RFguy

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yes, fuel flow *may* edge up due to square law related losses. and and volumetric / airflow behaviour + efficiency has its own curves for each engine system with RPM/ MP

the only practical way the 3300 makes >115hp is with a pitch adjustable prop. then it is fantasic, can run it down at 2400-2600 etc

yeah I think the OP is getting confused with where the VW aerovee engines make their best power Jab 6 cyl : note flat torque curve

WRT sonex - it's unsurprising that a the 120 hp jab goes faster the 100 hp 912ULS rotax . why ? because at any altitude, it has more power. simple...... and power = rpm x torque so forget about talkign about torque. I dont 't know why that is in any contention. ideally, thrust would be presented. that's the final say...

if you change to the composite prop (from the wooden prop) you'll find its worth quite a few horses....

Justin(e) , the Jabiru 2000 hour overhaul... might require a crankshaft , camshaft etc, likely raises the cost significantly. If you are a 19- flyer, then you have your own discretion to assess things like camshaft and crankshaft condition. I understand a 2000 hour full overhaul of the 912 , replacing all the parts that rotax specified must be checked for wear .....is essentially uneconomical . I believe it runs more than 70% of a new engine (in parts) to do all the items. Rotax make it that way intentionally I am sure . They want to sell engines. The Rotax at 2k hours still has plenty of reliable hours left in it , assuming it has a good life with clean oil and little avgas . The Jabiru you really do need to pull it down and do a overhaul. The Lycoming.. well they are known for going more cycles than cats have lives. Again, rebuild cost can vary in experimental categories. As JackC said , flying is not cheap or free to just open your chequebook.

skippy , your comment of : " My current Rotax aircraft seems to be delivering about 15 L/hr, 5200 rpm at 130 knots indicated - how would a Jab compare?" Is not valid for this discussion. We're talking about a specific fuel consumption for a specific shaft horsepower (in cruise for total fuel consumption argument ~ 75% ) . The discussion is aircraft invariant . And no correspondence will be entered into

Yes, agreed, the 2000 hour rotax still has more than likely plenty of hours left in it. you might get a 2000 hour 912ULS for 3k-8k that will do another 1000 hours without cracking a sweat But if it breaks, be prepared to chuck it in the bin (with a set of four sets of rings = $1400 !!! ) The 2000 hour Jab is ready for another top end overhaul. 6k-8k inc new pistons, lifters etc . and Then you could get another 1k hours from it if it was well looked after and had nice clean oil all its life..

LOL. trouble with trying to compare apples for apples with jab and rotax 2000 hour cost is what value are you goign to use for normalizing the ULS (100hp) for the either 80hp jab or 120 hp jab. Let's talk fixed pitch props and sea level and continuous power, all day, ULP. The Jab 120 hp jab is really only 115hp (for a fixed pitch prop) where you can actually run it up to in the usual service pitch/RPM. The Jab 80 hp, is really 80hp, since it likes to rev and generally they're propped finer and revs to 3300rpm in normal service/pitch rpm use. The 100hp ULS should be called a 90hp, because that's all it is rated at continuously. Prop spins a bit slower on the Rotax, that's worth a few % in efficiency. Rotax runs lean in cruise. Jab runs compatratively rich, costing perhaps 5 to 10% in fuel What's good about a 3300 jab compared to the 912 ULS is that up high, the Jabiru has a fair bit of spare capacity to rev higher and make up for the altitude. AT 2000 hours, Rotax has had a gearbox service @ 1000h maybe about a grand, Jab has had a Jabiru factory TEO at 1000h Both have had two sets of plugs. Both have had 1 set of hoses (if you buy the rotax specified manufactuter's hoses from a sensible place they dont cost much at all) . Both have had a fuel pump service (kit cost is similar) Both have had a carb service.(kit cost is similar but x2 for 2 carbs in the rotax ) Both have had 40 x oil and filter changes. if you buy oil filters from Jab, similar money. I'm a strong believer that a Gen4 should get to 1000 hours without incident if run on fresh ULP95/98 and 15W50 oil. There's some teething problems at the moment with PD42J carb changeover, and also ignition coil changes. (due to sourcing problems) . 2200 4 cyl Jab is probably 5200+probably $1200 parts = $6400 (valves, rings, rocker bushes, screws and bolts, o rings, seals ) 3300 jab is 6400 + 1800 parts = $8200. Remember at 1000 hours, with the Jab, you are goign to need to remove the engine and ship it both ways unless you do it on the plane (like I would) The rotax fuel consumption is worth a bit, at 2000 hours, youve probably put 1 litres more per hour into the 2200 = 2000 litres = $4000 more ! and proportionaly more for the 3300 6 cylinder.$6000. Jabiru have lowered their max exhaust temps in recent manuals.... - but that doesnt necessarily mean they're running richer . EGTs generally follow CHT, so if the gen4 CHTs are lower, the EGTs will follow. Well the other possibility is that the manufacturer has become more nervous and is running richer than ever. Dunno. $24000 for the 4 cylinder jabiru (80hp) and $ 30500 for the 6 cylinder (115hp) , $35000 for the rotax ( 90hp)... (yes 1000$ more than the jab site but the jab site numbers dont include the accessories you need like the oil cooler.......) My feeling is the 2200 you end up costing about the same as the rotax, and the 3300 end up costing quite alot more - but you have a far more powerful engine that can do 115 hp all day. so the comparison needs have have proportionality in there if we said $/hp, then the 34400/80, 44.7/115, and 37/90 80hp jab : $430/hp 90 hp rotax : $411 / hp 115 hp jab : $389/hp 210hp IO390 Lycoming : $720/ hp (hoses, lean etc) wow..... so , it's about same.

