Russ Posted December 8, 2014 Posted December 8, 2014 Why the "PM" to find out your mods, share them for all to see / evaluate. Post a disclaimer if that helps. Strange to me, to express your " fix" but only accessed privately. .????
jakej Posted December 8, 2014 Posted December 8, 2014 My question re number of probes was to make a point or three - Why were/are only 1 or 2 CHT probes fitted on 3300 Jabbies & are they on coolest or hottest cylinders ? Is is because of cost ? Most of the aircraft I have seen have had the CHT/EGT loom only connected to 2 cyl - curious that because when you order a standard engine sensor kit for the Jabby it includes ALL 6 of each. What is the sense of having an engine monitoring capability if you don't monitor ALL CHT's as those temps are one of the most important parameters needed to be maintained at a level to ensure reliable ops by keeping an eye on Oil press, Temp & CHT's. TREND monitoring & downloadable data capture is a feature of many EMS systems when analysed can prevent grenade events. Dave, Dynon & others offer the same but generally better quality but not as cheaply, YGWYPF Jake J 3
biggles Posted December 8, 2014 Posted December 8, 2014 A picture is worth a thousand words . This shows my CHT's running at 200 degrees F . Bob
Russ Posted December 8, 2014 Posted December 8, 2014 Sure does... 16.3 LPH ...28ish revs........me same revs 15 ish. Latest jet kit too. ( did you jet even bigger ) ??
facthunter Posted December 8, 2014 Posted December 8, 2014 Running at 200 f is a bit cold. You try to get above that with liquid cooling, where fitted . Probably about 225 would be ideal. The head temp cannot be uniform as there will always be higher temps near the exhaust port. That is the nature of the design. Extra airflow means more drag, so utilising whatever airflow you already have more efficiently is a good idea. Some kind of inflight adjustable cowl flap will get you the best situation. but a little more trouble to organise and potential for finger trouble . Having a set warning signal would overcome that. Nev
biggles Posted December 8, 2014 Posted December 8, 2014 Don't get too excited fellas , this was taken on descent into Southport , and there is some lag in the fuel flow indication . The CHT' s normally run around 220F , with OAT around 22F , and flying S&L . Fuel flow at or near MTOW is 16.9 - 17 l/hr at 2950 RPM . Jetting and fuel flow are as recommended by Jabiru . A bit of parallax error there I think Deb but I'll have to speak to the photographer , anyway battery nearly 7 yrs old now since manufacture . Engine now has 340 hours and untouched apart from mandatory upgrades . Bob
biggles Posted December 8, 2014 Posted December 8, 2014 [quote="deborahlwayman, post: 464886, member: 8539 Dlegg, we need to talk. Those temps need to come down and believe me they are quite typical for a standard Jab. That fuel flow looks a tad low for a 3300 @ 2800 RPM. Bob 1 1
dlegg Posted December 8, 2014 Posted December 8, 2014 That fuel flow looks a tad low for a 3300 @ 2800 RPM. Bob I read conflicting reports on recommended head temps for cruise....Jabiru don't publish a range to aim for, rather just a max to avoid. Limbach recommend cruising at between 150-170c , but to keep below 200c at all times, as per http://byrongliding.com/wp-content/themes/common/docs/Limbach_Tech_Bulletin_44.1.pdf That fuel flow is with standard jab bing and drops down to 17lph at 2750 rpm, goes up markedly above 2850. I presume the tapered needle is doing its job....
jetjr Posted December 8, 2014 Posted December 8, 2014 Old non jabiru targets are egt below 690 at all times, cht low as posible but 120-150, oil around 90 Cht is critical and 180 is too hot, 200 deg getting close to where head material can be permanently changed Watch for uneven egt, unless theres all cyl monitoring you might be running way hotter. Also cht measurement errors, air blast can cool sensor plus cold junction location.
facthunter Posted December 8, 2014 Posted December 8, 2014 You are using degrees .C. We need to not confuse. Nev
Captain Posted December 8, 2014 Posted December 8, 2014 While we are into show and tell, here is mine on a 230 at 2880 rpm, just levelling off at 6,900 ft with 11 C OAT. CHT & EGT were usually highest for me on 2 and 4 with plenty of air getting to the back to cool 5 & 6 (and this needed to be watched on descent to stop them getting too cold, so usually needed power on a little while descending). I also always suspected that the J intake plenum was a bit of an issue and did not evenly distribute to the cylinders, but that can never be perfect. Note carb temp was 3 C at top of climb and oil was 74C. 1
Jaba-who Posted December 8, 2014 Posted December 8, 2014 Be careful with fitting those lips and ensure that they are not level with or below the tip of the exhaust as you will get significant blowback of exhaust fumes into the cabin. How does that happen. If the doors are closed and the air flow is deflected downwards how does it get into the cabin? .
