REFLECTOR: Hot oil

Doug Kanczuzewski doug at customstudio.com
Tue Jul 5 09:24:23 CDT 2011


My hottest cylinder is number 2, than 6,4,5,3,1 so the plenum seems to be working the best on the pilot side and the turbo is under the number 6 cylinder, which is the warmer side.
Timing was my next consideration as I am running the dual Light Speed.
Doug

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Bob Jackson (Jax Tech)
Sent: Monday, July 04, 2011 8:59 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Hot oil

Doug,

To me, having your hottest CHT cylinder be one of your lowest EGT cylinders
might mean that that cylinder is running more efficiently than the others,
with a higher portion of the fuel/air charge burning inside the cylinder and
doing work, rather than still burning on the exhaust stroke on the way out
and in the exhaust stake (near the EGT sensor).  Maybe that cylinder has
better rings with slightly higher compression (and valve sealing) than the
others.

In general, if your timing is a slightly advanced (but not too far advanced)
the fuel/air charge has a little more time to burn completely (and more
completely transfer power to the piston) so that less of the charge is still
burning in the exhaust stack on the way out.  But if your timing is slightly
retarded, the fuel/air charge doesn't burn as completely and can cause
higher EGTs.  More power transferred and work produced results in higher
CHTs (where the work is being done).  

Or if you're running ROP, that cylinder's injector may be providing
relatively more fuel than the others, or if you're running LOP if may be
providing relatively less fuel than the others to explain the relatively
lower EGT.

However, other factors, such as cylinder location (WRT to the best cooling
inlet airflow, or proximity to a hot turbo, or a bad plenum seal) could be
the more likely explanation for the higher CHT on that cylinder.  Which one
is your hottest CHT cylinder?  Is it closer than the others to the turbo?
Is it getting poorer cooling air flow?

I would look for plenum and cooling air improvements first, then maybe
consider changing your fuel injector sizing and balance.

Bob Jackson


-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Doug Kanczuzewski
Sent: Monday, July 04, 2011 9:38 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Hot oil

I just flew my plane today to try out the new pistons. Running an IO-540
with turbo normalized and saw high CHT at 403 / EGT at 1319  with fuel flow
at 22.3gph and oil temp stayed at 185 at 80 degrees out.
When I circled the field at 6000 feet the CHT dropped to 389 and EGT to 1320
with oil staying at 183. I kept the speed to 29" MP and 2400 rpm. Most times
before the new cylinders I was showing 210-220 on oil temp
but that was 40" MP and 2500rpm. 
Question for the group, my one hottest CHT at 403 was also my coolest EGT at
1219, why would that be?

Doug K

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Bob Jackson (Jax Tech)
Sent: Sunday, July 03, 2011 11:18 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Hot oil

Scott,

It sounds to me like your WOT fuel flow may be too low.  Ours (custom turbo
IO-550N) is a different engine, I know but our EGTs range from 1375 to 1425
at take-off power (31" MAP and 2700 RPM) with the fuel flow at the standard
IO-550N 29 gph.

Once we get to 1000 AGL and start our sustained climb to altitude (>10 Kft)
we leave the power at WOT, but increase the fuel flow to 34 gph, as is
standard to keep the temps as low as possible during the turbonormalized
climb out, and the EGTs stabilize between a low of ~1150 and a high of ~1300
all the way up.  It's often 95 OAT in Florida, too, and our oil temp's will
reach 210 even 220 by the time we reach 10 Kft, and two of the CHTs will be
around 400 degrees, though most are below 360 degrees -- we're still working
on CHT cooling, especially at altitudes above 10 Kft.

Bob Jackson
Custom turbo IO-550N
N2XF 'heavy'

PS  I forgot to mention that I think a lot of our problem is our weight,
which will typically be 3000 lb single pilot with full (93 gal) fuel --
that's a lotta lard to push up to those high altitudes!

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Tuesday, June 28, 2011 6:49 PM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Hot oil

I took off from Henderson(Las Vegas) this morning it was 95 degrees. By 
the time I rotated what with taxiing and waiting in line, the engine was 
pretty much hot.

I climbed from 2500 ft to 5,000(clear of the surrounding dirt) and my 
oil temp was 230-240.  My Dynon has an irratting oil temp display that 
rapidly changes temps all the time. A smoothing function is needed o 
that sensor.

Anyway I leveled off and pulled the power back to cool things off. The 
one thing I noticed immediately was the EGT's  were pretty high, high 
1400's.  I would have expected 1200-1300's at full rich. This was the 
first time I've had this new engine at such a low altitude and I think I 
have the (idle) mixture or high pump pressure set to lean.

I eventually gave up on it cooling down, climbed to 8500 and the temps 
started to drop, both egt's and oil temps.

What temps do other big engines +500CI see on hot day climb outs..

Scott


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