Mark was that seafreight or airfreight ? as u'd know, at that size, single shipment, airfreight rules... bring 10 of them, that would be a different story.

Archer, 180hp, non-tapered constant chord wing.

Today was goign to be a skill build / challenge Short field TO practice in Xwind. Cowra departure, 2pm flight. PA28, 20 gallons on board and me. OAT 24. windy up high. Short field TO practice with pure X wind at Young. Young (YYNG) is known for its swirling challenging winds. It's something I need to work on, only done a couple in the past year. Flaps 25 , get it up to full smoke and let the brakes go. TO roll, into wind at Cowra, gusting to 10 kts on the nose . Woops ! she wants to fly at 35 to 40 knots (instead of the usual 65) . lifts off unexpectidly with big roll wobble - I hold it in ground affect until it accelerates then off we go. lesson #1 refreshed. It's thermal bumpy down low, windy mountain bumpy up high. Not much fun. NOT a 'never flown before ' passenger day/ .... I nav myself the 31nm down to Young on the VNC , go into circuit, bumpy, 10 kts pure crosswind on AWIS, not much for the PA28 but holding off the drift feels like about 15 kts on final. Ditch full flap (40).. I want to land a bit airspeed faster with a bit less drag so the decay is not as quick...., so back to flaps 25 . I hold the approach nicely stabilized. uneventful landing bit fast not all that pretty but OK...but needs work...would get about 5/10 from judges on the fence ..... backtrack for the departure. maybe some trim change for this TO. .... Normal 0 flaps TO, generally trim a fair way back. I usualy set the trim so It will fly off when its ready, consistently and well behaved. IE it just flys off, hands off around the TOSS (60-70 kts weight dependent ) when its good and ready. But this time, after being caught a bit unaware, trim the nose down a bit more. Short field TO... a bit of left roll in with the X wind. bit gusty. But this time I am ready for a bit of excitment when its time to fly....... again it jumps off the ground before I am really on top of it, woh boy ! If I had not anticipated to unruley behaviour, then I could have put a windtip on the ground ......careful with that roll you have in - needs to be moderated and be ready for the leap off the ground ... and replaced with some rudder to hold centreline on departure a bit earlier Land back at Cowra, perfect greaser into 5 kts down the runway. Takeaways :The flaps 25 TO is more like a leap off the ground rather than a nice steady rotation and liftoff. That probably reflects my incorrect pitch / trim input during the TO roll . TO with pure crosswind with LOTS of lift dialed in , (with lift off speed about 40% below usual) in needs LOTS of attention. The roll (wing a bit down into the wind) needs to come out early and rudder in as soon as the aircraft is flying ....and held close to the ground in ground effect under we reach TOSS (65-70 kts) .

Justin if you ever decide to get a gender reassignment (I think that's the modern term) , you'll very easily be able to go with "Justine".

