Russ Posted March 30, 2015 Share Posted March 30, 2015 Jab instructor my way, has been on 95, plus Lucas for some yrs, no tank probs at all. Link to comment Share on other sites More sharing options...
Icarus Posted March 30, 2015 Share Posted March 30, 2015 Gday Guys . New here and first post. Will post proper intro in welcome thread soon. A couple questions about these engines. I have no experience with them. 1.......Has anybody used a knock sensor and indicator light on these engines? CHT and EGT are good but dont indicate actual knock 2......What are the cylinder head chamber cc and how much variation between chambers is considered acceptable/normal? 3......What is the normal hot cranking cylinder pressure of these engines? I ask because it sounds like these engines have been operating at near detonation threshold. Possibly one or two cylinder chambers are smaller than the others at manufacture. This would raise the compression in those cylinder s. Combine this with an air cooled head already running hot on that cylinder and post ignition detonation would be likely. Then the cylinder heats up and pre ignition detonation occurs. The exhaust valve will then run extremely hot , as the cool fuel helps the intake valve cool ,but not exhaust valve. Exhaust valve can then fail /jam etc.. These detonation event would be putting massive strain on the pistons ,big end etc. possibly causing the big end to put excess pressure on the through bolts. Running higher octane will help ,but only up to a point. Perhaps this is why compression was dropped? Who knows......... Im no engineer ,just an interested wannabe pilot! The above is just an opinion and should not be taken as factual info Brendan Link to comment Share on other sites More sharing options...
Oscar Posted March 30, 2015 Share Posted March 30, 2015 Hi Brendan, welcome to the site. You've made some very thoughtful points there. Different head volumes won't be the problem though - they are completely CNC machined and laser-measured in a controlled environment room to extremely tight tolerances. However, all the other points you have made are very cogent. The actual cooling air distribution between heads is a significant problem, and it changes with flight attitude and airspeed. Too few engines are equipped with reliable ( and by reliable, I include the entire wiring between the cht probe and the instrument, especially the cold-junction position/s) cht reporting for all cylinders. People who do have good total engine monitoring can tell you of significant changes between cylinders throughout the flight envelope; different cylinders will run hotter or colder in different circumstances, so a single cht probe set-up is almost useless and in some circumstances is very probably providing a completely false belief to the pilot that everything is going along nicely when some of the un-monitored heads are being fried! Detonation is an absolute killer for the through-bolts, but that result is exaggerated by bending of the barrel base in standard Jabiru barrels when detonation occurs. The CAMit modified barrels have a thicker base specifically to address this problem, plus considerably revised through bolts that have been developed to address this issue and also address the crankcase movement issue that is largely a problem resulting from the standard Jabiru case-join methodology - CAMit engines use a different methodology. Fuel-quality issues are a considerable problem for Jab. engines and this is an area where the inter-relationship of fuel and the issues it raises need a very good understanding of what are complex situations; there is quite a lot of speculation and experimenting 'out there' with varying levels of success - and not all of those take into account all of the subtleties between using different fuels, results can be very much influenced by how the engine is operated (which may suit one fuel better than another in a particular situation of operation). 100LL is the most 'reliable' fuel, but brings its own circumstances (lead fouling); 96 RON mogas is probably the next best, with 98 being a lottery in some cases. We see regular reporting of problems with Jab engines, but very little reporting 'in depth' of the gamut of 'operational' use for engines that just tick along without problems - this is an area where more information exchange would benefit the entire Jab engine-using population considerably. The recently-released 'check-list' for inspection released by Jabiru is very much worth consideration, as it identifies the types of operation that are likely to produce problems, but it could (and hopefully will) be further refined. 1 Link to comment Share on other sites More sharing options...
jetjr Posted March 30, 2015 Share Posted March 30, 2015 I believe knock sensors dont work well on air cooled aero engines Hard to place correctly and too much mechanical noise + some other issues to do with how ECU would handle it - from SDS injection website I still put my bets on poor fuel distribution and cooling - you can manage everything else if its even. Some informative stuff here good work 1 Link to comment Share on other sites More sharing options...
