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Permalink Reply by Bob Simmons on January 30, 2022 at 1:33pm

Normally on a Jabiru when it's really cold you would pull prop through by hand 6 or 8 blades to draw fuel into the intake manifold, but I don't know if that would work on a TBI. I'm not a gearhead type.

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Permalink Reply by James Neirinck on January 30, 2022 at 1:46pm

Winter / cold weather engine starts and flying does have its challenges. Pulling your battery out and warming it up ahead of time will help.  But if you don't want to do that have you tried pre-heating the engine prior to starting?   I live in Canada so winter / cold weather flying is something we deal with every year.  Put a cowl cover / blanket on and use a heater, which can be as simple as an interior car warmer, placed in the lower part of the engine cowl area. An hour of pre-heat at the temps you are taking about should make starting easy.  Just be careful where you put the heater / interior car warmer so the heating element does not touch anything.  Also, if you fly somewhere and stay for the day put the cowl cover / blanket back on when you get there as it will help keep the engine warm.  Has worked well for me for over 4 hours at minus -20F and engine still started no problems.  I have a custom made engine blanket but you can make one up in a pinch using a couple old sleeping bags. 

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Permalink Reply by John Austin on January 30, 2022 at 1:58pm

I have a Jab 3300 - it has a magneto ignition and permanent magnet alternator, so the engine has to spin fairly fast to generate a healthy spark to start.  There are several things you can do to help this situation:

1. Preheat the engine so that the oil is less viscous and the engine can spin more freely. My plane is hangared and I keep a solid state "Hornet" heater inside the cowl set at 50 degrees F and drape a blanket over the cowl.  The heater is explosion-proof and can't thermally run away - very safe, but pricey!  An added benefit is that everything under the cowl stays warm and there are no cold-heat cycles day-to-day so less chance for internal engine condensation and rust.
2. Use iridium plugs instead of regular electrode plugs - the correct iridium plug for the 3300 is the NGK DR9EIX.  Iridium plugs fire on about 30% less voltage so should fire better at the lower starting rpms during cold weather.  They're more expensive but last much longer than conventional plugs.
3. Upgrade to an EarthX battery.  The EarthX's use lithium chemistry and have a higher resting voltage than lead-acid batteries.  They also have very low internal resistance so you get a very high initial current flow, spinning the prop very vigorously!  Even in cold weather, I can't really "count the blades" to start as the prop spins very fast and the engine starts instantly.
4. Rotec sells an electronic ignition that supposedly helps cold starts - I have no experience with that because I do all the things listed above and have zero problems in winter!

You might want to consider working your way through the items above - perhaps from least expensive (iridium plugs) to more expensive (cowl heater - if you have a hangar and power) to most expensive (EarthX battery), but you may find that just going straight to the EarthX battery will negate using the other methods.  You'll also save about 10 lbs of weight vs a lead-acid battery, so that's a nice bump in useful load!

I also happen to have a TBI carb (Sonex AeroInjector), but I don't know if, as Bob suggests, pulling the prop through several times would help or not as I have no problems with my present setup, but perhaps pulling the prop through at least a time or two might "free the oil" a bit and make the initial starter revolutions easier?

John

N750A

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Permalink Reply by James Nichols on January 31, 2022 at 10:43am

I have a Tanis heater installed on my J3300 with EarthX on a 750 STOL.  Thought it was a waste of money/weight until this winter...  15F - 1 hr preheat, 55F on start with full choke - started immediately.  I think they recommend 2-3 hrs preheat, but I now plug in anytime under 40F while I preflight and it seems to get 1/2 - 1 degree per minute of preheat.  300hrs and now very glad to have installed the Tanis system.

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Permalink Reply by John Burns on January 31, 2022 at 4:11pm

I have a Gen 4 engine with just 30 hours on it, but mine is starting fine with just a Kat's 24100 100 Watt 4"x 5" Universal Hot Pad Heater on the side of the oil sump.  I have started it as cold as 18° F without any problems.  Starts just like it does when it is 40 outside.  

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Permalink Reply by John Austin on February 1, 2022 at 7:38am

The reason I use a thermostatically controlled cowl heater is that it heats the entire engine to the same temperature. (Also, if your battery is on the firewall, it'll keep that warm, too!) Tanis systems are also good in that they heat the entire engine. Probably not a problem if you fly frequently, but I've seen criticism that only using pad heaters on the sump, while effective at heating the oil, will drive moisture out of the oil that then condenses on the cooler upper internal areas of the engine such as the cam and valve train, etc., and can cause corrosion  Like I said, probably not a big problem in a frequently run engine that gets the oil moisture driven out in-flight and also leaves a fresh coat of oil in the upper engine at shut-down, but might be good to at least use CamGuard oil additive which supposedly helps prevent internal corrosion better than oil alone.

There's a catch, though, in that I think Jabiru does not approve of any oil additives - but I've used CamGuard for years and no problems.  I change my oil every 25 hrs and Blackstone Labs oil analysis always come back "much better than the wear metal averages for Jabiru engines" and frequently the tech also puts on the note "I don't know what you're doing but keep doing it!"

John

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Permalink Reply by Eric Inkenbrandt on February 6, 2022 at 8:14pm

I recently also had this same problem. I was moving my plane from Florida to Massachusetts. I stopped overnight at an airport in NC and I was having trouble starting my 3300 after it sat two days in below freezing weather. An old timer came over and told me a trick…no preheating required. He said, set the throttle full closed, turn the prop over 6 times, start engine with throttle full closed and full choke. I did this and it fired right up. I advanced the throttle a tick and feathered the choke until it idled with no choke. It might be worth a try before investing in expensive heaters. One caveat, I haven’t tried this in extreme cold temps. Good luck!

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Permalink Reply by John Austin on February 6, 2022 at 9:49pm

The expense of a preheater is nothing compared to the expense of the damage caused by starting a cold engine. Mike Busch, the AOPA/"Savvy Maintenance" expert, says a cold start can sometimes cause as much wear as 500 hrs of flight time. He said if it's cold enough that you have to wear a warm coat to do your pre-flight, you need to pre-heat.

BTW, a bit of trivia for those not familiar with the Jabiru/Bing carb setup:  Actually, the Jabiru's do not have a choke.  What everyone calls the "choke" is actually a separate starting jet that produces a rich mixture for starting.  That's why you completely close the throttle when doing a cold start - it forces the suction to pull fuel from the starting jet, bypassing your main jet.  If you open or crack the throttle, it'll pull mixture off the main jet and bypass the starting jet, defeating the "choke."

John

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Permalink Reply by Bob Simmons on February 7, 2022 at 1:03pm

Throttle closed, full choke and pulling the prop through is the standard cold start procedure for the Jabiru, though they do recommend a Tanis heater.

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Permalink Reply by Eric Inkenbrandt on February 8, 2022 at 9:02pm

Bob & John, thanks for the info, good to know. I’m learning, appreciate you sharing the knowledge! -Eric

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