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RV7A OVERHEATING

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smoothweasel(at)juno.com
Guest

Posted: Sat Mar 29, 2008 6:35 am Post subject: RV7A OVERHEATING

Hello all, It's been a long time since i have found time to read "the list".  I have been helping a friend finish a rv-7a and test fly it.  It has a new superior 360 parallel valve engine, Hartzell blended airfoil prop, the oil cooler is the one that comes with the finishing kit and is mounted on the firewall with a 3.5 in scat duct going to it (with no sharp bends in the duct). the cowl air exit is the standard size. ie. no extra openings.   

His problem is over heating oil.  With 52 deg. F. Outside air crusing at 24 in map. and 2350rpm on the prop the oil will run about 220-225deg F.  The CHT runs about 360-370 deg. F.  The engine now has 30hr or more on it.    

Will the Oil temp drop any more with "break in"?  Should it have more exit air leaving the cowl....some have suggested installing "luvers" on the botom of the cowl to help with that...? 

Also the airplane cruises at the above power setting at 8000ft at 164kn TAS he thinks this is a little slow......  Is this what most of you are seeing with the same engine/prop combo??? 

btw i tried to search the archives on this but didnt find the specific info..........probably dont know how to look it up right... 

  

Thanks for any thoughts 

Weasel RV-4 400hr 



_____________________________________________________________

Click here to become a professional counselor in less time than you think.

   [quote][b]

khorton01(at)rogers.com
Guest

Posted: Sat Mar 29, 2008 7:49 am Post subject: RV7A OVERHEATING

On 29-Mar-08, at 10:28 , smoothweasel(at)juno.com wrote:

 	  Quote: 	
		   Hello all, It's been a long time since i have found time to read  

 "the list".  I have been helping a friend finish a rv-7a and test  

 fly it.  It has a new superior 360 parallel valve engine, Hartzell  

 blended airfoil prop, the oil cooler is the one that comes with the  

 finishing kit and is mounted on the firewall with a 3.5 in scat duct  

 going to it (with no sharp bends in the duct). the cowl air exit is  

 the standard size. ie. no extra openings.



 His problem is over heating oil.  With 52 deg. F. Outside air  

 crusing at 24 in map. and 2350rpm on the prop the oil will run about  

 220-225deg F.  The CHT runs about 360-370 deg. F.  The engine now  

 has 30hr or more on it.



 Will the Oil temp drop any more with "break in"?  Should it have  

 more exit air leaving the cowl....some have suggested installing  

 "luvers" on the botom of the cowl to help with that...?



 Also the airplane cruises at the above power setting at 8000ft at  

 164kn TAS he thinks this is a little slow......  Is this what most  

 of you are seeing with the same engine/prop combo???



 btw i tried to search the archives on this but didnt find the  

 specific info..........probably dont know how to look it up right...


	


Has the oil temperature sender been calibrated?  You can put it in a  

pot of boiling water to check its accuracy, keeping in mind that the  

boiling point changes slightly with altitude.



Has the tachometer been calibrated?



I agree that the TAS sounds a bit low.  How have you determined TAS?   

If you used IAS corrected for altitude and temperature, it is possible  

that there are errors in the airspeed system, and/or the indicated OAT.



How much EGT rise can you get in cruise if you lean from full rich?



At the cruise condition you mention, how many degrees rich or lean of  

peak EGT were you?  What manifold pressure do you get at full throttle  

at 8000 ft?



--

Kevin Horton         RV-8 (final assemby)

Ottawa, Canada

http://www.kilohotel.com/rv8

khorton01(at)rogers.com
Guest

Posted: Sat Mar 29, 2008 7:52 am Post subject: RV7A OVERHEATING

On 29-Mar-08, at 10:28 , smoothweasel(at)juno.com wrote:

 	  Quote: 	
		   Also the airplane cruises at the above power setting at 8000ft at  

 164kn TAS he thinks this is a little slow......  Is this what most  

 of you are seeing with the same engine/prop combo???




