wingdingy(at)gmail.com
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 Posted: Tue Jan 26, 2010 7:49 am Post subject: Europa-List Digest: 8 Msgs - 01/24/10 |
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| Quote: | Time: 11:14:51 AM PST US
From: "Creighton Smith" <crouton(at)well.com (crouton(at)well.com)>
Subject: Jabiru engines
>>>>>One thing about Jabiru installation perplexes me: Every Jabiru
installation I have looked at over the years has had presumed cooling
issues addressed with little deflectors inside the cooling cowl which is
part of the engine package.
This is heartening since it shows they (Jabiru) have been paying
attention. The perplexing thing is: why is there no provision for
inter-cylinder baffling? <<<<<
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Hello Creighton,
There is inter-cylinder baffling on mine, at least I think we're talking about the same thing. Check the Jabiru factory website, or the Jabiru USA or Jabiru Pacific for pictures and details. The so-called "gull wing" deflectors that go in between the cylinder bores have been recommended to be removed by the factory last spring, but they do still recommend baffle deflectors above the cylinders. The arrangement that seems to work best on airframes like the Europa or Lightning is baffles roughly 3/4" tall that are installed internally in the head cooling duct from the inside wall, over the top of the duct and down the outside to above the rocker arm area of the heads. That prevents the air from blowing over the rocker arm area of the head where it does little or nothing to cool the head, and instead forces air through the cooling fins where it is needed to take heat away from the heads. Mine has them on the left side, above and in between cylinder #2 and #4 and also over cylinder #6, with the cylinder #6 baffle being slightly taller and shaped more to conform to the profile of the cooling fin shape. These balance the CHT temps very well between the cylinders. The baffling needed on the right side on my engine (clys 1, 3, & 5) is much smaller and more subtle because the right side runs a lot cooler due to the direction of rotation of the prop. More air enters that side, and that side runs cooler. These baffles are not installed by the factory because every engine installation is different. What works on a Jabiru airframe doesn't necessarily work on a Titan Tonado or Europa airframe. So, the factory expects the owner to install the baffles and adjust them as needed. You also have to get your carb jetted properly for the airframe and, along with it, adjust the pitch or choose a prop with a pitch that properly loads the engine to keep the EGT's in line. When you get the EGT's in line it helps a great deal with the CHT's. The baffling does the rest.
In regard to the Rotec TBI, I tried to fit one in my Europa, but I couldn't make it work because of a conflict with the engine mount and footwells in a horizontal arrangement, and the distributors and throttle cables in a vertical installation. Similar conflicts exist with the Lightning airframe. Without a major redesign of the intake plenum on the 3300, something that is beyond my machining skills, I don't see how you could make one work on a Europa with the stock plenum without making the distribution tubing longer and more complicated. I tried to talk the the Rotec guys into building a new plenum for the 3300 that would incorporate the Rotec TBI in an updraft arrangement. The Rotec folks clearly have the machining skills and other knowledge that would be necessary to do it, but they are so busy building radial engines they said they just don't have time. I do know of several Rotec TBI's operating on Jabiru engines in other airframes, though, both on the 2200 and the 3300. There are a few running Ellison TBI's, too, as well as Aerocarbs. Don't look for Jabiru to switch to anything different from the Bing, though. Their strongest desire seems to be to keep things as simple as possible and for them, that means sticking with the Bing. I certainly would love to have mixture control, though.
There is a way that you can lean the Bing carb, above and beyond what it does itself. There's a little gizmo that is made by Green Sky Adventures in Florida. This is a precision valve that allows you to adjust the air flowing into the balance tube on the carb that normally goes between the upper side of the diaphragm chamber and the airbox. By bleeding in ambient pressure into the top side of the diaphragm on the Bing you prevent the needle from rising just enough to lean the engine. I'm told by the folks at Jabiru USA that you can achieve as much as a 1 gph reduction in fuel flow above 8000' or so by using this valve arrangement. I haven't tried one, but I did notice during the engine seminar that virtually every Lightning and Jabiru airframe that was on the production line had it installed. There is also a version that is designed to work on the Rotax 9XX series with twin carbs, as well as most of the Rotax two bangers.
I talked to a company over in Greenville, South Carolina a while back that makes custom direct injection systems for aircraft engines. They had never done a Jabiru, but they were interested and said they could do it, but their $4000+ price tag stopped me cold. There is ample room on the Jabiru head to install direct injection.
Regards,
John Lawton
Whitwell, TN (TN89)
N245E - Flying
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