BCM Community

In another thread the topic came up about an exhaust wrap, rather than hijack that thread I thought I'd start a new one, I'm interested in finding out more on this.  One thing that was brought up was that it would increase HP and MPG on a turboed DD, along with the added benefit of a cooler engine compartment, sounds like a win/win situation but it must have drawbacks too, whats the good and bad of this and cost involved, any idea's?

Cody,

The cost is the only down side and I don't know what the cost is.  I have heard it is not cheap but look at the pains we go thru to insulate the darlings.  How much is too expensive? 

I have seen this on Prevost 8V92 engines and I think it was installed by the manufacturer but don't know.

This was a long topic on a board that I frequent that deals with turbochargers.  They always do a test before and after and the wrap worked measurably well.  Real gains.

The logic of this is HEAT IS ENERGY.  If you cool the gas before it goes into the turbo the gas will shrink in volume, loose some of it velocity and can do less work.  I thought cooling the gas AFTER the turbo would not matter but it seems that cool gas is more dense and doesn't flow as well as hot gas.  I don't think it should matter all that much but they measure those pressures, compute the impact and then verify the results on a dyno.  The friggen "teenagers" are so smart it scares me and there doesn't seem to be all that much bull shXXt about them.  When the gas enters the muffler it expands and cools dramatically so they don't bother with the wrap after the muf inlet.  The tests and evals I read did not have efficiency as a subject but more power from a given ....is more efficiency and that is power and MPG.

I have read posts by bus owners that absolutely raved about how cool the engine compartment had become.  I don't think they were related to the mfr.  They wrap all these hot pipes in Navy ships and I understand the environment would be lethal without that feature.  Unfortunately they used asbestos till not to long ago.  This isn't cutting edge science but it is valid.

Hope you get more opinions,

John

Cody,

We talked about this last summer.  Do a search here for wraps, heat wraps or something like that.   Believe you will find a coupld websites that sale the stuff.  It's not that expensive, for what it gets you.

If you can't find it,,,, let me know.

Bill

It looks like there is some affordable stuff on ebay but how much would one need for this size engine?

Cody, I had mine custom made down in Texas. I sent the drawings and pics of what I had. Price seemed reasonable. I'll get the # if you are intrested. Tom Y

Most Speed shops carry the stuff  comes in different widths.  I  own a Corvette and it is common to use it to prevent the ultimate burn out ;D   as well as Starter heat soak.  I also used it on my 6.5 Onan works great.  One line name is DEI

Cody,

    There has been volumes written about keeping the hot side of the turbo hot and the cold side cold.

    Some trivia.......
       There can be a 200 deg drop in temp from the head exhaust and the turbo exhaust.
        There can be > 100 deg rise in temp from the ambient temp to the head intake.
         (not including intercoolers at this point)

    Both situations reduce the effectiveness of the turbos ability to raise the air to fuel ratio.
    Diesel top ratio is 16:1 air/fuel. A raise in the intake temp has a noticeable effect.

   So wrapping the hot side helps keep the intake cooler and the exhausts warmer.
   Another trick that is being used is coolant cooled turbos.

   The only things I have read that is negative is moisture trapping causing exhaust pipe rusting.

    Of coarse any HP modifications can add more to the complexity.

  FWIW
     Mine is wrapped with a blanket style and does keep things a lot cooler. No scientific stats on that.
   Skip

Cody,

All the stuff I found on ebay and the net under "wet wrap" or "DEI" or "exhaust wrap" is NOT the correct stuff.  All that is is a fiberglass webbing that you wind on the ex pipe/header.  They say that reduces underhood temps by 70% and would a vendor lie?  Me thinks exaggerate most assuredly.  Imagine what the "REAL" stuff achieves.

The stuff I saw on the Prevost was at least 3/4 inch thick and had a fiber glass "mat" covering that was stitched along the longitudinal axis of the pipe.  Under the glass was a thick layer of fluffy ceramic cloth.  I don't know what they painted the glass with but it had a really firm feel.  The stuff had to be hand sewn/stitched to the pipe.  Owner said that the glass was cool to the touch so not much ex heat was getting in there.

It sounds like Tom got the "real" stuff if he had to send measurements and such and have it made for his engine.

Tom,

Can you send me the source info on the insulation you got....better yet post that data for Cody and me and others.  Please!

Thanks,

John

From the research I just did, you should coat the wrap with a paint sealant that is designed for this.  To keep things from soaking into the wrap and keep it from falling apart.  I could easily be wrong so take this at face value

Skip,

"Blanket" style?  Can you give us more info on that?  All the stuff I see advertised is a belt like webbing made of fiberglass.

