Exhaust Insulating Wrap [How To...]
Posted: Mon Jan 30, 2012 8:51 pm
*Disclaimer* This was my first and only attempt. There may be a number of better ways to do the job.
Hopefully this guide will give you some ideas to make it easier.
How To Wrap Your Stainless Steel Exhaust Manifold
There are arguments for and against heat wrapping your exhaust manifold.
I went for *50’ x 2” pre-coated graphite black exhaust insulating wrap made by Thermo-Tec and a can of their recommended ‘Hi-Heat Coating’ paint, in black.
They also do copper and aluminium paint colours.
You will also need about 10 stainless steel ties. I bought cheap ones from ebay, that were not very good, so try and get some quality ones.
Alternatively, you can use tying wire, which you can ‘hide’ when securing the wrap. This will make the finished job look much neater.
*I found that 50 foot of 2 inch wrap was plenty, with some left over.
Some tools I found useful:
2. Remove your manifold from the engine bay.
3. Measure out and cut your wrap into four equal lengths.
4. Moisten the first piece of wrap.
Get your first piece and dunk it in some warm water.
DO NOT SOAK IT!
You just want it moist, so wrap it in a dry cloth after dunking, to remove the excess water.
Alternatively, you could use a 'bug spray' gun and give it a damn good 'misting'.
5. Start wrapping the first pipe.
Preferably start your wrapping on an outside pipe.
As my manifold is a 4 – 2, I worked on one branch at a time.
I used the plastic cable ties to secure it temporarily until I was sure I had it right.
After each wrap, pull it tight. You want to overlap each wrap by about ¼ inch.
Once you’ve finished the first one secure the end with a plastic tie it should look like this;
DO NOT CUT OFF THE EXCESS YET!
6. Start wrapping the second pipe.
Start wrapping the second pipe, the one that’s connected to the first one you did.
When you get close to the join in the branch, you will have to cut the first wrap you did, at a convenient place, ensuring there is none of the metal exposed.
Wrap the second layer over the first cut one and pull it tight.
Finish wrapping down to the flange, make sure none of the metal is exposed, and cut the second wrap at a convenient place.
Tuck the end under a previously wrapped portion. This is where the pliers and screwdrivers come in handy.
Finish, by securing all ends with your steel ties or tying wire.
7. Do the same procedure to the second branch.
You will find it increasingly more difficult to wrap the lower portion because of limited space between the pipes.
The screwdrivers and pliers come in handy here too.
It should look something like this when you have finished;
If you’re not using the Hi-Heat paint, then this is ready to be fitted back onto the engine.
________________________________________________________________________________________
8. Allow to dry.
If you are using the paint, you will need to dry the wrap overnight ready for painting.
I put mine in the airing cupboard.
9. Mask up the flanges.
Once it’s dry, you will need to mask up the flanges so that they don’t get painted along with the wrap.
If your flanges look rough and you want them painted, this won’t hurt, but you’ll have to prevent paint from entering the insides of the manifold.
10. Spray on the coating.
Spray paint the wrap in a well ventilated area, as per the instructions on the can.
Two or three light coats will avoid running and sagging. Allow paint to become tacky between coats.
The finish will dry to the touch in 15 to 20 minutes and will cure for maximum heat resistance during normal operation on the hot manifold.
11. Fit the manifold back onto the engine.
12. Start your engine.
Once the manifold is fitted, start the car and run up to temperature.
The wrap will start to smoke while it’s curing.
Try not to breathe this smoke in, as it’s nasty stuff.
13. When the smoking stops, you can stand back and marvel at your handywork.
Hopefully this guide will give you some ideas to make it easier.
How To Wrap Your Stainless Steel Exhaust Manifold
There are arguments for and against heat wrapping your exhaust manifold.
