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................................................................................................................... The interesting thing about 98 was shown in the BP study on Petrol life in vehicle tanks done in 2010 when they found that as the lighter aromatics began to evaporate off the octane rating went from 98 to 99.5 over a period of 5 weeks although this was found to then increase the likelihood of detonation in high revving engines.

 

Hi Kg - My reading of this report,is, if the fuel is kept in a sealed container, at 75% capacity or better, the changes you refer to take many many months to occur and then at much slower rate. If this is correct storing 98 for 6 months is perfectly acceptable/satisfactory.

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The Jab and Bing were developed in the days that we were limited to 5k feet, so it all worked out nicely, thanks very much.  Now we have 10k feet and where you lean a LyCon carb  above 5k,  we never v

Topical 😁

Yesterday I tried, from a cold start, opening the throttle a few seconds after the engine started with choke, and sure enough it stopped.  In nearly 20 years of avgas, I had fallen into the habit

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I think they have just dropped the idea of going to the higher EURO standards. Sulphur has been one of the issues it will still be meeting the (lower) standard but what happens during the distribution is not controlled. It's definitely an issue, particularly for aircraft use.

Keeping the standard where it has gone to is POLICY as is varying the ethanol state by state to different levels. The Rotax has never recommended 100LL except for short periods where no other is available. Years ago when I was more involved with them I was aware of several 912's that had lost a bit of compression and they recommended running on Mogas for a while before doing much about it.

The theory is and I believe it ,that lead action does not work well on 912's because the head and exhaust valve temps are not high enough for the lead to do it's usual job of coating the valve seat thinly and helping it seal as well as reducing wear. It forms a thicker build up which fails in some places and allows leakage and MAY damage the seat as well. Often it does not do permanent damage and after a while with use it goes to normal.. I've observed this happen.

Best you can do for the Rotax is get your fuel from the most reliable source with a rapid turnover. on a main road. Detonation is not an issue with these engines. They will however NOT keep running with coolant loss without risk of failure as was often touted around the place. Getting good information is the best policy, but not that simple at times.

Re the lead build up If there's an possibility of dust don't ignore it as it'd often a component of the build up. Avgas used to have a bromine compound that removed the excess lead from the combustion camber. THAT was what caused the white exhaust you sometimes observed THEN. Bromine is a halide and is very toxic and may have been removed or reduced. Nev

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Hi Kg - My reading of this report,is, if the fuel is kept in a sealed container, at 75% capacity or better, the changes you refer to take many many months to occur and then at much slower rate. If this is correct storing 98 for 6 months is perfectly acceptable/satisfactory.

I agree. If the container is sealed then the aromatics cannot evaporate off. The study though was entitled "Petrol life in vehicle tanks" and it states in the summary that "petrol will last for MORE than 6 months when stored in sealed containers,

while some breathing will take place this is not enough to significantly affect product quality. In underground storage tanks the rate of replenishment prevents the fuel from becoming stale" The last statement is true for most petrol stations but perhaps not for one in the middle of nowhere that only services a local community.

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Can some one please advise the maximin current a jabiru 2200 engine starter motor uses , I wish to fit a power meter which is inserted on the earth to battery negative connection and I need to size the shunt.

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It will be about 100 amps rendrag. I figure this from 1200 watts and 12 volts. The 1200 watts is bigger than my starter motor, but I think they went a bit higher later. Similarly, the 12 volts might be a bit high for a lead-acid battery while its cranking.

A 100 amp shunt can certainly be used for a bit more than 100 amps. The blurb will say something like " 75mV at 100 amps". It will only produce 7.5 watts of heat at 100 amps.

I have a LiFePO4 battery with a hobbyking 90 amp plug and I reckon this will be ok but I haven't tried it yet.

You can easily buy 100 amp shunts to work an ammeter. A few dollars from banggood.

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Rendrag, put a clamp meter on your starter cable to see what amperage it's drawing when you hit the starter. A cold morning will see the amperage draw go up by an appreciable amount.

It's fairly important to find the manufacturers specifications on the starter. The starter manufacturer should provide a graph of the current, power, cranking speed, and voltage in the starter circuit.

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It will be about 100 amps rendrag. I figure this from 1200 watts and 12 volts. The 1200 watts is bigger than my starter motor, but I think they went a bit higher later. Similarly, the 12 volts might be a bit high for a lead-acid battery while its cranking.

A 100 amp shunt can certainly be used for a bit more than 100 amps. The blurb will say something like " 75mV at 100 amps". It will only produce 7.5 watts of heat at 100 amps.

