Exhaust Insulation Wrap

[Vev]

Has anyone had any experience (or an opinion) with Exhaust Wrap in a Jab 160 and what has been the impact in terms of CHT/EGT/Oil Temp or power improvements?

 

 

Regards

 

Jack

 

 

[facthunter]

Exhaust insulation.

 

As a general practice I believe it is considered a BAD idea as the pipe overtemps. If it is applied near the port this must help retain heat in that area. I would explore other means of keeping heat away from associated areas, cowl etc. Nev

 

 

[Vev]

Exhaust Wrap

 

Hi Nev,

 

Many thanks for your response … I share your concerns too. However the manufactures claim otherwise, which feels is a little counterintuitive to what one would expect, but there seems to be some technical logic. I have heard of this being fitted to RV's to improve HP and reduce heat build-up around the engine but I really don’t know any details and can't find much on the internet, other than automotive applications, hence my question for views, which I thank you for providing.

 

I have attached one of the manufactures claims .. I've removed the band (????) name.

 

"The original Exhaust Insulating Wrap was developed over 14 years ago by ???. Exhaust Insulating Wrap is an innovative way to create more horsepower and reduce under-hood temperatures. Wrapping headers maintains hotter exhaust gasses that exit the system faster through decreased density. Increased exhaust scavenging is produced along with lower intake temperatures. Exhaust insulating Wrap withstands continuous heat up to 2000°F, and contains no asbestos. ???? exhaust wrap will not over-insulate a system when properly installed due to a proprietary coating developed by ????. --Thermal Conduction Technology (TCT) -- that conducts heat across the wrap's surface. This coating controls heat build-up and dissipation".

 

Regards

 

Jack

 

 

 

[facthunter]

Source.

 

My source is EAA, and is based on good practice. The proponents of exhaust wrapping cannot have it both ways. It either holds the heat in or it doesn't. Hot gases due to their lower viscosity/density, do flow better and If you have a close cowled set-up you might have some difficulty doing it any other way. Ie insulated baffles. Some extra cooling air can help, but a lot of the real performance seekers don't want the extra drag. Cross-over exhausts for the flat-fours are a superior system, (no interference, and can be tuned) but the more pipe length , the more heat to get rid of and the difficulty of supporting it on the engine . Theoretically, the heat should be able to offset some of the drag. Nev..

 

 

[Guest thrasher]

Hey Guys

 

I know of one pilot who had used a Ceramic Coating on his Jabiru 2.2 Engines Exhaust. I haven't had a chance to find out his temps...But it's just a thought.

 

I found this place that does it...http://www.jet-hot.com.au/

 

 

[Captain]

I used JetHot to apply a ceramic coating to the muffler and outlet pipe (but not the header pipes) on my J230, purely as a attempt to reduce the heat load inside the engine cowls ........ but don't have any figures with which to evaluate any gain. It just seemed to be an easy and relatively cheap way to achieve some reduction, and IMHO is a more elegant solution, with less potential problems down the track, than a wrap. Regards Geoff

 

 

[Vev]

Geoff,

 

Thanks for this idea … I have heard the use of ceramics in this type applications which does sound like a nice approach. I presume you have managed to reduce your heat load inside the cowls, however can you quantify any values in terms of engine oil temp or CHT reductions?

 

Regards

 

Jack

 

 

[Captain]

Sorry Jack, but I had the coating applied when I built my 230, so don't have any before & after figures. All I can say is that my CHT & Oil temps are at the low end of the recommended figures so that is good and in my view anything that will reduce the total heat load inside the engine bay has to be good. I had a good read of the ceramic coating literature back when I decided to do it about 2 years ago and it certainly appeared to keep the temp in the exhaust gasses and get it out of the pipe rather than thru the pipe but I don't have an EGT at that end as my 6 EGT's are all in the individual pipes about 110 mm from the heads, and those pipes are not coated. Sorry about that. Regards Geoff

 

 

[Yenn]

I would have thought that the laws of physics would apply to exhaust gases and if so as the temperature reduces the volume would reduce, leaving less volume to get rid of. there should be enough air getting through the inner cowl area to cool the pipes and i would have thought that the main reason for cooling the area is to keep heat from the fuel pump area. If you are worried about inside cowl temps, have a look at the heat there 5 minutes after shutting down the engine. You will find it hotter then than it was in flight.

