header wrap


60 replies to this topic
  • phat_450f

Posted June 09, 2005 - 08:26 AM

#1

I have seen alot of thumers riding around with that heat wrap on the headers. 2 questions where can i get some. Preferably black or blue in color. then also how do yo intall it to keep it on are there special clamps, or some kinf of spot tie. Thanks. oh yeah and i really dont wish to pay an arm and a leg for it eaither.... Thanks guys

  • mkporn

Posted June 09, 2005 - 09:02 AM

#2

I think Western Power sports has it... Best solution is to get together with a couple of buddies and by a rool at Napa or an Auto parts store. It's usually held on by clamps..

For anyone that doesn't nknow why you would do this, there are 3 good reasons

1. protect you and your gear.
2. keeps exuast gas temp's high to aid in evacuating them
3. the heat shield on stock exhaust collects grass and burnable debris between it and the pipe. (header pipe is hot enough to cause this material to start burning and is aided by the air as you ride......Big fire starter in dry conditions)

  • grayracer513

Posted June 09, 2005 - 10:01 AM

#3

2. keeps exuast gas temp's high to aid in evacuating them

There is no documented support for this contention that I have ever seen, at least not in the form of a dyno test showing any improvement whatsoever for keeping exhaust gas temperatures elevated. The amount of time that an individual exhaust event spends in the system does not really allow it to loose a significant amount of heat in any case, and more than 95% of the heat the passed the exhaust valve leaves by way of the tail pipe.

Some say that there are gains to be had in turbocharged applications, since it keeps exhaust velocities higher, but there again, the gases move through the system at speeds that don't afford much opportunity to shed heat in the header. The headers obviously get very hot, but it's the result of the cumulative effect of thousands of individual exhaust events.

In a car, with a closed engine compartment, insulating the exhaust can lower the under hood temperatures, which will lead to a cooler fuel system and intake air, and all kinds of good things can come from that. The same benefit can't be had on a bike, except maybe from insulating the airbox where the exhaust passes under it. But if it doesn't melt the plastic, how hot does it really get inside?

Insulating the header on a motorcycle can also lead to a prematurely burned out header due to prolonged overheating of the very light guage metals used in them.

  • phat_450f

Posted June 09, 2005 - 10:54 AM

#4

cool thanks man

  • YZ250F_Rider

Posted June 09, 2005 - 11:30 AM

#5

jeez man why not tell him the world will melt if he uses it. :)

The wrap does indeed help to keep the exhaust gas velocity up, the faster it moves the more exhaust can exit the cylinder. The more exhaust that leaves the cylinder the more room for fresh mix there is, and thus thats how you get higher hp.

It will not cause any damage to the header. I have had it on the 450 since new and on the 250's for several years now. None show any sign of burn thru.

A side benefit will be the lowered risk of 3rd degree burns if you get trapped under the bike.

You can buy the wrap here on TT's store, and if you drop by a local speed shop in your town you can pick up some stainless steel zip ties to hold the wrap on the pipe. Or if you want you can always use a hose clamp.

The idea started with nasa and was quickly picked up by all racers, including 1/4 milers and nascar (find a car that doesnt have it on).

  • Scooter426

Posted June 09, 2005 - 01:42 PM

#6

I know in 4 cyl superbike racing engines, we would see a benefit because header wrap helped keep temps higher to the point of the collector. The net effect was that the cooler exhaust pulses (past the collector) helped pull the hotter pulses (still in the header pipe). We always wrapped the header up to the collector. (this was in 1990-1995 era bikes). It was a turbo type effect that was definitely noticeable in accel/topspeed. They were messy in rain races though.

  • mkporn

Posted June 09, 2005 - 01:43 PM

#7

jeez man why not tell him the world will melt if he uses it. :)

The wrap does indeed help to keep the exhaust gas velocity up, the faster it moves the more exhaust can exit the cylinder. The more exhaust that leaves the cylinder the more room for fresh mix there is, and thus thats how you get higher hp.

It will not cause any damage to the header. I have had it on the 450 since new and on the 250's for several years now. None show any sign of burn thru.

A side benefit will be the lowered risk of 3rd degree burns if you get trapped under the bike.

You can buy the wrap here on TT's store, and if you drop by a local speed shop in your town you can pick up some stainless steel zip ties to hold the wrap on the pipe. Or if you want you can always use a hose clamp.

