Paul davenport

I hope I got this right and the photos re attached of the oil stains on cowling of air flow ,interesting to see where the oil -air flows around this area

Admin This is thin ice here

Some people would say (rather unkindly) that I am hoarder ,just cannot find it in me to throw out that item that could be usefull .

You seem to be in the right place at the right time ,first a savanah then a rotax . Where do I sign up for this program

Back from an early fly around the traps on Saturday cht at 300 on climb and 270 in cruise at 2900 rpm, back off to 2600 rpm and temp drops to 250 ,I am using around 21 lph at cruise,a quick call to Jabiru and a new main jet is on its way ,stay tuned

Down this way we call those bits Jobber bits. Good to see you back in harness ,you are doing something most of us would like to try ,keep going you have our complete attention

I try to do a BFR in something other than my a/c just to try them out and sharpen my skills, and as stated it's lots of fun

I will follow with interest, to see how you repair it . Compared to a new build what would be the time and monetary input . Please lots of pictures to show build and repair

Gliding comps at Benalla ,so the Benalla gliding club is opperating out of Wang for a few weeks, give Geoff a ring on 0413152288 for the details and restrictions (if any)

Just a thought I wonder why jab went and put there cooler there and not where the normal Cessna piper mob put theirs ???

There is a picture of an oil cooler some where on this thread that has been encased in a chamber that allows it to discharge its heated air to a low pressure area not into the engine cooling lower cowl area,that has merit and I may next oil change try some thing similar. Give the dirty oil dot on the cowl trick and let us know what your results are

Installed some cowl inlet ramps looks good and I think a marginal improvement. Also had some vg,s left over so installed them under the prop and under the oil cooler lip, with dobs of oil on cowl off I went , air flow under cooler is better but the top vg,s did nothing (so off they come) . So what can I relate to you all NOTHING but I had a great end of the day flight so it was not total loss . Next step to make up some perminant lower cowl cooling ramps

Just back from a flyin to Mt Beauty and before I left I put some small dobs of oil on the cowling to check air flow and was surprised to see that the air flow was great around the front to sides of the cowling BUT it did not flow down and passed the cooling lip on the bottom cowl, there was a stagnant patch of air above the oil cooler inlet and interestingly air was actually spill out of the cowling at the inner cowling surfaces. Air flow down the cowling seems to split well before the nose wheel. My cht gauge indicates 250/275 on cruise 290to 300 on climb and the oil temps range from 70 to 100 depending on situation so any improvement will be great. Looking at the profile of the cowl it always looked like the oil cooler was shielding a large portion of the cowl lip and I was right. Now what ,any

The more we learn the more we don't know? !

Just saw your post JJ seems to me that there doesn't seem to be two jabs the same,what works for you may not work for me or others cooling science seems to be a black art indeed

From my investigation to date (and I cannot remember where I found it ) the top and bottom of the Cowl inlet are of equal importance ,something to do with a pressure wave and pressure recovery ,where the cowl inlets accept far more air than the engine and low pressure area can get rid of causing drag and a spilling out of air from the cowl (correct me if I am wrong but that's the best way I can describe it) . I have some expanding foam and at the earliest chance I intend to try it out. Getting it to stay put with out moving and blocking off the cooling system is a concern

Just a thought has any one experimented with the inlet ramps on the cooling system, on looking at Lo Presti and the like they all seem to have smoothed out the flow in . Jabs blunts and crude looking head and cylinder covers seem to be counterintuitive to smooth airflow in ?

Gentle men with the greatest respect to you and the experience you have in aviation could I ask that we keep the discussion to relevant modern ideas and actual confirmable, quantifiable and documented evidence ,reference to second or third hand ,"I know some who saw or experienced etc etc " does not do this discussion justice. I am asking question because I don't know the answers ,if you don't know either ,but have a verifiable reference please please refer me to your information source . In MY experience EFI systems in autos WHEN correctly serviced are reliable and trouble free ( and I must say some owners don't do any maintainence and the systems certainly are not maintained like aero systems are ) and when combined with electronic ignition and a knock sensor result in outcomes which simply cannot be replicated by ancient magnetos and carburettors . Im sure aviation fuel quality in some countries leaves a lot to be desired even if it is still available and as you said it is being phased out. The system I am envisioning will stand alone without an alternator functioning for at least 30 minute ( depending on battery size) while you decide what you are going to do or go . Systems like this eliminate the need for such stringent controls on fuel quality ( no I am not advocating using any old fuel but there maybe circumstances where you may have to use a lower octane fuel to top up to get home, GA pilots have done this before ) as ignition timing is adjusted to suit fuel quality while still keeping the maximum power available for the fuel used . A pilot simply cannot monitor the fuel and ignition system in the same way. I would agree that aero engines have been optimised for 3 basic operating conditiions start, full power and cruise that leaves a lot of areas in between which could be optimised (cruise for endurance ,loiter etc )In the cruise mode even this could be improved as injection and timing would be in a constant state of flux with the system always looking for the peak operating conditions adjusting for temperature ,air density cylinder head temp egt . The current series of auto engines run just such a system ( without CHT) AND a compression ratio of 13 to 1 plus and all on 91 Ron and mogas which lack quality assurance so what I am asking for on our modest compression ratio,s is not really going to be an issue

