped the header and the downpipe. I've always read/heard that exhaust wrap was supposed to keep your engine bay cooler....I had assumed they had meant "...than stock". Is it supposed to be hotter now, with a wrapped header, than it was with stock exhaust?

Here's pics of it... Looks the same as every other pic I've seen:

https://i68.photobucket.com/albums/i38/corr...derWrapped1.jpg

https://i68.photobucket.com/albums/i38/corr...derWrapped2.jpg

https://i68.photobucket.com/albums/i38/corr.../EngineBay1.jpg

Either way my intake pipe gets hot, which helps to negate the idea of an aftermarket intake if it's just sucking in hot air. What can I wrap the intake pipe with to help keep the intake temp down? I was thinking about just using the exhaust wrap, but the last thing I need is fiberglass up in the filter. Thanks for your suggestions!

Yup - unless you get the header thermally coated inside and out - no amount of heat wrap will help pull those temps down below stock temps. Just the price you pay for a better exhaust. If it is that hot now - just imagine what the temps would be like with no wrap!! That is what they mean by reduced underhood temps - not compared to stock setups.

Not much you can do for the SRI - I wouldn't worry about it too much, the temperature differential from ambient outside air and under hood temps is not that much. Once you get air moving there - it will be much cooler. The only issue you will have is with heat soak at a dead stop or very low speeds. Only way around that is to go with a true CAI setup and insulate the intake tract or go with an ice box design (kind of like a box that seals against the hood and all around the sides of the filter to insulate it from direct heat). Remember - will all that you can do with the SRI or CAI intakes and insulating them - once the air hits the TB and intake manifold, it will be hot again. A wrap will only provide insualtion for the pipe - the filter will still suck in hot air. The amount of heat transferred from the intake tubing to the incoming intake charge is pretty much neglible - air will form different temperature boundaries inside the tube, most of the air will go through without being heated at all - only the portion that is closest to the tube will be heated and only slightly at that.

Really paranoid about wanting a cooler intake charge and don't want to use a wrap ore replace the setup - try water injection. A proven method to cool the intake charge and works great with S/C setups which don't have any other method to cool down the intake charge. Just do a search for Aquamist, Snowperformance or similar - makes more sense on a forced induction project, but can be used in a N/A application.

my engine bay isnt any hotter than it was before with my wrapped header, but before the top heatsheild on the stock manifold was off. it had been loose and rattly so i took it off.

the wrap is amazing stuff, i can TOUCH the header with my fingers for a second and not be burned. after a long drive, the hood is only slightly warm, it gets hotter sitting in the full sun all day!

Yup - unless you get the header thermally coated inside and out - no amount of heat wrap will help pull those temps down below stock temps. Just the price you pay for a better exhaust. If it is that hot now - just imagine what the temps would be like with no wrap!! That is what they mean by reduced underhood temps - not compared to stock setups.
Not much you can do for the SRI - I wouldn't worry about it too much, the temperature differential from ambient outside air and under hood temps is not that much. Once you get air moving there - it will be much cooler. The only issue you will have is with heat soak at a dead stop or very low speeds. Only way around that is to go with a true CAI setup and insulate the intake tract or go with an ice box design (kind of like a box that seals against the hood and all around the sides of the filter to insulate it from direct heat). Remember - will all that you can do with the SRI or CAI intakes and insulating them - once the air hits the TB and intake manifold, it will be hot again. A wrap will only provide insualtion for the pipe - the filter will still suck in hot air. The amount of heat transferred from the intake tubing to the incoming intake charge is pretty much neglible - air will form different temperature boundaries inside the tube, most of the air will go through without being heated at all - only the portion that is closest to the tube will be heated and only slightly at that.
Really paranoid about wanting a cooler intake charge and don't want to use a wrap ore replace the setup - try water injection. A proven method to cool the intake charge and works great with S/C setups which don't have any other method to cool down the intake charge. Just do a search for Aquamist, Snowperformance or similar - makes more sense on a forced induction project, but can be used in a N/A application.

An ice box or cai is the only reasonable choice, but no ice boxes are made for the 7th gen (that I can find), and cai a may look into, but probably not.

I read up on the water/methanol injection - very fascinating stuff! I'd consider getting it if I had a twin turbo Supra or something, but it'd be ridiculous for a corolla. default_tongue

my engine bay isnt any hotter than it was before with my wrapped header, but before the top heatsheild on the stock manifold was off. it had been loose and rattly so i took it off.
the wrap is amazing stuff, i can TOUCH the header with my fingers for a second and not be burned. after a long drive, the hood is only slightly warm, it gets hotter sitting in the full sun all day!

I can touch it for a second or so too without a burn, but the strut bar and intake pipe are up there in temp too. I've felt the top of the hood immediately after driving - it's way more than slightly warm. I can't remember the last time I put my hand on my black car on a bright sunny summer day but I can't hold my hand there for too long after a drive.