The idea started with nasa and was quickly picked up by all racers, including 1/4 milers and nascar (find a car that doesnt have it on).



Yeh, what he said..... :)

  • grayracer513

Posted June 09, 2005 - 02:01 PM

#8

The wrap does indeed help to keep the exhaust gas velocity up, the faster it moves the more exhaust can exit the cylinder. The more exhaust that leaves the cylinder the more room for fresh mix there is, and thus thats how you get higher hp.

Please produce ANY actual evidence supporting your contention.

:)

  • cobra427

Posted June 09, 2005 - 02:09 PM

#9

Hey thanks alot guys! Due to the full Pro Circuit system on my yz420 I'm just getting over a nasty burn to my inner calf....mind you I was not trapped and removed my leg as soon as it touched. What do you know, riding last week and in the same area I burned a hole right through my mx pants...luckily I didn't burn myself. Thanks for the tips, I was already brainstorming mods but now, problem solved. I don't care if there isn't one shred of evidence in terms of exhaust gases enhancement...."after having no skin on my leg and a nagging burn, I'm sold!!!" Thanks again guys

  • adrian

Posted June 09, 2005 - 02:18 PM

#10

Here I'll be a nice guy and send you 4 feet for free if you pay for shipping.....
if your interested PM me your address

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • YZ250F_Rider

Posted June 09, 2005 - 03:11 PM

#11

Please produce ANY actual evidence supporting your contention.

:)


Send your request to nasa and nascar and NHRA. I'll take their side.

I will give you a common sense way to prove it though.

I'm sure you'll agree higher exhaust velocities lead to better scavenging of the cylinder. And that better scavenging leads to higher hp soley due to more room for fresh intake charge. I'm also sure you'll agree that touching the header at the headpoint will be a sure way to get 3rd degree burns if you manage to get your fingers off with any skin at all.

Hot gas cooling down also slows down. Keep it hot, and it wont slow down.

Wrap the header with the wrap at 50% overlap and you can touch it without melting your skin off. Since the heat doesnt pass readily thru the tape it is retained by the exhaust gas and keeps the velocity of the exhaust up leading to better scavenging of the cylinder.

  • Hick

Posted June 09, 2005 - 03:59 PM

#12

I used to wrap my header for these reasons:

-Protect from dings
-Keep my gear from melting

A couple of reasons I quit doing it:

-Wrap stores moisture and contributes to rusting of header
-Brush that I ride through destroys the wrap pretty quickly

Jegs (a hot rod catalog, Google it) is a good source for header wrap.

  • grayracer513

Posted June 09, 2005 - 04:26 PM

#13

Send your request to nasa and nascar and NHRA. I'll take their side.

I will give you a common sense way to prove it though.

I'm sure you'll agree higher exhaust velocities lead to better scavenging of the cylinder. And that better scavenging leads to higher hp soley due to more room for fresh intake charge. I'm also sure you'll agree that touching the header at the headpoint will be a sure way to get 3rd degree burns if you manage to get your fingers off with any skin at all.

Hot gas cooling down also slows down. Keep it hot, and it wont slow down.

NASCAR teams do this to lower underhood temperatures, as do those who use the technique in the NHRA. Note that you don't see it on open-engined cars. And I was not aware that NASA used four-stroke gasoline engines in any of their space vehicles, or have they taken to hopping up the yard goats?

And no, I don't agree that there's a relationship between "higher" velocities and improved scavenging. There is an ideal range of velocity that builders work for, which is determined by the size of the head pipe. The rule of thumb was always that the pipe size should be the same as the head of the exhaust valve, or roughly that, or in the case of multivalve engines, the cross-section of the pipe should be about the same as the area of both valve heads. You will see this varied up or down some but not by very much. (Before anyone points out the headers on a fuel dragster, supercharged engines are totally different. Scavenging is a non-issue since the exhaust is forced out by blower with the incoming charge). Actual "scavenging" of the last remnants of the fuel charge is accomplished by negative pressure waves generated as the initial positive pressure wave of the exhaust on valve opening exits into the first major cross-sectional increase it comes to.

