What is the Wisdom on "Exhaust Pipe Wrap" ?

[John Bennett]

I'm thinking about running to Austin and buying this old R1200R because she's so darn cheap.

In the photos I notice "pipe wrap". The whole bike is rough, sun burned, and neglected. They probably wrapped the pipes to cover up rust.

How bad a problem is that? Does pipe wrap actually do anything other than aesthetics? I've only seen it on old Harleys and old hot-rod cars.

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[Cagiva 549]

Pipes are probably rusted out under it . Ive used asbestos pipe wrap for heat protection but the cosmetic stuff does nothing but corrode the metal under it .

 

[jgrm1]

John,

Strip off the wrap and polish the stainless pipes underneath.

-Jeff

 

[TNC]

John, it's a good question about possible benefits of pipe wrap, and there are actual performance benefits in certain applications as well as a heat insulator in certain applications to limit heat radiation to parts in close proximity or to a rider in some motorcycle applications. No engineer here, but reading and actual dyno results from Motor Trend TV programs like "Engine Masters", it's clear that there "can" be a benefit. This also applies in a similar way to quality ceramic coated headers. Retaining the heat within the exhaust manifold, header, or pipe from the combustion process does some interesting voodoo...or science ....in exhaust flow and in some cases how the intake charge comes in.

However, from everything I've seen and read these performance benefits are only noticeable and measurable to some degree in fairly high performance applications. Probably the biggest benefit for most situations in automobiles and motorcycles is the heat insulation from the engine compartment or the rider. Obviously comfort for the rider, and in the case of the automobiles protection of nearby components and minimizing under hood temps. I did the ceramic headers on my pickup's hemi engine to reduce heat in the engine compartment more than enhance performance...the headers themselves being the performance enhancer and not so much the ceramic coating. I tow with this truck and exhaust temps get up there.

I've not owned a BMW, especially a boxer, so I don't know about heat insulation from the pipe being a benefit or not for rider comfort. As to performance, I doubt little is accomplished with header/pipe wrap. That bike is not a BMW S RR 1000. As to the owner wrapping the head pipes to hide rust, it's likely the owner either did it for foot and ankle comfort or an ill conceived search for performance. I'm obviously speculating there. I don't know the quality of those BMW head pipes to begin with, so they could be a ragged, rusty mess or a quality metal that could be brought up to acceptable standards with serious polishing.

 

[blupupher]

Well said @TNC, most bikes it is for looks, some is heat protection for rider. Rare cases it can help with performance by keeping combustion temps a little higher and allow better complete combustion. But that last one is probably not the case here, neither is the heat protection since the pipes are forward of the rider. So either just a look they are going for or covering up problems.

 

[jgrm1]

It wasn't that long ago that many were doing poor jobs trying to 'build' cafe racers.

Step 1: Wrap the header pipes (never mind cafe racers in the 50s and 60s did not have pipe wrap)

I suspect that is the case here. Judging by the condition of the rest of the bike, I don't think the seller is too concerned with tarnished headers.

-Jeff

 

[Cagiva 549]

Long ago I knew a guy that swore chrome valve covers made is ole beater go faster , less wind resistance , under the hood .

 

[Boulder Ed]

pipe wrap is useless. Its hiding something. If you buy a cheap beat up bike that's been out in the sun, rain or humidity for years you could be headed for major repairs soon. My .02 There are so many great used bikes out there these days that its just not worth trying to say a grand or two, then having to spend it in the first 4 months to repair stuff, and still own a beater.

 

[John Bennett]

There are so many great used bikes out there these days that its just now worth trying to say a grand or two, then having to spend it in the first 4 months to repair stuff, and still own a beater.

I'm coming to the realization that you are right Ed.

I keep imaging this R1200 sitting outside every night soaking up dew, and the slow, deep corrosion that causes inside electrical connections and circuit boards.

Buying a beater BMW is False Economy.

 

[mr72]

The physics of it are that exhaust header wrap has the effect of making the header primary effectively shorter. Contrary to your grandfather's old wives tales, shorter header primaries tend to improve low-end and midrange performance and throttle response. The difference is not insignificant, BTW; probably in the range of 10-50% reduction in effective header length. Also, higher temperature exhaust makes the pipe effectively larger in diameter, because there are fewer molecules of exhaust per cc. The trick here is that these effects are dynamic vs. engine rpm. So at low rpms, the pipes are effectively "longer" and "smaller", since the rate of heat being put into the exhaust is lower. As RPMs and exhaust pressure increase, the effect is to shorten the primary effectively, and reduce restriction along the length of the pipe. If these theories are correct, which is to say, if I am correct (which is suspect...), then it would have the effect of broadening the torque curve.

Just like cone filters, "pods" etc., most of the actual reason people do it is not for the marginal performance changes, but cosmetic. There's a big downside, which is that keeping this heat in will actually enhance corrosion, and the wrap itself can hold moisture against the pipe which as you know will increase corrosion. So if the pipes are rusted and you wrap them, they will rust more, and faster, without you seeing it happen. Also, the exhaust sounds a little different with the wrap.

Full disclosure: I do have this header wrap on my GS500 pipes, which are not particularly rusted but had a pretty ugly paint job that I wasn't really able to improve. It did have a noticeable effect on performance for that bike. It was enough change that it was tricky to get it tuned to run just right with the pipe wrap. Point is, it was not no effect, but just enough to require some carb tuning to get it to run perfectly. It's not something you can fix with just a half a turn on the pilot screw. It's a small enough effect that you wouldn't likely notice it riding before and after but if you had two identical motorcycles, one with the pipe wrap and tuning and the other stock, you could probably detect the change if you rode them back to back.

I am considering doing the pipe wrap on my Scrambler for cosmetic and sound reasons, but it's dialed in enough right now that I hate to have to retune it.

 

[Cagiva 549]

Ill bet you a buck you can wrap those pipes all you want and you will not feel an ounce of difference performance wise . Heat protection is the only advantage . Now if you start thinking about custom built tuned exhaust you might feel a difference . No factory pipe is built to the standards of a tuned system . It is built for cosmetics and price point only .

 

[John Bennett]

keeping this heat in will actually enhance corrosion, and the wrap itself can hold moisture against the pipe which as you know will increase corrosion. So if the pipes are rusted and you wrap them, they will rust more, and faster, without you seeing it happen. Also, the exhaust sounds a little different with the wrap.

I did not know that. Thank you for the information.

I'm going to pass on this bike.