Zenith Aircraft Builders and Flyers
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3300 low power ?
HiHo,
I suspect that my Jabiru 3300 motor is underpowered because it does not get up to the required RPM when stationary on the ground. I reach a maximum of 2100 rpm.
It has no measurable effect when using different propellers from the same manufacturer and identical length (Helix). I have tried propellers with 10, 11 and 12 degrees pitch and always the same effect, never more than 2200 rpm when standing on the ground.
Today I removed the air filter and the supply air now comes directly into the Bing carburetor, again without significant effect.
More RPM does not come from this.
It also doesn't matter if you turn on the additional electric fuel pump or not.
What else could it be and in what order do I best proceed to isolate the problem?
Too little fuel, possibly the wrong jetting, no or too little compression?
Does anyone have a suggestion for me please ?
Thank you and happy new year to you all.
Replies to This Discussion
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Permalink Reply by John Austin on
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I have an AeroInjector throttle-body carb on my STOL 750/Jab 3300 and really like it, but I love to tinker and experiment and wanted a manual mixture control - works great for my plane/engine configuration! However, I would not recommend an AeroInjector carb for a 601/650 series airplane. The problem would be that your 601 is a low-wing plane and I presume does not have a header tank like Sonex planes do. The AeroInjector works best with gravity-feed only, and in a low wing, that requires a header tank at a level above the carburetor, which is what Sonex planes have. The reason the AeroInjector works well in the STOL 750 is that it's a high-wing with the tanks in the wings, so gravity-feed works great (in fact, the mechanical fuel pump is removed and a block-off plate installed to provide gravity feed only to the AeroInjector).
I think you need to sort out what is the actual source of your problem. Start with the basics, checking compression, ignition, carb, fuel flow, etc.
John
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Permalink Reply by Steffen Glatz on
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Since the jabiru has a mechanical fuel pump, what do you think, or do you have any experience with the Fuel Pump + 1-2 psi regulator installation ?
One can combine it with an additional electrical pump for security.
But first I will check the Main-Jet and Needle-Jet for they numbers on it.
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OK, today was craft time.
We checked the fuel line and filter, everything was clear.
Then we removed the jets from the Bing carburettor and ran the electric fuel pump with the result of approx. 500 ml of fuel in 20 seconds, which is more than enough.
What irritated me about the Bing carburettor was the strange washer (photo) and the fact that the main jet is a 245 (photo), which is recommended as default for the 2200 engine?
The needle jet with 2.85 seems to be the right one.
I think I will now get a handful of jets in 250, 255, 260, 265 and 270 to try out what power I can get.Do you have any other suggestions for me ?
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Permalink Reply by Darrell Doerhoff on
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Steffe, it sounds like you're on the right track. I would assume that with the 245 main jet, you're running too lean at full power. Do you have an EGT gauge?
I've had my plane for a year now, and it ran good, except for a bad vibration at full throttle. The spark plugs showed that the mixture was running too rich. I replaced all the plugs, and after one local flight, the plugs showed it was definitely running too rich.
I removed the main jet (280), and it also had a washer like in your photo. The carb manual doesn't show this washer, so I left it out. Also, I installed a 250 jet that was in the parts I got with the plane.
Now, it was running too lean, and I got alarms for high EGT and too big a spread on EGT's. I ordered a 260 and a 270 main jet. I installed the 260, and also turned the bottom of the carb towards the hotter side. When I climbed out, I got a high EGT alarm, but it cleared when I reduced rpm by 100 rpm. The EGT's were all closer together, so I didn't get the spread alarm.
I haven't tried the 270 jet, and want to have a few more flights witht he 260 so I can get more data. Then, I'll install the 270, and compare the differences.
Good luck with yours.
Darrell
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Permalink Reply by Don Burkholder on
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The washer was to prevent or break up any fuel swirl to prevent air entrainment. Darrell, you could try and install the washer to see if there is any effect. Make this change only to be scientific. Interesting!
Steffe, YES 245 is too small. 255 to 260 is a good start. Be careful if you do not have any EGT gauges! You're on the right path!
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My apologies. In my earlier post I was wrong on the position of the Bing throttle blade which is on the EXIT side of the carb and of course can't be seen at the intake side! The only way to verify full throttle is to position the throttle arm is against it's wide open stop coincides with the hand throttle limit. Sorry for any confusion. Here is some info and a detail and a nice exploded view...
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Don,
I wanted to let you know that I put the washer back in. Yesterday, I was finally able to get the plane out, gave it a good test run, and the engine ran great! The temps all looked good, too, with no alarms! Thanks for your advice.
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You are welcome Darrell! So glad to hear this. The Bing is actually a very fine mixer of fuel and air!
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Permalink Reply by Michael Greene on
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Hi Darrell was curious where you were ordering your Bing jets from. Needing to tweak mine a bit.
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Hi Michael,
Here's a link to the Main Jet page of BingCarburetor.com
http://bingcarburetor.com/store/p116/Main_Jet_44-051.html
There's a warning on their main page that these are for motorcycles and ground equipment only, and if you put them in an aircraft, they are not liable for anything. A couple of weeks after I got mine, I got an email requesting me to complete a satisfaction survey, and one question was what I installed them in. I deleted the survey and the email. I would have liked to tell them that I was really happy with their service and products, though.
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I've ordered from BingCarburetor.com a few times and once talked to the proprietor when I had a question. There was no reluctance or problems selling me jets for my Jab 3300's Bing carb.
John
N750A
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Permalink Reply by Thomas Norris on
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Steffen: My Jabiru 3300 4th gen had a similar problem when it was new--I couldn't get more than 2500rpm which didn't change much with different prop pitches. It also had very dirty exhaust. I switched from the 245 main jet that it came with to a leaner 260 jet and got improved performance and cleaner exhaust. I used that for 40 hours and noted that I was getting hot EGTs, some up to 1400---CHT's were all fine. I talked with several people and switched back to the 245 that I started with. I don't know if it was completion of breakin, valves that were seating better, or what, but I now get 2800-2900rpm and cleaner exhaust. I think you are on the right track to try changing jets. I'll be following the forum to see your results. Good luck! Tom
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