Online Community of Zenith Builders and Flyers
I recently bought a 601XLB with a 3300 Jabiru. I've learned now that in cold weather the engine does not like to start very well and that part of the reason for that is the charging system is a little less then a stellar performer at low RPM's.
I found a procedure from Jabiru that once completed should definitely help but I'm wondering if anyone has come up with a better solution for the issue. I've attached the Jabiru bulletin below.
I've got a 3300 in my STOL 750. It is hangared and I keep a 200w thermostatically controlled Hornet Heater in the cowl and a blanket on top. I prefer this to a block preheater because it preheats the engine and keeps the battery warm. The Hornet heaters are very safe with dual fans, dual heating elements and dual thermostats - explosion proof and heating element can't overheat. I'm sure our winters are more moderate than yours, but the engine cranks the same ... instantly! ... winter or summer. If you're hangared and have power, this likely would work for you. My flights are typically an hour or so and the battery always seems to have plenty of charge for the next time, but you're correct, I don't think it starts charging until 1900 rpm!.
The alternator mod looks like it would be a little tedious, but not too difficult - I've never heard of anyone doing it. Guess a good time would be at a 200 hr interval when you have to take it off, anyway, to do the flywheel bolt torque checks.
You should not have to rewire the alternator. Yes, the Jabiru may not be great at low temperature starts but it won't start warm either if the cranking speed is not great enough for the magnetos to fire. Some things to do first. See that the additional ground cable is installed on the starter motor. Check that the starting jet opening is at current specs. Check that the plugs are set to minimum gap. The battery must be in good condition and the charging system functioning properly. You may still need to preheat. I have a sump heater that works well.
What would probably work the best is to install a Rotec battery ignition on one side. Rotec uses the system on their radial engines and configured it to be installed on the Jabiru. If there is decent battery voltage the plugs should fire even at reduced cranking speeds.
Its also worth making sure you are getting full choke travel. It should be hard up against the stop when full on. I believe the Jabiru electronic ignition module should help with cold starting also. Maybe someone that has fitted one could comment?
What battery are you using. Our demo 750 at QSP would not start if the temp went below 60 degrees. I had a brand new Odyssey 680 turned out it could not hold the cranking rpms high enough i switched it out to the Odyssey 925 has a lot more power and can turn the jab over for a longer time. Have had no problem since. On our trip to Copperstate air show we had temps down to 30 degrees started every morning. My procedure trottle to idle crand engine and pull out cold start slowly to full choke..
By the way, it's not cheap, but CAMIT, the company that manufactures Jabiru engines to Jabiru's specs., has an alternator kit for the Jab that they claims produces charge at idle. They also optionally allow you to retain the original alternator so you would have dual alternators if desired!
I agree the alternator kit is the best solution but a little outside my budget right now. I'm going to attempt the alteration that Jabiru suggests and see if that makes the desired difference. I'm also saving for the cold weather start kit to help cure the low voltage cold starting issues I've faced.
The past few times I've flown I used a heater to warm things up and that seams to be working for now but I still feel I need to work towards correcting the underlying issues to ensure I'm able to fire it up on those clear flying days during the winter months.
Thanks for the link, it's now on my wish list!
You need to establish more facts before wasting time on the windings of the original PMA.
If the 3300 was installed correctly according to the Jabiru wiring specification, there are 2 minor issues. Jabiru USA published guidance on removing the automotive spade connections between the stator winding and the regulator, because they frequently burn up. Check this first. Secondly, there is a small discharge while the plane is switched off and hangared. If you are leaving it more than 3 weeks it may be better to leave a small trickle charger or low power solar panel across the battery to maintain it.
The minimum battery is 18 amp-hours, so the Odyssey PC925 is the closest battery for the 3300.
Buried within old issues of Jabba Chat on their website is the statement that sparkplug gaps should be lowered to .020" in cold climates.
The other replies about choke operation and starter cable connection are important too.
Once all the above are met, there are a couple of options available in the market:
Jabiru have a cold start ignition kit, also Rotec have something similar along with their alternator kit
An Odyssey PC680 is more-than-adequate for the Jab 3300! I had approx. 200 hrs on a PC680 and it always cranked and started the 3300 almost instantly whether winter or summer. Even with a prolonged idle while warming up the engine and the alternator not producing output, there never was any low voltage issues despite having lights, transponder, radio, etc. on. The only reason I changed it out was to go to a LiFePO4 battery to help with useful weight. In fact, I'm using the PC680 in my '82 Porsche with a 3.0 L engine and it cranks it fine, too!
Although the alternator can't "run away" with high voltage and doesn't need a typical split alt/batt master switch (so I've been told?), if you do put the alternator on a split master, you can eliminate the small current drain.
I recently had the female spade connectors start to overheat - my first symptom was that my tach quit registering rpm's below 1600 (it picks up the pulses off the alternator output wire). Pete at Jab USA said there was a run of engines with inadequate connectors, but they have addressed that in current production. He advised to replace the connectors with quality connectors such as AMP, and so far, so good!
Since the alternator can't "run away" and there's no absolute need to be able to turn it off, it was/is common practice to run the yellow/alternator "excite" wire directly from the voltage regulator to the battery. The advantages were a short wire run forward of the firewall and eliminating more switches, etc. However, if wired like this, the VR will draw a small, continuous current and drain the battery over long periods of inactivity.
To me, it seemed preferable to run the alternator excite wire through a split master so it can be switched off. If you have a single master, just run the alternator excite to the main bus. Either way, it'll be disconnected from the battery and no current drain. Apparently it's a relative low amp current, so really no hazard having it behind the firewall.