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sarg314(at)gmail.com
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 Posted: Sat Jun 26, 2010 2:23 pm Post subject: Two cooling questions |
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The airworthiness inspection my RV-6A will be next week, so first flight will be soon after that. I'm wondering about cooling the engine. The 2 main things that steal cooling air form the engine are the oil cooler and the take-off for the cabin heat.Â
1- I certainly don't need cabin heat in Arizona in June. If I block off the opening in the baffles that is plumbed to the heat muff, no air will circulate thru the heat muff. Is that OK? Will that stretch of exhaust pipe get too hot? Is that what most folks do in the summer?
2- I did the oil cooler installation on the baffles behind cylinder #4. I used the Stewart Warner 7 row oil cooler, so I expect it to be pretty effective; that is, I doubt it needs the full opening that it has. Will I do better to block off, say, 1/3 of that to start with, or should I leave it wide open and just see what happens on the first flight?
--
Tom Sargent, RV-6A, ready for inspection.
[quote][b]
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timb
Joined: 16 Apr 2008
Posts: 77
Location: Frankston, Texas
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| Posted: Sun Jun 27, 2010 5:09 am Post subject: Two cooling questions |
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I don't think you mentioned what engine and such you have but here is my situation.
RV-6 with 0-360 carb and constant speed prop.
I have my oil cooler mounted on the back of the baffle and two cabin heat muffs.
My engine ran very hot initially so I tried just about everything to get the CHT temps down.
The two things that did NOT add significant help were: blocking off the cabin heat, blocking off part of the oil cooler.
I now have a door behind my oil cooler so I can block it as needed. I see vans has a new slider that goes between the oil cooler and the baffle and that looks real nice. I may adapt mine to that. The only reason however is the oil temps are usually very low so I use the door to try to get my oil temps up. It does not add significantly to the CHT problem.
I finally got my CHT's to an acceptable level by adding louvers in the bottom of the cowl. I did everything that was suggested and all my baffles are very tight.
My CHT's now run in the low 400's during initial take off and climb out. I climb out between 110 and 120 to keep them in the 410 - 420 range. Once in cruise, my CHT's run more about 375 or a bit lower. I wish it was all lower, but can't seem to get that to happen.
I would entertain the idea of leaving things the way they are for first flight until you know what your temps look like. Plan a shallow climb as this is where the high temps would come into play if it was going to be a problem. You will soon know what is or isn't an issue. Double check the baffles are all sealing and that will show up after you fly as it leaves marks on the inside of the baffle. Also another area that creates a problem is at the air intake ramps if the air can go around them as in over the top and escape to the low pressure side.
Good luck and I look forward to hearing of your first flight.
Tim Bryan
Frankston, Texas
RV-6 (N616TB)
140 hours and counting
________________________________________
From: owner-rv-list-server(at)matronics.com [owner-rv-list-server(at)matronics.com] On Behalf Of thomas sargent [sarg314(at)gmail.com]
Sent: Saturday, June 26, 2010 5:18 PM
To: rv-list
Subject: Two cooling questions
The airworthiness inspection my RV-6A will be next week, so first flight will be soon after that. I'm wondering about cooling the engine. The 2 main things that steal cooling air form the engine are the oil cooler and the take-off for the cabin heat.
1- I certainly don't need cabin heat in Arizona in June. If I block off the opening in the baffles that is plumbed to the heat muff, no air will circulate thru the heat muff. Is that OK? Will that stretch of exhaust pipe get too hot? Is that what most folks do in the summer?
2- I did the oil cooler installation on the baffles behind cylinder #4. I used the Stewart Warner 7 row oil cooler, so I expect it to be pretty effective; that is, I doubt it needs the full opening that it has. Will I do better to block off, say, 1/3 of that to start with, or should I leave it wide open and just see what happens on the first flight?
--
Tom Sargent, RV-6A, ready for inspection.