 

 

[Vev]

Hi Ian, I don’t think there is anything wrong with your thinking on exhaust fluid mechanics here, in fact I think this is precisely one of the actions that helps scavenge the exhaust gases effectively…. I guess the argument is about efficiency and if higher exhaust temps reduces gas density and frictional resistance enough to create better scavenging through the exhaust port. Whilst I could spend time calculating the fluid dynamics there is nothing like the real application to know if this is just nice theory or a practical option.

 

My interest in this technology is two fold; 1. reduce my CHT as I would like to see it slightly lower… my CHT is always in the green but I think a lower number will improve long term engine durability and safety. 2. see if I can find a few more HP without resorting to any engine modifications, albeit this is secondary outcome.

 

By the way, I have followed up on Geoff's suggestion and spoken to the chaps that do the ceramic coating … they tell me they have done this on a number of aircraft (almost all GA) and feedback has indicated that lower CHT have been achieved…. Sadly, he doesn’t have any metrics to quote!

 

Many thanks for your contribution … regards Jack

 

 

[Chird65]

If you can find a copy of Kent Passers book "Speed with economy" he worked through a series of Exhaust modifications, some that cooled the under cowl area. All his ideas were completed and compared over many years on his own plane.

 

 

[vk3auu]

My initial exhaust system in the CH701 had the exhaust made from mild steel pipes as supplied by Zenith. I initially suffered from fuel in the carby bowls vaporising after engine shut down, so I put insulation on the pipes where they went under the carbys. After a comparatively short time, the exhaust pipe on one side became completely oxidised and blew out right where the exhaust gases could get into the air cleaner on that side. It happened at about 500 feet on take off with a rather heavy passenger, so after a pan call, we did a 180 and landed with just sufficient power to maintain altitude.

 

Made my day, particularly as said passenger kept his cool too.

 

I got rid of the insulation after that.

 

David

 

 

[Vev]

David,

 

This is one (thankfully) to be able to tell the grandchildren!

 

Regards

 

Jack

 

 

[Ross]

Talk of Ceramics reminds me that the CSIRO at Hyatt I think in Vic in about the 1960's had successfully developed machineable ceramic materials for use in manufacture of engine cylinder liners, heads and pistons.

 

I did not ever see any details except to remember that it resulted in substantial improvements in specific fuel efficiency.

 

Speaking generally the current internal combustion engine is a very inefficient machine.

 

 

[Yenn]

Ross you are dead right about ceramics being touted as the coming engine material, but time has not been on their side. No engine manufacturer has considered it to be suitable technology and I am sure that if ceramics were as good as they were supposed to be all cars would now have ceramic engines. The aviation diesel has a rather similar history. Thielert spent many years taking government handouts, then produced engines for Diamond and Cessna, only to go broke.

 

 

[Vev]

I have decided to give the exhaust wrap a try as a starting point and may progress to ceramic coating if things look to be heading in the right direction. The wrap is something that is reversible and will allow me to undertake any procedure in a graduated way.

 

I will develop a test process to try and quantify any metrics I can obtain as well as institute a high frequency engine inspection and oil analysis programme to track any oxidation impact from thermal stress. I am hopeful accelerated oil oxidation will provide a good precursor for potential adverse engine problems caused from the wrap particularly around the cylinder head… I will also include wear metals analysis to keep a finger on engine fatigue. Whilst I won't be able to measure HP output I do have fitted a ground adjustable prop which may allow me to ascertain a proxy measurement and see if there is any +/-ive movements.

 

Once done I will share the outcomes.

 

Regards

 

Jack

 

Ps.

 

Yenn (Ian)……. I agree ceramics seem to have eluded engine builders so far, albeit Honda did actually build an oval piston motorcycle 4 stroke GP engine in the late 70's that seemed to work, even though it was uncompetitive against 500cc 2 strokes … Isuzu and a couple of others have built and ran engines in field trials but still seem to struggle with over all durability. Never the less there is a trend towards after market ceramic coating which are running successfully and showing some remarkable performance and durability improvements… I guess time will tell.

 

 

[Vev]

Whilst it has taken me sometime I have installed the exhaust wrap today. I have yet to do any extensive testing, but so far I can tell you that I have seen approx 15deg F reduction in climb and a 10 deg F in cruise temps on my CHT. My oil temp is also showing about 10 deg c cooler. I can’t say I can feel any difference in power output at this stage but I will think about this a little more to try and find an objective proxy to measure performance.