I have a LiFePO4 battery with a hobbyking 90 amp plug and I reckon this will be ok but I haven't tried it yet.

You can easily buy 100 amp shunts to work an ammeter. A few dollars from banggood.

I have 150Amp slow fuses on my batteries as a main fuse. The only unfused wire in the plane is 5cm of cable from the positive battery terminal to the fuse mounted on the battery box (the AC from the alternator is also fused). It frightens me that people fly with a potential arc welder via the starter cable! The starter motor clearly draws less than this. I started at100A, but this blew on the third start. I also monitor current drain/charge using an Arduino module (not in the starter circuit though) which doesn't use a shunt but an Hall effect sensor. Works for me and just plug and play with my MGL EFIS/EMS. On my home power system (off grid with 13kWh lithium batteries) I monitor power & battery state of charge via a 'Coulomb counter', also Hall effect. Mine goes up to 300A and quite a few kilowatts, but you can get them for smaller currents and power. Only a few grams in mass, and cheap.

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Why bother with a 150A fuse just for the starter. How many instances of starters causing meltdowns are there? A 150A breaker will trip within 30 minutes at 135% of load and within 60 seconds of 200% load. That is 2.4kw power draw at 135% or 3.6kw at 200% in a 12 volt system. This is why we have solenoids to control the high power drain of the starter motor. You should never run your starter for more that 15 seconds at a time anyway & then leave it for several seconds before trying again. Cranking for more than 7 or 8 seconds without the engine firing indicates other issues anyway.

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Those sorts of currents are too high to use fuse protection because a leakage at well under fuse setting will do a lot of damage. Your +ive terminal and the heavy cable are lethal as a fire risk and to a lesser extent structural.. Nev

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kgwilson, I have never had a starter motor cause a fire type problem either, but when I asked a guy who was once an auto-electrician, he said that it sure did happen. At the time, I was worrying about what would happen if the solenoid welded itself on. The engine would be running at idle but making enough noise to mask the sounds of distress coming from the starter system.

One solution is to use 2 solenoids in series but I didn't like the idea of the extra weight. My compromise was to put a red light on the instrument panel which indicated if power is applied to the starter . The idea being that if this red light stays on when the starter button is released then it would be a good idea to close off the fuel and the mags. The engine would continue to crank without firing until the battery was depleted.

I hope this never happens.

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Be very aware of the weight of the new prop Mhalc.

I did rework the W&B sheet for the additional weight. But I am looking to take advantage of other changes I am making under the cowlings.

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Bruce , I've had what you speak of actually happen. #1 is the last engine to be started on a 4 engined plane.. # 3 caught fire on a restart and after extinguishing it, we cut all engines to inspect everything. #1 kept turning on the starter, and we had to operate the electric "crash bar" to cut supply. IF the situation we experienced had not required everything to be shut down, we would have had another fire in#1 ,this time in flight. If you run a small warning light from the main STARTER terminal telling you starter is energised, you have it covered.. Nev.

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I watch my Amp/gauge like a hawk after start and monitor it for the whole flight. An Amp gauge is a very handy instrument to have, tells you a lot.

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A starter with no load doesn't draw a lot of current but will eventually destroy itself by heat build up and the fact it's overspeeding . You can trouble shoot the electrics quite well with the ammeter but usually the starter circuit is not through it as it's too high a draw when in normal use. Starter energised lights should be mandated. but some are air where you DO monitor pressure changes because they disintergrate.Nev

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A starter with no load doesn't draw a lot of current but will eventually destroy itself by heat build up and the fact it's overspeeding . You can trouble shoot the electrics quite well with the ammeter but usually the starter circuit is not through it as it's too high a draw when in normal use. Starter energised lights should be mandated. but some are air where you DO monitor pressure changes because they disintergrate.Nev

Agree, easy enough to fit just wire an LED or light into to solenoid circuit on the positive circuit to the starter and it will only be lit when power is through the solenoid when it’s a closed circuit. I have one fitted.

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We have had a load of waffle about Jab engines and the thread drift is going on all the time. Here is your chance to say what you "know" about Jab engines.

I have a 2200 Jab in a Corby Starlet, it runs well although I got poor mogas and busted a piston with detonation. Avgas is the go for me. I would like to try a different carburettor from the Bing, although the Bing runs fairly well.

Don't bother talking about the engine if you don't run one or regularly fly one.

 

 

I'm on my 3rd Jab 2200. Jab gen 2, 3 and now 4.

 

On the gen 2 it sucked an exhaust valve at 1145 hours as did the engine on my friends Gen 2 at the same time. Replaced it with the Gen 3 and flew that for about 1500 hours.

