Zenith Aircraft Builders and Flyers
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Oil Cooler Airflow Shutter/Flap?
My STOL 750 has a Jabiru Gen 4 with a 7-row Aero Classic oil cooler. The Jab 3300 Gen 4 was virtually "plug and play" as far as both oil and air cooling was concerned - no tweaking or mods necessary. In fact, it oil cools a bit too good because in cold weather (for East Tennessee) the oil temps run at the very lower acceptable limit and I usually put a piece of aluminum tape across approximately 50% of the oil cooler fins to keep the temp up. We recently had an unusually warm day (for November in East Tennessee) and I just guessed and peeled-down the tape to about 25% coverage and that worked out well.
However, at the time I did think "It sure would be nice to have a shutter or flap to be able to adjust the oil cooler airflow on-the-fly!" (pun intended!) I know that "Anti-Splat-Aero" makes an oil cooler shutter for just that purpose:
Just wondered if any of our builders have experience with this, and if on a Jabiru 3300 Gen 4, all the better! It can be mounted either in front of, or behind the cooler. Behind (downstream) seems counter-intuitive, but if sealed between the cooler and the shutter, it should work equally well. I bring that up because the area behind my cooler would make access and installation much easier.
I also guess that some of our builders have probably devised their own versions of oil cooler airflow control and would be interested to see alternatives to the Anti-Splat-Aero shutter.
Thanks,
John
N750A
Replies to This Discussion
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Permalink Reply by Matt Pope
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No experience with the Jabiru here, but that looks like an elegant solution, and mounting it behind the oil cooler makes sense if it's more convenient. The Open position of the shutter looks like it still blocks almost half the flow though, so if you've been getting close to the max oil temperature on hot days then it might be a problem. Then again, if the oil cooler is just as restrictive as the open shutter then it might not be a problem.
I'm not sure if this would work on the Jab, but here in Canada some Rotax guys use a thermostatically controlled valve that automatically lets oil bypass the oil cooler when it's too cold, and I've heard nothing but good things about it: https://www.aircraftspruce.com/catalog/eppages/xcomthermostat.php?c...
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Permalink Reply by John Austin
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Anti-Splat claims the shutter flows 35% more air than the cooler can utilize, but who knows?
I've got Steve Rance's TOCA (Thermostatic Oil Cooler Adapter - very popular with Jabiru engines), but even with that, in really cold weather, the temps are borderline low. I must admit, however, it just occurred to me that I do have a 1" x 4"slot cut in the silicon rubber collar between the cowl and the cooler that flows air over the engine's finned oil sump to help out in hot weather - again, a popular mod. Perhaps that is diverting enough air to cool the sump and therefore defeating the TOCA's ability to keep the temps up? I think I'll see if I can devise a convenient way to block that off for winter and see what happens before going to the shutter. Thanks for jogging my memory!
John
N750A
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Haha, glad I could help in a roundabout way. I wonder if the slot is necessary in your case. Did you fly it before cutting it?
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I had forgotten about that slot until your post jogged my memory, so I guess I did do a "tweak" although it's a frequent mod on Jabiru engines. I cut it after initial testing - as I recall, the oil temps were at the upper limits of normal, but only in extremely hot weather (for East Tennessee) and cutting the slot dropped them down several degrees. I'm thinking of making a couple of aluminum plates that are oversize for the slot so that they'll secure the rubber edges of the slot and seal it off. Could pull the plates together with either a couple of bolts or safety wire. I might even incorporate a piece of silicon rubber between the two plates to keep them oriented with the slot. Too bad I can't just tape it closed, but nothing sticks to the silicon rubber very well!
John
N750A
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That sounds reasonable - though by covering up the slot I guess you'd be back where you started, pushing the maximum on hot days. Covering half the slot might get you into a sweet spot, but then again, maybe there is no sweet spot and a shutter is the best option. If you try covering the slot, it could be something you change seasonally - cover goes on in the fall and comes off in the spring... that shutter looks like a more interesting project though!
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Sorry if I was not clear! Changing the slot cover in and out seasonally is exactly what I intend to do. I agree the shutter would be slick since that provides in-flight adjustment capability.
John
N750A
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