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08-24-2014, 06:29 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Quote:
Originally Posted by hlangebro
Let me clarify.
Climb temps are compensated by the OAT and 100f delta, as it should be done. So, actual temps were lower since it was not a 100F day. The temps stabilize fairly quickly, so I would say about 1500ft or so. You should always normalize the cht temps to 100F.
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I'm not sure that really works for our engines.
Some cooling is created by the oil system, and that has a thermostat in it which makes it non-linear with the OAT.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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08-24-2014, 06:39 PM
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Join Date: Mar 2012
Location: San Diego, CA
Posts: 133
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It is a standard flight test standard to compensate for 100F day. Any flight test pilot will agree. I have worked with quite a few. I am an aerospace engineer. Places I have worked for, Piper for instance, would agree.
You can not use just actual temps. That doesn't mean anything. The standard is to normalize to a 100F day to get data you can compare to.
The 100F was chosen as a standard for a "hot" day. Anytime you do your climb test, this is the temp you normalize to, to get accurate data.
Last edited by hlangebro : 08-24-2014 at 09:43 PM.
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08-24-2014, 08:10 PM
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Join Date: Apr 2012
Location: West Fargo, ND
Posts: 1,073
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How
How do you normalize then?
I'd be happy with your temps before "normalized". I was curious how your #4 was so cool but looking at your build log, your oil cooler is mounted sooooo low that it appears all the air cooling your oil also has to pass through the #4 cylinder fins first. Vans instructions says to mount it as high as possible. But considering #4 is my hottest, maybe I should have gone lower.....
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Derek Hoeschen
EAA Tech Counselor
RV-9A #92103 - N803DK
G3X, Superior XO-320, Dual Pmags, Catto 3B
www.mykitlog.com/dbro172/
1974 Bellanca Super Viking - N16AW - Flying
RV-8 #83565 - N184DK - building
1968 Mooney M20C - N6801N - Sold
1956 C-182 - N744W - Sold
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08-24-2014, 09:18 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Quote:
Originally Posted by hlangebro
It is a standard flight test standard to compensate for 100F day. Any flight test pilot will agree. I have work with quite a few. I am an aerospace engineer. Places I have worked for, Piper for instance, would agree.
You can not use just actual temps. That doesn't mean anything. The standard is to normalize to a 100F day to get data you can compare to.
The 100F was chosen as a standard for a "hot" day. Anytime you do your climb test, this is the temp you normalize to, to get accurate data.
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You can normalize for atmospheric conditions and density altitude, but I know my Tiger does not normalize CHTs with temp.
I do fly on actual 100F days here in AZ, and I know my CHTs are not running 50 F lower when I fly on a cool winter day. Measured with a temp. compensated GEM 610 system
Has anyone else seen this effect?
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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08-24-2014, 09:45 PM
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Join Date: Mar 2012
Location: San Diego, CA
Posts: 133
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Quote:
Originally Posted by Dbro172
How do you normalize then?
I'd be happy with your temps before "normalized". I was curious how your #4 was so cool but looking at your build log, your oil cooler is mounted sooooo low that it appears all the air cooling your oil also has to pass through the #4 cylinder fins first. Vans instructions says to mount it as high as possible. But considering #4 is my hottest, maybe I should have gone lower.....
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The oil cooler location is what Sam James recommends for his baffles and plenum. Yes it is a bit cold, but rather a bit cold than too hot 
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08-25-2014, 10:39 AM
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Join Date: Mar 2012
Location: San Diego, CA
Posts: 133
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Mine seem to show a reasonable correlation between OAT and CHT. I am sure there can be minor differences, but that is in general the way to do it...
Last edited by hlangebro : 08-25-2014 at 10:48 AM.
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09-06-2014, 03:04 PM
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Join Date: Mar 2012
Location: San Diego, CA
Posts: 133
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Drilled the Power jet from a #42 to a #40. This really helped both CHT's and EGT's.
I average the CHT's dropped 10-12F.
Here are the normalized climb temps at 100kias, which is 15kias slower than the first post:
1 390
2 402
3 385
4 365
Cruise CHT's, 75%, cowl flap closed
1 347
2 355
3 353
4 370
Leaned at cruise, 75%, 8500ft DA, EGT's Delta F, rpm increased 100rpm during leaning.
1 116
2 100
3 241
4 250
I am happy with this. I am glad a drilled the jet 
I could go to a #39, but I think this is good.
I have an afterbody fairing for the cowl exit that I will put back on. Before this I couldn't use it. I will do some mods to it and then I will try it again.
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09-06-2014, 06:45 PM
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Join Date: Dec 2006
Location: Oakland CA
Posts: 771
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Quote:
Originally Posted by az_gila
You can normalize for atmospheric conditions and density altitude, but I know my Tiger does not normalize CHTs with temp.
I do fly on actual 100F days here in AZ, and I know my CHTs are not running 50 F lower when I fly on a cool winter day. Measured with a temp. compensated GEM 610 system
Has anyone else seen this effect?
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I am still wondering about this as well. It would be lovely if it turns out to be standard flight test technique, but I've never heard of it. That could simply be my own ignorance though.
My own experience is that a climb at 60 degrees F OAT is NOT going to end in the same CHT plus 40 degrees F for the identical climb at 100 degrees F. Now, is it standard technique? I don't know, but maybe this explains some of the differences in "cooling" capabilities of different airplanes...significantly different measurement techniques and extrapolations.
It would be great to get more feedback on this.
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All Best
Jeremy Constant
RV7A "Stella Luna" ECI IO-360 WW200RV Pmags 360hrs
VAF 2019 paid plus some for those who can't
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09-06-2014, 06:53 PM
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Join Date: Mar 2012
Location: San Diego, CA
Posts: 133
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It is a standard. Sure you might see some differences, but that is how you normalize, otherwise there is no way to compare data. 100F is considered a "hot day".
Today, for me, I had a 92F day so it was close.
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09-06-2014, 07:44 PM
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Join Date: Feb 2005
Posts: 592
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I think you may want to reconsider your full rich fuel flow as part of your solution.
I had a -4 for 10 yrs, O-320-D1A with Ellison TBI and Catto prop and I never came remotely close to running the high CHTs you indicated. I'm down in central Georgia where high temps and humidity are the norm this time of year.
At full rich on takeoff I'd get FF of 14+GPH and could climb at best rate with full throttle and never get beyond 350 CHT(if that high) to whatever altitude I chose.
I know there were several factors in my favor, like the greater efficiency of the TBI, and could easily adjust to any fuel flow I needed. There was also much more even fuel distribution and better atomization. Also the -4s have a well earned reputation for very good cooling.
Also check out Mike Busch's articles on the value of higher FF.
Good Luck,
Glenn Wilkinson
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