The engine got "morning sickness" meaning on first start up it ran rough until it warmed up.

 

Also should note that I have always thought that the top end was the weakness of the engine due to the inadequate lubrication of the valve train. I had to reline the valve guides 3 times on two engines. The gen 4 has better lubrication through the push rods.

 

I am running mostly mogas on this engine. I use 91 AKI ARCO gas with ethanol. Had to install a 5 gallon seat tank for this since the resin in my glass tanks can handle ethanol. The 5 gallons handles all my local flights since i get 1.5 hours from the tank. The only noticeable difference is that the EGTs run about 50-70 F higher. After several tankfuls the borescope shows that the lead accumulation is flaking off my piston.

 

The cause was a stuck hyd lifter which was replaced and it had worn the lobe on the cam. Sold it to a pilot in Canada for $1K with the knowledge of the cam wear. The engine ran fine, but I opted for the new Gen 4 and I'm glad I did. This engine will take me to the end of my flying days since I am 82.

 

What difference I have noticed with the Gen 4? Never have to add oil between 25 hour oil changes. Since the piston and the jug is the same material tolerances can be held tighter.

 

I will need to come up with a different valve remover since the one I built only works with the removable head.

 

Just spoke with a pilot friend who has just had the engine on his Bonanza overhauled for what it cost me to buy my new Gen 4.

 

So when Jab says 1000 hours TBO for the top end you should take that to heart.

 

I have 180 hours on my gen 4 and the only issue I had was lower oil pressure with higher RPM. Cleaned the pressure relief valve and all is OK now.

 

Should mention that this engine is smoother and can idle down to 600 RPM after warm.

 

John M

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We have had a load of waffle about Jab engines and the thread drift is going on all the time. Here is your chance to say what you "know" about Jab engines.

I have a 2200 Jab in a Corby Starlet, it runs well although I got poor mogas and busted a piston with detonation. Avgas is the go for me. I would like to try a different carburettor from the Bing, although the Bing runs fairly well.

Don't bother talking about the engine if you don't run one or regularly fly one.

 

 

Forgot to mention in that last post...

 

The starter Bendix cover developed a crack at 50 hours. It was cast, as much of the Gen 4 is now. Jabiru replaced it with a CNC cut cover. Then the Bendix itself failed to engage properly and they replaced that on warranty.

 

John M

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kgwilson, I have never had a starter motor cause a fire type problem either, but when I asked a guy who was once an auto-electrician, he said that it sure did happen. At the time, I was worrying about what would happen if the solenoid welded itself on. The engine would be running at idle but making enough noise to mask the sounds of distress coming from the starter system.

One solution is to use 2 solenoids in series but I didn't like the idea of the extra weight. My compromise was to put a red light on the instrument panel which indicated if power is applied to the starter . The idea being that if this red light stays on when the starter button is released then it would be a good idea to close off the fuel and the mags. The engine would continue to crank without firing until the battery was depleted.

I hope this never happens.

I like the indicator idea! I’ll have mine apart in a few weeks for it first 100hr inspection, getting the parts together for the indicator idea. I did weigh my spare solenoid, your’s must be much heavier than mine.

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Probably the same weight Mhalc. I admit to being a bit silly over weight. My plane has a ball-type compass from supercheap, while the aircraft - approved compass is in the spares box... all to save about 200 grams. I have since found out that this substitute compass is illegal, but bugger it.

Getting back to the second solenoid, I think the "proper" job is to put in the second one as a key-switch . So you could shut off the stuck solenoid by turning the key to off.

Another way is to use a battery-disconnector, with a pull-cord or twist-rod to turn the battery off. This seemed to me to be a bit dangerous in that the thing could disconnect when you didn't want it to, like on take-off. Routing the starter cables right up to the panel could eliminate this, But the cables is where most of the weight comes in.

Thanks Nev for the story about the stuck solenoid. That is the first real account I have heard.

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...Another way is to use a battery-disconnector, with a pull-cord or twist-rod to turn the battery off. This seemed to me to be a bit dangerous in that the thing could disconnect when you didn't want it to, like on take-off...

Bruce I'll be installing an LED near my key to show when the starter is getting juice.

I have an automatic battery isolator near my right knee. A weighted lever connected via a wooden rod to the battery's earth pole; any sudden forward or downward acceleration disengages the power.

I have on a long flight accidentally disconnected the battery by hitting it with my knee; no drama, engine keeps going, just a few instruments drop out.

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I run a battery isolator mounted under the panel. 1/4 turn to disconnect. It serves to stop any possible battery leakage as well when hangared.

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