Header wrapping

Wrapping a header can't possibly affect the flow of gases inside the pipe.  Also, wrapping a header inside an enclosed engine compartment will just cause heat to linger.

First of I’m not an engineer, 

that being said I always hesitate doing changes that could possibly affect the integrity of the components.

I have heard that wrapping headers could cause cracking that may not be noticed until it’s too late.

headers tend to crack anyway, especially the cheap ones.

I have also seen many hot rods with wrapped headers, I must admit on some I like the look.

I don’t understand how wrapping headers will increase the flow.

maybe someone smarter than me will chime in, (the list is long)

as for you it’s a no brainer, wrapping headers adds a weight gain.

Posted by: @cspidy

 

I don’t understand how wrapping headers will increase the flow.

As the gas cools down, the speed deminishes. If the gas column can be kept hot, the kinetic energy of the column stays marginally higher which increases the scavenging effect. A better scavenging gives more space for fress gas i.e. increases flow.  This is the one and only reason the thing started.

On a road car.... méh: The prinicple still applies ofcourse!, but the cat and muffler slow down/ hold up the gasses a lot more ánd the engine is not operating at full bore near/at max revs.

So; it ís a real thing. More for comp. cars with a high flow exhaust and running at max output for a relatively short time. Ceramic coating on the ínside works towards the same goal but without (over)heating the headers.

Posted by: @cspidy

 

that being said I always hesitate doing changes that could possibly affect the integrity of the components.

 

as for you it’s a no brainer, wrapping headers adds a weight gain.

The significantly!!! increased thermal load is a thing. Even for good quality products. 

It also speeds up oxidation. Again also on quality steel.

On the road it is worse still as the wrapping will get moist/wet which speeds up oxidation more still.

´Quality´ is relative in this case as the better the material/construction, the longer it will last but unwrapped it will all last longer...

The weight thing is a coin flip as the heat shields weighs about the same as a tight wrap plus metal ties.

Posted by: @cspidy

I have also seen many hot rods with wrapped headers, I must admit on some I like the look.

Plus it actually wórks!  So there you go.   The crux is; on thát application. So there you do a 180.

Im not smarter than anyone else but I have done my research into it and now have my own observation. 

The theory passed around the internets

The header wrap or ceramic coatings can keep the heat in the header. Keeping the heat in the header increases the scavenging of the hot exhaust gases increasing flow. 

 Keeping the heat in the header and not having it radiate out will also lower intake temps. Lowering intake should result in increased power. 

As far as the bad effects of the header it has a greater potential of warping or cracking due to the heat. On some race cars its used as an advantage and after a race the header is trashed. 

Here is the reality.

Header wrap does increase weight of the header more than the factory heat shield. 

 It depends on what you use. Fiberglass that absorbs water and can cause corrosion is not good. The newer Titanium wraps use crushed lava rock which is supposed to be a better as an insulator and doesn't absorb and hold water for long period.   

 I have noticed absolutely no difference in power with the wrap. My intake charge is a little lower but it never yielded a any perceivable  power to be noticed. On a cold day I do feel the car has more but on a summer day even if I isolate the intake at the side vent with shielding to bring the temps down it did absolutely nothing. What does make a difference is a good amount of clearance around the filter to it is not obstructed from gulping in large quantities of air.  I imagine if its a bigger displacement engine it might increase some power benefit but for our little engines I don't think so. 

 The whole warping thing is way over blown. I never entertained it a decade ago because of all the fear mongering although Im sure some have had headers crack. In reality those that I know that have wrapped never had any cracks or issues and this was with the fiberglass stuff that absorbs water. I imagine with the Titanium wrap its even less so.  I know people that wrapped the cheap Che header and no issues.  

  The main reason why I wrapped my header is to reduce under hood engine temps which it does and is remarkable. Since I do not have a heat shield I thought this would be a good idea because it will preserve and protect the rubber, plastic and electronics from heat radiation damage and corrosion  that occurs in time that can be a nightmare to diagnose as electrical resistance creeps and components wear out. I also plan to use some heat reflective tape and insulate much of the wires near the header so I can get the most out of my car for the long run. My lithium battery is also insulated using cool tape. 

 I feel that if you can reinstall your factory heat shield on to the Che header it should be good enough and will serve the same purpose. 

Some further thought on it:

In thís application he would best not wrap the exhaust pipes. Again because it is not straight out ánd longer running. A NoGo.