No, I don't race around or anything - I rarely hit over 4500 rpm. I also have checked all the exhaust connections: they're all tight, no leaks.

I'm not overly concerned about the extra heat. Mostly just gathering information, as this is my first project car and I have money here and there to dump into it, for no other reason than to learn. I can't wait until winter now...I won't have to brush off the hood ever! default_biggrin

hmm. are you sure you overlapped enough? i overlapped 1inch for each wrap of my 2" heat wrap and i went all the way to the bottom of the header.

https://img.photobucket.com/albums/v335/huz...ne/e225bf75.jpg

https://img.photobucket.com/albums/v335/huz...ne/821eb290.jpg

hey, how much of a difference have you noticed with the header, in terms of performance.

hmm. are you sure you overlapped enough? i overlapped 1inch for each wrap of my 2" heat wrap and i went all the way to the bottom of the header.
https://img.photobucket.com/albums/v335/huz...ne/e225bf75.jpg
https://img.photobucket.com/albums/v335/huz...ne/821eb290.jpg

Holy crap - 1in overlap? Crap! I could have sworn it said 1/2in... I'd check the box but I threw it out. I still have the extra wrap though. Yup looking at your pic yours is definately overlapped more than mine. Darn, I was hoping my exhaust project was done. Since it's a two piece 4-2-1, I can just take the header off and rewrap thank God.

hey, how much of a difference have you noticed with the header, in terms of performance.

I played around with it quite a bit the first two weeks... Lost a little low end torque, but a very noticeable increase in 4000rpm+ hp. IMO worth it. I do mostly city driving so my dead stop to 40mph, or highway 55mph is a whole lot better. I did a lot of gear hops - 1st to 5500/6000, 2nd to 5500/6000, then straight to 4th to keep it at speed. In the 25/30mph zones I'd do 1st to 3rd. Good times. default_biggrin It's louder than I'd like, but it's a very low deep tone.

Depends on the wrap - how wide it was to begin with and if you had to pre-soak it or not. I had some 1" and 2" exhaust wrap - both had to be overlapped by about 1/4 the width on the 1" and about half the width on the other.

Was way easier working with the thinner wrap - messy, came with some weird type of heat paste smeared all over it - but was thin enough to wrap around the maze of pipes pretty easily and curves and bends were nothing. The wider wrap worked pretty well too - but around bends, it bunched up a bit (if you made it look good) - was a plain fiberglasss wrap, no goop on it.

I'm curious whether the statement on

http://www.stahlheaders.com/faq.htm

to the effect that wraps reduce the lifespan of headers is true.

Depends on the wrap - how wide it was to begin with and if you had to pre-soak it or not. I had some 1" and 2" exhaust wrap - both had to be overlapped by about 1/4 the width on the 1" and about half the width on the other.
Was way easier working with the thinner wrap - messy, came with some weird type of heat paste smeared all over it - but was thin enough to wrap around the maze of pipes pretty easily and curves and bends were nothing. The wider wrap worked pretty well too - but around bends, it bunched up a bit (if you made it look good) - was a plain fiberglasss wrap, no goop on it.

I used the 2in fiberglass wrap without any goop - had to pre-soak. I had 1in and 2in - I must've read the 1in box and assumed just to wrap 1/2 instead of reading the 2in box.

Mine bunched up quite a bit around the bends, so around the bends it's more overlapped than on the straighter parts. Oh and what's that string stuff you used to tie it down? Looks to be more easily manageable than hose clamps.

I'm curious whether the statement onhttp://www.stahlheaders.com/faq.htm

to the effect that wraps reduce the lifespan of headers is true.

I've read it so many places I'd say yes. What I've read makes sense to a certain extent, too.

Here's another one:

http://www.centuryperformance.com/heatwraps.asp

Just also keep in mind the sources. I can explain anything I want, any way I want, if I'm selling something. default_wink

How damaging is the increased heat focalized to the headers going to do? With all the heat being kept on the exhaust headers, wouldn't they fail sooner?

The reason I went the stainless steel header and wrap route is because this is my first experience with either - If I screwed up or didn't like it I'd be out a $102 ebay header, not a $250/$300 ceramic header.

How damaging is the increased heat focalized to the headers going to do? With all the heat being kept on the exhaust headers, wouldn't they fail sooner?

With my ebay header in particular (because there's no way to know what kind of crap metal it's made out of) I'm betting yes.

i dont know what kind of wrap you guys are buying....

i used DEI 2" wide wrap and overlapped it 1", which is more overlap than recomended. there was no soaking, no goop, just a fiberglass wrap treated with some chemicals.

i used bailing wire to tie it down, just wrap it around once and give it a tight twist with a pair of pliers, clip the excess, then tap the little tab of metal down flat.

the header runners are made from 304 grade stainless and im not sure what the flanges are made from.

