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[rebel-builders] CHTs

Posted: Sun Feb 19, 2012 10:53 am
by Bob Patterson
Hi Clay !

Gee, those don't sound that high - I've run hotter than that
on long climbs..... typically, I used to see 430, and the oil
would sometimes get to 220 - on days when the oat was +30 or so.
You sure want to be running straight 100 weight oil though...

I dropped the rear of the cowl down a couple of inches to
let more air out - solved the problem. Do NOT cut forward -
it makes it worse !!! The air will swirl UP into the bottom
and slow down the cooling. You could try just making the lip
bigger - add a couple of inches onto it & see if it helps ...

I actually have a moveable section at the bottom rear of
the cowl that I can open & close to 3 positions, just by undoing
2 bolts & repositioning - works great. If I were doing it
again, I'd make the moveable section wider ...

If you are using the 'under spark plug' type CHT probes,
and they are on the bottom plugs, they read about 40 degrees
hotter than the top plugs, so you may be just fine !

Sounds like you're having fun !!! :-) Enjoy it !!!

--
......bobp
http://bpatterson.qhealthbeauty.com

-------------------------------orig.-------------------------
On Saturday 10 June 2006 11:52 pm, Clay Smith wrote:
Hi Guys,
I have some concerns about my CHTs still being a little too high on high
power settings (above 2500 rpm) even after 5 hrs on a rebuilt 0320 with a
metal cowl. They run around 390 and as high as 420 on # 2 which is the front
pilot side. Oil temp is good around 185. My guess would be that the bottom
exit open is not big enough. So, my question is which is the best way to
correct this? I could cut back (actually cut forward) the bottom cowl metal
to make a bigger opening (I do have a lip on the bottom trailing edge
already) or, maybe I could place some kind of grill openings further forward?
I'm sure some of you have already gone through this and may have some advice.
I did block off the oil cooler scat hose input on the rear baffle some to
increase the oil temp and this did seem to lower the # 2 a little, but not
enough.
Thanks for any help.

Clay
C-GZZO




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[rebel-builders] CHTs

Posted: Sun Feb 19, 2012 10:53 am
by Clay Smith
Hi Bob!
It's nice to hear from you and thanks for your reply. Yeah, I thought about
searching the archives after (sorry ...!) I left my message and I'm now
beginning to realize that maybe my temps are OK, maybe not the lowest, but
probably nothing to worry about. I am using the 'under the spark plug
probe' (bottom plugs) and have subtracted 40 degrees from the gauge reading.
( I wonder how accurate these probes are ... maybe I should swap 2 probes
around to see) I think I might block the oil cooler input a little more to
get my oil temp up where it should be. Maybe that will force more air down
around my highest cylinder. I'll also try to extend the lower lip somehow
...? Where exactly is this moveable section or cowl flap that you have. I
think, according to the archives some have a cowl flap in the middle section
behind the carburetor. Is that correct? Thanks again.

Clay

Looking for floats soon!

----- Original Message -----
From: "Bob Patterson" <beep@sympatico.ca>
To: <rebel-builders@dcsol.com>
Sent: Saturday, June 10, 2006 11:40 PM
Subject: Re: [rebel-builders] CHTs

Hi Clay !

Gee, those don't sound that high - I've run hotter than that
on long climbs..... typically, I used to see 430, and the oil
would sometimes get to 220 - on days when the oat was +30 or so.
You sure want to be running straight 100 weight oil though...

I dropped the rear of the cowl down a couple of inches to
let more air out - solved the problem. Do NOT cut forward -
it makes it worse !!! The air will swirl UP into the bottom
and slow down the cooling. You could try just making the lip
bigger - add a couple of inches onto it & see if it helps ...

I actually have a moveable section at the bottom rear of
the cowl that I can open & close to 3 positions, just by undoing
2 bolts & repositioning - works great. If I were doing it
again, I'd make the moveable section wider ...

If you are using the 'under spark plug' type CHT probes,
and they are on the bottom plugs, they read about 40 degrees
hotter than the top plugs, so you may be just fine !

Sounds like you're having fun !!! :-) Enjoy it !!!

--
......bobp
http://bpatterson.qhealthbeauty.com

-------------------------------orig.-------------------------
On Saturday 10 June 2006 11:52 pm, Clay Smith wrote:
Hi Guys,
I have some concerns about my CHTs still being a little too high on high
power settings (above 2500 rpm) even after 5 hrs on a rebuilt 0320 with a
metal cowl. They run around 390 and as high as 420 on # 2 which is the
front
pilot side. Oil temp is good around 185. My guess would be that the
bottom
exit open is not big enough. So, my question is which is the best way to
correct this? I could cut back (actually cut forward) the bottom cowl
metal
to make a bigger opening (I do have a lip on the bottom trailing edge
already) or, maybe I could place some kind of grill openings further
forward?
I'm sure some of you have already gone through this and may have some
advice.
I did block off the oil cooler scat hose input on the rear baffle some to
increase the oil temp and this did seem to lower the # 2 a little, but not
enough.
Thanks for any help.

Clay
C-GZZO




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[rebel-builders] CHTs

Posted: Sun Feb 19, 2012 10:53 am
by Bob Patterson
Hi Clay !

There is some research in the archives on those probes - that's
where we found out about the 40 degree difference in reading ! The
long, inserted probes work best, but are more expensive ...

