[pmanaz1973]

Weird....I have an EFI Classic Silencer on my 2014 C5 - I have about 300 miles on it at various speeds including some sustained 50-55mph runs and it is not changing colors at all.  No power commander on my bike - About the only thing I do different than other guys I know is I am religious about running non-ethanol fuel(usually supreme grade since that's all I can find around here).

[NorEaster]

Yeah... I feel it's slightly defective and would like to try swapping it for another; but NFG will only do a return or let me buy a Power Commander 

[mattsz]

I put the "regular" EFI silencer on mine - it started turning colors right away!  A little at the after end of the wide bit, but more at the front, in the narrow portion of the pipe just aft of where it clamps to the header.

Doesn't bother me, though...

[NorEaster]

I thought the EFI self adjusted from some various posts on the forum, is that correct?

[wildbill]

all will colour up just depends on how you ride them. if you sit on 70 mph for a while -they will colour up really quick...lol

[SteveThackery]

I thought the EFI self adjusted from some various posts on the forum, is that correct?

I take it you are referring to the systems which "self-map" (and automatically re-map to compensate for engine wear, etc).  No, it isn't that sophisticated.  Having said that, it runs "closed loop" a lot of the time - more or less all the time you are riding around on moderate throttle, so in that sense, yes, it will compensate for any changes you make because it monitors the O2 sensor and adjusts the mixture until it is stoichiometric. 

However, when you are really giving it some beans it runs open loop (i.e. ignores the O2 sensor) and rich.  The amount of extra fuel it injects to achieve that extra richness comes from an internal map, which the ECU cannot update itself.  So under those circumstances you can assume that the degree of richness is no longer optimum if you've changed the intake or exhaust system.

It won't be far enough away to do any harm - but it might not release all the extra performance that your new exhaust or air filter promised.

In summary: unless you're a full-throttle kinda guy, then it will be running closed loop and stoichiometric most of the time, and that won't change with a new silencer.  It won't self-adjust for the new silencer at high speeds or large throttle openings, when it runs open-loop.  Thus you may not get all the extra power promised by the silencer.

[tooseevee]

I didn't make any changes to the FI... however the latest on the muffler is that mine is turning black. I have only put about an hours worth of use on it going a maximum speed of 50-55mph and two black bands are forming on the muffler.
I contacted the folks at NFG and have been told that I should be running it with the Power Commander. It's too bad that their wording only suggests using them together only as a means of getting you to spend another $400.
They have offered to let me return it but am unsure what to do. The bike runs good and I like the style of the short classic better than the stock torpedo.

        I don't understand the big surprise when metal turns colors when it gets heat put to it. It's physics. Simple physics. All exhaust systems turn colors of some shade somewhere along the way. It might be in the header pipe or it might be in the silencer, but some color is gonna happen somewhere.

[NorEaster]

I expect it to happen at some point. Mostly in the bend of the header pipe. It's not my first bike. My previous bikes experienced some discoloration in the bend of the header pipe, but not in the muffler and not after about 45 minutes of use.

[pmanaz1973]

Maybe the silencers are kind of like the bikes - it all depends on the individual unit  .  Maybe you should exchange it for another one and see what the new one does.  Couldn't hurt.

[tooseevee]

        I don't understand the big surprise when metal turns colors when it gets heat put to it. It's physics. Simple physics. All exhaust systems turn colors of some shade somewhere along the way. It might be in the header pipe or it might be in the silencer, but some color is gonna happen somewhere.

    I got my '08 AVL with zero miles in January 2011 (unsold from an out of business dealer). It was cosmetically perfect. I spent that winter learning the bike & getting it right. The first week I had it running good out on the road the giant muffler already had two straw colored rings around it that continued to darken & the header pipe was bluing. I removed it the very first season to begin making the engine capable of running as it was meant to.

         The engine was running very lean to begin with (Fed Regs) so I started learning about Mikunis & it evolved from there.

       The stock AVL & UCE exhaust systems run way hotter than in the old days. Cut the hot tube out of your header pipe & it will cool down the muffler, but then all the computer controls in the UCE might take up arms against you so I really don't know what to tell you.

       I did away with all the air pulse stuff, cut the hot tube out, put the giant $600 muffler up on a shelf & made everything black.

[Arizoni]

Changing color on a steel or chrome part is just the oxidation of the surface due to heat.

The color it becomes can be used to tell how hot the surface became.  This has been used for years when "tempering" steel parts.

On a steel part the colors begin to show in the following order:
430 degrees F = yellow
470 degrees F = straw
500 degrees F = brown
540 degrees F = purple
570 degrees F = blue
600 and higher degrees F = gray

An example of using this coloring is seen on this flintlock which I heat blued the bridle on.



Like steel, chrome goes thru the same color changes but the temperatures needed are several hundred degrees F hotter.

[mattsz]

Wow - I had no idea that the muffler temps were getting that high!  No wonder it melts my nylon jacket so easily! 

[tooseevee]

Wow - I had no idea that the muffler temps were getting that high!  No wonder it melts my nylon jacket so easily! 

               Yeah, but it's a dry heat     

[Kevin Mahoney]

All exhaust pipes change colors. Coating can help but sooner or later it is inevitable. Double wall pipes can help. Heat + steel = color.
The EFI on the RE does NOT "learn" over time. It learns in micro seconds about what is going on in that moment but it is hard programmed.

[SteveThackery]

The EFI on the RE does NOT "learn" over time. It learns in micro seconds about what is going on in that moment but it is hard programmed.

I just said that!  Mind you, you said it in one sentence, rather than a whole essay like I took. 

Yeah, yeah, I know - life's too short to read my posts.