Guest spacewalker Posted March 26, 2010 Share Posted March 26, 2010 Jabiru carb conversion I noticed a previous posting with a comment regarding 'lean burn' which is I believe a condition like 'stratified' charge where exceptionally lean mixtures can be burnt because of the cylinder head design. A lean mixture under 75% power will not overheat the engine or the valves. In fact, going Lean of Peak is a common method to gain fuel economy and actually run the engine cooler. The is a lot of discussion on this over the years but check out 'The Pelicans Purch' for more info... Cheers Martin Link to comment Share on other sites More sharing options...
Guest check-in Posted March 27, 2010 Share Posted March 27, 2010 I am no expert on 'lean of peak' but what I have read suggests that you need individual cylinder CHT and EGT probes and GAMI or some other calibrated injectors. Can't see how a carby would control the fuel delivery accurately enough. Surely the risk with any carby would be that one or two cylinders could actually be getting a mixture too close to the harmful range, ie right at 'peak' ? Question, not statement, because I have seen some claims for non-standard carbies to replace the Bing on the Jabiru which supposedly deliver better fuel economy. They did run the big radials lean of peak, so there's nothing new in the concept. However they also had a flight engineer constantly monitoring the engines. The 1830's in the DC3 had an 'auto-lean' position for cruise, but I am not sure that it was lean of peak or just a bit less rich than 'auto-rich' which we needed to provide extra cooling fuel in the climb. The carby was a pressure-compensated gadget, which had four mixture positions 'emergency rich' 'auto-rich' , 'auto-lean' and 'fuel cutoff', so there was no intermediate leaning required. But its inner workings are long-since forgotten as it has been 44 years since I did the engineering course. Link to comment Share on other sites More sharing options...
Guest spacewalker Posted March 27, 2010 Share Posted March 27, 2010 Lop Check-in, thanks for the info. It is not the type or brand of carby that influences LOP operations. The induction system and the consequent fuel distribution is the problem in trying to get all cylinders running the same mixtures and hence temps. That is why it is easier to run LOP with injected engines, at least those that have an injector per cylinder, thus avoiding the distribution problem of having the fuel separate out of the mixture or having some cylinders favoured over others when it has a circuitous path to follow. The is a lot of info with facts and figures and experiences on the 'Pelicans Perch' column on the AvWeb aviation site - Just Google it. The big radials were quite sophisticated in their day ( maybe not the 1830's you mention, maybe you meant the R1830 radial ;-) but with their supercharging, the fuel mixture distribution was likely to be better than a flat four with a single carb. Certainly having all cylinders monitored for CHT ( the most important) and EGT would give you a clearer understanding on what is going on when attempting to lean. Link to comment Share on other sites More sharing options...
bushpilot Posted March 27, 2010 Share Posted March 27, 2010 I watched Mark at Jabiru do mine on Monday and noticed the one little sneaker behind the grub screw. Mark also did a full leak down as well. For me at YCAB it's a no brainer to fly up and have 50hrly's done by the experts. I know this is possible only for a few of the thousand + in service. The bill was reasonable as well- cheaper than a lot of bikes I get serviced! There is clearly a lot of highly experienced but dispersed knowledge within this thread on Jabiru engines and history- and we can all learn lots from it. For my two dollars the guys at the factory see and hear just about all of it and when their spanners are on my engine I fly more relaxed!.... Having Jab do servicing still gives no guarantee of QA: One of our local guys had his rings replaced by Jab recently and the mechanic cross threaded 2 of the 4 grub screws in the heads. Result - Flew back home and enroute (landing for a break) noticed oil pouring out everywhere.... Link to comment Share on other sites More sharing options...
bushpilot Posted March 27, 2010 Share Posted March 27, 2010 Has anyone heard about the 'major' changes made to latest build 2200 engines? One delivered to a customer here in Bathurst last week looks quite different to any we have seen before: For instance oil feed lines to top of heads are not there any more - and he has been told all oil feed is now internal in the heads.... Link to comment Share on other sites More sharing options...
bushpilot Posted March 27, 2010 Share Posted March 27, 2010 We have just had a similar situation with a flying school aircraft we maintain. We replaced the through bolts and put the aircraft back into service.The operators then complained that the engine was stiffer than others when pulled through. Further examination leads us to believe that the crankshaft may have be out of alignment with the bearings. We hope to find out after the enfine has been pulled down at Jabiru. Old Man Emu Hey OME = Any update on this engine??? Link to comment Share on other sites More sharing options...
