Vev

Hi Ross, For what it’s worth, I have the same brackets and cooler as you but it sits 180deg to your set up with the brackets turned around and facing fwd. This allows my cooler to fit snugly into the air intake without the sock, which means it’s quite some distance from the muffler. I wonder if this is why I hear from time to time some jabs having an oil temp problem, which I have never experienced??? Cheers Jack

Hi Student Pilot, It is sometime very hard to sort between perception/impression of performance and scientific fact. However I think there is a lot of evidence out there to support most of the claims made by manufactures, albeit generic and non-specific information associated with a particular aircraft. I guess the good thing about this forum is it allows one to test assumptions against actual experience, of which many contributors have a great deal. Here are a couple of interesting things to read re VGs http://www.nasa.gov/centers/langley/news/factsheets/Micro-VG.html http://www.flxsys.com/Applications/Active%20Flow%20Control/Vortex%20Generator/ http://www.avweb.com/news/reviews/182564-1.html Regards Jack

Hi Ross, Where is your oil cooler located? It sounds like you must have a different set up to my 160 … mine hangs off brackets in front of the sump and fits snugly into the air intake, which is quite some distance from the muffler and therefore I think not effected by radiated heat. Regards Jack

Geoff, Thanks for your contribution. Can you tell us typically what has been your long experience in fitting VGs in terms of performance improvements and are there any down sides? Regards Jack

Hi Walter… Many thanks for your input. It sounds like you must have stuck the VG’s on with some sort of double sided tape to try out the optimum position? If this is the case, what did you use and did you loose any of them in the process? Still keen to hear from someone with a Jab that has used VGs ??? Cheers Jack

Thanks for the responses everyone…. Greatly appreciated. I have been doing some reading on the net which mostly seems to concur with your feedback. I also spoke to Joa (designer and owner of Land Short in the US) following Ian’s suggestion to take a look at the web site. He was stating the best placement is to have the centre of the VG's at about 10% of the cord, which is about 100mm in from the leading edge for the wing on my J160. He said that some wings work best at 8% and others at 12% but 10% is about right for most. However he said to be mindful that one takes into account if you have swept back or forward wings as the cord length will be different to the actual wing itself, which is not an issue for my Jab. One the things I’m interested in is the potential to increase climb rate on my Jab 160, particularly of hot days. Most of the information seems to indicate that this is possible but I can’t seem to find a lot of documented support for this other than manufactures claims…. Any thoughts??? Cheers Jack

Hi … did any of you guys decide to fit VG’s to a Jab??? I spoke with a fellow in the US a couple of days ago that has fitted them to his SK and said that it made a huge difference to stall & manoeuvring speed including improved climb rates. He said that he has fitted them to both his wing as well as the underside of his tail so as to maintain elevator authority. He also said that his max speed has not really changed but may have dropped a 1 knot. I have to say there seems little down side … keen to hear views? Regards Jack

Hi Ross, Thanks again for the feedback … Whilst your post make sense of the probable cause, in my case, I don’t feel that carbie icing is anymore likely than before as the heat generated around the carbie and the intake manifolding is exposed to quite warm surrounds. The muffler is uninsulated and contains hotter gases, as there has been less heat loss through the headers, which sits directly below the carbie … to be honest I was more concerned about too much heat around the carbie as the heat has increased. Just as an update … I’ve now done 8 hrs over the weekend and tried every combination to get the CHT to get past 300 deg F (on the gauge, 288 deg corrected) and it just won’t go beyond that mark. In cruise it is sitting around 275 deg (264 deg corrected) … my oil temp is sitting on 75 deg C in climb and 70 in cruise. All in all these seem to me to be acceptable numbers and feel that the exhaust wrap is doing what I had been looking for and has significantly reduce my operating temps. Best regards Jack

Hi Ross & et'al, May be a dumb question... but why would insulation on the exhaust headers cause carbie icing??? The carbie sit directly over the muffler (which is not in scope for insulation) and intake air is drawn from outside the cowl, therefore I presume no more hot or colder than before? Cheers Jack

Hi Ross, Thanks for the update on the header materials ... I guess this should put the oxidation concern to bed. I will however still undertake a high frequency inspection progamme until I'm convinced there's no harm re cracking etc. Cheers Jack

Hi Martin, Thanks for the feedback and your insight into exhaust wrap, particularly with your 11 years + 2 aircraft experience… I don’t feel like Robinson Crusoe in trying this after hearing your account. To be honest I’m not completely sure about the metallic composition of the headers on the Jab, although I’m almost certain it’s not mild steel … may be someone out there will know off the top of their head? I do like your thinking in terms of the positive impact on other ancillary components such as rubber and seals etc. I hadn’t thought about this outcome but it will be a nice bonus if I can replicate this in the Jab too. Like you, I have so far seen a reduction in temps, which in my case are quite acceptable levels, but as I have already said, I won’t be surprised if my oil temp get too low and I may need to reduce air flow over the oil cooler… I guess time will tell once I get a few more hours under the belt and experience different ambient temps. Thanks again for the input. Cheers Jack

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

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

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

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

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

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.

David, This is one (thankfully) to be able to tell the grandchildren! Regards Jack

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

Composite report Attached is a link re a Research and Analysis on Composite Materials undertaken by the Australian Government ATSB … if nothing else read the conclusion but there is quite a bit of useful info on safety for composite LSA a/c http://www.atsb.gov.au/publications/2008/pdf/AR2007021.pdf Regards Jack

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

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

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