- Just so you can make an informed decision before proceeding;
- FOR
Exhaust Insulating Wrap (Graphite Black) The original Exhaust Insulating Wrap was developed over 12 years ago by Thermo-Tec. Exhaust Insulating Wrap is an innovative way to create more horsepower and reduce under-hood temperatures. Wrapping headers maintains hotter exhaust gases that exit the system faster through decreased density. Increased exhaust scavenging is produced, along with lower intake temperatures. Exhaust Insulating Wrap withstands continuous heat up to 2000°F, and contains no asbestos. Thermo-Tec exhaust wrap will not over-insulate a system when properly installed due to a proprietary coating developed by Thermo-Tec - Thermal Conduction Technology (TCT) - that conducts heat across the wrap's surface. This coating controls heat build-up and dissipation.
- AGAINST
1. Buy your products.Exhaust wrap. I was waiting to discuss with my friend Dr Keith McMullan at Cork CIT before providing a properly constituted answer. I have always been against it because it causes the pipe material to cycle repeatedly thru extremely elevated temperatures as the radiant and convective heat transfer to atmosphere is blocked. Since pipe contains stresses from manufacture and welding and since it is often made from steel or stainless with relatively low strength at high temperature the metal can degrade very badly. This is the effect of thermal stress as it's called. No need to go into the metallurgy. As far as impact on performance Keith is great guy to ask because he does a terrific amount of dyno test and software analysis, apart from being a very experienced automotive engineer in his own right. I asked him about pressure wave behaviour in this regard:
GC - how much does wrapping raise the average gas temperature?
KM - very high - can be as much as 150deg C (allowing for unimpeded heat transfer from the pipe to surrounding air the typical 4 stroke normally aspirated mean gas temp in the pipe would be normally 450-500 deg C or so, very high boost turbocharged engines - 30psi plus - can see nearly twice that)
GC - does that high temp affect the pressure wave significantly in practice?
KM - yes because the huge temperature effectively 'shortens the pipes' and so it dramatically alters the 2 way time ( Gas speed varies as square root of (Gas constant x Temperature x ratio of specific heats, for ex gas 1.4) The 2 way time being the time for pressure wave pos & neg to travel to collector and back into the cylinder)
GC - so for a fully optimised header - wrapping it could actually upset the tuning
KM - yes precisely. But in fact if you wanted to 'effectively' generate the effect of the pipes being shorter because they were too long or you wanted more 'top-end' you could wrap them to increase the gas speed. The only possible benefit - if you are prepared to accept severe deterioration of the pipes themselves is reduced under-bonnet temperatures. The massive flow of heat coming off the exhaust - especially in highly tuned front-wheel-drive installations when not moving at reasonable forward speed - can cause the fuel in the carb to boil, the oil and engine to overheat. The underbonnet temperature can be easily surveyed with an inexpensive hand-held probe from Halfords or other auto shop and will shock anyone who has never done it. Certainly cold air ducting is great when your vehicle is moving but not so effective when it's not. If you must use wrap to reduce underbonnet heat - give the insulating material some stand-off from the pipe to avoid those high metal temperatures. One must also remember that the heat doesn't just flow outwards radially thru the pipe and down the pipe - it gets into the port, the valve and seat - even piston - region and can cause all sorts of dramas: seats cracking, detonation etc etc. General increases in head temperature are going to degrade the inlet charge density too. And, if, for argument sake, you have a very highly tuned motor and you wrap your exhaust tightly and you're running a cooling system with plain water and no water-wetter or antifreeze your cooling system on the ex side of the head is likely to be totally overloaded due to nucleate boiling = no heat transfer at all to the coolant system - and the first thing you'll know about could well be a blown head gasket, or worse. Ferriday Engineering (see links) do a special heat-block mica gasket to help inhibit heat flow from header to head - it is well worth consulting with them. Do you want to wrap ex header/manifold on turbocharged units? No, no way just speculatively, even if it brings a performance gain - unless you know for sure by means of traceable metallurgical data and via accurate thermocouple measurement in the pipes etc that you are not exceeding the maximum rated temperature for the turbine blades and casing and exhaust port/valve region too. Never mind all the nuts and bolts that hold it together. Otherwise you put the whole unit at risk. Remember I was a Chief Engineer with a world-class turbocharger company so I know more than most about the degrading effects of heat on things. Coatings - though I have no hard test data, I imagine - are an attempt to do the same kind of thing as wrap. I would not use them at all. I hope this is helpful.
