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Discussion Starter #1
It seems like exhaust wrap is a fairly inexpensive way to get a little more out of an engine. Assuming I already have a quality exhaust (Jemco, Rosko, Gianinni...):
Can I harm the headers by using exhaust wrap?
Is there any noticeable benefit from wrapping?
 

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There are different opinions on the benefits.

I do know that when I didn't use the exhaust wrap on my bike I melted a hole in my fairing where it came into contact with the header. When I put the exhaust wrap on the headers I no longer had that problem.

Craig
 

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Keeping heat in the pipe can help scavenging but may also help them rust out quicker. Skip the top couple of inches as the some heat dissapation for the exhaust valves is managed by the collars and start of the header pipes.
 

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+2 for TT

Failing that, back in the days before ceramic coatings dirt car headers were wrapped. So raced, brutally pressure washed, sit a week, repeat. I never saw headers fall apart from rust as people claim they will on bikes. YRMV
 

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They make no measurable performance improvement despite some silly claims about more exhuast energy and faster speed of sound pulses etc.

Cons: Wrapped pipes look like crap IMHO.
 

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I wrapped the pipes on my sportster last weekend ( actually my dad did). We did it for two reasons: 1) the rear pipe ran so close to the oil tank it blistered the paint and was transferring heat to the oil, 2) when the magneto was installed the nose of it runs kinda close to the front header and I was worried about heat transfer.

On a stock motor or stock heads you will never see a gain in performance. Doesn't mean it isnt there, just means it is so small it isn't measurable. But there must be a reason race teams from top fuel to f1 use the stuff.
 

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While at University, I worked on a project where we tuned a motorcycle engine to go into a small race car. We had a dyno and could not detect a performance difference with any type of exhaust wrap or coatings. In my opinion the small performance gain is probably smaller than what you will lose with the additional weight. That being said, as people have stated it helped out a lot with heat management in some of the tight enclosed areas we routed the headers, although so did heat shields which turned out to be lighter.

Geeto, maybe top fuel teams (I don't know much about that world) but I will all but guarantee that it has been 20+ years since a Formula 1 car has seen any header wrap. Or for that matter any other professional open-wheel car. If anything, they would use some sort of ceramic coating. Even then, every race car I have seen uses heat shields and reflective tapes to manage heat under the bodywork. Sorry to nit-pick your post as I agree with the rest of your reasoning. It seems like a good solution on motorcycles where a heat shield would be hard to pull off well.
 

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The idea behind exhaust wrapping boosting performance is in keeping the exhaust gases hot for longer. The hotter the gas is, the less dense it is, therefore it has less mass. It is easier to push a lighter gas out of the exhaust - hence the increase in performance.

This is of course a miniscule amount in the engines we are using, but in extreme performance applications this can be the difference between winning and losing. No doubt ceramic coating and other newer technologies do this just as well as wrap nowadays.

As for the downside of wrap on bike exhausts, they can hold moisture against the exhaust wall, which can quickly lead to rusted out pipes if they aren't painted / coated first.
 

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Discussion Starter #17
Excellent information and advice from everyone. Thanks to all.
I probably won't worry about the wrap then until the dollar makes some huge gains on the British pound - found an excellent Vic Camp full-fairing for the CB, but I'm not going to pay the crazy exchange rate right now.

Price is enough better than Clubman Racing to have it shipped from U.K.
 

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pavement magnet. keep workin on riding. fairings are cool and all....but present their own issues.
 

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Discussion Starter #19
quote:Originally posted by joe c

fairings are cool and all....but present their own issues.
But I was going to have your mug screened on the side?! Face on the left side, ass on the right...
 

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Funny thing about exhaust gasses, the hotter a gas is, the more viscous it is -> as temp rises, so does restriction.(http://www.mhtl.uwaterloo.ca/old/onlinetools/airprop/airprop.html) FWIW the gas doesn't have any less mass when you heat it up. Conservation of mass says this isn't going to happen.

The speed of sound in the gas changes as it heats up. If you are using the pipe lengths to modify the torque curve than this is important because what you are trying to take advantage of are pressure pulses that travel up and down the pipe at the speed of sound. (As opposed to the exhaust flow, which travels down the pipe at speeds much less than Mach 1) Wrapping the pipe will make it respond like a longer unwrapped pipe IIRC. If the pipe lengths weren't chosen to boost torque at some specific rpm to begin with than there's no reason to think that wrapping the pipe will improve anything.
 
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