Thanks,

John

Trevor,

The stuff I saw WAS painted with something that made the fiberglass exterior hard/real firm.  You are right.  I never considered it being to keep the wrap from admitting water spray but that sure makes sense.  I not some of the stuff in kits has a couple cans of high temp paint included.  At least it looks like high temp paint.  It might be some sort of sealant though.  I would sure as heck paint my ex system before wrapping regardless.

Thanks for your post,

John

 No problem...I'll take a picture tonight and post. There is a tag on it so hopefully
I will be able to read the manufacture.

  It looks like a grey canvas type material sewn to fit the pipe. with a batting.

  Please remember I am running an inline not a V block :) So my set up is easier to
 do. (no cross over pipes and the like)

 There is one on this board that if memory serves used a type where
 you get wet, install and it dries in place (kind of like setting Plaster) and has a foil exterior.
  I still haven't been able to find a supplier for that or his post (picture) :)


Skip

One persons solution. (he did a nice job)

go look at
ChuckMC8 pictures page 5

His web site is in his profile.


Skip

Skip,

That is the stuff.  Looks like canvas....me thinks it is fiberglass with a painted on coating.  Under that "blanket" should be some sort of ceramic blanket material..."I think".

The foil with batting attached stuff is used to wrap the convoluted pipes on the input to a turbo.  It is on the net under heat wrap or exhaust wrap.  I know the real stuff got its name of "wet wrap" because you wet the stuff before application and the engine heat "fixed" it to that contour.

The comment about "WATER COOLED" turbo's isn't quite complete.  It should read "water cooled turbo bearings".  Just like oil cooled didn't mean you cooled the entire turbo, water cooled doesn't either.  Heat kills the bearings with "coke" build up from the oil so they added water to that so the things don't get as hot under load and you don't have to let the turbos cool before shutting down the engine.

John

John,

   You are correct I was sloppy in my water cooled comment.

  The main reason is to keep the bearing cool (relative term)
I would also submit to you the concept that by keeping the
bearing cool one also sets up a minor thermal barrier to absorb
some of the heat that normally would be transfered through the
cartridge to the intake.

in short every little bit helps when dealing with 1100+ deg F.
 
Dejavu I think we have been here before :)

Thanks
Skip

Skip,

You are right.  It is a heat sync but in this case it is a trade off.  Life span vs performance hit. 

You are NOT sloppy...i didn't say that nor mean to imply it.  Great posts on your part but admittedly I am not the expert.

Hope you can come up with that mfr or source for the wrap you have.

Thanks,

John

Talk to Penn Lenson (pennsue@earthlink.net) at EHP.  He can give you the straight dope and is very helpful. Their ad is in BCM.

I used their wet blanket wrap on my generator exhause and it works great.

The blanket wraps around whatever you want to insulate and dries into a hard casing. It can assume almost any shape and can be cut into strips to wrap around exhaust pipes.

I've used it on two different generators and wouldn't have anything else. It is not cheap but it does the job.

Quote from: JohnEd on January 31, 2008, 11:43:33 AM
Cody,

All the stuff I found on ebay and the net under "wet wrap" or "DEI" or "exhaust wrap" is NOT the correct stuff.  All that is is a fiberglass webbing that you wind on the ex pipe/header.  They say that reduces underhood temps by 70% and would a vendor lie?  Me thinks exaggerate most assuredly.  Imagine what the "REAL" stuff achieves.

John

I'm sure there is better stuff out there ie: space shuttle stuff. I can confirm for the $'s  spent on  the DEI  stuff it is money well spent.  In the case of my Corvette the headers are wrapped leaving only a 1/4 inch exposed from the previous wrap around. You can grab the header tube with your bare hand.  The statement by the manufacturer about it reducing the tempeture under the hood by 70% I was not aware of but I do believe it.  In a Corvette with the firerglass body /  floor pans you can cook your own feet.  I'm just a satisfied customer not a shareholder of DEI. :)

John

  Here is a picture of the tag......somewhat washed
out by time.....Kind of looke like AIP out of Santa AN....couldn't
read the rest.   There was no ceramic just a batting with
a mesh to hold it on.

Hope that helps.

Skip

I had great results with a racing product that is sold at longacreracing.com.

This is a 58X24 sheet of aluminized cloth that you can cut with scissors that they will ship to you. The cost is $57.95 and it may take 2 sheets. Click on catalog and insulation when you get to their site. Part # is 64150.

