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Jabiru 2200 with low power output.

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Jabiru 2200 with low power output.

Postby Steve_R » Thu Mar 21, 2019 12:23 pm

Hi,

I purchased a low hours Hydraulic Jab 2200A (sn 2621) for my home build project. The engine was built in 2010 and currently has 70hrs in the logbook. It has no known history of low power output, no accidents or prop strikes. It was bought from a reputable aircraft manufacturer when they built a new demonstrator.

The engine has clearly had long periods of time between runs and had corrosion in the barrells. This has been successfully honed out by a local specialist and new rings fitted.

It starts very easily, and runs smooth throughout all availble power range. Mag drop at 2000rpm is 20-30rpm. Oil temp 70. Degrees and 55psi. BUT...max rpm on a 60x40” wood Newton prop is around 2680rpm. This same prop is turned on another 2200 jab at 3100+.

Fuel is Mogas. 98Ron 5% ethanol. I have tried AVGAS and 0% ethanol mogas...no chnage at all.

I have cleaned the carb and replaced all perishables inc carb mount rubber. The induction system is tight and with new hose. I have the mechanical pump (I haven’t stripped yet) and a facet electrical pump. No change to rpm with electric pump running.

Hydraulic lifters have been out, disassembled, cleaned and refitted. Valves have been checked and are mostly clean (small carbon depsoits, but nothing out of ordinary) cam shaft inspected and found in good condition.

Engine turns over freely and with good compresion. During running there are no unusual sounds or misfires or rough running. Infact many witnesses state it is one of the smoothest running jabs they have seen.

So why is it not producing power??

Could the Carb not be commanding full power? The butterfly goes fully open and the choke is definitely off.
Could the ignition system be to blame?
Is it possible for the timing to be advanced by one tooth gear and the engine run smoothly?
Has anyone had a similar issue and can shed some light? This is now the only issue stopping me from getting my project in the air (and don’t worry, I won’t fly until its resolved!)

Thanks

Steve
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Re: Jabiru 2200 with low power output.

Postby diablo » Thu Mar 21, 2019 12:49 pm

Hiya steve,

Have you checked your induction system and your air filter ? What about your leak down tests, what do you get on those. A good way to test whether you have issues with compression when engine is running is by monitoring your EGTs. I doubt very much is cams are out by a tooth. However, it may be worth spinning up on one mag and seeing what max RPM you reach on just left and on just right ...
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Re: Jabiru 2200 with low power output.

Postby Steve_R » Thu Mar 21, 2019 2:36 pm

Hi,

Thanks for the reply.

Leak downs are all good. 72/72/74/72 over 80.

I have cleaned the air filter, and run with it off altogether! Induction system was removed, disassembled, cleaned and re-installed when barrel honing was carried out. RPM still identical before and after.

Also, i have tried single mags up to full power....no change!! I don’t have EGT probes unfortunately. I have thought about using an infrared temp sensor on the exhaust pipes to determine if one is cooler than the others. Not sure how much that will tell me though.
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Re: Jabiru 2200 with low power output.

Postby diablo » Thu Mar 21, 2019 6:37 pm

It is a long shot but is oil correct spec? If you are using thicker oil, it may cause valves to not shut properly at hi revs as viscosity of oil would cause it to leak out of hydraulic pushers at a slower rate... egt's would show higher temps if exhaust valves were not fully closing and you might see black soot in carb throat if inlet valve is staying open.
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Re: Jabiru 2200 with low power output.

Postby Steve_R » Thu Mar 21, 2019 7:08 pm

Good thoughts! But I’m currently using Total Aero 80 (straight) during the colder months and while running in the new rings and barrels.

I didn’t notice any soot in the intakes while they were being rebuilt, but the exhaust I can’t really say to be sure. The fact it runs so sweetly is making me think its not a valve or ignition problem...but I’m no expert at all!

I am wondering if I have a blockage in a sense port somewhere so the carb isn’t allowing a full fuel/air mixture. I have noticed a very slight difference in RPM depending on the atmospheric pressure. (Pressure 1032 the ither day and I only saw 2640rpm. Lower pressure seems to gain me 40 or 50 rpm!

Maybe a blockage in the Air slider sense port?

I think I have managed to secure another carb from a fellow Jab flyer so that may help.

I really appreciate your thoughts, please keep them coming!
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Re: Jabiru 2200 with low power output.

Postby skyjeep » Fri Mar 22, 2019 4:19 am

Jabiru made your s/n with high leak lifters and the std. cam. I think they didnt make the quoted 85hp of the solid lifter motors.
they changed to slow leak lifters and a different cam at #2850, then another cam at #3095

This is where I'd be looking
probably easier to run a smaller prop.
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Re: Jabiru 2200 with low power output.

Postby Kai Lyche » Fri Mar 22, 2019 9:50 am

Ralph- agreed,

Over here we have had a small number of engines (say 8-10) with the same issue. There is nothing mechanically wrong with the motor- save for the fact that it has the wrong combination of camshaft and lifters.