I fly 0.5 to 1.1 per week to maintain recency. I do it week after week after week.... and that is whether I have somewhere to go or not, "PILOT HAS TO FLY" is my mantra longer than 2 weeks and the rust starts like I said a couple of weeks ago, fly regularly and you will encounter challenges often enough that the competence to deal with them stays in your brain. fly less regularly and challenges overcome etc get lost in time and you dont remember how to deal with it.

get onto the facebook site and ask https://www.facebook.com/groups/piperwarrior/ and also https://www.facebook.com/groups/1235943279809596/

interesting.... Drop octane? -Not true according to the chemist at BP and I have it in writing . Octane increases slightly briefly. Volatiles burn off, playing havoc with controlling the vapour pressure / vapourization behaviour. the forming non soluble solids is the problematic one I thought.

Gen4 is good. I'm only selling my J230 because I have the big Piper, and need something like a Savannah as a 2nd aircraft . I do have a Thruster in the works.

There is Currendooly

fresh ULP98. if in plastic container, or place where it can breath oxygen, ditch it or use it within a month. always filter and water check. The octane doesnt fall with time- what happens is some components react with oxygen and form non soluble solids.... Avgas only if nothing else is available, or the heads run red hot (>165 cruise, >180 climb) .

Justin, what EGTs in cruise are you running on your Gen4 ? Rotax engines tends to run leaner , a little more economical on fuel. In the past Jabiru has tended to err on the rich side to stop valves dropping ..... and have been playing around with the jetting forever. This rich running exacerbated the avgas buildup issues.

mmm Agree 100% Justin with everything you have written. Yes no issue with Jab airframe- its awesome. yeah (IMO) the AVGAS de-coke is needed every 400 hours worst case, for a jab on AVGAS. a solid day's work for a four cylinder. It doesn't actually require any parts as such, except for rings, since you're likely to change out the rings if cleaning the ring lands. You might be able to do it without pulling the pistons off the conrods..... Actually a running hot jab engine might burn the avgas better.... so one's mileage may vary. run hard and hot, a gen4 is probably capable of running hot enough (since it doesnt have to live in fear of head recession) of being better with the avgas gunk. I dunno. As usual, engines that are babied tend to look worse. Jabiru Rings are cheap. $35/set Rotax rings $270/set. WTF ????!!!! Yes $270/set ! like I said, Rotax is good if you dont have to fix anything..... Jabiru factory is always helpful I think people need to watch quality of oil filters. there have been a few split. Dunno what the source was of them.

that place is so foggy I'd be surprised if that would catch on.

The thing is, the Jabiru top end overhaul, is still 1000 hours, isn't it ? which leads to a cost per hour of about 1.5x the rotax, assuming nothing in the rotax breaks..... The Jab engines still face a sizable problem on AVGAS. -- AVGAS running ----They don't run hot enough to evap/ gas the lead compounds, so this cakes-up the crown, rings, chamber, guides. and leads to a TEO/TBO of around 400 hours best. This is well known. There is no getting away from this, apart from using Decalin runup with seems to reduce/ eliminate this problem, but not recognized by Jabiru (but is by rotax). - solution - run ULP95/98. problem solved. Don't run ULP more than a couple of months exposed to air. Lesser evils I'm not sure they've completely got on top of the rather inelegant oil pressure control. There's many documented problems. It's OK, just...... and I would have liked to see a heavier thru bolt, since the margin between [ sufficient preload AND the material yield AND tension errors due to torque application on unknown lube threads } They've gone to much high temperature rated valves, which is good. and about 3x the price per valve, as expected. and I they've gone to a more solid, non split skirt/crown piston. Gen4s broke alot of pistons before they got that part of it stable..... Head recession should be a thing of the past. the bolted head , like everyone else, should solve that. In the past, head recession (due to less than ideal choice of aluminium) led to valves hanging open and loss of valves.... Nothing economical is perfect. -glen

Gen4 is OK now. Had a shaky start. (2017 to 2020) I'm going to sell my J230, umming and ahhing whether I do a top end overhaul and sell with a late Gen3 (and the last of them) even has the prop frange dowels..... or I put a Gen4 in it and flog it with that..... Jabiru have had to change from the Bing carb to some Mikuni copy. so far so good, wonder how their jetting is going, that might take time to figure out.