I can only base my comments on personal observations . Cherry pick and leave out the stuff that we don't want NO EGR As I see it experimental will have to do the bulk of R&D so we can move forward . Some might say that's just what Jab have been doing all along

Now this is more like it a real conversation. My working life has been generally speaking spent working on Japanese and european cars MAZDA (our dealership is Mazda and was the other two) PEUGEOT RENAULT with a fair amount of every thing else in the middle. I still spin nuts and I must say on the vast majority of the cars now worked on I just don't see the problems you have been talking about.it may have been so back in the 80 s and I can only report on what I saw but even then we had relatively little failure of emission equipment BUT it is not and has never been my intention to introduce emission equipment to aero engines (other than the infamous crank case vent system ) Nev I have heard about the infamous under the power pole stopping and stopping at other rf signal points but until someone gives me proof you know ,who what where and it can be replicated I will have to put it in the myth buster files to be conclusively confirmed or busted Jet I don't think in my shop we ever tampered with a pcv system as we never saw problems with them that a wash and clean would not repair at the time of servicing and if some one presented a car for a road worthy with such a blatant modification it would not have passed ,EGR on the other hand was not so easy to check BUT in the cars we sold the failure was in the closed position no gasses passed to the combustion chamber. These failures are really red herrings as I am not suggesting we use them ( except for that pesky pcv) The type of technology I really want used is the fuel injected ignition integrated systems where advance and mixture is tightly controlled and cruising at lower than 75 % would be more economical . CHT and EGT would be more even ac cros the engine operation range Nev I know you and jet you think this is out of our reach but I have a little more confidence in the designers and technology

Found the reference to potential blockage it was by another contributor to this thread

Nev either some one has removed some of your earlier post or I read it incorrectly saying potentially blocking inlets if you did not say this pleas accept my apologies

Great discussion and I detect perhaps a slight change in ALL our posts .i have started some few weeks ago to separate oil from the bypass gasses keeping the original catch can at the end of the vent line, at the moment I have not had to add any oil to the engine and no oil is accumulating in the catch can so after some more flying I will move to the next phase of creating a drafting tube on the inlet system up stream of the carburettor (the reason for the first post).I will keep you posted. Nev A VALIANT how old did you say you were! They were discontinued in the 70s no wonder it was blocked (sounds like we are the same age) . EGR now there's a nice subject remember we are talking advancements here , that was introduced in petrol and Diesel engines to lower combustion temps and lessen nox gasses and apart from making jobs for my trade was NEVER considered an improvement . I have Never in this thread suggested we adopt some of the crazy ADVANCED ? ideas from the auto industry , but I think the word used was cherry pick to our advantage, and although I have used the auto industry as a stepping stone (and I fly behind a subaru ea81 with an Amax redrive in the avid) I am not suggesting we use auto engines as best practice ,aero engines are as you quite rightly put it the athletes of the engine world and opperate under special conditions. Having said that there are some mighty fine alloy engines coming out from auto manufactures the quality of the castings and engineering is mind blowing (makes aero engines seem crude in comparison) These engines have some demanding testing conditions placed on them,runing them fully loaded for 24 plus hrs on an engine dyno is something not done to my knowledge on aero engines. When you pull down an engine these days (and that's not as often as it used to be) they are relatively un worn and you would be hard pressed to measure the wear. Temperature control seems to be the answer here and you just cannot beat liquid cooling for that. Trotting out AUTO yes I would agree it just not realistic to grab an auto engine and lace it up to an aircraft without a properly designed redrive unit but I was never suggesting that in the first place .it takes MONEY to R&D a redrive unit and quite honestly I don't see anyone with deep enough pockets to volunteer for the job ,so we are stuck with a couple of engines to choose from, old design aero engines, new (and improved although some woud disagree with improved) jabiru engines (I like mine ) rotax who to there credit are putting some effort into some of those modern ideas I keep talking about and a smattering of other manufacturers who are at least trying . Great discussion let's keep it up