I used hose clamps to hold the insulation in place, Its going on its 3ed year and is still looking as new. I double wrapped the head to turbo pipes and you can put your hand on the insulation when you pull over. I think it runs better too. I have more insulation to do the intake side parts to get cool air to the engine intake but haven't got around to it yet.

If the pipes were @ 900 degrees before, I bet I dropped the bay temp by at least a couple hundred degrees. I can open and close the engine bay doors without gloves now.

A good exhaust wrap does 2 things if you have turbo but only 1 thing for non turbo.
Biggest of two is increase respond time & less fuel as well keeping compartment cooler & protect nearby heat sensitive part.
Engine's exhaust to turbo must be maintained in same high temperature as possible to avoid air pressure shrinkage via cooling effect from non-insulation. Other word longer time lag during beginning of acceleration. Also while turbo is being use in climbing and high wind drag, will cause to burn more fuel (depress pedal further) then wrapped set-up.
However turbo to exhaust outlet should be cool as possible to reduce back pressure. Otherwise increase diameter exhausts pipes & wrap for compartment coolness from turbo to outlet with the least bends.

After all turbo perform according of the exhaust given pressure at turbo exhaust inlet, not from engine's exh port.

FWIW

Sojourn for Christ, Jerry

Skip,

That is the stuff.  I think the batting you mention is the ceramic I mentioned.  Fiberglass batting will powder off from vibration and heat cycles.  I think that must be Santa ANA or ANNA near LA.  I got nothing from AIP except a half million hits.

The guy that steered us to BC magazine was a Prince.  Page 41 of this months issue lists E.H.P. (Engine Heat Protection.com) in San Juan Capistrano at 949 661 8482 as the source of 1/4 inch "wet wrap" ceramic-based material (?).  They say it is usable to 3,200 degrees...cough.. gasp.  Doesn't matter if that is F or C.  Only problem I see is that it is held in lace with clamps instead of the stitching.

As was mentioned earlier, there are several good threads on this subject.  In this one (http://www.busconversions.com/bbs/index.php?topic=2805.0) I detailed how I did my system.

The source for the commercial sewn blanket is:  http://www.atpwrap.com/html/motorcoach.html

The EHP material mentioned above is absolutely great (I used to be a distributor, but finally figured out it was better to have customers buy directly from them since the wet blanket kits had a shelf life).  They have two products that can be used.  The wet blanket material can be formed much like making a cast for a broken leg.  The wet blanket material is used to form around the manifolds. The other material is sheet material about 1/8 thick that can be wrapped the exhaust pipe.  Both of those materials are a bit fragile.  I wrapped them with HIGH TEMPERATURE aluminum tape (see photo at:  http://www.rvsafetysystems.com/busproject2.htm)

When I installed the Series 60, I used the commercial blanket for the manifold and turbo.  I then used the EHP/foil for the first few feet of the exhaust pipe.  I then purchased exhaust wrap tape (http://www.thermotec.com/product_detail.php?prd_id=3) to put on the rest of the exhaust pipe (have not installed yet).

As has been mentioned several times, there are several reasons to insulate the exhaust:  possible increase in HP, reduced heat in the engine compartment/bedroom, and safety (virtually eliminates high temperature source if you have a combustible fluid leak).

Jim

 Thanks Jim(rv_safetyman)

    I went out to the site you mentioned low and behold in the lower left right hand corner
is an ATP logo   and the T really can look like an I..........Something when I look at the
tag could be a stylized T............The wraps on the web pages look just like I have

   So now I can get a better one for my turbo....the one that is there just looks like
a flap of material.

Thanks
   Skip

The materal I bought was from Coverflex  866-268-3735 on the web also. I talked to Norberto,I did the turbo and pipe to the floor. Later as an after though I covered the top of the manifold. Norberto was good to work with and did lower a price when I talked to him. It is wrapped in a stainless mesh and wired on with stainless wire.  Tom Y

Tom,

   Nice job......

  From your pictures I see 2 sending units one on the turbo and one on the intake housing.
  Boost and temp?

   Exactly which L10 are you running.....L10 LTA10 or LTA10E or maybe oh could it be m11 select?
  IT just looks different than  most of the plain L10's I'm used to...:)

Thanks
Skip

Prices, what about prices, I would really like to know.

Ray D

Skip, Nothing on the turbo. Maybe the oil line you see? The other is aair intake senser. The engine is a L10E Celect.

Ray, I paid 142.10 to my door and another 23.00 for the top of the manifold. Covered the turbo, an elbow and about 16-18 inches of pipe down to the floor. I also did the manifold on my gen and the pipe going down. That cost 83.00 plus shipping

Thanks Tom,

I was expecting more, sounds like good money spent.

