header wrap


60 replies to this topic
  • grayracer513

Posted June 13, 2005 - 09:39 AM

#41

To me, the entire question of whether keeping the exhaust hot is beneficial remains unanswered.

> Expanding gases such as those in the initial phase of an exhaust event, contained in a fixed size tube like the exhaust, open at one end, will go faster when they are hotter because they are under more pressure. "Simple physics" (Newtonian) tells us that the pressure of this body of gas will bear equally in all directions; against the sides of the pipe, against the lower speed gases the pulse encounters, AND against the gases still trying to leave the exhaust port. Anything that lowers the pressure of the gas body will lower that resistance.

> Nothing so far offered has answered this question: If it is so important to keep the exhaust velocity high, why do modern exhaust systems feature so many increases in section over their length, each of which not only slows the exhaust, but also cools it? (Abrupt drops in pressure cause a corresponding drop in temperature. That's how refrigeration works.) I know why they are there, but I want to know how something that so obviously works against high gas velocity could be a good thing, given the assertion that higher velocity is so important.

> There is simply no support for the idea that even fractionally more heat can be drawn off of a single exhaust pulse during the less than 20 milliseconds it spends in the header and midpipe by exposure to an uninsulated exhaust system than results from the loss of pressure that occurs from just letting it out of the cylinder. There is also no hard evidence that I have seen that shows that increases of velocity actually result from insulating the exhaust.

  • YZ250F_Rider

Posted June 13, 2005 - 10:30 AM

#42

Well there you have it. Two against, and the rest for it. Odds are they havent tried it on anything at all, yet they are still exspurts on the subject. :)

I led you to the knowledge yet gray grabbed a single sentence of cooler intake charge also helps in a whole page on how keeping gases hot leads to more power, and then claims victory. And you claim that since the dynos were of big blocks that it's not directly transferable to these motors and want me to run dynos to convince you. It's now expanded into a completely different aspect of exhaust tuning (pulse reflections) to somehow argue against the original debate.

You guys knock yourselves out. No one is here to convince you of anything. Gray asked for dynos showing that using wrap led to higher hp, I did. He asked for an explanation of how keeping the gases hot and the velocity up led to higher hp, I also did that. If you want to talk reflections then start a different thread because it's that different.

  • WheelsUp

Posted June 13, 2005 - 04:54 PM

#43

Gray asked for dynos showing that using wrap led to higher hp, I did. He asked for an explanation of how keeping the gases hot and the velocity up led to higher hp, I also did that.

You offered marketing hype from one company that happens to sell insulating tape, complete with dyno tests that are 100% unverifiable by an independent third party.

Where's your NASA and NASCAR tests?

  • YZ250F_Rider

Posted June 13, 2005 - 05:25 PM

#44

LOL what ever dude. The request was for anything to support the claim, as if nothing at all existed. I provided the data. If you need to disbelieve well, feel free in knowing it's your bike that you are dissing because you refuse to wrap it before use. You know I think thats a recurring theme for you california guys, the lack of wrappers. :)

  • WheelsUp

Posted June 13, 2005 - 06:31 PM

#45

As far as your comment about it being "two against everyone", you are the only one claiming that the gains are from the magical effects on exhaust charge temp.

Why not ask Burned... he runs a Dynojet dyno for a living.
He says that the dyno will show no difference on any of the three scenarios I outlined.

Like I said... until someone tests it in our particular application, it's junk science to claim otherwise.

  • RC876

Posted June 13, 2005 - 07:56 PM

#46

I think everyone is in agreement that there is no question one can stop heat from being radiated form your exhaust to other parts of your engine. The benifits from doing so is obvious.

The differences are stemming from two questions.

1. Does wrapping your header make enough difference to maintain a higher egt for the length of the primary tube?

2. If the answer to number 1 is yes, then is wrapping your primary tube beneficial to the point of increasing scavenging and making substantial power gains.

I allways like to simplify things. Why even discuss question 2 till someone proves if #1 has positive results.

Now Grayracer and Wheelsup obviously have tons of technical knowledge on the subject. I would say much more than me (big dummy here). So I have to resort to real world tactics.

All we need is YZ250FRiders primary tube. I will weld in a thermocouple bung. Then supply a digital guage. Just so happens I ordered 7 more last week(suplying guages to other t talk members). We dont need a dyno. We dont need some extensive test.

Just fire the bike up on the stand. Warm it up and do few revs to the limiter. Then ride the bike on a Paved road and though all the gears. Log all temps. Then go back to the stand, add header wrap and do the same test again. You either increase EGT's or you dont. Till you know the results from this test why even ask any other question or even debate it.

Takes about 15 minutes to mount a guage and a head pipe. 10 more minutes to run the first test. 20 minutes to wrap the tube and perform the second run. Peace Norman

  • revolucien

Posted June 13, 2005 - 08:06 PM

#47

It sounds like the tape would keep the heat in but... does that inability to get rid of heat weaken the pipes structural integrity? I'm still curious if this tape would help without hurting. Specially for someone who dumps his bike a lot. :)

  • RC876

Posted June 13, 2005 - 08:11 PM

#48

We actually discussed that earlier. On Ti and stainless pipes they dont fatigue as fast. On mild steel tubes especially on cars go away pretty fast. If you peel off the wrap a year later the tubes will show signs of foalige. On an uncoated steel header in Florida dont expect it to last much more than 16 months or so.

I agree it will keep heat in. But at what amount??

I have done the above test before on a couple of occassions. First to assure myself. Then a few other times to prove a point.

