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  #21  
Old 08-16-2022, 01:02 PM
NinerBikes NinerBikes is offline
 
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What did Van's do in the redesign on the RV-12IS such tha high oil temps while climbing is no longer an issue?
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  #22  
Old 08-17-2022, 07:29 PM
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MartySantic MartySantic is offline
 
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Quote:
Originally Posted by NinerBikes View Post
What did Van's do in the redesign on the RV-12IS such tha high oil temps while climbing is no longer an issue?
Will let Scott comment.... but think the distance between the muffler and oil cooler was increased a few inches with the new exhaust pipes.
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  #23  
Old 08-17-2022, 07:40 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by MartySantic View Post
Will let Scott comment.... but think the distance between the muffler and oil cooler was increased a few inches with the new exhaust pipes.
The distance between the cooler and the muffler is increased but I think the more significant change is the fact that the oil cooler is right out in the open on the front of the cowl (below the coolant radiator).
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  #24  
Old 08-18-2022, 08:14 AM
bobg56 bobg56 is offline
 
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I believe the props pitch setting will also help lower oil temps, I made a blade wrench that enables me to be a lot more accurate, I have it set to 71.4 and have picked up about 150 rpm at climb to around 5200-5250 so the engine is not lugging so much. I'm in S.C. and in the summer it's normally mid to high 90's and I'm just flying local less than 2000' 5200-5300rpm and my oil temp is around 215.
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  #25  
Old 08-18-2022, 09:12 AM
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F1Boss F1Boss is offline
 
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Default Has any of you tried a scavenger tube?

A larger tube - maybe 1.5x diameter of the standard exhaust pipe - wrapped around the smaller hot exhaust pipe would seem to help get the hot gasses out of the cowling? You see the same thing every day - underneath the right side of a Ford F-250 - but you would fabbed up a somewhat smaller second pipe...having a cone inlet around the second tube inlet might also help.

You might look at early Apaches and Beech twins too...it's called an extractor exhaust.
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  #26  
Old 08-18-2022, 10:41 AM
seagull seagull is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
The distance between the cooler and the muffler is increased but I think the more significant change is the fact that the oil cooler is right out in the open on the front of the cowl (below the coolant radiator).
The increase in airflow volume going through the cowl looks to be an increase of 300% over the legacy cowl. There is the additional opening for the coolant radiator also 3 additional NACA scoops and louvers, and a bigger exit to accommodate all that.
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  #27  
Old 08-18-2022, 10:50 AM
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Quote:
Originally Posted by seagull View Post
The increase in airflow volume going through the cowl looks to be an increase of 300% over the legacy cowl. There is the additional opening for the coolant radiator also 3 additional NACA scoops and louvers, and a bigger exit to accommodate all that.
Lucky sobs! lol.

can I retrofit that cowling to my ULS?! lol.
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  #28  
Old 08-18-2022, 11:37 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by seagull View Post
The increase in airflow volume going through the cowl looks to be an increase of 300% over the legacy cowl. There is the additional opening for the coolant radiator also 3 additional NACA scoops and louvers, and a bigger exit to accommodate all that.
It doubtful that it is that much of a difference.
If it were, the RV-12iS would be quite a bit slower just from the cooling drag difference.

For the purpose of adding a bit more clarity to my other post, the 12iS cowl wasn't redesigned in order to correct a cooling deficiency that exists on the ULS RV-12. It was to deal with the higher cooling requirements that exist in the 912iS, compared to the 912ULS.

There are numerous differences between the two engines that increased the cooling needs for the 912iS engine. One that very few people know about is the cooling of the charging system. Many people know that the 912iS has dual generators that provide for a lot more ships power capability than the ULS has, but few people know that they are cooled by the engine oil. This alone puts a much larger cooling load on the oil cooling system.
There are other differences as well. All which have some increased level of load on the oil cooling.

