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  #1  
Old 10-04-2012, 04:03 PM
vgb vgb is offline
 
Join Date: Aug 2007
Location: northern Cal
Posts: 111
Default High oil temps

Hello rvers
I have a question. I have always fought high oil temps on my 7A, 0-360 carbed, with magnetos. Oil cooler behind the cylinder. Installed a steward warner oil cooler. Made sure the cowl was sealed, fiberglassed the tunnel on the top front cowl. New vernatherm
With the van,s supplied cooler in cruise it would climb to 240 degrees so would back off power to cool it down. New oil cooler helped a lot but still would like to run at least 200 degrees in cruise. Now with new cooler its about 215-220. If I do very much slow flight it will go to 240 degrees.pretty fast
Looking at the inlets and outlets with the exhaust pipes in the outlet it seems to me that I need to cut the opening up more.
Has anybody done this and does it help.
Vern
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  #2  
Old 10-04-2012, 04:39 PM
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What make engine and how are the CHT's?
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  #3  
Old 10-04-2012, 04:46 PM
vgb vgb is offline
 
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Location: northern Cal
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360a3a lycoming, cylinder heads 380 to 390
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  #4  
Old 10-04-2012, 06:56 PM
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rv9av8tr rv9av8tr is offline
 
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Location: Portland, OR
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Default OAT & temps

That's pretty high for cruise temps. Needless to say, the other HUGE factor is OAT. You have to dissipate X BTU's which requires Y Temp change to get rid of the heat. Since oil temp is a direct heat exhanger, when the inlet air temp is high, the oil temp will be proportionally higher.

The high CHT's could also be directly caused by advanced timing... which causes more heat in the engine, which will raise oil temps also. I'd make sure your timing is correct, at least rule it out!!

Your top cowl inlet ramps are blocked off on at least one side so air can't escape behind them?
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Last edited by rv9av8tr : 10-04-2012 at 06:58 PM.
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  #5  
Old 10-04-2012, 07:31 PM
vgb vgb is offline
 
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Location: northern Cal
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I blocked off inlet ramps at one end and have checked timing several times.
Has anyone trimmed the outlet. I didn't really want to trim it but if it would solve the cooling it would be worth it.
Vern
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  #6  
Old 10-04-2012, 09:56 PM
N427EF N427EF is offline
 
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Default Fuel Consumption?

What is your precise fuel consumption on take off and at what altitude is your
home field?
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  #7  
Old 10-05-2012, 07:08 AM
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AlexPeterson AlexPeterson is offline
 
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Vern, the questions asked are all good and important ones. I have a few more questions: - are you using the stock cowl and have you verified the oil temp probe's accuracy with boiling water? Also, fuel flow, MAP. and rpm at the cruise settings would be extremely helpful. CHT (and oil) temps are very sensitive to mixture on RV's.
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  #8  
Old 10-05-2012, 05:58 PM
vgb vgb is offline
 
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Location: northern Cal
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Home field is 2725'. Take off is 14-gph at 8000' cruise 8.5 gph
Stock van's cowl with blocked air ramps.
I did not check probe with boiling water but landed and took cowl off and check with a heat gun at the probe. and it was within a couple of degrees.
2300 rpm at cruise.
vern
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  #9  
Old 10-06-2012, 12:40 AM
rvsxer rvsxer is offline
 
Join Date: May 2007
Location: Inver Grove Hgts, MN
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Vern,
I have the same setup as you and I flow about 15.5 gph after takeoff, but my field elevation is only 900' or so. I've been told this is a little low but my temps are good. Your carb may need to be modified to run richer. Check these threads: http://www.vansairforce.com/communit...706#post225706
http://www.vansairforce.com/communit...l+flow+takeoff
Post #29 in the first thread gives some figures about how much EGT rise should be attainable with a carb that is rich enough. If you do that test and have that much "room" for EGT rise your problem is elsewhere.
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Last edited by rvsxer : 10-06-2012 at 12:57 AM.
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  #10  
Old 10-06-2012, 05:32 PM
N427EF N427EF is offline
 
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Your Fuel flow seems to be in the neighborhood at that altitude where your engine is able to produce about 155 HP. (.55#of fuel/hp)
rv9av8tor pointed to ignition timing and ruling out too lean a mixture you are left with magneto timing. Your engine ID tag will tell you what the timing should be. 25 degrees BTDC for a low compression engine I am pretty sure.
It is highly unlikely that other factors contribute to such high oil and CH temperatures.
Since you posted that the plenum is well sealed and your oil cooler is obviously
working especially after you replaced it with a new one.
I am assuming that your probes are reading correctly.

Quote:
Made sure the cowl was sealed, fiberglassed the tunnel on the top front cowl
Not sure what you mean by fiberglassed the tunnel?
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