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Tim Bryan
RV-6 Flying
N616TB |
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dan.pat.b(at)gmail.com
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| Posted: Sun Jun 27, 2010 6:31 pm Post subject: Two cooling questions |
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TOM: RE YOUR "ANTICIPATED" COOLING PROBLEMS - FLY THE AIRPLANE FIRST AND FIND OUT IF YOU EVEN HAVE A PROBLEM. YOU'RE PROBABLY GOING TO FIND NO PROBLEM AT ALL.
LIKE MOST RV BUILDERS - I HAVE TWO OPENINGS CUT INTO MY REAR BAFFLES - ONE FEEDS AIR INTO THE OIL COOLER PLENUM, AND THE OTHER INTO A HEAT MUFF ON ONE EXHAUST PIPE, FROM WHERE IT FEEDS INTO A SECOND MUFF, THEN TO THE HEAT CONTROL UNIT ON THE FIREWALL. I HAVE A SLIDING GATE VALVE, MOUNTED BEHIND THE BAFFLE, WHICH CONTROLS AIR FLOW INTO THE OIL COOLER PLENUM VIA A PUSH/PULL CABLE. ON HOT SUMMER DAYS THAT VALVE IS ALWAYS WIDE OPEN - TYPICALLY MY SUMMER OIL TEMP RUNS IN THE HIGH 170S - IN WINTER OF COURSE I CLOSE THE VALVE DOWN AS NECESSARY TO KEEP THE OIL TEMPS WHERE THEY NEED BE. REMEMBER THAT ENGINE OIL PLAYS A BIG ROLE IN KEEPING YOUR ENGINE COOL AND HAPPY. I'D LEAVE THAT OIL COOLER DOOR WIDE OPEN UNTIL YOU SEE WHAT'S WHAT. THE OTHER OPENING, WHICH FEEDS AIR INTO THE HEAT MUFFS IS ALWAYS GOING TO BE OPEN - IN THE SENSE THAT THE HEAT CONTROL BOX ON THE FIREWALL IS EITHER DIRECTING WARM AIR INTO THE CABIN, OR IT'S DUMPING IT OVERBOARD.
IN A CLIMB ON A HOT DAY YOU CAN REDUCE THE CLIMB ANGLE TO KEEP YOUR CLIMB SPEEDS ABOVE 100 KTS. HECK - WITH FULL POWER AT 120 KTS YOU'RE STILL CLIMBING AT APPROX 900' A MINUTE. YOU CAN REDUCE THE CLIMB ANGLE EVEN FURTHER AND CLIMB AT PARTIAL POWER YOU CAN ALSO STEP CLIMB IF NECESSARY TO KEEP YOUR CYL HEAD TEMPS BELOW 400. I RECENTLY FINISHED A BOOK, "FLY THE ENGINE" BY KAS THOMAS. HE STATES SOMEWHERE IN THERE, AND I'M PARAPHRASING: "COOL TEMPS ARE THE WHOLE STORY IN EXTENDING ENGINE LIFE," AND "KEEP CYLINDERS HEALTHY BY KEEPING THEM COOL." HE RECOMMEND KEEPING CHTS BELOW 380 AT ALL TIMES.
GOOD LUCK AND FLY SAFE.
DAN BERGERON
RV-7A - N307TB
154 HOURS SINCE FIRST
FLIGHT ON 08/04/09
On Sun, Jun 27, 2010 at 9:07 AM, N616TB <N616TB(at)btsapps.com (N616TB(at)btsapps.com)> wrote:
[quote]--> RV-List message posted by: N616TB <N616TB(at)btsapps.com (N616TB(at)btsapps.com)>
I don't think you mentioned what engine and such you have but here is my situation.
RV-6 with 0-360 carb and constant speed prop.
I have my oil cooler mounted on the back of the baffle and two cabin heat muffs.
My engine ran very hot initially so I tried just about everything to get the CHT temps down.
The two things that did NOT add significant help were: blocking off the cabin heat, blocking off part of the oil cooler.