  • revolucien

Posted June 13, 2005 - 08:23 PM

#49

Right on, thanks, I guess I didn't get the earlier posts. I think it's funny that this argument goes on, but it doesen't seem like the change in exhaust flow is that much to give a gain.
If it was, you would think you would have to retune your fuel and air mix like when you rejet for a new pipe, or it would run crappy. How many people have retuned after wrapping their pipe with tape?

  • WheelsUp

Posted June 13, 2005 - 09:32 PM

#50

How many people have retuned after wrapping their pipe with tape?

LOL! Excellent point.
I'll let you know after I wrap my pipe.... to protect the fuel in my new IMS tank.

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

Posted June 13, 2005 - 09:50 PM

#51

Grayracer makes a valid point. The empirical method is always the best. If somethis is hotter molecules moves farther apart, more pressure, thus higher velocity. That being said...

Several people pointed out that on older race bikes (street) they would wrap the headers. I have done the same thing and also on cart 2 stroke motors. Both of those had much lower exhaust temps just like older car motors which is where it filtered to the motorcycle world from. Exhaust temps are much hotter today on both street and dirt than the days of old that it's a bad idea. :)

Put a Termignoni, Arrow, or Graves (Ti system) wrap it and see what happens, but not on anyones I know.

  • YZ250F_Rider

Posted June 14, 2005 - 02:44 AM

#52

The main advantage of the wrap is keeping things cool. If you need to rejet after wrapping the header then you simply needed to rejet period. You wont be able to detect a 1% change, but it will still be a 1% change.

Keeping the shock resevoir and the carb cooler is the most significant advantage to using it.

  • YZ250F_Rider

Posted June 14, 2005 - 02:46 AM

#53

Grayracer makes a valid point. The empirical method is always the best. If somethis is hotter molecules moves farther apart, more pressure, thus higher velocity. That being said...

Several people pointed out that on older race bikes (street) they would wrap the headers. I have done the same thing and also on cart 2 stroke motors. Both of those had much lower exhaust temps just like older car motors which is where it filtered to the motorcycle world from. Exhaust temps are much hotter today on both street and dirt than the days of old that it's a bad idea. :)

Put a Termignoni, Arrow, or Graves (Ti system) wrap it and see what happens, but not on anyones I know.


Are you saying it will melt or something?

  • DigilubeJay

Posted June 15, 2005 - 04:57 AM

#54

The reason exhaust temps are higher today than yesturday is obvious. Global Warming.
(good grief)

  • kawy

Posted August 20, 2005 - 08:43 PM

#55

Well, time for my 2 cents. All i have to say is thank you to everyone, this thread has been extremely informative for me since i was just considering wrapping my head pipe.!

  • stealman

Posted August 21, 2005 - 07:49 AM

#56

I wrapped my header and mid pipe because the sub frame, where the mid pipe goes behind it, was getting hot enough that it was melting my pants. I only did the header as well because I had the tape. I do not feel any difference in how the bike runs, but it has stopped the melting of my pants. I do not want to ruin my exhaust system because of using the tape. Does anyone know of another way to stop the heat from transferring to the subframe so I can take the tape off and still not melt my pants?

  • Satch0922

Posted August 21, 2005 - 12:10 PM

#57

Wow I can't believe I actually read this entire thread. :D

This was just a pissing match because the truth of the matter is no one on this board would be able to detect or benefit from a performance gain (if indeed there was one) from wrapping their header. Crazy talk.

BUT...if you want to keep the carb cooler they sell carbon fiber heat shields...I had one ...looked cool...did not make me faster on the track.

I did however weld studs onto my PC T-4 header and install a CF heat shield that was designed as a replacement for the stock 450 header heat shield. Worked like a champ and looked better than wrapping a pipe...(which always reminds me of an outside water pipe at a low rent house :D )

  • grayracer513

Posted August 21, 2005 - 06:27 PM

#58

the truth of the matter is no one on this board would be able to detect or benefit from a performance gain (if indeed there was one) from wrapping their header. Crazy talk.

wrapping a pipe... always reminds me of an outside water pipe at a low rent house :eek: )

:D :D :D

  • mickeydee

Posted August 22, 2005 - 09:36 AM

#59

i,ve had it on my yzf400 for years.i didn,t notice any more hp but it definitely saved my leg many times. and for my pants as well.it also has that look, you no,when everybody has to look twice, cool. :D i used muffler rap to keep it on.when the pipe heats up it shrinks and looks cool. one downside is that you will have to replce it every once in a while(rocks, roost ,low lying stuff) eventulally take it off bit by bit. :D

mickeydee
99yzf400
05drz400sm soon to be as fast as my yzf

  • Zeniac

Posted August 23, 2005 - 08:41 AM

#60

I recently purchased a Clark 4.8 gallon fuel tank and will lose the wings when I install it. I am concerned about heat because I live in South Texas where the temps run consistently in the mid 90's during the spring to fall period.

I am considering the header wrap to lower temps around the head area and installing a passive heat sink on the oil filled down tube of my XR650L to reduce both air oil temp. I do not have a dipstick temp gauge to read temps, but with the headers on both sides of the down tubes shouldn't removing heat from this area help the BRP run a little cooler? I thought that the heat sink would help to dissapate heat from the down tube without and extra lines to worry about. I am also planning to cut the back of the front fender up about 1 1/2 higher to provide more air flow to the head.

Does this make sense to you guys? Do you believe that the stock header pipe will withstand the extra heat? Personally I wouldn't be too bothered by having to re-wrap the header pipe every six months or so, but I'm not too keen on having to replace the header every 16 months.

Thanks in advance for any advice.

ps I have removed the smog stuff and performed Dave and Brian's carb mods already.





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