The blanket on the turbo will noticeably! reduce spool up time but also increase load on the turbo with a doubtfull underhood effect. A depends.

Posted by: @dev

I

 I feel that if you can reinstall your factory heat shield on to the Che header it should be good enough and will serve the same purpose. 

 

 

 

Quite. Without potential issues with increased thermal load. 

Posted by: @dev

On a cold day I do feel the car has more but on a summer day even if I isolate the intake at the side vent with shielding to bring the temps down it did absolutely nothing.

 

 

 

In my previous life I had a portable ´weather station´ and used a relative air density table to adjust the jetting even for the fourstrokes! They would not behave as temperamental as the two strokes who could literally have a seasure 🤣  but it would make a difference in performance.

Makes a surprisingly large difference; a cold day with high air pressure and a bit of rain in the air versus a low pressure hot, dry summer day.

Wrapping a two-stroke exhaust was/is a NoNo btw as it changes the speed thus timing of the interference as well.

Posted by: @dev

 What does make a difference is a good amount of clearance around the filter to it is not obstructed from gulping in large quantities of air.  

 

 

It is hére where the OEM air intake has some room for improvement.

The filter box takes in air through the horn shaped elbow, then through the duct behind the rear quarter panel and this is bolted to a flat hole in the engine bay side panel behind the battery, under the fuse box. Air must get in there from the side vent.

Taking the duct out makes a plenum chamber from the space behind the quarter panel but to put the issue in a perspective; even our none too large capacity 1ZZ at 6000 rpm sucks in the volume of that space in a second... It could do with a duct from an intake in the front bumper 😎 

Posted by: @petrus

Posted by: @dev

 What does make a difference is a good amount of clearance around the filter to it is not obstructed from gulping in large quantities of air.  

 

 

It is hére where the OEM air intake has some room for improvement.

The filter box takes in air through the horn shaped elbow, then through the duct behind the rear quarter panel and this is bolted to a flat hole in the engine bay side panel behind the battery, under the fuse box. Air must get in there from the side vent.

Taking the duct out makes a plenum chamber from the space behind the quarter panel but to put the issue in a perspective; even our none too large capacity 1ZZ at 6000 rpm sucks in the volume of that space in a second... It could do with a duct from an intake in the front bumper 😎 

 

  I would say you want two things. A short intake and a cool charge. 

  I have done comparisons using the ODB2 data logging on multiple Spyders back in the day to compare intakes and here are my findings.  

   The factory intake is actually quiet good as far as drawing in cool air and insulating from the heat. 

      Advantages

      Cool air when driving but over time it gets heat soaked and increases air temp but its mostly stable. 

        Great filtration, noise reduction and better part throttle response because of the vanes so the MAF gets a good reading. 

            Disadvantages

                Heat creep over time as the plastic absorbs heat. Filter gets clogged early and will reduce power gradually. The entire air intake can weight quiet a bit. 

        Aftermarket Air intakes that makes its way towards the rear of the car.

           No advantages except for looks.

          Disadvantages

          Because its longer it takes more energy to suck air. Because the piping is close to the radiation of the header it absorbs tremendous amount of heat. We recorded some temps in the high 130f.  Because there are no vanes like the stock intake it feels like you lost some power down low because the MAF under reports.  The stock set up feels like you have more torque. Some of the ones that go all the way back into the fender liner have been known to pick up water and hydrolock the engine during a heavy rainstorm where water is splashed in the area. 

   Best set up is a short ram intake with vanes. 

 Advantages       

There is a direct path of air to the throttle body so no restrictions. Air filter is in the front of the engine and away from the hot side. It is also shielded by the battery. Air from the side vent makes its way to form a pocket of cold are where it can draw from.  Air intake temps are some of the lowest recored. I was able to get near ambient temps while driving. Heat does creep in at a stop light but once moving it goes away quickly. It weighs next to nothing compared to the other options and is a great way to shed weight. 

   Disadvantages   

       It is loud but that is a good thing because it sounds great near your ear. Filter cleaning can be a pain if you have a big battery which might need to be removed.  Installation can be challenging because everything is tight.  