Guest Pioneer200 Posted April 21, 2010 Share Posted April 21, 2010 Hi, we had our groups AGM on Monday night and it is sad to hear that a couple of guys in our group do not fly our planes now as they have lost faith in the 2200 engine. We have a J160 and an Alpi Pioneer 200, both have the 2200 engine The pioneer is about 6 years old done just over 1000 hours and has had a few flywheel bolt breaks. The J160 engine gave up at 550 hours (thru bolt failure). Now the new J160 engine (200 hours) is thought to be down on compression on 3 cylinders. Its a shame that we have nice aircraft to fly, but pilots with no faith in the engine. We have just changed our maintenance team so it will be interesting to see how things perform when both engines are back in A1 shape. I have had my concerns that the past maintainer was not doing all that was needed to the engine at the hourly service intervals recommended by the maker. Q. Do Jab engines that are maintained by LAMES last longer than engines serviced by their owners etc,, ??? I will continue to fly the J160 ,but as any pilot should, be prepared for when the prop stops. Link to comment Share on other sites More sharing options...
jetjr Posted April 21, 2010 Share Posted April 21, 2010 A few questions What prop is on the Alpi? Has it been overhauled and/or had flywheel SB implemented in that 1000hrs? Premature engine wear is also a known issue possibly incorrect ring clearance and there was an issue with bolts holding heads on causing out of round cylinders. Very easy to see and check. I believe it was in a Jab newsletter or maybe a JSB. Through bolt is a problem with no correction or AD associated that I know of. Link to comment Share on other sites More sharing options...
Guest spacewalker Posted April 21, 2010 Share Posted April 21, 2010 Rod Stiff from Jabiru told me that a Jabiru engine, properly maintained, will not give trouble. Certainly the engines that I maintain have not given trouble, and it is very important that the cylinder heads are regularly re-tensioned and that the engine operating temps never exceed those recommended. There has been instances where the cylinder hold down nuts have had to be radiused so as to prevent distortion of the cylinders, causing excess friction that can be felt when turning the engine over by the prop. I have seen these engines that have flywheels come off, seized big-ends, dropped valves etc etc. - some with less than 100 hours, so I am not so sure that proper maintenance and operating procedures will prevent every problem, but it is a good start. My suggestion would be to have the engine(s) stripped and rebuilt according to the manual. That way anything untoward can be addressed, and you can have peace of mind. Link to comment Share on other sites More sharing options...
Vev Posted April 27, 2010 Share Posted April 27, 2010 Has anyone heard about the 'major' changes made to latest build 2200 engines? One delivered to a customer here in Bathurst last week looks quite different to any we have seen before: For instance oil feed lines to top of heads are not there any more - and he has been told all oil feed is now internal in the heads.... The new engine feeds the oil up through the push rods and then through the rocker arm to the rocker shafts and valve stem. Cheers Jack Link to comment Share on other sites More sharing options...
jetjr Posted May 11, 2010 Share Posted May 11, 2010 Bit off topic and old but found these interesting claims - from a company who supports alternative aero engines inc auto types ie has it in for Lyco and TCM. Theres worse stuff on Continentals. Jab says 1000hrs till top end OH. 12/05/00 Lycoming Woes A class action lawsuit has been filed against Lycoming concerning an alleged 10% inflight failure rate on its TIO-540-AE2A engines powering Piper Mirages. This engine has a TBO of 2000 hours however, a survey of 92 owners found that only 4.3 percent made it to 1500 hours. The average was 727 hours. 41% needed a top everhaul before 1000 hours and many needed topping at 200-300 hours. Why Lycoming sets the TBO at an unrealistic 2000 hours is puzzling when probably not one engine ever reached that without topping. If it was set at a more realistic 750 hours, owners would expect a more realistic operating cost. Link to comment Share on other sites More sharing options...
facthunter Posted May 11, 2010 Share Posted May 11, 2010 "Top" Overhauls. Lycomng put an enormous amount of work into the valve technology. Nearly all (or ALL exhaust) valves are sodium filled, and the valve and seat metallurgy is exotic. There has always been an aim to run to full TBO without removing cylinders. Not getting over 2,000 hours is not unusual but some helicopter engines (Supercharged) are running over the TBO. So I was told recently. Normal servicing will detect the need to attend to these issues. There are a lot of factors involved. Engine management, cowl flap and mixture and boost and shock cooling being some of the areas that are critical. (as well as sitting idle for extended periods without being inhibited.) If the engine basically was not good enough to list a TBO of "whatever" the aviation authority would impose a lower figure, on the basis of "field experience". The manufacturer does not decide a TBO. The engine starts off at a nominal one and "earns" the higher one, in the light of experience, or demonstrated reliability. I can recall the flight engineer on a four prop. turboprop that brought the russian ballet out to australia, boasting that the engines were doing 400 hours without overhaul, in the late 60's.,The DH gypsy engines did not do a lot of hours without the heads off either. The service life of a Merlin was a couple of hundred hours. Reciprocating engines are a bit of an abomination, but they have been the principle method of propulsion for about 105 years and are the most efficient as far as fuel consumption is concerned. High bypass ratio fan jets are going well now with very high combustion temperatures but not an option for us. Nev Link to comment Share on other sites More sharing options...
