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Author Topic: exhaust wrap  (Read 7899 times)
JohnEd
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« Reply #45 on: February 03, 2008, 08:13:45 PM »

Darrell,

That will be quite enuff of that eye witness testimony and plain facts. Roll Eyes  If you can't come up with specific feet temps and convection flow velocity....welll Grin

Nice post, Bud.  Did you ever get the feeling that some people are just not hearing what you are saying? Angry Grin Grin Grin

Post long and often Young Skywalker and Bus Rider Wink

John the Kidder
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The price of apathy towards public affairs is to be ruled by evil men." Plato
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JohnEd
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« Reply #46 on: February 03, 2008, 08:53:23 PM »

A while ago I contacted a diesel engineer at a research and engineering shop.  Lets not go into where and when and who....there is no money on this.  Anyway, I wanted answers to how many degrees the "A", as in aftercooler, version of the DD8V71 actually cooled the air temp going in the chambers.  He didn't know but conceded that it was a legit question but certainly not common.  He thought that the amt of BTU's added to the air was dependant on a bunch of stuff like ambient, turbin psi, engine temp, BTU's subtracted by "intercooler", BTU's added by compressor and BTU's subtracted by "aftercooler".  He said there was no pat answer for all diesels but it should be info retained by DD in its engineering dept. for a specific engine config.  The interesting thing he mentioned was that 400 degrees F was the absolute max inlet air temp.  Well, its a start and there we have it...hot air is even bad for diesel engines. Roll Eyes Grin

John
« Last Edit: February 04, 2008, 11:55:37 AM by JohnEd » Logged

"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
Darrell
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« Reply #47 on: February 04, 2008, 11:43:43 AM »

Well with my seat-of the-pants engineering degree, I'll have to disagree with the no need for heat wrap on a NA engine....... Grin
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JohnEd
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« Reply #48 on: February 04, 2008, 11:59:00 AM »

Darrel,

Me too!  Less heat is moving in the correct direction and worth it if it isn't breaking the bank.  It seems that all the guys that do it rave about its benefits.  I haven't heard a single guy say he wasted his time or wouldn't do it again.

Thanks,

John
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
NJT5047
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« Reply #49 on: February 04, 2008, 12:11:37 PM »

An aside to wrapping old steel exhaust pipes...check them for cracks frequently. 
Wrapping exhaust will keep the heat in for sure.  That trapped heat has been known to induce cracks in the  pipes. 
Most tube exhaust manufacturers void warranties on wrapped pipes.
Wrapping the exhaust to prevent engine room heat buildup may be a great idea.  Clearly it works.  Just keep an eye on the steel tubes for leaks.   This would be especially true on Eagles and GM coaches.  Unlikely to set an exhaust fire in an MCI with a clean engine room.   
JR



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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
Dreamscape
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« Reply #50 on: February 04, 2008, 03:23:07 PM »

Our Eagle doesn't need the wrap.......It doesn't go anywhere much..... Cry Cry

Too much to do.....To little time...... Embarrassed

Have fun you guys with your turbo's.....More horsey's equal more heat.....I'll stick with my 8v71N.....at least for now.... Wink
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compedgemarine
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« Reply #51 on: February 04, 2008, 04:34:46 PM »

on race engines the exhaust is wraped to keep the heat in which helps keep the velocity up which helps with the scavanging effect to the cylinder. a naturally aspirated gas engine is only around 90 percent effecient so anything that helps the scavanging helps the effeciency. so yes there is a benefit for all engines in addition to the reduced heat around and into the engine. even pulling outside air in you still absorb a lot of heat into the duct work going into the engine so everybit you can reduce it helps power.
on some of our race engines we saw a temp reduction of air inlet temps of 150 to 160 degrees from after the blower to after the intercooler. of course that is on a boat where we had 80 degree water in the intercooler and the biggest radiator around(the ocean).
steve
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buswarrior
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« Reply #52 on: February 04, 2008, 05:19:15 PM »

Another seat of the pants engineer just thinking out loud:

If you think about trying to warm up something in the colder climates... the engine room is a fairly open space that has a giant fan displacing all the air quite forcefully... that would be one heck of a tent or cabin to try and warm up with the doors open and the wind blowing through...

Jack's engine represents one awfully big campfire burning to get the compartment up to 170 degrees, and as noted a turbo motor will be a bigger campfire again...

Wrapped exhaust, and the tip some busnuts observe of opening the engine room doors on arrival after shut down to dissipate the heat, seems like a good combination to lower the heat transfer to the coach interior,

There is some inherent safety of reducing the exposure of hot surfaces for misadventure in the engine room.

The same benefit of reduced heat soaking might also reduce the heat transferred to the incoming air charge via the heating of the air filter housing and piping. (after a long run, that air cleaner is a little too hot to leave your hand on it) so it has got to be adding heat to the incoming air,

That much more cooling of the motor will be needed, or a little more incoming air charge density, whichever you like. This might just be what helps tip the balance into your favour more often in a marginal cooling system?

Count me as a fan of insulating the exhaust, and perhaps the intake too!

happy coaching!
buswarrior

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Frozen North, Greater Toronto Area
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