In very hot conditions, it is normal for oil temps on the iS engined airplanes to get to the upper end of what is acceptable during climb (refer to the Rotax operating manual... short term operation in the yellow range is not a criticle situation).
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Scott McDaniels
Hubbard, Oregon
Formerly of Van's Aircraft Engineering Prototype Shop
FAA/DAR, EAA Technical Councelor
RV-6A (aka "Junkyard Special ")

Last edited by rvbuilder2002 : 08-18-2022 at 11:41 AM.
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  #29  
Old 08-18-2022, 12:32 PM
seagull seagull is offline
 
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I do not agree the 912is produces that much more heat than the ULS, especially enough requiring 3X more airflow. Maybe the voltage regulator produces a bit more but it has a dedicated NACA scoop to keep it cool.

The difference in amp draw from the legacy to the current 912is model is probably not 42 amps but I will use that number since it is easy. To produce 504 watts (12 volts @ 42 amps) of power requires .373 hp. That is not creating enough additional heat to consider.

Heat for our purposes is wasted energy, since the 912is is producing the same 100hp as the ULS on the same or less fuel intake it isnít wasting much energy (producing extra heat).

Heat is a form of energy, you donít produce it for free, either you use fuel or take from HP to produce it.

The 3X cowl opening area will produce some drag but a cooler running engine is more efficient and that may make up for the small speed loss. There are a few small improvements in the airframe that may also offset the slight speed loss.

I HAVE increased the airflow into the cowl, I DID see a small increase in cooling, I did NOT notice an airspeed loss.

I opened the oil door 1 Ĺ ď, sealed 3 sides so only the front was open. The area of the opening is small about 4.5 square inches. This forced a lot of air over the top of the oil tank and out the cowl bottom taking some heat with it. Clearly not the most efficient method or position for an inlet but it was just a test. I am not going to keep it that way because it looks terrible, I donít want to cut into the cowl either and mess up a good looking plane. I am going to go in the direction of a more efficient oil cooler.
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  #30  
Old 08-18-2022, 12:55 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by seagull View Post
I do not agree the 912is produces that much more heat than the ULS, especially enough requiring 3X more airflow.

I HAVE increased the airflow into the cowl, I DID see a small increase in cooling, I did NOT notice an airspeed loss.

I opened the oil door 1 Ĺ “, sealed 3 sides so only the front was open. The area of the opening is small about 4.5 square inches. This forced a lot of air over the top of the oil tank and out the cowl bottom taking some heat with it. Clearly not the most efficient method or position for an inlet but it was just a test. I am not going to keep it that way because it looks terrible, I don’t want to cut into the cowl either and mess up a good looking plane. I am going to go in the direction of a more efficient oil cooler.
You are of course free to not agree, but that doesn't make you correct.

It is well known within the industry that the iS engine has higher cooling requirements than the ULS does. One interesting indicator of this is that the oil temp on a 912iS warms up waaay faster than it does on a ULS. 912iS installations do not utilize an optional oil cooler by-pass to speed up oil warm up because even in very cold temps it warms up very quickly without one.

There are many test points for temp. values spelled out in the install manual that must be met. We went through many hrs of testing and iterative modifications to get to the point where the RV-12iS met all of them.

The mod you did with your oil door shouldn't have help at all with cooling because it is adding extra air to the cowl plenum aft of the heat ex changers. This will have the net effect of reducing the delta P (pressure difference) across the radiator and oil cool, effectively reducing their cooling efficiency. So even if you were adding some cooling to the oil with some colder air blasting on the oil tank, your are at the same time reducing the effectiveness of the oil cooler.

One additional tidbit of info.... the louvers on the front top of the RV-12iS cowl aren't for additional cooling in flight. In fact, because of their location (in a rather high pressure area), we don't think there is any outflow during high speed flight. Their purpose is to act as passive vents to let hot air escape when the airplane has been parked and shut down. The ign. coils are directly below the louvers, and there is a max. temp for them that must not be exceeded. The louvers made the RV-12iS meet that requirement.
__________________
Opinions, information, and comments, are my own unless stated otherwise.
You are personally responsible for determining the suitability of any tips,
ideas, etc. obtained from any post I have made in this forum.


Scott McDaniels
Hubbard, Oregon
Formerly of Van's Aircraft Engineering Prototype Shop
FAA/DAR, EAA Technical Councelor
RV-6A (aka "Junkyard Special ")

Last edited by rvbuilder2002 : 08-18-2022 at 01:27 PM.
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