To extend the lower lip, you can just cut a strip of aluminum
about 3" wide, and rivet it to the bottom of the current lip -
1/2" + overlap should do .... Sounds like your temps are just
great the way it is !

Straight 100-weight oil provides the best lubrication when
it's really hot -- the 20-50 multigrade is best in fall, winter,
& spring, when temps are mostly low.

My moveable section is behind the carb - there are pics in the
archives, but I'll try to post new ones, as I enlarged it & dropped
it down lower since the original pics.

--
......bobp
http://bpatterson.qhealthbeauty.com

-------------------------------orig.-------------------------
On Sunday 11 June 2006 03:30 am, Clay Smith wrote:
Hi Bob!
It's nice to hear from you and thanks for your reply. Yeah, I thought about
searching the archives after (sorry ...!) I left my message and I'm now
beginning to realize that maybe my temps are OK, maybe not the lowest, but
probably nothing to worry about. I am using the 'under the spark plug
probe' (bottom plugs) and have subtracted 40 degrees from the gauge reading.
( I wonder how accurate these probes are ... maybe I should swap 2 probes
around to see) I think I might block the oil cooler input a little more to
get my oil temp up where it should be. Maybe that will force more air down
around my highest cylinder. I'll also try to extend the lower lip somehow
...? Where exactly is this moveable section or cowl flap that you have. I
think, according to the archives some have a cowl flap in the middle section
behind the carburetor. Is that correct? Thanks again.

Clay

Looking for floats soon!

----- Original Message -----
From: "Bob Patterson" <beep@sympatico.ca>
To: <rebel-builders@dcsol.com>
Sent: Saturday, June 10, 2006 11:40 PM
Subject: Re: [rebel-builders] CHTs

Hi Clay !

Gee, those don't sound that high - I've run hotter than that
on long climbs..... typically, I used to see 430, and the oil
would sometimes get to 220 - on days when the oat was +30 or so.
You sure want to be running straight 100 weight oil though...

I dropped the rear of the cowl down a couple of inches to
let more air out - solved the problem. Do NOT cut forward -
it makes it worse !!! The air will swirl UP into the bottom
and slow down the cooling. You could try just making the lip
bigger - add a couple of inches onto it & see if it helps ...

I actually have a moveable section at the bottom rear of
the cowl that I can open & close to 3 positions, just by undoing
2 bolts & repositioning - works great. If I were doing it
again, I'd make the moveable section wider ...

If you are using the 'under spark plug' type CHT probes,
and they are on the bottom plugs, they read about 40 degrees
hotter than the top plugs, so you may be just fine !

Sounds like you're having fun !!! :-) Enjoy it !!!

--
......bobp
http://bpatterson.qhealthbeauty.com

-------------------------------orig.-------------------------
On Saturday 10 June 2006 11:52 pm, Clay Smith wrote:
Hi Guys,
I have some concerns about my CHTs still being a little too high on high
power settings (above 2500 rpm) even after 5 hrs on a rebuilt 0320 with a
metal cowl. They run around 390 and as high as 420 on # 2 which is the
front
pilot side. Oil temp is good around 185. My guess would be that the
bottom
exit open is not big enough. So, my question is which is the best way to
correct this? I could cut back (actually cut forward) the bottom cowl
metal
to make a bigger opening (I do have a lip on the bottom trailing edge
already) or, maybe I could place some kind of grill openings further
forward?
I'm sure some of you have already gone through this and may have some
advice.
I did block off the oil cooler scat hose input on the rear baffle some to
increase the oil temp and this did seem to lower the # 2 a little, but not
enough.
Thanks for any help.

Clay
C-GZZO


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[rebel-builders] CHTs

Posted: Sun Feb 19, 2012 10:53 am
by Bruce Georgen
Clay,

I have the fiber glass cowl and one of my my CHT temps runs 420 all the time above 2500 RPM. I understand your exite air should be 150% of the inlet. Walter reduced his CHT's by enlarging his inlet after having enlarged his exite without good resolts. If your oil temps are good I don't think your 400 or 420 CHT is all that bad. Glider Tow planes run 450 CHT all the time without any problems. I have 200 hours and my cyl. compression has not changed. Lycoming says 450 and below is OK. 500 is max.

Bruce


-----Original Message-----
From: Clay Smith <cbsmith@nf.sympatico.ca>
Sent: Jun 10, 2006 7:52 PM
To: rebel-builer glass cowlders@dcsol.com
Subject: [rebel-builders] CHTs

Hi Guys,
I have some concerns about my CHTs still being a little too high on high power settings (above 2500 rpm) even after 5 hrs on a rebuilt 0320 with a metal cowl. They run around 390 and as high as 420 on # 2 which is the front pilot side. Oil temp is good around 185. My guess would be that the bottom exit open is not big enough. So, my question is which is the best way to correct this? I could cut back (actually cut forward) the bottom cowl metal to make a bigger opening (I do have a lip on the bottom trailing edge already) or, maybe I could place some kind of grill openings further forward? I'm sure some of you have already gone through this and may have some advice. I did block off the oil cooler scat hose input on the rear baffle some to increase the oil temp and this did seem to lower the # 2 a little, but not enough.

Thanks for any help.

Clay
C-GZZO



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