	


One more thing - Please confirm that all the fairings and wheel pants  

are installed.



--

Kevin Horton         RV-8 (final assemby)

Ottawa, Canada

http://www.kilohotel.com/rv8

aerobubba(at)earthlink.ne
Guest

Posted: Mon Mar 31, 2008 4:31 am Post subject: RV7A OVERHEATING

HI Weasel!



 	  Quote: 	
		  the oil cooler is the one that comes with the finishing kit and is m

 ounted on the firewall with a 3.5 in scat duct going to it (with no shar

 p bends in the duct). the cowl air exit is the standard size. ie. no ext

 ra openings.  



 His problem is over heating oil.  


	


 	  Quote: 	
		   Will the Oil temp drop any more with "break in"?  


	


That seems to be common.



 	  Quote: 	
		  Should it have more ex

 it air leaving the cowl....some have suggested installing "luvers" on th

 e botom of the cowl to help with that...?


	


My thought is that if the CHT's are good, then you've most likely got

enough air going through the cowling.  Not to mention, that engine flies in

that plane all the time without cooling issues, as do angle valve engines

that have a much higher heat load on the lubricating system.  So, the

question becomes, 'what are you doing with the available airflow?'



The way I look at it, your friend needs to make his cooler, and only the

cooler,  breathe easier.  You don't mention any sort of diffuser to connect

the SCAT to the cooler.  A reasonable diffuser, properly sealed to the

cooler, could make all the difference.  If there is a diffuser in place,

I'd up the SCAT diameter.  Last, I'd consider a NACA scoop and / or a

properly shaped outflow duct in the side of the lower cowl to service the

cooler directly.  But again, there should already be more than enough mass

flow through the cowl to meet all your cooling needs. If I added a

dedicated NACA scoop for the cooler, I'd also reduce the size of the

cooling inlets at the front of the cowl.   



I would absolutely not consider gills in the cowl.  Although it would

potentially / probably solve the oil cooling issue, it would markedly

increase the airflow through the whole of the cowl, not just the cooler. 

Every molecule passing through the cowl represents more cooling drag and

less efficiency, which is of course contrary to our basic goals.    



FWIW-



glen matejcek

aerobubba(at)earthlink.ne

smoothweasel(at)juno.com
Guest

Posted: Thu Apr 03, 2008 6:45 am Post subject: RV7A OVERHEATING

Just an update. we are continuing to work on the cooling issues.....

the numbers i gave previously are higher now (probably due to higher O.S.A. temp).

On a flight yesterday at low alt level flight the numbers are as follows

n616tb(at)btsapps.com
Guest

Posted: Thu Apr 03, 2008 7:26 am Post subject: RV7A OVERHEATING

Temperature comparisons are real hard to get but when I added louvers to the bottom of my cowl I gained about 10 degrees cooler CHT temps.  I later opened up the exit air and gained about another 5 or 6 degrees.  My oil temps run cool at about 165 degrees.  My CHT’s are still high.  Very few things I have done made as much difference as the louvers and opening the bottom cowl up a little more.  

   

In my case a -6 I just cut the center lower part of the cowl about 1 ½ “ back as it was actually a little past the metal skin on the fuse.  

   

This is just a reference point for you.  

Tim  

           

  

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of smoothweasel(at)juno.com

 Sent: Thursday, April 03, 2008 8:39 AM

 To: rv-list(at)matronics.com

 Subject: RE: RV7A OVERHEATING  

  

   

Just an update. we are continuing to work on the cooling issues.....  

the numbers i gave previously are higher now (probably due to higher O.S.A. temp).  

On a flight yesterday at low alt level flight the numbers are as follows.  

