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  #11  
Old 11-06-2018, 07:50 AM
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M McGraw M McGraw is offline
 
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Default RV14 CHT and Oil temperatures

For the purposes of this thread I elected to post only ROP (Rich of Peak) data at or above 70% power (worst case). As you can see the RV-14 cooling system leaves significant margin for CHT cooling. Oil temperature is what I find more limiting, but still quite acceptable. I have eventual plans for a cowl flap and this data shows careful placement of the oil cooler exit in an area of low pressure will be necessary.

This data was collected over 16 months and 230 hours of flight time. THE AREAS CIRCLED IN YELLOW ARE DURING ENGINE BREAK IN.

CONDITIONS:
Percent Power between 70 and 75%
Stabilized in cruise flight at 100ROP for 2 to 7 minutes.
Altitude various but always high enough to be WOT.

NOTE: Timing in this data varies from 20 to 24 BTDC accounting for some temperature variations. 23BTDC was the best condition for speed; however, it did increase the temperatures. The breakin temperatures in the yellow circles are all at 20BTDC.

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Last edited by M McGraw : 11-06-2018 at 08:13 AM.
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  #12  
Old 11-06-2018, 09:22 AM
TimO TimO is offline
 
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I don't think you have anything to worry about, Chris. My RV14 CHTs are significantly better than my IO-540 in the RV-10. They're lower than expected. The engine gets very good cooling. I just added an oil cooler throttle valve too, because my oil temps get too low in the cold weather.
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  #13  
Old 11-06-2018, 09:43 PM
drillr1 drillr1 is offline
 
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Hi Jesse. Actually the temps rarely get over 320 during climb at 100 knots on a hot day with 300 in cruise with oil temps around 200. Autumn temps now are running about 270 in cruise and oil temps are 190. That's a OAT of 33 F.
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  #14  
Old 11-06-2018, 10:42 PM
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Marvin was the only respondent to note ignition timing, a very significant CHT factor.
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  #15  
Old 11-07-2018, 07:33 AM
KeithB KeithB is offline
 
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Ignition timing is, of course, important. However, for the 390 (in my case XP-400) it seems that CHT is less of an indicator. I have dual PMags and I have run my engine timed 20 BTDC., 25 BTDC, jumper in and jumper out (even more advanced) with very little change in observed CHTs. In discussions with Superior, I believe the extended stroke of this engine opens the sweet spot and makes it less sensitive to timing changes.
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  #16  
Old 11-07-2018, 08:57 AM
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Quote:
Originally Posted by KeithB View Post
Ignition timing is, of course, important. However, for the 390 (in my case XP-400) it seems that CHT is less of an indicator. I have dual PMags and I have run my engine timed 20 BTDC., 25 BTDC, jumper in and jumper out (even more advanced) with very little change in observed CHTs. In discussions with Superior, I believe the extended stroke of this engine opens the sweet spot and makes it less sensitive to timing changes.
Don't know about a sweet spot, but FWIW, the 390 has the same stroke as the 360.

Care to quantify "very little change"? Last check I made said running 20~30 LOP results in approximately 1.6 degrees F per degree of advance, which matches Nigel's data for his parallel valve. I would expect 2.5 degrees per degree running ROP.
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  #17  
Old 11-07-2018, 09:39 AM
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M McGraw M McGraw is offline
 
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Default CHT as a function of ignition advance

This is for 75% power at 100ROP and constant OAT. I stopped testing at 25BTDC because temperature continued to increase and speed decreased indicating I had exceeded a useful advance. Speed peaked at 23BTDC.

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Last edited by M McGraw : 11-07-2018 at 09:47 AM.
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  #18  
Old 11-07-2018, 10:02 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by M McGraw View Post
This is for 75% power at 100ROP and constant OAT. I stopped testing at 25BTDC because temperature continued to increase and speed decreased indicating I had exceeded a useful advance. Speed peaked at 23BTDC.

A similar data display at 20 degrees or so LOP would be appreciated.

Carl
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  #19  
Old 11-07-2018, 11:07 AM
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M McGraw M McGraw is offline
 
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Default CHT LOP data

Hello Carl,
I do have LOP data. In fact, I have too much. This is my first engine which could run LOP so I tested way too many variables to understand the effects. I only post data that has been repeated at least three times. That was easy for ROP because I did everything at +100. For LOP I tested -25, -50, -75, -100, etc... I focused more on speed and fuel flow since CHT was always lower than the ROP number and my goal is to create a cowl flap; that exit dimension is controlled by the ROP temps.

A summary would be that 25LOP CHTs increase by less than 2 degrees per degree of ignition advance.
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Last edited by M McGraw : 11-07-2018 at 11:10 AM.
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  #20  
Old 11-07-2018, 12:40 PM
KeithB KeithB is offline
 
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It looks like there are differences between the original (Lycoming) and the clone (Superior). The XP400 is stroked an additional 0.25. Whether or not that is material is beyond my pay grade.
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