 

 

For what it’s worth, I did a quick check my CHT gauge and have found it is over reporting by 4% … not a big deal but things are a little cooler than what the gauges says.

 

 

It’s still early days and will need to look at these numbers in relevant context of ambient temps and fuel flows. Never the less the sky didn’t fall in and all the numbers went the right way.

 

Cheers

 

Jack

 

 

[Ross]

Hi Jack.

 

I am very interested in your exhaust wrap ideas as the Jab engines seem prone to damage from even short bouts of overheating so anything that can keep the engine temps down a bit including oil temp would have to be a plus in our weather conditions.

 

I have already purchased the modified bottom cowl to extract more air from the engine bay and will probably fit the extended lip to extract more air again.

 

So what material are you using for your exhaust wrap and where can you get it?

 

Regards

 

 

[Vev]

Hi Ross,

 

 

The material I used is called Cool It by Thermo-tec I bought a 50’ roll of 1” which is more than enough for the 4 cylinder jab and should do a 6 cyc.

 

 

Before I used the wrap I did alter my bottom cowl with an extension as per Jabs advice, this only had a marginal effect in flt ops although it did seem to keep taxi temps down a little lower… however to honest it is a marginal call to say it really did a lot. I also increased my fuel burn by fitting a larger needle jet and a larger main jet, this increased my fuel flow in cruise by about 1ltph… I followed this strategy up and increased my main jet again which really helped pull down the CHT temps in climb and kept them away from the edge of the yellow and closer to about 310 - 320 deg.

 

 

It terms of the oil cooler I repositioned the angle on this and also improved the fit in the cowling … since then my oil temp never gets over 80deg c even on very hot days.

 

 

Whilst the wrap is a new thing and I only have a about 1.2hrs of flt time, it’s clearly a quantum leap in pulling down the CHT and oil temps. I will not be surprised that I may need to reduce air flow over the oil cooler on cold day (we get them in Melb) but I do feel very certain this is a real fix for pulling down the CHT... My climb temp last weekend was between 275 – 300 deg, which is excellent in my book.

 

 

In terms of fitting … I simply wrapped it and secured it with lock wire in several place (about 6) along the headers… I probably used more lock wire than I needed but I didn’t think there would be any prizes to be won if it came adrift and tangled up inside, it took a couple of hours to fit and it actually look very good too… I would send you a photo but I’m working overseas in Africa this week and not home until Sat week.

 

 

Once I get past the testing I will look at either going to ceramics as per the Captain’s (Geoff) suggestion or sick with this and make it pretty.

 

 

http://www.aircraftspruce.com/catalog/eppages/graphblkwrap.php

 

 

http://www.thermotec.com/

 

 

Hope this helps?

 

 

Best regards

 

Jack

 

 

 

[Guest Maj Millard]

Big problem with both ceramic coating and thermal wrap is that they both hide from sight the biggest problem with exhausts, the ability to see cracking. Just like powder- coated fuselage frames, can't inspect for any cracking. Seems to me that many of you are Jab owners ?. Does the Jab have a heat scavaging problem with the cowl design ?. A well designed cowl should be capable of removing suffecient heat from around the engine, even during taxi, prior to take-off. You want your engine( and especially crank) to warm up a bit then anyway.

 

Also have heard the retaining all that heat in the pipes has led to metalic crysalization which will considerably shortens the life of your pipes. As far as thermal thrust from a small capacity engine out of the exhaust, you'r simply playing with it too much my friend.

 

 

[Vev]

Hi Maj Millard

 

 

Many thanks for your comments on this subject.

 

 

Apart from David’s (vK3auu) comments re a blow out in his exhaust system (this is the only 1st hand account I have been provided for an aircraft) I have yet to find one example of exhaust failure from wrapping, even after talking to a number of manufactures i've found none. However I have heard plenty about a mate of a mate stories, which mostly come to nothing (mostly poor maintenance and cleaning) when I have tried to follow them up, although I’m sure there must be some but I have yet to personally see one as a direct result. In any case I would like to know more about this as it will help me to make a more informed call about inspection frequency, so please pass on any specific 1st hand experiences you have.

 

 

My plan today is to do a visual before every flt day, which is only a 5 minutes job, and remove the wrap at 10hrs to do a closer inspection and then step it out when I feel comfortable that all is well. I suspect that if cracks appear before hand I should see exhaust gas leak stains around the wrap, just as one can see now at the header/muffler interface, owing to its deliberate loose fit.