TAS 162 (verified by GPS)   

MP 23 in  

rpm 2350 (Verified correct)  

Oil Temp. 232 deg F  

CHT 395 deg F  

EGT 1350 (rich of peak)  

this information was established in constant flight for approx. 45 min.  

also we connected a magnahelic to the low pressure side of the cowl. (behind the baffle) at 150 knots we have 4.5" w.c.. we have not tested it on the entering side yet but 4.5" on the low press raised my eye brows. I then measured the outlet cross sectional area and after taking into account for the ext. stacks it was much smaller than the rv-8 it shares a hanger with and also has a lot more obstacles tripping the airflow and therefore causing turbulence. I then measured the outlet on my rv-4 and the -7a even has a smaller outlet than my -4. These are all stock cowls.  

bottom line we still feel like we have to small of outlet on the cowl.  

we are still testing.........we shall see.  

Weasel  

   



 

 _____________________________________________________________

 Earn up to $300 hour. Click here to get information on starting a medical career.   	  Quote: 	
		    http://www.matronics.com/Navigator?RV-List 	
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mrobert569(at)hotmail.com
Guest

Posted: Thu Apr 03, 2008 7:34 am Post subject: RV7A OVERHEATING

With any 'a' model you have tons of obstacles in the outlet area that coause all kinds of turbulence.  Several people have installed louvers to the left and right of the outlet with great results.  Your CHT's seem just a tad bit high for the power, rpm, and cruise time you gave.  Granted, with a new engine a bit high can be normal but I think they level you gave indicates one of a couple of things.  first, check your baffles to make sure they are tight around the engine and upper cowling.  Second, make sure the ramp areas of the inlets are smooth and don't have any excess holes.  Tthe third thing is the outlet flow area.  Go ahead and get the pressure reading in the top inlet area.  Once you compare the top and bottom you will have a much better idea.

  

 A friend, with an RV-9A, decided to install louvers and had great results.  Even though he did not have any temps out of limits, he wanted to see what effect it had.  Both the oil temps and the CHTs went down significantly.  And with the louvers painted the same color as his cowling they do not look out of place.  One quick reminder though.  If you do install the louvers, when you cut through the honecomb part of the cowling, make sure to apply some eposy glue or resin to the cut areas to stop oil, grease, and water from getting into the honeycomb area of the cowling and causing delamination.

  

 Mike Robertson

 Das Fed

 Repeat offender  





  	  Quote: 	
		    From: smoothweasel(at)juno.com

Date: Thu, 3 Apr 2008 14:38:51 +0000

To: rv-list(at)matronics.com

Subject: RE: RV7A OVERHEATING



 Just an update. we are continuing to work on the cooling issues.....

 the numbers i gave previously are higher now (probably due to higher O.S.A. temp).

 On a flight yesterday at low alt level flight the numbers are as follows.

 TAS 162 (verified by GPS) 

 MP 23 in

 rpm 2350 (Verified correct)

 Oil Temp. 232 deg F

 CHT 395 deg F

 EGT 1350 (rich of peak)

 this information was established in constant flight for approx. 45 min.

 also we connected a magnahelic to the low pressure side of the cowl. (behind the baffle) at 150 knots we have 4.5" w.c.. we have not tested it on the entering side yet but 4.5" on the low press raised my eye brows. I then measured the outlet cross sectional area and after taking into account for the ext. stacks it was much smaller than the rv-8 it shares a hanger with and also has a lot more obstacles tripping the airflow and therefore causing turbulence. I then measured the outlet on my rv-4 and the -7a even has a smaller outlet than my -4. These are all stock cowls.

 bottom line we still feel like we have to small of outlet on the cowl.

 we are still testing.........we shall see.

 Weasel

  

_____________________________________________________________

Earn up to $300 hour. Click here to get information on starting a medical career.

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t=_blank>http://www.matronics.com/Navigator?RV-List

p://forums.matronics.com

blank>http://www.matronics.com/contribution



	
	
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khorton01(at)rogers.com
Guest

Posted: Thu Apr 03, 2008 8:30 am Post subject: RV7A OVERHEATING

Speaking of baffling - have a look at the two duct ramp pieces that  

were fibreglassed to the inlets on the upper cowl.  I understand that  

depending on how you set up your baffles, that it is possible for high  

pressure air on the top side of the engine to go through the tunnels  

between those duct ramps and the cowl.  The high pressure air may be  

able to go through those tunnels and end up on the low pressure side  

of the baffles.  It this can happen, it would greatly reduce the  

amount of air that is available to go through the cylinder fins and  

the oil cooler.  You may need to block off one end of that tunnel with  

fibreglas.