The only cure is to split the crankcase and reassemble the motor with correct parts. At the time the national Jab distributor got some conversion kits up from Bundy, and undertook the work himself- that is; the engines were rebuilt back to the mechanical lifter variant. When end users complained about involved costs, which were frankly on the high side, parts (1 new camshaft, 8 new lifters, 8 new rockers and 8 new pushrods) and labour became free of charge. I don’t think the same policy was adopted in the UK. Jab accepted no responsebility- at the time they still adverised the motor with 80HP, which it marginally and barely reached with considerable effort.

Before we learned what was actually going on, we were up the walls with several propellers, different make/type of carburettors (slide type included), air filters (and no air filter), lubeoil- you name it........

I seem to recall that Camit also had something going with conversion kits at the time. Maybe Kev Hyam could supply some more information.

Thanks
Kai
Last edited by Kai Lyche on Sat Mar 23, 2019 11:31 am, edited 1 time in total.
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Re: Jabiru 2200 with low power output.

Postby Steevo » Fri Mar 22, 2019 2:01 pm

Just one thought. You say that the barrels have been honed and new rings fitted.

I would evaluate it after you have run the engine in. I have access to 4 x Jabiru engined aircrafts (well 3 now as my colleague sold his J160 a few months ago). For all of them, the static RPM is between 2700RPM and 2900RPM (one is not in a Jabiru airframe which is the one that is 2700RPM). Obviously, the variation could be to do with prop pitch differences.

But, when I had my 450 overhauled and new rings were fitted, the static RPM was a bit lower than the norm and gradually built up a bit after it was run-in. The engine could be a little bit tighter than normal which would decrease the power a little bit. Personally, I think I would run it hard for 25hrs and then see how it is. 2680RPM is a little low but not that low compared to the other Jabs I have access to. It may come up 100RPM once it is fully run-in and then would be on par with the others I have seen.

My own engine in my J160 is a similar serial number to your one. I achieve 2900RPM static.

Have you checked the RPM with any other source of RPM measurement? I have found quite a variation between different sensors and measuring gauges etc. I have an analogue RPM gauge in mine and a digital one and when both are setup exactly the same, I get a different reading on both. When I checked it with my laser RPM reader, I found that both were wrong and the true reading was somewhere in between. They were both around 50RPM out.
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Re: Jabiru 2200 with low power output.

Postby Steve_R » Fri Mar 22, 2019 2:24 pm

Thanks for the info.

Kev Hyam is the chap who did my barrel honing. Great guy and brilliant workmanship. He is the one who has said that RPM’s really are too low, especially for such a fine pitch prop. He’s a busy guy and the nature of the beast means lots of trial and error is needed and I’d like to try and solve it without bothering him too much. Especially if the problem is something that I can fix myself. Hence posting the question on here.

I certainly understand that the Hyd engines aren’t as powerful as the solids. I didn’t realise that Jabiru had changed the cranks and lifters a few times though, so that is certainly very telling.

I can only take another look at the carb, perhaps rig up a camera so I can see if the slide is travelling fully at full throttle. Likewise, I have this other carb to test. If nothing changes then I’ll have to get Kev down again.

The engine is already booked in for a strip and rebuild to solid lifters, but I had hoped to get some life out of its current configuration before exposing the wallet to more daylight!

Hi Steevo,

The big issue is that with such low RPMs my inspector is unlikely to sign the aircraft off for flight. (It hasn’t flown yet) changing the prop is also problematic as a finer pitch or smaller diameter also hasn’t been used on my engine/aircraft type (to my knowledge!)

Unfortunately I have tried various Tachos and they all agree within 20-30rpm that my onboard tacho is telling the truth!
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Re: Jabiru 2200 with low power output.

Postby Steevo » Fri Mar 22, 2019 4:18 pm

Question - Was the engine run before the top end was overhauled? I just wondered if the static RPM was known before any changes were done.

The only things that would really affect the performance (externally I mean), would be ignition, induction etc. If you have checked all of these then you could be getting on the path of having to open up the engine again. The only other things you could try is using the carb off another Jab engine or borrowing from someone who has a spare so the carb can be completely ruled out. If you have confirmed that there are no leaks in the induction and no blockages from the air box through the scat hose and the scat hose is a relatively straight run. Ignition can be ruled out by putting new plugs in, checking dizzy caps and changing leads/rotors. Swapping and regapping coils can rule that out.

If you get to the end of that, then you are looking at something in the engine itself. Not sure the timing being out would just give you a small reduction in power, I think you would notice that in a lot of other ways as well (very bad idle, maybe even a misfire). It's possible I suppose but not likely if you say the engine appears to run fine in every other respect.

But, from experience, my aircraft lost 100RPM from static when I had new rings put in. They did come back though after it had been used a bit.
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