If maintaining high exhaust velocities were of such importance, why then would modern exhaust systems deliberately feature so many increases in pipe diameter along their length? The first one on a stock YZ250F header is located near the center heat shield bolt. You will have trouble seeing it, but you can feel it by running your fingers along the pipe, and of course, you can measure it easily. The next is typically in the center of the midpipe, and then there is a larger one as the pipe exits into the silencer. Each of these increases in size reduces exhaust velocities. On purpose.

Hot gases cooling down becomes denser and takes up less space. Becoming less bulky reduces the pressure on a contained volume of gas, but the increase in density helps it maintain its kinetic energy, so one offsets the other to a degree. Remember that the exhaust in the system is flowing in a series of individual events, not a steady stream. And as I pointed out, the entirety of a single exhaust cycle stays in the system for less than 70 milliseconds; not nearly long enough to be cooled by the metal of the pipe anywhere near as much as it is by the simple pressure drop it undergoes in leaving the cylinder.

A common sense way to prove it works would be to have a dyno chart that shows an improvement resulting from insulating the exhaust. Of course, we could also observe the number of factory teams doing this, too. :)

On the question of insulating to protect yourself, that is obviously a good reason, if you have a problem the pipe trying to burn you, but it won't make you go fast.

  • YZ250F_Rider

Posted June 09, 2005 - 05:05 PM

#14

cough -- bullchit -- cough. :)

Nasa invented the ceramic tape.

NHRA and nascar do not use it to lower temps although it is a benefit of using it. They use it to create more hp. (I should say used it as most have went to ceramic coatings now) Do some reading, it will do you good.

  • YZ250F_Rider

Posted June 09, 2005 - 05:14 PM

#15

A couple of reasons I quit doing it:

-Wrap stores moisture and contributes to rusting of header
-Brush that I ride through destroys the wrap pretty quickly


The titanium headers and none of the midpipes have ever rusted. I dont recall the 02's SS header rusting either. It could I suppose but I havent ever seen it.

If you think brush will shred the tape, you should see what 14 year old with a pressure washer can do to it. :)


Ideally you are supposed to paint the tape with high temp paint to further reduce the heat transfer of the pipe. I never have, and the cost is having to rewrap about every 6 months or so.

  • grayracer513

Posted June 09, 2005 - 06:43 PM

#16

cough -- bullchit -- cough. :)

Nasa invented the ceramic tape.

not wrap headers with

NHRA and nascar do not use it to lower temps although it is a benefit of using it. They use it to create more hp.

Lowering intake temperature results in more horsepower.

(I should say used it as most have went to ceramic coatings now) Do some reading, it will do you good.

Post a dyno chart. I'll read that. You might want to read the following from the June MXA:

"If you are looking for performance, chemically bonding a ceramic coating to the surface of the pipe yields no measurable gains in a motocross bike..."

Sorry.

  • cobra427

Posted June 09, 2005 - 08:14 PM

#17

Thanks adrian but I already ordered some. I appreciate the offer though

  • Speedracer747-400

Posted June 10, 2005 - 02:26 AM

#18

I wrapped my stainless headpipe and haven't had any problems with corrosion. It keeps some of the radiant heat from being transferred into my right radiator since I have a WB highboy headpipe which is really close. It's also really nice not having holes melted in your riding pants. I bought a 1"x15' black roll and the snap straps pretty cheap at Speedzone24-7. The 15' roll was exactly enough so make sure you wrap it very tight. I wrapped mine dry, but if you soak the role in water first you will get a little tighter wrap. :)
http://www.speedzone...aphite-wrap.htm

  • YZ250F_Rider

Posted June 10, 2005 - 05:13 AM

#19

will this due gray?

http://www.thermotec...ynamometer.html

dont forget their explanation of how it works. It backs up what I said.

http://www.thermotec...gy/how/how.html

This is what jethot says about their ceramic coating which most have went to these days. It exactly agrees with what I said.

At the same time, it accelerates the pulsed-vacuum effect on “tuned” headers, resulting in more effective scavenging of cylinders. The increased velocity of exhaust gases produced by higher exit inertia not only clears each cylinder more quickly; it also draws in the next fuel/air charge more efficiently



  • TexN343

Posted June 10, 2005 - 03:07 PM

#20

Your comparing a dyno on a big engine compared to a motocross bike? Isn't the size of the exhaust on a motorcycle a lot smaller so the effects would be close to nadda but the safety factor might be a good enough reason for the header wrap. Just my 2 cents.





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