Kevin Horton

On 3-Apr-08, at 11:27 , Mike Robertson wrote:

 	  Quote: 	
		   With any 'a' model you have tons of obstacles in the outlet area  

 that coause all kinds of turbulence.  Several people have installed  

 louvers to the left and right of the outlet with great results.   

 Your CHT's seem just a tad bit high for the power, rpm, and cruise  

 time you gave.  Granted, with a new engine a bit high can be normal  

 but I think they level you gave indicates one of a couple of  

 things.  first, check your baffles to make sure they are tight  

 around the engine and upper cowling.  Second, make sure the ramp  

 areas of the inlets are smooth and don't have any excess holes.   

 Tthe third thing is the outlet flow area.  Go ahead and get the  

 pressure reading in the top inlet area.  Once you compare the top  

 and bottom you will have a much better idea.



 A friend, with an RV-9A, decided to install louvers and had great  

 results.  Even though he did not have any temps out of limits, he  

 wanted to see what effect it had.  Both the oil temps and the CHTs  

 went down significantly.  And with the louvers painted the same  

 color as his cowling they do not look out of place.  One quick  

 reminder though.  If you do install the louvers, when you cut  

 through the honecomb part of the cowling, make sure to apply some  

 eposy glue or resin to the cut areas to stop oil, grease, and water  

 from getting into the honeycomb area of the cowling and causing  

 delamination.



 Mike Robertson

 Das Fed

 Repeat offender





 From: smoothweasel(at)juno.com

 Date: Thu, 3 Apr 2008 14:38:51 +0000

 To: rv-list(at)matronics.com

 Subject: RE: RV7A OVERHEATING



 Just an update. we are continuing to work on the cooling issues.....

 the numbers i gave previously are higher now (probably due to higher  

 O.S.A. temp).

 On a flight yesterday at low alt level flight the numbers are as  

 follows.

 TAS 162 (verified by GPS)

 MP 23 in

 rpm 2350 (Verified correct)

 Oil Temp. 232 deg F

 CHT 395 deg F

 EGT 1350 (rich of peak)

 this information was established in constant flight for approx. 45  

 min.

 also we connected a magnahelic to the low pressure side of the cowl.  

 (behind the baffle) at 150 knots we have 4.5" w.c.. we have not  

 tested it on the entering side yet but 4.5" on the low press raised  

 my eye brows. I then measured the outlet cross sectional area and  

 after taking into account for the ext. stacks it was much smaller  

 than the rv-8 it shares a hanger with and also has a lot more  

 obstacles tripping the airflow and therefore causing turbulence. I  

 then measured the outlet on my rv-4 and the -7a even has a smaller  

 outlet than my -4. These are all stock cowls.

 bottom line we still feel like we have to small of outlet on the cowl.

 we are still testing.........we shall see.

 Weasel


	


--

Kevin Horton

Ottawa, Canada

mcculleyja(at)starpower.n
Guest

Posted: Thu Apr 03, 2008 8:36 am Post subject: RV7A OVERHEATING

Can you provide the following additional data that could be helpful:



1. Ambient temperature at the flight altitude.



2. Indicated (calibrated) airspeed.



3. Actual measurements, or best estimate of square inches of clear area 

of cooling air outlet.



4. Same as 3 above for inlet cooling area.



5. Make/model and face area of oil cooler; Is this a new or used cooler? 

Also the cross section area of any scat tube feeding the cooler and 

where that air is sourced; Are all the air leakage cracks at the cooler 

face thoroughly sealed with the equivalent of red 600 fahrenheit silicon 

sealant? Does the exit air from the cooler flow out through the same 

cooling air exit as in item 3 above?