I got mine from jcwhitney.com Directions said something like "wet the wrap, but don't submerge it in water", just to get it wet but not soaked I guess. That was tons of fun with gloves on.

Wraps and headers really depends on the material of the header itself and how it was wrapped. Some headers have a bad rep for cracking when wrapped (most mild steel ones, medium to thin metal). Some of the heavier ones and stainless steel variants (cromed ones as well) can take the extra heat - will eventually crack, but by that time, most would have moved onto other designs - biggest problem there is in hydrogen embrittlement (not permanent, given enough time and heat - can rediffuse the hydrogen out of the metal).

I've wrapped the ones that I expect to last only a year or less - or ones that I will be constantly taking off the car. The others are Jet-Hot coated or similar coatings - not quite as effective as a good wrap (Jet-Hot around 60% reduction of heat compared to plain header - wraps are around 70% or so for the same), but doesn't suffer the same cracking issues. Key here is that the coating has to be applied to BOTH sides, not just the exterior. I had one header on a SB Chevy that got holed - upon inspection - the header was almost completely rotted out on the inside, coating was keeping it together.

weird, what brand? my DEI said nothing of wetting it. i just wrapped it on, tied it down, and put it on the car. it smoked for about 15 minutes of driving and smelled like burning pancakes. after that the smell persisted when they got hot for a day or 2 and then it was fine.

people stared like crazy when i stopped at a light and the smoke was pouring from underhood, i dont blame them! it looked bad, but by the time i got home from my little late night trip, the smoke was all gone. it was about 7 miles round trip, with a topspeed of about 50mph.

The 8th generation corolla has the exhaust headers at the rear. My exhaust headers have a shield over them. So................How about wraping the (what I believe to be aluminum) shield to help insulate as oppose to wrapping the headers directly to help alleviate the corrosion of the headers? Or do I just sound like a retard?

no point in wrapping over the heat sheild, the wrap has to be in contact to work. you could add some thermal padding to the heat sheild, but why? is it making something too warm?

weird, what brand? my DEI said nothing of wetting it. i just wrapped it on, tied it down, and put it on the car. it smoked for about 15 minutes of driving and smelled like burning pancakes. after that the smell persisted when they got hot for a day or 2 and then it was fine.
people stared like crazy when i stopped at a light and the smoke was pouring from underhood, i dont blame them! it looked bad, but by the time i got home from my little late night trip, the smoke was all gone. it was about 7 miles round trip, with a topspeed of about 50mph.

Here it is:

http://www.jcwhitney.com/autoparts/Product...tt=exhaust+wrap

[i wish I would have saved the directions now] It said wet the wrap, wrap it on tight overlapping 1/2in, and let it dry by leaving it in the sun for the day. (I remember that part because it sounded really weird. I just baked it in the oven at 175 for 45 minutes and installed it the next day.)

Mine didn't smoke too bad - but I had the hood open and just let it idle for 20 minutes, giving it a strong rev every 5 or so.

I had also considered buying the following but ended up deciding against it...

http://www.jcwhitney.com/autoparts/Product...tt=exhaust+wrap

yea, thats why i stuck with a name brand. try the DEI stuff, i got mine on ebay for like $30. i think it was a 50ft roll and i used 30ft.

http://cgi.ebay.com/ebaymotors/DEI-010102-...09990QQtcZphoto

Bikeman982

My oem exhaust manifold had a crack in it so I replaced everything from that manifold back, and decided to opt for a stainless steel racing header (4-2-1), hi flow cat, and catback exhaust/muffler.However, since replacing the exhaust it seems hotter under the hood that it did oem. In fact the strut bar and intake pipe are pretty darn hot when I check them immediately after driving at normal temp. I could have sworn I followed the directions on the exhaust wrap to a "T" when I wrapped the header and the downpipe. I've always read/heard that exhaust wrap was supposed to keep your engine bay cooler....I had assumed they had meant "...than stock". Is it supposed to be hotter now, with a wrapped header, than it was with stock exhaust?

Here's pics of it... Looks the same as every other pic I've seen:
https://i68.photobucket.com/albums/i38/corr...derWrapped1.jpg
https://i68.photobucket.com/albums/i38/corr...derWrapped2.jpg
https://i68.photobucket.com/albums/i38/corr.../EngineBay1.jpg
Either way my intake pipe gets hot, which helps to negate the idea of an aftermarket intake if it's just sucking in hot air. What can I wrap the intake pipe with to help keep the intake temp down? I was thinking about just using the exhaust wrap, but the last thing I need is fiberglass up in the filter. Thanks for your suggestions!

Looks like my engines (except I don't have headers).

Maybe you could put some additional wrapping around the pipes??

it is your engine dude.

you cant put on more than one layer of wrap, too much heat rentition is bad.

Bikeman982

Maybe a hood scoop will help??