| Author | Message | ||
     Whodom |
I accidentally discovered something pretty cool. The pipes on my 2000 S3 looked like crap when I got it; they were heavily oxidized, especially the rear pipe where it comes out of the cylinder head. After seeing some of the posts here about polishing XB pipes, I thought I'd try and clean mine up some. I started with Mother's Alum/Mag polish, then tried Brasso, then Eagle 1 Alum/Mag polish (all with little effect) and finally broke out the wet/dry sandpaper. I started with 320 grit, then 400, then 600. Then I hit the pipes with Eagle 1 Aluminum/Mag polish and they were nearly chrome shiny. OK, the pipes now look a lot better, but here's the cool thing I found out. Prior to this, the back pipe on my bike would absolutely cook my right leg in stop and go traffic. At first I thought I must have an exhaust leak at the cylinder head, but I could not find it. It wasn't not too bad in the winter or when I was on the road, but in traffic I'd have to shift position to "right foot down" when stopped or my leg would roast. (BTW, this is with jeans on.) I was seriously considering putting header wrap on the pipes (as many here have done). Well, since polishing the pipes, the heat coming off the rear pipe is amazingly reduced. Coming into work this morning, it was about 70 degrees F, and I got caught at a couple of long lights, and barely felt any heat in my right leg. It was a marked difference. I haven't pulled out my heat transfer book, but IIRC what I changed by polishing the headers is the "emissivity" of their surface, which would reduce their ability to radiate (or absorb by radiation) heat. If I touch the pipe, it'll be at least as hot as it was before, it's just not radiating the heat out at as high of a rate. Based on this, I don't see any need to install header wrap. Pretty neat practical demonstration of heat transfer principles. (Message edited by whodom on May 10, 2005) | ||
| Jlnance |
Thats neat! I would never have guess that would happen, but your explanation makes good sense. Dark surfaces radiate heat better than light ones. | ||
| Blackbelt |
well i know that my ceramic coated header was cooking my knee this morning in construction traffic.... but since mine is coated w/ that blue stuff, i dare not polish them... maybe down the road i will get a 2nd pipe and innerchange the pipes....lol | ||
| Rock |
Less radiation was an unexpected bonus when I installed a header from a millenium (nickel like finish). My bike, like yours, would cook my leg in stop and go traffic; but after the swap, I would swear the radiation was lessened by 50%! | ||
| Cyclonemaniac |
I Ceramic coated the header on My M2 and got the same result. My ceramic coating looks like polished aluminum. Another benefit, is because it keeps the heat in the pipe, it increases exhaust gas velocity and improves engine performance.  | ||
| Ara |
I suspect that polishing the pipes reduces their surface area. There may also be some blackbody radiation effects going on here, too. Engineers, speak up! | ||
| Whodom |
You would have to have some seriously crusty pipes for polishing them to significantly reduce their surface area. I'm convinced the change is due to reduced heat transfer by radiation (black body radiates perfectly, perfectly shiny body doesn't radiate at all). | ||
| Charlieboy6649 |
OK, so for those of us with a dent on the header; would header wrap also reduce radiated heat?...and uh cover up my bump as well? | ||
| Whodom |
Charlie, several of the XB guys have wrapped their headers. Check Glitch's posts for details. I'm sure that would cut down the heat too. | ||
| Kevyn |
Charlie, spend some time prepping your pipes before you wrap them--quick wipe down with a 00-000 steel wool and they're ready to go. 2 schools of thought; wrap dry, wrap dampened. I wrap dampened. Wrap carefully with good overlap. I wrapped all the way to where the muffler slips on to the collector. I secured the ends with stainless band-style clamps. Let dry or oven cure(smelly, real smelly). Some folks just leave the wrap alone, natural looking. Others like to spray the wrapped headers with a high-temp sealant. The sealants come in colors and adds some additional heat insulation and protection against rain and road debris to the wrappings. It will hide the dents and scrapes. It's a fun and easy project you can do at home in an afternoon. Have new clip rings and exhaust gaskets on hand along with some band-style clamps to hold the wrappings in place. Take your time, be neat with the wrapping and coating and you're good to go! The wrappings really stink while they 'cure' but be patient it will go away!! | ||
| Charlieboy6649 |
Thanks for the hints Kevyn... Now, to get online and buy some... I'm sure it's easier if you take of the header. How much of a pain is it to wrap with header installed. I'm asking those who have done it. Should I or shouldn't I take the header off? | ||
| Wardog3187 |
It is way easier if you take the pipes off and wrap them verses wrapping them while on the bike. I wrapped mine to cover a "road rash" on the front pipe and did this while the pipe was still mounted on my bike. It's a pain to do, but it can be done. |