6. What is the sensor pickup location of your oil temperature indication?



Are your CHT temperature probes in the cylinder head wells or under the 

  spark plugs?



Jim

--------------------------------------------------------------------------------------

smoothweasel(at)juno.com wrote:

 	  Quote: 	
		   Just an update. we are continuing to work on the cooling issues.....

 

 the numbers i gave previously are higher now (probably due to higher 

 O.S.A. temp).

 

 On a flight yesterday at low alt level flight the numbers are as follows.

 

 TAS 162 (verified by GPS)

 

 MP 23 in

 

 rpm 2350 (Verified correct)

 

 Oil Temp. 232 deg F

 

 CHT 395 deg F

 

 EGT 1350 (rich of peak)

 

 this information was established in constant flight for approx. 45 min.

 

 also we connected a magnahelic to the low pressure side of the cowl. 

 (behind the baffle) at 150 knots we have 4.5" w.c.. we have not tested 

 it on the entering side yet but 4.5" on the low press raised my eye 

 brows. I then measured the outlet cross sectional area and after taking 

 into account for the ext. stacks it was much smaller than the rv-8 it 

 shares a hanger with and also has a lot more obstacles tripping the 

 airflow and therefore causing turbulence. I then measured the outlet on 

 my rv-4 and the -7a even has a smaller outlet than my -4. These are all 

 stock cowls.

 

 bottom line we still feel like we have to small of outlet on the cowl.

 

 we are still testing.........we shall see.

 

 Weasel

 

  

 

 

 

 _____________________________________________________________

 Earn up to $300 hour. Click here to get information on starting a 

 medical career. 

 <http://thirdpartyoffers.juno.com/TGL2112/fc/REAK6ZpPCf5s36c9PRQtFyClaNN5axaGezer7vCfQ07T4GItaLqiML/>

 

 * 

 

 

  *

walter(at)tondu.com
Guest

Posted: Thu Apr 03, 2008 9:22 am Post subject: RV7A OVERHEATING

On 04/03 12:18, Kevin Horton wrote:



 > 

 > 

 > Speaking of baffling - have a look at the two duct ramp pieces that  

 > were fibreglassed to the inlets on the upper cowl.  I understand that  

 > depending on how you set up your baffles, that it is possible for high  

 > pressure air on the top side of the engine to go through the tunnels  

 > between those duct ramps and the cowl.  The high pressure air may be  

 > able to go through those tunnels and end up on the low pressure side  

 > of the baffles.  It this can happen, it would greatly reduce the  

 > amount of air that is available to go through the cylinder fins and  

 > the oil cooler.  You may need to block off one end of that tunnel with  

 > fibreglas.



Follow this thread for more information dissemination and pretty pics

about what Kevin is writing about:  Also, check out the poll results.



http://www.vansairforce.com/community/showthread.php?t=8209



-- 

Walter Tondu

http://www.rv7-a.com - Painting

http://www.evorocket.com - Empennage

bicyclop(at)pacbell.net
Guest

Posted: Thu Apr 03, 2008 9:41 am Post subject: RV7A OVERHEATING

Weasel,



Just as a data point, on our 6A with O-320, we used to see oil temps in 

the 200 to 220 degree range on not very hot days until we moved the oil 

cooler from the firewall to behind the baffle at #4 cyl. Do the math of 

cross sectional area in the scat tube to surface area of the oil cooler 

then think about length of tube, bends etc. In our case, with 3" scat, 

it was 1.5" squared x pi, or about 7 sq" with 18" of scat and 1 bend vs. 

4 x 5 or about 20 sq" directly in the airflow. Now we see 180 to 190 

degrees on warm days. This is the Niagara cooler. I'm not sure which one 

Van's supplies now, but I don't think that it is the Stewart Warner 

which is the one you really want.