gwillimm Posted May 16, 2010 Share Posted May 16, 2010 jabiru3300 top end o/h Gooday all been running a jab 3300 for 3.5years and done 750 hours, the lean burn economy kit that was supplied and fitted just after motor was run in. Just pulled down top end due to compression leaking betwean head & barrels on all 6 cylinders and o'rings leaking at the barrels. leakdown test showed the ring wear but valves ok. Just sent the heads barrels and pistons away from inspection. The motor was running well but down in power. We run 2 oil coolers one through a duct & one at the front of the engine cowl which gives us continous oil temp of 80 deg and max of 100deg on long climb. oil ppessure @ 220kpi. CHT temp on cruse @ 280 deg F and on climb max 320deg F, I have done 500 hours + in Jabs and rearly had such constant temptures on climb. Verry happy with the Brumbys temptures have done there homework. Hope this is intresting to you all Yours in flying Mick :thumb_up: Link to comment Share on other sites More sharing options...
Guest skyscooters Posted May 16, 2010 Share Posted May 16, 2010 l Last time i was at the jabiru factory they were testing feeding the oil to the top of the head through the push rods the same as most push rod engines get their oil to the top. Link to comment Share on other sites More sharing options...
Vev Posted May 16, 2010 Share Posted May 16, 2010 Skyscooter, As mentioned in a previous post ... the push rod oil feed to rocker gear is already in production on current engine. In fact I retro fitted this system to my thick finned 2.2 head 2 weeks ago. Cheers Jack Link to comment Share on other sites More sharing options...
bushpilot Posted May 16, 2010 Share Posted May 16, 2010 push rod oil feed to rocker gear Skyscooter,As mentioned in a previous post ... the push rod oil feed to rocker gear is already in production on current engine. In fact I retro fitted this system to my thick finned 2.2 head 2 weeks ago. Cheers Jack In fact the new system is in production on both the 2.2 and 3.3. Link to comment Share on other sites More sharing options...
zodiac3813 Posted May 21, 2010 Share Posted May 21, 2010 Hi Mick, when you say two oil coolers, are they in series? How are they coonected? Any chance of a photo? Cheers, Jim Link to comment Share on other sites More sharing options...
Guest spacewalker Posted May 21, 2010 Share Posted May 21, 2010 Hi Mick, I can see why your engine has proved reliable - those temps and pressures are the key. Here is a quote from the Yahoo Jab list. Some of these guys have done extensive testing of oil pressures and have concluded that it is better to measure the pressure at the main oil gallery rather than at the pump. In cold weather, it seems that it takes a while for the oil pressure to build up throughout the engine, and adding oil coolers can make it worse - something to consider now that winter is approaching.... "When Roger and I tested our engine 2200-2618 fitted with an oil cooler, at 2C ambient the pump pressure was 57psi and the gallery reached 10psi after 2 minutes and only reached 20psi after 5 minutes. Even with oil at 50C and above the pump pressure was again 57psi and the gallery about 25 to 30psi. This is with a cooler in the circuit. We then took the cooler out and the pressures came up straight away to 57psi pump and about 50psi gallery. Since the tests we have been running our engine without an oil cooler and the pump/gallery pressures have been within 5psi of each other at all times, even up to an oil temp of 100C. Regards, Jim." Link to comment Share on other sites More sharing options...
Guest Crezzi Posted May 24, 2010 Share Posted May 24, 2010 Seems like the UK AAIB have been investigating a few accidents caused by Jabiru engine failures - http://www.aaib.gov.uk/cms_resources.cfm?file=/Savannah%20Jabiru,%20G-CEED%2005-10.pdf http://www.aaib.gov.uk/cms_resources.cfm?file=/Jabiru%20UL-D,%20G-JAAB%2005-10.pdf Link to comment Share on other sites More sharing options...
facthunter Posted May 24, 2010 Share Posted May 24, 2010 Pressure Where it Counts. spacewalker you are right on the ball. You cannot put filters and coolers in the oil system and not take account of what is happening to the the pressure in the oil galleries that feed the bearings. They restrict the oil flow. Everyone should heed what you have said . Nev Link to comment Share on other sites More sharing options...
