Hi John,
Could you provide a picture of your turbulator please?
Thanks
Brian
G-BYFG
XS trigear, Jabiru 3300
----- Original Message -----
From: TELEDYNMCS@aol.com
To: europa-list@matronics.com
Sent: Monday, October 01, 2007 2:30 PM
Subject: Europa-List: Jab cooling
In a message dated 10/1/2007 2:58:40 AM Eastern Daylight Time,
europa-list@matronics.com writes:
Concerning the Jabiru, there is little room between the prop and the
front cylinders to provide a correct diffuser, so the inlet must be
of
larger size, and the efficiency will be lower.
But the engine can be adequately cooled all the same, at the price
of a
little more drag, of course.
Hi Gilles and all,
I've had a chance to test my turbulators installed at the mouth of my
left cooling intake and they worked exceedingly well. I've seen, on
average, a 25F drop in CHT's on the left side now that I have turbulated
the airflow entering the left side intake. One cylinder dropped 45F and
went from being the second hottest of the six to the coolest.
Interestingly, the engine is now running in the 240F-260F range on all
CHT's, but the delta pressure did not change! This has left me with the
impression that all this talk about 6" of water column being needed for
adequate cooling is a bunch of bullshit put forth by the engine
manufacturers to make you go away and be quiet.
I still have 3" WC on the right at cruise and the hottest CHT is about
250F. The coolest CHT on the right is 219F in cruise. I still have 5" of
WC at cruise on the left side and the highest CHT is now about 260F,
down from 295F on the hottest cylinder in cruise. The coolest on the
left is now 235F, down from 275F prior to the turbulators. All of my
testing results indicate that pressure is the absence of flow, not a
sign of flow. Internal cooling duct pressure, measured against static
pressure inside the cowl, seems to be have an inverse relationship to
flow, if indeed it has any relationship at all. My test results show
pressure is meaningless and FLOW is what we're after.
I think ultimately what I'm going to do here is dimple the area around
my intake ducts like a golf ball. The zigzag tape is ugly and I can't
think of a way to make it pretty, so I think dimples are the answer.
Should make for quite a conversation piece, don't you think?
Clearly, Andy Silvester used the Lancair cowls as a model for his
Europa cowl set. I've studied close up pictures of the Lancair cowl to
try and find out what the difference between the two really is. The only
thing I notice is the Lancair inlets protrude about 1" farther in front
of the cowl than mine do., I think this has something to do with the
pressure wave I've observed in front of my left intake with my crude
string tests. So Gilles, you are likley correct in your analysis.
FWIW, every Sonex cooling suggestion I've tried has lead to hotter,
not cooler temps. So, Jabiropaphiles, my suggestion is don't bother with
anything Sonex has to say.
The moral of this story is: for better FLOW, excite the area just
outside the hole. Almost pornographic, isn't it? (notice how I didn't
say for better PRESSURE?)
Now, I'm back to analysis of boundary flow on the wings.......
Regards,
John Lawton
Whitwell, TN (TN89)
N245E - Flying
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