jetjr Posted December 8, 2014 Posted December 8, 2014 Captain those are awfully similar to my numbers, good to see, thx
Guest Ornis Posted December 8, 2014 Posted December 8, 2014 The question CASA is addressing is, if you buy a new Jabiru and fly it prudently, as it comes from the factory, will it be reliable? (By any reasonable standard.) Well, the answer used to be "No". A flurry of "fixes" followed purchase, mostly wild, woolly and wrong. Jabiru seems committed to hydraulic lifters. The early engines failed utterly and completely. Maybe, after conscripting hundreds of unsuspecting buyers into its development programme, Jabiru has stumbled on an answer. But I very much doubt it. The problem wasn't maintainers couldn't adjust the tappets. The problem was that the tappets required persistent adjustment, and that announced something was seriously wrong. So, shoot the messenger and throw another red herring into the pickle.
Guest Maj Millard Posted December 8, 2014 Posted December 8, 2014 How does that happen. If the doors are closed and the air flow is deflected downwards how does it get into the cabin?. Deflected downward into the props slipstream which then swirls it around the fuselage to enter the air vents and any area where the doors don 't seal properly.
jetjr Posted December 8, 2014 Posted December 8, 2014 Reading article on D motor, it looks interesting A important design feature is side valves, which is good because in the event a valve doesnt close the engine will keep going unlike overhead setups - (sort of a quote from Belgian makers) Sticky valves arent unique to Jabiru and flycut pistons are doing the same thing. In my view both approaches are good.
Russ Posted December 8, 2014 Posted December 8, 2014 "draft proposal for jabiru aircraft" ....that's the topic to this thread... Gee.....we've well and truly deviated to engines and issues that are far removed from topic, the bulk of inputs here belong elsewhere. ( yes, mine too )
JimG Posted December 8, 2014 Posted December 8, 2014 The question CASA is addressing is, if you buy a new Jabiru and fly it prudently, as it comes from the factory, will it be reliable? (By any reasonable standard.)Well, the answer used to be "No". A flurry of "fixes" followed purchase, mostly wild, woolly and wrong. Jabiru seems committed to hydraulic lifters. The early engines failed utterly and completely. Maybe, after conscripting hundreds of unsuspecting buyers into its development programme, Jabiru has stumbled on an answer. But I very much doubt it. The problem wasn't maintainers couldn't adjust the tappets. The problem was that the tappets required persistent adjustment, and that announced something was seriously wrong. So, shoot the messenger and throw another red herring into the pickle. I've been following this thread from the very beginning and this post in my view is without doubt the most accurate description of this situation. JimG 3
fly_tornado Posted December 9, 2014 Posted December 9, 2014 The D-Motor looks an easier conversion for Jabiru 4 cylinder airframes than a rotax Slightly off topic but it seems that every manufacturer faces having to roll out a fix this at some point. http://www.verticalmag.com/news/article/FAAwillrequirereplacementofcertainRobinsonmainrotorblades
Teckair Posted December 9, 2014 Posted December 9, 2014 just levelling off at 6,900 ft[ATTACH=full]33117[/ATTACH] Mmm is that where you should be?
rankamateur Posted December 9, 2014 Posted December 9, 2014 Mmm is that where you should be? Not above 5000', 4900" would have been better. Maybe he was IFR?
biggles Posted December 9, 2014 Posted December 9, 2014 Mmm is that where you should be? Mmm , do you think that he should have been levelling off at 7500 Teck ? Bob 2
Captain Posted December 9, 2014 Posted December 9, 2014 Sheeeeeeeeeeeesh you blokes, Traversing a little bit of rough country sitting behind a 3300. How high do YOU think is safe? And with a number of saleplanes above & below at the time. Plus an ingrowing toenail. 4 2
Teckair Posted December 9, 2014 Posted December 9, 2014 Mmm , do you think that he should have been levelling off at 7500 Teck ?Bob Yes, 7500 or 6500 depending on which direction he was going. Richard. 1
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