Ok, I am an engineer and have been an engine design and development engineer for the past 40 years.  Do not wrap headers!  You can get away with wrapped headers if you almost never drive at full power and only do it briefly (like in most street driving), so that is why a lot of folks seem to have reasonable experiences with wrapped headers.  When we run engines at full load on the dyno (where we can just stay at full power) we place powerful fans blowing right on the header tubes, which are glowing red-hot.  With the big fans blowing, the headers can survive months of engine development without cracking.  Sometimes they crack anyway.  Without good airflow, experience shows that we can expect headers to crack in hours or days at high power.  There is a reason why oem's use heat shields instead or wraps or blankets.  Shields are designed to allow cooling air to reach the hot pipes, yet still shield other items from radiative heating.

The idea that insulating the header improves flow is really wrong.  On the average it does the opposite.  Keeping the heat in does raise the average gas temperature in the tubes and this theoretically will increase the pressure and velocity in the primaries, but at the expense of backpressure!  A hotter primary acts like a cooler primary but of a smaller diameter in terms of flow.  This higher pressure and velocity does effect breathing (slightly) and might help if your cams are not optimally timed (for a specific speed and load), but you would be better off doing a more careful engine calibration (or choosing smaller diameter headers).  You optimize scavenging in an engine by careful tuning of cam-phasing, optimizing port-flow, and minimizing backpressure; not by insulating headers.

Also, if you have wrapped headers, you won't get any real benefit from idling before a shutdown.  The exhaust temp cools down extremely rapidly when you back off the throttle.  Idle and light-load exhaust temps can be as low as 400-500F and full-power can be 1600-1700F.  Temps under 1000F are no issue to stainless-steel.  Also thin SS pipes have very little heat capacity.

See this also: https://rothautomotivescience.com/forums/topic/why-you-should-not-wrap-headers/

Dave

Funny thing is that Cap Weir´s MAF mod deletes the vanes...

I am loathe to faff a round woth the OEM intake btw. as it is a very well sorted combo of air filter box, MAF housing, throttle body and intake manifold playing well together with the ECO program.

It took me a lóóóng time to get conviced to try the MAF mod as it fooling the ECU to read too less load so it advances the ignition and turning the wick of the oversize yellow fuel squirters down through the =2 sensors.

It is easy to see though that the removal of the vane plate also removes quite a restriction. Removing it shoúld make the MAF less sensitive to changes in load but in combination with the rest of the mod it does not. Weird.

I am surprised about the water logging. The plastic wheel liner may not be hermetic but closes off the space quite well. I´d expect you´d need to wáde the car for the filter to suck só much water.

The size of the drain hole in the bottom points to Toyota not expecting ingress of a lot of water either. Maybe enlarge the hole a few mm.?

Posted by: @petrus

Funny thing is that Cap Weir´s MAF mod deletes the vanes...

I am loathe to faff a round woth the OEM intake btw. as it is a very well sorted combo of air filter box, MAF housing, throttle body and intake manifold playing well together with the ECO program.

It took me a lóóóng time to get conviced to try the MAF mod as it fooling the ECU to read too less load so it advances the ignition and turning the wick of the oversize yellow fuel squirters down through the =2 sensors.

It is easy to see though that the removal of the vane plate also removes quite a restriction. Removing it shoúld make the MAF less sensitive to changes in load but in combination with the rest of the mod it does not. Weird.

 

I am surprised about the water logging. The plastic wheel liner may not be hermetic but closes off the space quite well. I´d expect you´d need to wáde the car for the filter to suck só much water.

The size of the drain hole in the bottom points to Toyota not expecting ingress of a lot of water either. Maybe enlarge the hole a few mm.?

    Cap Weir's MAF mod deletes the vanes for a good reason. He was able to bench test it and tune for it using the spacer to create the ofset to get the right response from the MAF signal he was looking for to maximize tuning with the larger injectors which is completely R&D.  Basically what he did was the equivalent of turning with a piggyback as that also fools the ECU. 

It is much worse to just eliminate the vanes as most aftermarket intakes do without reason and much later it was found out that those intakes lose power.  One  company in particular actually necked the area where the MAF meets to make  a smaller diameter tube so the MAF reads correctly and although it works it is a bad way to do it. Vanes are better because it simulates a smaller diameter without restricting the flow of air.

 There have been quiet a few that have ruined their engine because of hydrolock with the filter in this area.  It also gets cruddy with swamp water that ruins the filter with chewed up leaves and other debris.  Just a bad design and a complete rip off from what they were asking.  The solution for this issue was to use a valve attachment so it bypasses water from being sucked up.