Others have made good suggestions about cowl airflow. I think that you 

probably need to address the airflow through the cooler as a separate 

issue. One approach might be to combine 2 or more scats into a plenum 

above the oil cooler. What out that you don't create a bunch of 

turbulence, though. Stuff in the exit airflow path from the cooler can 

have a negative impact on cooling performance, too.



Pax,



Ed Holyoke



smoothweasel(at)juno.com wrote:

 	  Quote: 	
		  

 Hello all, It's been a long time since i have found time to read "the 

 list".  I have been helping a friend finish a rv-7a and test fly it.  

 It has a new superior 360 parallel valve engine, Hartzell blended 

 airfoil prop, the oil cooler is the one that comes with the finishing 

 kit and is mounted on the firewall with a 3.5 in scat duct going to it 

 (with no sharp bends in the duct). the cowl air exit is the standard 

 size. ie. no extra openings. 



 His problem is over heating oil.  With 52 deg. F. Outside air crusing 

 at 24 in map. and 2350rpm on the prop the oil will run about 

 220-225deg F.  The CHT runs about 360-370 deg. F.  The engine now has 

 30hr or more on it.  



 Will the Oil temp drop any more with "break in"?  Should it have more 

 exit air leaving the cowl....some have suggested installing "luvers" 

 on the botom of the cowl to help with that...?



 Also the airplane cruises at the above power setting at 8000ft at 

 164kn TAS he thinks this is a little slow......  Is this what most of 

 you are seeing with the same engine/prop combo???



 btw i tried to search the archives on this but didnt find the specific 

 info..........probably dont know how to look it up right...



  



 Thanks for any thoughts



 Weasel RV-4 400hr



 _____________________________________________________________

 Click here to become a professional counselor in less time than you 

 think. 

 <http://thirdpartyoffers.juno.com/TGL2112/fc/Ioyw6iigjRkllMv4ZGFXw1J0mnPH95dNcFS3uxBE5YnuT7oNq7kzGL/>

 *

 *

smoothweasel(at)juno.com
Guest

Posted: Wed Apr 09, 2008 4:14 pm Post subject: RV7A OVERHEATING

Just an Update.... 

We have the rv-7a cooling better and flying at Van's published speeds..finally. 

When i say better thats what i mean its still to be improved on but we can manage now. 

We found that the air outlet was just to restricted.(training wheel bracket, assembly, mess, junk ect.) We intalled 2 "Louvers" under the lower cowl and let more air out of the bottom of the cowl. Also made sure there was no air bypassing the baffle via intake ramps.  

Thanks for all the ideas. 

  

Weasel RV-4 (no training wheel required) 



_____________________________________________________________

Compete with the big boys.  Click here to find products to benefit your business.

   [quote][b]

ronlee(at)pcisys.net
Guest

Posted: Wed Apr 09, 2008 4:44 pm Post subject: RV7A OVERHEATING

I got about a 10 degree drop with the louvers and also with opening the  cowl a bit.

 Last night I saw that Avery Tools sells the louvers.

  

 Ron Lee

    [quote][b]

khorton01(at)rogers.com
Guest

Posted: Wed Apr 09, 2008 5:04 pm Post subject: RV7A OVERHEATING

On 10 Apr 2008, at 00:09, smoothweasel(at)juno.com (smoothweasel(at)juno.com) wrote: 	  Quote: 	
		  

Just an Update....

We have the rv-7a cooling better and flying at Van's published speeds...finally.

When i say better thats what i mean its still to be improved on but we can manage now.

We found that the air outlet was just to restricted.(training wheel bracket, assembly, mess, junk ect.) We intalled 2 "Louvers" under the lower cowl and let more air out of the bottom of the cowl. Also made sure there was no air bypassing the baffle via intake ramps. 	




Congratulations.

At the start, you were unhappy with both the high engine temperatures and the low TAS.  Now you have managed to improve both the cooling and the speed.  How much has the speed increased, and what changes did you make that affected the speed?