Ray D

I have to disagree with Jerry on insulating the exhaust, turbo or not.

My theory, subject to correctiion, is that an insulated exhaust system blows heat out the exhaust faster than an uninsulated one thus keeping the engine space cooler.

The hotter exhaust gases will exit the exhaust system much faster with insulation and decrease back pressure, not increase it.

Many turbos get red hot, you really don't want anything that hot uninsulated inside the engine compartment.

The EHP wet blanket will handle anything you will ever find on an exhaust system. I am a believer in that stuff.

Gus....yes what you said is correct in regard to the fact that the exhaust coming out is greater force than cooler exhaust (un-insulated) because back pressure is greater.
However read further to under stand what is happening.
Back pressure affects engine efficiency to breathe in more or less (oxygen+) intake air. The lower the back pressures the better.
Other word exhausts pulses are working harder to escape due to higher volume of expanded (heated) gases within given size pipe. Cooling to shrink the volume.

So by cooling somewhat will be freer & takes less forces to come out of exhaust opening to a point of softer pulses.

Do your self a favor...make an inexpensive & hook up water manometer gauge to compare results.
Such this link but use clear Tygon tubing instead of glass "U" bends, that can be purchase at any major hardware store for your "U" tube meter.
http://www.rverscorner.com/manometer.html
http://www.dwyer-inst.com/htdocs/pressure/ManometerIntroduction.cfm
I do not know the factory spec. back pressure number on your bus. I suggest trying at least 30"or more of water to start.
Tap in exhaust steel tubing nearest to turbo's outlet flange. Use 1/4 "metal tubing at least 30" or longer to isolate heat and slide on Tygon over it. Fasten metal tubing onto engine wherever to keep it from vibrating & breaking off.

Manometer is one of the most over look tools to determine differential pressure or vacuum points. At work I use it almost every day of testing & diagnostic.

Thank Gus for bring up your point.

FWIW

Sojourn for Christ, Jerry

Jerry,

   I hope you are talking about putting the manometer after the turbo not between the turbo and head
exhaust pipe.............

   If you are running 20# of intake boost pressure you will be running that or more between the turbo
and the exhaust head. turbo efficiencies are the measurements between exhaust pressure and intake
pressures. The intake impeller creates the pressure that the exhaust impeller must over come inorder
for the gases to escape.

   Just my personal opinion :)

Skip

If wrapping the exhaust manifold and turbo is such a great thing to do, why don't any of the OEM's do it on their engines?  We have new trucks in with the particulate trap and NONE are wrapped between the exhaust manifold and the turbo.  The exhaust pipe from the turbo to the particulate trap is wrapped to retain as much heat as possible to facilitate the maximum chance of the particulate traps catalytic converter to produce its' own heat to burn the soot down into ash.

I have my generator exhaust manifold and exhaust pipe through to the outside custom wrapped to reduce the heat in the generator compartment since the compartment is very tight. 

Personally- if you have a turbo engine, wrapping the exhaust manifold and exhaust pipe might get you a little more boost on the turbo.  Otherwise, I'd only wrap them if you want to control heat. Good Luck, TomC

Just because OEM does not do it, does not make it right or wrong most of the times.  So where is the trade off, are we better with reduced back flow in the exhaust pipe or lower engine compartment & turbo intake heat?????

Ray D

Skipn....Thanks for pointing my incorrect stating "manifold" instead turbo.
So sorry to confuse anyone....I try to my best to give my experience facts of results from working at General Motor test lab running dyno, from rotary, gasoline and diesel as well chassis dyno. I never post any post anything that I cannot prove and/or have no experience about the subject.
I corrected that post.

I appreciates your responds...I never want to miss lead anyone.

TomC....This only pertain V-6, V-8 with long pipe to turbo. Only reason I can think of that it not worth extra production cost to keep sale prices within competitor's market. Turbo equips with automatic transmission will be most benefit from it. Quicker responding time from stand still into motion and passing performance.

I appreciate your update about the today world in class 8 engines and transmission....I look for your post when I can.

FWIW

Sojourn for Christ, Jerry

Jerry,

   I was more confused trying to make sure I could picture what you were saying....I was not doubting
your knowledge.

   I think we sometimes major in the minors..... If one looks at it from the 30K feet level the question
should be what part of this system has the greatest chance of being effected by higher temps?

