Exhaust wrap-- how effective?

[Gsx_hooptie]

I was wondering how effective exhaust wrap is at reducing temperatures under the hood, and if it's a worthwhile mod. The guys on tuners said that it prematurely rusts things, but I was wondering if anyone on here has had first hand experience with it.

[drdisque]

I wouldn't do it on a turbo car, it causes more heat to stay inside the exhaust which means more heat going into your turbo.

[96spyderman]

I have heard that the wrap is good for a few reasons...
1..It keeps heat down in the engine compartment which is good to lower the intake air temp...

2..The hotter exhaust is more expanded for more push on the turbo... I don't quite see how the hotter temp is good for the turbo but can see that if it is hotter it's volume is greater which would help with spooling...
Another thing is the exhaust gas shouldn't really be any hotter going through the turbo with a wrapped header...it comes out of the cylinders to damn fast to make a real difference.. I think the wrap is more for keeping the bay cooler...

As for it prematurely rusting stuff... I haven't heard that... I doubt it would happen if you bought a new set of 4-1 headers or new manifold and wrapped each tube when it's new... there is a high temp paint sealant that you are supposed to use after wrapping it to help seal it up and keeps the wrap from coming loose....if you are going to do an older manifold that already has rust... yeah it probably could speed up the process unless you super cleaned the metal and stripped/grinded off ALL rust. Just like doing autobody.. if ya don't get ALL the rust it WILL rust through the new paint no matter what you do...that's what sucks about sanding..getting into all the rust pits and having to use LOTS of that tacky cheese cloth..

I have talked to a few guys that have had the corvairs and aside from knowing that they are aircooled engines I don't know about their turbo set-ups... I do know that they wrap the turbos so that they produce more power and spool faster...
The corvair is kinda known as the poor mans corvette... from a stop they are kinda slow but on the highway they can rip shit up pretty good...

I have seen that there are these wraps designed especially for turbos kinda like a pull-up for kids... it just wraps right around them...
Here's the website for all to check out... this is the company that makes the wrap that I have...
http://designengineering.com/index.asp
I think this is the site I saw the turbo "pull-ups" lol
Have a look and decide for yourself....
WOW I just wrote a friggin essay...lmfao..sorry but I do hope this helps...... MY are if I were to get 4-1 headers I would deffinately wrap them, just look what difference air intake temp makes!!

[96spyderman]

here's the exact page for the turbo wrap...

http://designengineering.com/products.asp?m=sp&pid=31

[---]

There was some thread on DSM Tuners listing all the shit about why it's bad. I think it's pinned, shouldn't be hard to find.

[Shpyder]

A while ago I was really into getting a turbo wrap to keep heat away from my VIS cf hood. (I still have no wrap or heat shield, and at 10 psi, even after a hard run, the hood is simply warm to the touch, and not a bit more). But after a lot of opinions and thought, I concluded that though a wrap would only contain heat, and heat needs to exit the engine bay. There is really nothing under the hood that would be affected by the heat, at our street/semi-track power levels. I wouldnt spend my money on one, but thats just my 2 cents...In all essence, reducing engine temps can be effectivly done through vents placed here and there...simple idea, just an issue with rain and water (I have to ghetto tape my vent at the self-wash).

[kjewer1]

There is solid theory behind wrap reducing lag. Remember that while the turbo is spun by exhaust gasses "blowing" over the turbine wheel, the majority of the work of turning the shaft is done by extracting heat energy from the exhaust. This is why EGTs drop about 200 degrees across the turbine. That heat had to go somewhere It was converted to mechanical energy/work. Some of the energy also comes from pressure changes. High pressure before the turbine (exhaust gas pressure, goes up with intake manifold pressure or airflow) and low pressure after the turbine (the real reason for that pimp 3" exhaust) equals better spool. Same for heat. High heat before the turbine can create more mechanical work. The theory is that by keeping the heat IN the exhaust, you increase the pressure differential across the turbine, doing more work, reducing lag.

Now in theory this all works out. Its all physics and thermal/fluid dynamics. In reality, can you feel the difference? I'm not sure since I have never tried it or tested it. But I'm going to guess that the gains are quite small.

The effort to reduce underhood temps is worthwhile. If even parts under the hood can take the heat, the heat will shorten thier life by some amount. And that heat ends up in your intake air, reducing power, increasing knock propensity, etc.

Wrap will hold moisture and increase the rate of oxidation on your header/manifold. Many header manufactures will not honor the part's warranty if header wrap was used On a cast iron manifold, I can't really see it being as much of a problem, but I could definitely be wrong. Only way to find out is to try it, or find someone who has (and has checked the condition of the parts periodically of course).

[Gsx_hooptie]

Thanks for all the replies, guys.

I had been thinking about the simple ideal gas law stuff, and figured that spool would be helped. I didn't know the heat transfer affected things so directly, or about pressure drop. I feel like I should have figured that out... but it's cool to know, and I understand (now). As I read more of the Kevin posts, I think I'm garnering a little more.

I think I'll take most people's advice, all at once: I'll wrap the manifold, put the heat shield back on over it, see if I can partition off the intake, and look to see if I can make any super custom vents.

[1stGenRocks]

take some pics of your manifold now then in a couple months unwrap a spot and recheck it for us save the rest of us some work

[Gsx_hooptie]

Originally Posted by 1stGenRocks

take some pics of your manifold now then in a couple months unwrap a spot and recheck it for us save the rest of us some work

I will. I don't mind being the test subject

[96spyderman]

Kevin had mentioned that the wrap will hold moisture... I agree that it will... but I do believe that the HiTemp spray that you use over the wrap "seals" it up as not to let moisture in.... but water can get anywhere!!!

Kevin... you definately had a better way of explaining the reasons for wrapping the turbo and headers... better than mine!! he he he

I think that the wrap is more commonly used on bigger engines that produce larger amounts of heat than our cars do...