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  #71  
Old 10-01-2020, 10:08 AM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
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Quote:
Originally Posted by rwthompson67 View Post
Mehrdad, I struggle to keep my CHTs above 300 in cruise. What are you seeing now with the 5" scat tubing?

-Rick
Rick,
My CHTs are in the 320-330 range in cruise and 360-370s in steady climb. I had the same numbers as yours and that is why I didn't mind going to the 5" scat tubing.
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  #72  
Old 10-19-2020, 06:41 PM
RobB52 RobB52 is offline
 
Join Date: Nov 2013
Location: Shreveport, LA
Posts: 64
Default 5" SCAT Mod

All,

I have 20 hours on my new IO 390. I have been concerned about the oil temps. First flight I saw a steady 225 at 75% power cruise, 4500'. I spent a lot of time sealing baffles and on last flight I had 211 at 75% power cruise, 4500'. What concerns me is I cant seem to get temps much lower at other power settings. 24 squared gave me 207. And 23 squared gave me 210! (I attribute that to the slower speed and reduced airflow). CHT's have been around 320 or a little lower in cruise. OAT at altitude has been around 60 for most flights. EGTs around 1220 running full rich. Leaning at all results in increased oil temps.

The ONLY time I see oil temps below 200 is on final and after landing (197 degrees). Last flight, immediately after the prop stopped, I had a helper shoot the oil filter with a thermal gun and it read 196. Oil temp sensor showed 197. I am comfortable that my oil temp probe is accurate based on that check.

I ASSUME that my vernatherm is working correctly since it is a new engine. Thoughts?

I ordered the 5" SCAT modification kit from Vans and it arrived yesterday. It did not include part # FF-01406C (Oil Cooler Inlet Sides). I didn't want to drill out rivets and destroy the 4" transition so I ordered another 1406C. It should be here Thursday and I hope to install it this weekend.

I'm hoping the 5" SCAT helps, but based on previous comments I am going to have to wait and see.

Cowling and everything is stock. No cowl flaps, etc. Neither wheel pants nor gear leg covers are installed so there is some airflow leaving the cowling around the gear leg cutouts (taildragger).

My friend with an RV-14 thinks my temps are way out of where they should be and he swears he was seeing 185-195 in cruise during his break in sorties. He has the 4" SCAT AND cowl flaps.

I'm not ready to mod the cowl yet but I guess that is next if the 5" SCAT disappoints.

Any comments would appreciated.
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  #73  
Old 10-19-2020, 08:30 PM
Tom023 Tom023 is offline
 
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Location: Cypress, TX
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My oil temps rarely get above 200 unless in a climb but my CHTs are a little higher in cruise, typically 320-355 depending on OAT and power. I meticulously sealed the baffles...don’t miss the gap behind #3 which requires removal of the oil filler tube to properly seal. What I found is some of the baffle seals didn’t stay sealed in flight. Specifically right to the upper right of the air filter the seal would flip down, so I had to glass in a ridge to retain it. Around the prop controller is another area where the seal liked to flip out and the top corner near #1 sometimes seemed out of position. I check these before and after every flight but with some fiddling they now stay in place.

Also my oil temps continued to drop slowly until about 50 hours And then stabilized. If you are running pmag be sure the jumper is in ... and I retarded the timing approximately 5 degrees (two teeth on the ring gear).
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Last edited by Tom023 : 10-19-2020 at 09:03 PM.
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  #74  
Old 10-19-2020, 08:57 PM
RobB52 RobB52 is offline
 
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Location: Shreveport, LA
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Default 5" SCAT Mod

Tom,

Thanks. I will look for the area behind #3 cylinder you mentioned. I don't recall sealing anything there.
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  #75  
Old 10-20-2020, 08:05 AM
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DanH DanH is offline
 
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Good thread here:

https://vansairforce.net/community/s...le#post1292407

The big leaker tends to be a gap at the cylinder base. It's hard to see. The baffle tin has a tab there, but it may not be bent to fill the gap.
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  #76  
Old 10-20-2020, 08:07 AM
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KeithB KeithB is offline
 
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Location: Granbury, TX
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I would add that you should see lower temps when you install gear leg fairings and wheel pants. Their installation will add between 10 and 15 knots of airspeed (= cooling) for the same power settings.
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  #77  
Old 10-20-2020, 08:30 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Locations on the baffles that others have suggested you check/seal are good, but the best investigation process is the use of a flash light in a darkened hangar.
Shine the light from below, along the entire perimeter where the baffling interfaces with the engine. There should be no light able to pass from one side to the other. If there is, seal it up.
Also confirm there is a good seal between the baffle seals and the top cowl by looking for uninterrupted rub marks on the cowling (some portions of this can also be checked with the light method if you have a helper).
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  #78  
Old 10-20-2020, 09:31 AM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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All good suggestions especially Keith's about gear leg.

I have sealed my baffles meticulously and had the same issue with the baffle materials flipping inward around the Governor, a blub of RTV now works as a retainer to keep it in place. My oil temp is not as high as Rob and have installed the 5” scat mod with rather small decrease in oil temp. I also created a diffuser for the exit portion of the oil cooler with very little, if any, affect. I has been removed it since it was ineffective.
I am very interested to see the result of 5” SCAT tubing in Rob test.
My next annual is coming up next month and be interesting to see if there is an appreciable compression change to account and support ideal of hot gases escaping the cylinder and adding to the oil temp.
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Last edited by Bavafa : 10-20-2020 at 09:35 AM.
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  #79  
Old 10-20-2020, 09:54 AM
romaja romaja is offline
 
Join Date: Jan 2016
Location: Portland Oregon Area
Posts: 97
Default EXP-119 oil temps

Reading numerous posts it seems the larger 5 inch scat has had little effect at lowering the oil temps.

Wondering if the new "exhaust ramp cooling flap system" on the new EXP-119 package combined with the redesigned lower cowling have a greater effect at cooling the oil or does a cowl flap primarily effect mainly just the CHT's?


Curious,
Jim
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  #80  
Old 10-20-2020, 03:45 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by romaja View Post
Reading numerous posts it seems the larger 5 inch scat has had little effect at lowering the oil temps.

Wondering if the new "exhaust ramp cooling flap system" on the new EXP-119 package combined with the redesigned lower cowling have a greater effect at cooling the oil or does a cowl flap primarily effect mainly just the CHT's?

Curious,
Jim
It would control pressure in the lower cowl. DeltaP (upper vs lower) dictates mass flow for both cylinder fins and oil cooler.
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