   To me the most affected side is the intake. Usually longer piping in an already warm (hot) environment.
  Inline engines a lot of times have a heat deflector between exhaust side and intake side.
  V style engines tend to have long exposed pipes from the heads to the turbo.  Heat is always the enemy :)

   The back pressure from the turbo through the muffler can(does) affect turbo operation but heating up
intake air can be the greater issue.

  Just a thought or two or none :)
   Skip

RayD, it is OEM for heavy Equipment and if you are going to buy from ATP (advanced thermal products) sit down first my 3 pc wrap was 700.00 8 years ago

$700.00 ouch!! Now I have to think again, was it worth that much??

Ray D

Hello.

The transits are overwhelmingly being equipped with exhaust coverings from the factory now, and many over the road coaches being spec'd too.

As Jim points out, engine room temperatures, and engine room fires from leaking ignitables being the motivator.

Lots and lots of engine room fire suppression systems being spec'd from the factory as well.

Too many new buses catching fire.

If for-profit companies as well as government transit agencies are protecting their equipment with fire suppression, maybe we should be thinking about the cost benefit? We don't have the resources some of those others do to deal with the after effects of a fire....

My motivation to wrap the exhaust on the 8V71 would be lower the engine room temp, and reduce the heat soaking of the air filter cannister (incoming air temp being heated), and help the air-cooled alternator live a little longer.

happy coaching!
buswarrior

Ray,

I doubt that EHP would be more than $300 to cover the turbo, probably less. I think I covered all my gen exhaust system for less than $100 including the muffler.

The exhaust pipe cost of course depends on what size and how long.

It won't cost anything to call or email and find out.

We have Jim Shepherd's Fire Detection and Suppression system on our MC-8 8V71 NA. We have no exhaust wraps in the engine compartment (completely OEM). Normal engine compartment temperature (recorded by a thermistor directly above the engine, approx. 1" below top of compartment, and out of blower fans discharge area) run about 145-155 with ambient temps in the 80's-low 90's. The hottest we have seen was 171 last summer climbing a hill eastbound on I-20 coming out of Birmingham, AL. Outside air temp was 103.  Jack

I think Jack has made the case...in spades.  Using his numbers if I were climbing out of El Centro going west and it was one of their common 117-120 degree days I could expect to see 190 ish temps in Jacks bus.   Another MCI equipped with a 8V92 making another 125 HP might get temps approaching 210 or so.  All this is by guess and by golly but the inescapable point is that 171 at 90 ambient is pointing to some scary stuff ahead, especially if his engine temp goes up or air flow diminishes or exhaust gas temp goes up for any reason.

Think about the alternator and all the rubber stuff in there that thinks you hate it.  Thimk abut et.

How much of a discount could we get with a MASSIVE buy of that wrap?  Lets see....1,600 members at .....

ALL THE TRANSITS are coming with the stuff standard equip?   How did we miss this?

Time to buy stock in EHP.

John

I don't know what Jim Shepherd's Fire Detection and Suppression system is but 170* is certainly nothing to worry about in an engine compartment. I would guess that most autos run hotter than that.

Consider that your coollant is 180*+ and any exhaust manifold is bound to be 400*+.

That makes a good argument against heat wrap but he doesn't mention a turbo which is another situation altogether, turbos get hot.

JMHO, at the previously stated 170*, (I'm guessing mine was near that also) the bottom of my bed was getting very hot after a days drive.  It was very uncomfortable to sleep in the middle of the summer with all that radiant heat.  After wrapping the exhaust cross over on my 8-71NA, the radiant heat was gone.  I bought my Thermo-Tec header wrap from Speedway Motors.  To cover the cross over I ordered the 2" X 50', ($37.99) and I have enough left over to wrap my generator exhaust.  No scientific data to report, just my comfort level while sleeping was much improved.  Also, I can put my hand on the pipe wrap just after shut-down.....

There no need to wrap natural aspirate engine unless you don't have much air cooling around the compartment.

Turbo exhaust inlet & outlet temp is much higher than natural aspirated engine. It can get to 1200°F+ under full load.

Use tape that is rated 1200°F continuous.

FWIW

Sojourn for Christ, Jerry

Darrell,

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

Nice post, Bud.  Did you ever get the feeling that some people are just not hearing what you are saying? >:( ;D ;D ;D

Post long and often Young Skywalker and Bus Rider ;)

John the Kidder

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. ::) ;D

John

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....... ;D

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

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

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

Too much to do.....To little time...... :-[

Have fun you guys with your turbo's.....More horsey's equal more heat.....I'll stick with my 8v71N.....at least for now.... ;)

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

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