I now have a door behind my oil cooler so I can block it as needed. I see vans has a new slider that goes between the oil cooler and the baffle and that looks real nice. I may adapt mine to that. The only reason however is the oil temps are usually very low so I use the door to try to get my oil temps up. It does not add significantly to the CHT problem.
I finally got my CHT's to an acceptable level by adding louvers in the bottom of the cowl. I did everything that was suggested and all my baffles are very tight.
My CHT's now run in the low 400's during initial take off and climb out. I climb out between 110 and 120 to keep them in the 410 - 420 range. Once in cruise, my CHT's run more about 375 or a bit lower. I wish it was all lower, but can't seem to get that to happen.
I would entertain the idea of leaving things the way they are for first flight until you know what your temps look like. Plan a shallow climb as this is where the high temps would come into play if it was going to be a problem. You will soon know what is or isn't an issue. Double check the baffles are all sealing and that will show up after you fly as it leaves marks on the inside of the baffle. Also another area that creates a problem is at the air intake ramps if the air can go around them as in over the top and escape to the low pressure side.
Good luck and I look forward to hearing of your first flight.
Tim Bryan
Frankston, Texas
RV-6 (N616TB)
140 hours and counting
________________________________________
From: owner-rv-list-server(at)matronics.com (owner-rv-list-server(at)matronics.com) [owner-rv-list-server(at)matronics.com (owner-rv-list-server(at)matronics.com)] On Behalf Of thomas sargent [sarg314(at)gmail.com (sarg314(at)gmail.com)]
Sent: Saturday, June 26, 2010 5:18 PM
To: rv-list
Subject: Two cooling questions
The airworthiness inspection my RV-6A will be next week, so first flight will be soon after that. I'm wondering about cooling the engine. The 2 main things that steal cooling air form the engine are the oil cooler and the take-off for the cabin heat.
1- I certainly don't need cabin heat in Arizona in June. If I block off the opening in the baffles that is plumbed to the heat muff, no air will circulate thru the heat muff. Is that OK? Will that stretch of exhaust pipe get too hot? Is that what most folks do in the summer?
2- I did the oil cooler installation on the baffles behind cylinder #4. I used the Stewart Warner 7 row oil cooler, so I expect it to be pretty effective; that is, I doubt it needs the full opening that it has. Will I do better to block off, say, 1/3 of that to start with, or should I leave it wide open and just see what happens on the first flight?
--
Tom Sargent, RV-6A, ready for inspection.
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rv8tor(at)lazy8.net
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| Posted: Mon Jun 28, 2010 5:03 am Post subject: Two cooling questions |
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It has been the accepted wisdom that if the heat muff is on the pipe, then air should be flowing through it to keep it from overheating. I never tested that, but I would just take the heat muff off if I wasn’t running air through it. I think this is why all heat selector valves are two way rather than just on-off.
I would just leave the cooler as is…your vernatherm should keep the oil from being too cold, you can go for drag reduction later.
John
From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of thomas sargent
Sent: Saturday, June 26, 2010 4:18 PM
To: rv-list
Subject: Two cooling questions
The airworthiness inspection my RV-6A will be next week, so first flight will be soon after that. I'm wondering about cooling the engine. The 2 main things that steal cooling air form the engine are the oil cooler and the take-off for the cabin heat.
1- I certainly don't need cabin heat in Arizona in June. If I block off the opening in the baffles that is plumbed to the heat muff, no air will circulate thru the heat muff. Is that OK? Will that stretch of exhaust pipe get too hot? Is that what most folks do in the summer?
2- I did the oil cooler installation on the baffles behind cylinder #4. I used the Stewart Warner 7 row oil cooler, so I expect it to be pretty effective; that is, I doubt it needs the full opening that it has. Will I do better to block off, say, 1/3 of that to start with, or should I leave it wide open and just see what happens on the first flight?
--
Tom Sargent, RV-6A, ready for inspection. | Quote: | | http://www.matronics.com/Navigator?RV-List |
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[quote][b]
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http://www.matronics.com/Navigator?RV-List |
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