Old Koreelah Posted March 31, 2015 Share Posted March 31, 2015 What's happening with the CAMit engine Test Cell? A recent visit to Dafydd Lewellyn was very educational; he sure is a Renaissance Man of aviation. The test cell has been built and there is an awful lot more to it than I could have imagined. It's a bit like the space program. The engine is mounted on a massively strong balanced frame which allows torque changes to be accurately measured. Highly accurate sensors emerge from every part of the engine and the cables and tubes run into the sound-proofed control room where banks of instruments monitor every variable. A complex cooling system delivers air individually to each cylinder; valves can restrict air to test extreme variations in head temperatures. When all thus is working perfectly the engine testing program can begin. If you are going to test an aircraft engine for Certification you have to get it right. 3 3 2 Link to comment Share on other sites More sharing options...
Oscar Posted March 31, 2015 Share Posted March 31, 2015 OK, the CASA action had - as you can imagine - a large flow-on effect for CAMit. It has certainly necessitated changes in CAMit's commercial strategy that could have been addressed later but as a result, had to be bought up the list of priorities. A perhaps unintended consequence but a very foreseeable one. The test cell, as you have said, has been on a long and complicated path to get to where it is now, with many problems requiring solution (and most of those are hardly OTS-equipment solvable!) It's no accident that there aren't more certificated / certified aero-engines available in this class. If you don't have Bombadier-type financial resources, you have to find ways around that.. 1 Link to comment Share on other sites More sharing options...
Geoff13 Posted March 31, 2015 Share Posted March 31, 2015 Camit didn't do themselves any favours by not being able to give a delivery time frame for engines. Link to comment Share on other sites More sharing options...
ricky m Posted March 31, 2015 Share Posted March 31, 2015 Would the rotec liquid cooled style heads not solve a lot of problems? Rotax over cool there engines and they seem to be ok as is the jabiru with a bit of care and love...:) Link to comment Share on other sites More sharing options...
Icarus Posted March 31, 2015 Share Posted March 31, 2015 Thanks for the info guys. I have read some reports that Jabiru suspects detonation in many cases. We know Auto makers have the luxury of knock sensors to retard timing etc. Good to know about the accuracy of the head machining. Seems a shame that a small percentage of these engines are succumbing to this problem. I really like the look of the jabs and hope to own one, one day in the not too distant future. I still put my bets on poor fuel distribution and cooling - you can manage everything else if its even. yes, lean +plus hot head + poor fuel possibly? = broken jab?! I wonder if they {jabiru) ask for fuel samples with the busted engines.or if the unlucky owners get the fuel analysed after the event. For my vehicles I only use the one service station in my area as I have had problems with water in fuel, pinging and dirty fuel with all the others. Its also amazing how much more readily an engine pings when your cold air intake comes off and the engine inhales hot air. Brendan 1 1 Link to comment Share on other sites More sharing options...
Icarus Posted March 31, 2015 Share Posted March 31, 2015 Would the rotec liquid cooled style heads not solve a lot of problems? Rotax over cool there engines and they seem to be ok as is the jabiru with a bit of care and love...:) Maybe some good old fashioned water injection at high loads!! Link to comment Share on other sites More sharing options...
gandalph Posted April 2, 2015 Share Posted April 2, 2015 Would the rotec liquid cooled style heads not solve a lot of problems? Rotax over cool there engines and they seem to be ok as is the jabiru with a bit of care and love...:) Ricky, there's an interesting thread on liquid cooled heads. Seems that there may be some problems there too. Not everyone is happy with them. See link below: http://www.recreationalflying.com/threads/liquid-cooled-heads.61013/ 1 Link to comment Share on other sites More sharing options...
ricky m Posted April 3, 2015 Share Posted April 3, 2015 Thanks :) Link to comment Share on other sites More sharing options...
Jaba-who Posted April 3, 2015 Share Posted April 3, 2015 Just getting back to an earlier point on this thread. A couple of us were discussing engine fuel and oil additives the other day. Initially we thought it a good idea to use some morreys or Lucas upper engine lubricant but then we recalled that there had been some warnings about the effect of these additives on the fuel tank.So while it may be good for the engine I would need a guarantee its compatible with an epoxy fuel tank first. Just spotted today that the Jab manual says use of fuel or oil additives voids warranty. So I guess if you have a new engine and want to keep your warranty you have to not go down that path. 1.3.5 Additives Note: No Oil or fuel additives should be used. Use of oil or fuel additives will void warranty. 1 Link to comment Share on other sites More sharing options...
Russ Posted April 14, 2015 Share Posted April 14, 2015 What's an acceptable oil usage for a 2200 jab. Link to comment Share on other sites More sharing options...
biggles Posted April 14, 2015 Share Posted April 14, 2015 What's an acceptable oil usage for a 2200 jab. Acceptable to who Russ ? Yeah I know what you mean , I would consider 50ml or more / hour needs investigation . May just be sticking rings and certain oil additives may help , if used strictly as directed ..... Bob Link to comment Share on other sites More sharing options...