I went for *50’ x 2” pre-coated graphite black exhaust insulating wrap made by Thermo-Tec and a can of their recommended ‘Hi-Heat Coating’ paint, in black.
They also do copper and aluminium paint colours.
You will also need about 10 stainless steel ties. I bought cheap ones from ebay, that were not very good, so try and get some quality ones.
Alternatively, you can use tying wire, which you can ‘hide’ when securing the wrap. This will make the finished job look much neater.
*I found that 50 foot of 2 inch wrap was plenty, with some left over.
Some tools I found useful:
- Long-nosed pliers
Flat blade screwdrivers of differing sizes
Plastic cable ties
Latex gloves, (This wrap is made of fibreglass which will itch like hell).
2. Remove your manifold from the engine bay.
3. Measure out and cut your wrap into four equal lengths.
4. Moisten the first piece of wrap.
Get your first piece and dunk it in some warm water.
DO NOT SOAK IT!
You just want it moist, so wrap it in a dry cloth after dunking, to remove the excess water.
Alternatively, you could use a 'bug spray' gun and give it a damn good 'misting'.
5. Start wrapping the first pipe.
Preferably start your wrapping on an outside pipe.
As my manifold is a 4 – 2, I worked on one branch at a time.
I used the plastic cable ties to secure it temporarily until I was sure I had it right.
After each wrap, pull it tight. You want to overlap each wrap by about ¼ inch.
Once you’ve finished the first one secure the end with a plastic tie it should look like this;
DO NOT CUT OFF THE EXCESS YET!
6. Start wrapping the second pipe.
Start wrapping the second pipe, the one that’s connected to the first one you did.
When you get close to the join in the branch, you will have to cut the first wrap you did, at a convenient place, ensuring there is none of the metal exposed.
Wrap the second layer over the first cut one and pull it tight.
Finish wrapping down to the flange, make sure none of the metal is exposed, and cut the second wrap at a convenient place.
Tuck the end under a previously wrapped portion. This is where the pliers and screwdrivers come in handy.
Finish, by securing all ends with your steel ties or tying wire.
7. Do the same procedure to the second branch.
You will find it increasingly more difficult to wrap the lower portion because of limited space between the pipes.
The screwdrivers and pliers come in handy here too.
It should look something like this when you have finished;
If you’re not using the Hi-Heat paint, then this is ready to be fitted back onto the engine.
________________________________________________________________________________________
8. Allow to dry.
If you are using the paint, you will need to dry the wrap overnight ready for painting.
I put mine in the airing cupboard.
9. Mask up the flanges.
Once it’s dry, you will need to mask up the flanges so that they don’t get painted along with the wrap.
If your flanges look rough and you want them painted, this won’t hurt, but you’ll have to prevent paint from entering the insides of the manifold.
10. Spray on the coating.
Spray paint the wrap in a well ventilated area, as per the instructions on the can.
Two or three light coats will avoid running and sagging. Allow paint to become tacky between coats.
The finish will dry to the touch in 15 to 20 minutes and will cure for maximum heat resistance during normal operation on the hot manifold.
11. Fit the manifold back onto the engine.
12. Start your engine.
Once the manifold is fitted, start the car and run up to temperature.
The wrap will start to smoke while it’s curing.
Try not to breathe this smoke in, as it’s nasty stuff.
13. When the smoking stops, you can stand back and marvel at your handywork.
I too shall be using this in a month!