 --

Kevin Horton

RV-8 (FInal Assembly)

Ottawa, Canada

http://www.kilohotel.com/rv8



 



 [quote][b]

smoothweasel(at)juno.com
Guest

Posted: Wed Apr 09, 2008 7:00 pm Post subject: RV7A OVERHEATING

Well its not my airplane but thats beside the point.....just makin it clear that i dont have a "brake steering" RV.....We put the louvers in the bottom of the cowl and installed a larger oil cooler. 

As far as going faster there is a theory that if you block the cowl outlet off to much you can produce a "bubble" of air at the cowl inlet. This "bubble" equates to drag. So as you can see opening the outlet (via louvers) and removing the "bubble" makes the plane go faster. 

Now keep in mind before yall go yellin at me this is just a theory!!!!  u no where i got it joe. 

I personaly dont trade stock on that theory.  I'm still not sure where the speed came from. 

Weasel  RV-4   408hr 

Wanted: RV-8 and a HRII and a RV-10 and a CompAir 10 and a Zero Turn Lawn Mower  

do not archive 



_____________________________________________________________

Click here to find experienced pros to help with your home improvement project.

   [quote][b]

JFLEISC(at)aol.com
Guest

Posted: Thu Apr 10, 2008 2:43 pm Post subject: RV7A OVERHEATING

In a message dated 4/9/2008 9:07:44 P.M. Eastern Daylight Time,  khorton01(at)rogers.com writes:

  	  Quote: 	
		     Congratulations.

   



   At the start, you were unhappy with both the high engine temperatures and    the low TAS.  Now you have managed to improve both the cooling and the    speed.  How much has the speed increased, and what changes did you make    that affected the speed?

	


 

 10 years of operating air cooled engines on a dynamometer has taught me  that increases in cooling increases volumetric efficiency, thus more power  (astounding differences some times). Could be it.

  

 Jim



Planning your summer road trip? Check out AOL Travel Guides.

  [quote][b]

khorton01(at)rogers.com
Guest

Posted: Thu Apr 10, 2008 3:45 pm Post subject: RV7A OVERHEATING

On 10 Apr 2008, at 18:39, JFLEISC(at)aol.com (JFLEISC(at)aol.com) wrote: 	  Quote: 	
		     In a message dated 4/9/2008 9:07:44 P.M. Eastern Daylight Time, khorton01(at)rogers.com (khorton01(at)rogers.com) writes:

  	  Quote: 	
		    Congratulations.

  



  At the start, you were unhappy with both the high engine temperatures and   the low TAS.  Now you have managed to improve both the cooling and the   speed.  How much has the speed increased, and what changes did you make   that affected the speed?

	


 

 10 years of operating air cooled engines on a dynamometer has taught me that increases in cooling increases volumetric efficiency, thus more power (astounding differences some times). Could be it.

 

	




Interesting.  Do you mean that you actually measured an increase in the volume of air being inducted, or are you inferring the increase in volumetric efficiency from a measured increase in power?



 --

Kevin Horton

RV-8 (FInal Assembly)

Ottawa, Canada

http://www.kilohotel.com/rv8



 



 [quote][b]

JFLEISC(at)aol.com
Guest

Posted: Thu Apr 10, 2008 4:16 pm Post subject: RV7A OVERHEATING

In a message dated 4/10/2008 7:47:19 P.M. Eastern Daylight Time,  khorton01(at)rogers.com writes:

  	  Quote: 	
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		         Congratulations.

       



       At the start, you were unhappy with both the high engine temperatures        and the low TAS.  Now you have managed to improve both the cooling        and the speed.  How much has the speed increased, and what changes        did you make that affected the speed?

	


     

     10 years of operating air cooled engines on a dynamometer has taught me      that increases in cooling increases volumetric efficiency, thus more power      (astounding differences some times). Could be it.

     

	




   Interesting.  Do you mean that you actually measured an increase in    the volume of air being inducted, or are you inferring the increase in    volumetric efficiency from a measured increase in  power?

	


 

 Absolute measured increase in power. Think about it; You can fit more air  in a cold box than a hot one of the same size. Bolye's law.

  

 Jim



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