Guest Andys@coffs Posted April 14, 2015 Share Posted April 14, 2015 Check leak downs. If oil usage is up and leak downs are low or failing then rings are likely. You'll hear hissing in the oil tube with dipstick unscrewed.... What does your aircraft belly look like? Heaps of oil on it..same issue Link to comment Share on other sites More sharing options...
jetjr Posted April 14, 2015 Share Posted April 14, 2015 All good advice BUT make sure its being used not just pumped out Overfilling will see extra dumped I could easily. See 200ml/hr if i filled to top mark, if run at lower one its 20-50mm, thats a 3300 Link to comment Share on other sites More sharing options...
facthunter Posted April 14, 2015 Share Posted April 14, 2015 Some of these engines are running with a lot of blowby. Andy's idea of listening at the filler while you pull it over reasonably slowly is a good one. A stethoscope would help. It might identify a dud cylinder before it makes itself more evident. Nev 1 Link to comment Share on other sites More sharing options...
Russ Posted April 16, 2015 Share Posted April 16, 2015 sourced the problem...........blowback bottle full as......why, i was overfilling due to long enroute legs. Starting these long legs with oil level barely up the dipstick worried me, hence more oil in the sump. compressions, pull throughs all good. 1 Link to comment Share on other sites More sharing options...
jetjr Posted April 16, 2015 Share Posted April 16, 2015 Good stuff I still overfill a little on long legs - mainly just makes me feel better as I know extra is blown out in first 10 min flying I now work on 50mm per hour, often added at end of flight so level can be checked Ok before next start Also at service when emptying overflow, pour it back into old bottle, measure the waste. Tally back against that added and you should get pretty good number to work on for the next 25 hrs. 1 1 2 Link to comment Share on other sites More sharing options...
biggles Posted April 16, 2015 Share Posted April 16, 2015 Takes a long while for the oil to drain back fully Russ . I do the same , and usually add 50 or more mls. before next leg , knowing full well most of it soon goes into the overflow bottle , as jetjr says . A bit of a 'feel good' exercise I guess ,but I just don't feel comfortable leaving on a two hour leg with oil barely registering on the stick ..... Bob 1 Link to comment Share on other sites More sharing options...
Jaba-who Posted April 17, 2015 Share Posted April 17, 2015 Jabiru say that during their testing they ran a 3300 engine on one litre of oil at full noise for a full day without it seizing up. I know it's not a good plan to do this intentionally but knowing it makes the worrying voice in your head settle down a bit. 2 Link to comment Share on other sites More sharing options...
Guest Andys@coffs Posted April 17, 2015 Share Posted April 17, 2015 That is one of the things I'll never understand....if everyone knows that the oil level should be in the last 1/4 of the stick then can anyone offer an explanation as to why the dip stick (and stated oil capacity) have remained as they are to this day? I could, for argument sake, claim that the oil capacity of the engine is 5Lt's and presumably that would make someone who is brochure shopping feel good....but if within 5 minutes of starting the engine 1.5Lts is now on the aircraft Belly then .....I'm just left lost for words...... But that all said, if its 50ml's and hour, and it ran all day on 1Lt oil then there is a lot of hours burn rate before getting to problem areas, though I do note that the 1Lt of oil that was used for the day's running was probably completely shagged at the end...and who knows what a SOAP test would have found in the oil (http://en.wikipedia.org/wiki/Spectrometric_Oil_Analysis_Program) Link to comment Share on other sites More sharing options...
fly_tornado Posted April 17, 2015 Share Posted April 17, 2015 Andy, never forget ... its more reliable than a rotax 2 stroker... 2000Hr TBO just like Rotax 4 stroke... simple to fix like a holden six... Link to comment Share on other sites More sharing options...
facthunter Posted April 17, 2015 Share Posted April 17, 2015 A bit of a problem for long flights and also reported hotter running with oil to the top. This would only happen if the oil was being stirred by the engine internals when full. (Generally not a good idea. absorbs power and gives heat). 2 problems with running with small quantities. Air might get in to the oil flow in some attitudes, and a low quantity of oil MAY get hotter as it circulates more frequently. Air in the oil can kill an engine quickly at critical times, but bearing failure doesn't seem to be a common problem, does it? Nev Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now