 

 

To answer your question about cause … I can only tell you I think (meaning I don’t know for sure) there are a couple small design problems that effects CHT and oil temps in the 160: 1. the cowl design does not air scavenge as well as it could, which, I imagine, is why Jab have had a couple of goes with modes and variations of design to the cowl… I might add I have implemented the mod on my Jab as per the book. 2. I think (again this is an assumption) the exhaust scavenging is not as efficient as it could be, which is not allowing the incoming charge to help pull down the temps inside the combustion chamber through the latent heat of evaporation from the fuel as it goes through the inlet manifolds and ports. This is why to some extent the richer jetting (as prescribed by Jab) helps crudely cool things by wetting down the inlet track. 3. I think (educated guess again) the oil temp is affected by bad cowl design and some possible heat radiation from the headers being so close to the sump. I think the later is quite probable as I have already noticed an oil temp drop, intuitively I feel this has accrued from a reduction in radiated heat from the headers.

 

 

I also agree with you that an engine should be at the correct operating temp before flight for a whole stack of very good reasons … Personally I do make a point of seeing the oil & CHT temp needles get into green zones before I gas it up.

 

 

In terms of additional thrust from the exhaust … not sure what makes you think this was under consideration… in any case, I agree there will be zip.

 

 

Regards

 

Jack

 

 

[Guest Maj Millard]

Hi there Jack, thanks for your reply. My info on the crystalization of pipes by retaining too much heat could come from many info sources. I work in the GA industry as an engineer, I was also talking recently to a Lancair owner who had his pipes wrapped, plus I also devour Aviation related magazines by the gross, could have read about it there. Best I can do for you, is to contact an aviation friend of mine in the states who keeps up with it all, he should know what the latest story is.

 

It may also be percular to a particular exhaust metal, as many types are used. I will dig up what I can on it, and get back to you OK. Frankly to have to unwrap pipes every so many hours, which I assume would also require cowl removal, to do your exhaust crack checks, sounds to me like it would be time best spent aviating. I also have a mate who had his 80hp Rotax pipes ceramic coated on a Zamingo motor glider some time back, told me recently he wouldn't do it again as it was a waste of time and good fuel money.

 

As a general rule in designing engine cowls, in relation to cooling air in -hot air out, the general accepted ratio is 3 times larger exit apperture as to size of inlet opening. This of course is because air expands as it is heated inside the cowl. To use the radiant heat from surrounding exhaust pipes to achieve an efficient fuel/manifold situation, sounds a bit hit and miss to me also ?. Cheers

 

 

[Alan]

Interesting thing the variability of the effects of the Jab 230 cooling mods. There have been four Jab 230c's, that are about two years old, up here that have had all the required mods. The lip extension (at the time it was a copy of Brentc's mod and not the Jabiru fit which came out later) on the lower cowl brought about very varied results. Some saw no change at all in oil and CHT temp, one actually got worse, while the effect on my engine oil and CH temperature was quite a dramatic improvement in both. The difference would seem to be the angle of the lower lip extension; mine only had a shallow deflection the others had a more severe change causing a greater deflection of airflow. The others have now had the angle lowered and all have subsequently improved operating temperatures. Changing the oil cooler ducting lowered the oil temperature even further.

 

There must be a sweet spot for the cowl extension/deflectors where there is a maximum veturi effect drawing the air out of the lower cowl. Too high an angle may well cause turbulence that could hinder the exit of the air. We have never chased the optimum angle as what we have now is good for us.

 

As we are probably the most Northerly 230c's in Australia the original cooling problems made us keep an too much of an eye on the gauges (see and avoid!). The situation is much better now. Now if only we had some way to make the motor less lean when we have to slow for the inevitable turbulence up here-------

 

Alan

 

 

[Vev]

Hi Maj Millard

 

 

Many thanks again for your input and your very kind offer to follow up with your friend in the States.... I shall look fwd to hearing what you find out.

 

 

I somehow feel that you are probably right that the exhaust material variations may be the key to durability when exposed to high heat if crystallisation does turn out to be something to watch out for.

 

 

Regards

 

Jack

 

 

[Vev]

Hi Alan,

 

 

Thanks for the info on the cowl lip angles … I did fit the Jab supplied fibreglass extension which had little impact on my CHT. May be as you said the lip angle could be causing turbulent air and hindering the scavenging. I will take another look at this and make up a couple of variation in angle out of some polycarbonate and see if this has a positive impact.

 

 

Regards

 

Jack