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Old 09-26-2019, 08:40 PM   #1
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Holding Tank Exhaust Clearance

Iím looking at installing a rotomolded holing tank crosswise above the exhaust pipe. How much space does there need to be not to melt it?
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Old 09-26-2019, 08:53 PM   #2
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Where front to rear on the pipe are the tanks situated? I measured the exhaust out the back at 1500 high idle at around 125*. I wouldn't hang it near the turbo. And 6 -8" of clearance should work.
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Old 09-26-2019, 09:46 PM   #3
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Originally Posted by o1marc View Post
Where front to rear on the pipe are the tanks situated? I measured the exhaust out the back at 1500 high idle at around 125*. I wouldn't hang it near the turbo. And 6 -8" of clearance should work.
Itís mid-span on the shorty so about 6í back from the header
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Old 09-26-2019, 10:54 PM   #4
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Itís mid-span on the shorty so about 6í back from the header
Get you some of these temp test strips and find out how hot it gets where you want. I do custom powder coating and did a test once because it's a known "given" that exhaust gets too hot for standard powder on an exhaust pipe. Powder cures at 400*F, once cured it can withstand 100* over cure temp, 500*.
V-Twins like most Harley's get around 750* at the bend coming out of the head. So those pipes need to be coated in ceramic, with very limited colors. I decided to do a test and had these strips put on various places on the exhaust pipe all the way down to the entrance to the muffler on my buddies Kawasaki W-650 (Triumph 650 clone). Even at the head, the pipe never saw over 290*. I can coat that pipe any color I want.
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Old 10-11-2019, 06:33 PM   #5
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I wrapped tin foil around the pipe where I’m going to put the tank and jammed an accurate thermometer in between it and the pipe. When the coolant temp measured around 180 the pipe was at 220. So maybe the hottest it will get there is 300ish.

I contacted Heatshield Products yesterday before doing this test. The guy I spoke with claimed that I could wrap the pipe in “Heatshield Armor” and it would be OK. I’m still looking for more opinions. Please let me know what you think.

Again, I’d be spanning the exhaust pipe with an ABS tank with 6” of clearance. Thoughts?
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Old 10-11-2019, 06:55 PM   #6
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I wrapped tin foil around the pipe where I’m going to put the tank and jammed an accurate thermometer in between it and the pipe. When the coolant temp measured around 180 the pipe was at 220. So maybe the hottest it will get there is 300ish.

I contacted Heatshield Products yesterday before doing this test. The guy I spoke with claimed that I could wrap the pipe in “Heatshield Armor” and it would be OK. I’m still looking for more opinions. Please let me know what you think.

Again, I’d be spanning the exhaust pipe with an ABS tank with 6” of clearance. Thoughts?
Am I correct in thinking your measurement was taken with a thermometer sandwiched between 2 metal surfaces and it read 220*? If so, I suspect 4" away from the foil will be substantially cooler. Tape the thermometer the same distance as the tank will be and take a reading, I think you'll be surprised how cool it is. Keep in mind 99% of the time there will be roadgoing air venting that area.

I'm not a proponent of header wrap, as it's benfits are minimal and it's negative major. But in this situation it would help keep heat from the tank.
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Old 10-11-2019, 07:40 PM   #7
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I'm not a proponent of header wrap, as it's benfits are minimal and it's negative major. But in this situation it would help keep heat from the tank.
I think that any material that cannot dissipate heat is subject to loading so itís effectiveness minimized over time. Maybe the combination of insulator covered by a conductor makes for slower dissipation? My idea before I called them was to install an aluminum shield 3Ē away from the exhaust pipe and connected to the frame that would wick heat away. Iím still entertaining this idea.
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Old 10-11-2019, 08:21 PM   #8
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I think that any material that cannot dissipate heat is subject to loading so itís effectiveness minimized over time. Maybe the combination of insulator covered by a conductor makes for slower dissipation? My idea before I called them was to install an aluminum shield 3Ē away from the exhaust pipe and connected to the frame that would wick heat away. Iím still entertaining this idea.
Seems simple, just put an aluminum heat shield on the pipe where the tank is. The aluminum heat shield 1/4" off the exhaust pipe on my motorcycle doesn't get hot enough to burn me.
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Old 10-11-2019, 08:36 PM   #9
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Seems simple, just put an aluminum heat shield on the pipe where the tank is. The aluminum heat shield 1/4" off the exhaust pipe on my motorcycle doesn't get hot enough to burn me.
Wow, OK. Thanks thatís really good info!
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