bushpilot Posted June 2, 2010 Share Posted June 2, 2010 Hi Mick, I can see why your engine has proved reliable - those temps and pressures are the key. Here is a quote from the Yahoo Jab list. Some of these guys have done extensive testing of oil pressures and have concluded that it is better to measure the pressure at the main oil gallery rather than at the pump. In cold weather, it seems that it takes a while for the oil pressure to build up throughout the engine, and adding oil coolers can make it worse - something to consider now that winter is approaching.... I've wondered about this from the point of view of starting a cold motor. My 2200 fires instantly on even very cold mornings, so I'm thinking the oil pressure is going to take awhile to build. Anyone got a view on cranking with mags off before igniting her? Link to comment Share on other sites More sharing options...
Vev Posted June 2, 2010 Share Posted June 2, 2010 Bush Pilot, I always hand pull through to make sure all feels normal and then crank with mags off and look for the oil press needle to lift off the stop a little before running the engine. I'm sure it helps reduce wear at start up. Spacewalker, what viscosity oil where you running in that engine when you ran your pressure tests? Cheers Jack Link to comment Share on other sites More sharing options...
facthunter Posted June 3, 2010 Share Posted June 3, 2010 pre-pressuring the oil System There is no doubt that pre pressuring your oil system is desireable. Caterpillar tractors/graders do it. I NEVER rebuild a motor without doing it. It is recommended for all aero engine rebuilds. There is always a risk of damage starting otherwise. That is why you should carefully monitor oil pressure rise at start. Pulling the prop through must help provided you only do it to Jab and Rotax 912, it is an absolute No No for impulse mag or Auto type engine ignition systems. A lot of people will not like to see anyone "propping" any engine, because of the safety aspect. If your battery is good enough a few turns of the starter won't do any harm. With some engines you can't crank the engine without the engine ignition being ON. IF you don't apply the choke the engine will not start cold and with the throttle closed if it does start, it won't rev very much. generally starting with a carefully judged part opened throttle just off idle the engine revs are initially low enough not to put too much load on the motor, so it might be a bit academic, if you are gentle anyhow. Nev Link to comment Share on other sites More sharing options...
rick-p Posted June 5, 2010 Author Share Posted June 5, 2010 Seems like the UK AAIB have been investigating a few accidents caused by Jabiru engine failures - http://www.aaib.gov.uk/cms_resources.cfm?file=/Savannah%20Jabiru,%20G-CEED%2005-10.pdf http://www.aaib.gov.uk/cms_resources.cfm?file=/Jabiru%20UL-D,%20G-JAAB%2005-10.pdf It would I think be appropriate for all that read the quoted reports to read in each case the whole report as what is addressed is a past issue now rectified by the manufacturer and the reliability has improved and improves with time as has been the case with every aero engine ever manufactured, that is those that have remained in production and have not been pulled out. I have spoken to hundreds of Rotax and Jab owners and it is I now know the case that there is little difference in the reliabilty of each of the subject engines. One thing is certain to me that most of the problems on the simpler of the 2 engines has been finger mentality. That is those who think they know how to tinker really don't. The Jab engine was the tinker's dream as it is so simple whereas the Rotax is a mechanical God which instills fear even in the hearts of the most brave and fools alike. It has really come down whether you like Ford, GMH, Mazda or Toyota or what religion you are or what football team or political party you follow and it has very little to do with reliability or anything else. As for oil coolers my Jab engine didn't have one and I did have some issues and after speaking with many experts I decided to fit one and have never looked back both pressure and temperature wise and yes it is a good idea to crank the engine over a few times without the mag's on. Always do this after you have change the oil and filter. I have both a 912 and a 2200 and a Gypsy Major Mark 10 and the best engine out of all of them is the GM tractor engine (Gypsy Major) it is like the Perkins Engine used in trucks even if a piston falls out of it it will still keep going. Rick-p Link to comment Share on other sites More sharing options...
facthunter Posted June 6, 2010 Share Posted June 6, 2010 glad to hear..... You had me worried rick-p. Hadn't heard from you. Comment. The Gypsy major used to be very bombproof but a few years ago I heard of many not running quite so trouble free. Shows that if you make the effort you can muck up even the best of engines. You make a good point about the fiddling and one reason why the Rotax gives good service, is that people leave them alone. You don't have to tension the head constantly and you don't have to adjust the tappetts. Have seen some brand new ones that had to be fixed. (Go back to the beginning of this para. for reason.). Also reciprocating engines are self destructive critters, Use with caution in aeronautical situations. Nev Link to comment Share on other sites More sharing options...
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