expansion pipe wrap

tx246 · Apr 10, 2002

years ago there was a fiberglass wrap that you put around exhaust headers on a racing car. in theory the wrap would help keep the exhaust temp up which also ment faster flowing. would there be any benefit in insulating the expansion chamber. at the very least it would probably make the bike quieter. any thoughts?

jmics19067 · Apr 11, 2002

tried this a few years ago yes it will make your bike quieter. As for performance I cannot give you a good controlled experiment to tell anything . I did my top end and repacked my silencer at the same time I wrapped the pipe so the bike ran good. So it should of even if I didnt wrapped the pipe.I would like to think it did something but ...... :uh:

here is a guesstimate though from what I am learning. An expansion chamber designed to run at a higher temperature will favor a higher rpm.
so if you just bought yourself a torque pipe and wrap up the pipe to contain its heat well you kinda defeated its purpose.How much it raise the temp. I dont know but my silencer was hot enough to melt my plastic to a blob I would have to scrap of the swingarm. I tried it once but I doubt I would spend the money again .

MikeT · Apr 11, 2002

Years ago? They still have that stuff. The problem with it is that the pipe wrap holds in moisture and causes your pipe to rust. You should get a little performance increase, how much and where, I'm not sure.

Jaybird · Apr 13, 2002

A reputable four-stroke man tells me that all 4 bangers should be pipe wrapped. He sees noticible reduction in the temperature at the exhaust and it also helps to scavenge back unburnt gasses with the turbulence created.

MikeT · Apr 13, 2002

If you do put it on, I'd run the bike after you wash it to dry out the wrap. If you don't, you still have that rust problem....

Rich Rohrich · Apr 13, 2002

Originally posted by Jaybird
He sees noticible reduction in the temperature at the exhaust and it also helps to scavenge back unburnt gasses with the turbulence created.

No way you're posting that without SOMEONE throwing up a hand and exclaiming "SAY WHAT?".

Jaybird · Apr 14, 2002

Rich, I knew this would happen....
OK, I'm going to go talk to the guy next week and get his complete lowdown on pipe wrapping. I'm surely not qualified to give the complete analysis on this. I will add that I said "reduction of the temperature at the exhaust" when I meant "at the engine". The exhaust is actually hotter, creating turbulance, thus helping the scavenge of unburnt gases.
When I read tx246's post, it sonded very similar to what this guy was telling me. (Wade, if you are reading this, please weigh in and save me :))

dirtybkr · Apr 15, 2002

Originally posted by Rich Rohrich

No way you're posting that without SOMEONE throwing up a hand and exclaiming "SAY WHAT?".

Yup , LOL . I've got a black and blue mark from slapping my forehead .

David Trustrum · Apr 15, 2002

Kind of topical for me. Have been wrapping roadrace pipes for a while now -but rust is always a problem & it is not from the water as it rarely gets washed in this fashion.

Either way the idea is that the pipe is cooled by the airflow more at higher speeds so the wrap keeps the temperature more consistent (ie the cooler pipe acts as if it is longer which is likely the wrong way around).

The downside it is argued is the charge returned to the cylinder after it’s brief spill out into the pipe sits in a warmer header so is less dense when returned to the cylinder. Hmm.

Either way I wouldn’t bother on a dirt bike which is comparatively low speed. Please take that in context.

An alternative is to use a Titanium pipe which has better insulating properties (so I believe), or to get it HPC coated.

My choice to get my favourite RR pipe done was validated when a call from HPC (today) said once they had chemical bathed it, it was full of holes. Oh dear.

Pass the filling rod. :ugg:

Jaybird · Apr 16, 2002

The information I got on the pipe wrapping was like this:
"At lower rpm's, the wrap helps to keep the motor cooler. At higer RPM's the wrap helps to create turbulence/backpressure which aids in scavenging of unburnt gasses"

Smack your head all you want dirtybkr. I was simply passing on what I was told...and it was told to me by a very reputable four stroke tuner. Perhaps you could save Rich some typing and debate this issue with your obviously superior insight. Hope your head is ok.

shifter125 · Apr 16, 2002

just thought i'd throw my .02 cents in!! the thermal efficiency benefits described above are accurate for the most part. the one big thing (in my opinion) is the metal fatigue issue. your pipes will crack and break - specifically at the 180 degree bends in the system. this is a reliability issue and is directly related to the amount of use on the machine.

Matt ;)

Rich Rohrich · Apr 16, 2002

Originally posted by Jaybird
The information I got on the pipe wrapping was like this:
"At lower rpm's, the wrap helps to keep the motor cooler.

I think he'd have a hard time proving this on a water cooled engine

Originally posted by Jaybird

At higer RPM's the wrap helps to create turbulence/backpressure which aids in scavenging of unburnt gasses"

That just sounds like a simple lack of understanding on his part of what is actually happening in the pipe. No harm Jaybird I just find it funny the claims people make when they don't understand how things work, and it seems like this is the case with this guy :)

BEEF706 · Apr 16, 2002

The only solid benefit I could see from wrapping the pipe on my yzf was that it kept the FMF headpipe from burning more holes in my riding pants. I was told it would be more efficient but I never could detect a difference.

Jaybird · Apr 16, 2002

Rich, I think I may have actually posed a question about water cooled motors and the response I got was that he sees the difference with a simple thermal gun. Seems an easy way to prove or disprove it for low rpm's anywho.
On the theory of benefits at high r's...I'm at a loss.
For my money, I don't think the potential gains of wrapping vs the cost of pipes is worth the effort. Perhaps a ceramic coated pipe would benefit without worrying about oxidation...that is if you buy into the theories.

Rich Rohrich · Apr 16, 2002

Originally posted by Jaybird
Rich, I think I may have actually posed a question about water cooled motors and the response I got was that he sees the difference with a simple thermal gun. Seems an easy way to prove or disprove it for low rpm's anywho.

All it's reading is the skin temp of the outside of the barrel, which doesn't tell you much about the temp of the water circulating through the jacket.

Originally posted by Jaybird

On the theory of benefits at high r's...I'm at a loss.

Actually that's the only place where thermal wrap will likely show an difference. If you limit the heat transfer out through the pipe, then the internal gas temperature will be higher. Higher gas temps translate to higher gas velocities which makes the pipe act as if it were shorter. This shorter "acting" tuned length would tend to favor high rpm power.

Jaybird · Apr 16, 2002

All it's reading is the skin temp of the outside of the barrel, which doesn't tell you much about the temp of the water circulating through the jacket.

Ah, but wouldn't we be comparing wrapped vs not in a comparison to see if there is in fact a differnce in temp...a change in temp inside would surely reflect out.

Rich Rohrich · Apr 16, 2002

Originally posted by Jaybird

Ah, but wouldn't we be comparing wrapped vs not in a comparison to see if there is in fact a differnce in temp...a change in temp inside would surely reflect out.

The skin temperature of the outside of the barrel will be affected by outside air temps near it and airflow over or near the barrel. So if the bike is stationary with no air flowing over it and there is less heat radiating from the pipe in the vicinity of the barrel, then the skin temp will logically be changed. Assuming that somehow translates to a difference in engine running temperature with the bike moving is specious logic at best. :D

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