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  #1  
Old 10-02-2012, 08:07 PM
rwtalbot rwtalbot is offline
 
Join Date: Feb 2006
Location: Sydney, Australia
Posts: 255
Default Should I Remove Piston Oil Squirts?

I'm currently in the process of changing out my Group B ECI Cylinders (AD 2009-26-12).

Over the last 350 hours I have had issues with high oil temperature. I knew the engine had cam squirts but assumed no piston oil squirts. So imagine my surprise last week when I pulled the cylinders and the LAME commented that I had piston oil squirts.

I?m wondering if I should bite the bullet and remove these during the top overhaul? Has anyone done this and what was the effect on oil temps / CHTs? While I can see the advantages to reducing oil temperatures I don't want to just move the issue on to high CHTs.

A few other details about my installation:
The engine is a 180 HP Mattituck IO-360 with P-Mags. I have installed a Sam James Plenum.

I have tried many things to reduce temps including sealing baffles, fitting louvers, vernatherm testing, timing adjustments etc. Finally in desperation I installed a RV10 cooler and attached it to the firewall with a 4" SCAT hose.

All the work I have done to date has resulted in marginal oil temperature. I generally cruise 30F LOP and at that sort of power setting I see 180-200F oil temperatures. If I cruise ROP, the oil temperature rises to around 210-220F on an average day. On a really hot day (100F) I have seen oil hit 230F in the climb out.

CHTs have been reasonable - around 330-345F in LOP cruise. However, #4 runs about 30F hotter than the rest - no doubt due to the large volume of air being extracted from the baffling right behind the exhaust valve.


You can see what all the fuss is about below in the upper RHS of #1 cylinder.




A picture of my large cooler installation during assembly



Thanks for any help.

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  #2  
Old 10-02-2012, 08:24 PM
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Wesael Wesael is offline
 
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Default

Lycoming has no problem with 230 deg oil on climb out. I would not call that marginal.

I would leave them installed.
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  #3  
Old 10-03-2012, 12:15 AM
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Neal@F14 Neal@F14 is offline
 
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Location: Wichita Falls, TX
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Default

I'd keep the piston oil squirters too. With that large of an oil cooler, you should be seeing better oil temps, even with the piston squirters. Do you have a diverter plate in front of the duct outlet in the baffle to keep hot air from the #4 cyl exhaust valve area of the head from entering the oil cooler's duct? Fabricating some kind of curved or angled plate there to ensure that it captures cooler air from the upper part of your plenum and directing it into your oil cooler duct might help if the air being fed to the oil cooler is currently passing over the exhaust valve area fins of the cyl head and getting heated up too much from that.
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  #4  
Old 10-03-2012, 12:29 AM
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erich weaver erich weaver is offline
 
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Location: santa barbara, CA
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Default

The way you describe cruising LOP with 180 - 200 degree oil temps make it seem like a bad thing. This is exactly what you should be doing and this oil temp range is IDEAL. Your ROP temps are on the high side, but not unheard of. My suggestion is to stop cruising ROP.

Erich
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  #5  
Old 10-03-2012, 01:24 AM
rwtalbot rwtalbot is offline
 
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Location: Sydney, Australia
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Quote:
Originally Posted by Neal@F14 View Post
Do you have a diverter plate in front of the duct outlet in the baffle to keep hot air from the #4 cyl exhaust valve area of the head from entering the oil cooler's duct?
No I don't. I had considered this as an option, but just not tried it as yet. I suspect it would make my #4 cylinder run hotter. However it may infact improve both as it would allow a straight path of air past the exhaust fins and provide cool air to the cooler. On the other hand, Van's installation also has the cooler receiving potentially hot air so how much of a factor could this really be?

My issues at this point are that my oil temps on hot days and ROP are not where I want them. The cooler is huge for its application. I would like to remove the weight and/or improve the oil temps.

While I nearly always run LOP, racing flat out would be out of the question. That doesn't sit well with me so I want to improve the installation. I know removing the squirts will lower the oil temps. The question is how much and what the impact will be on CHTs.

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  #6  
Old 10-03-2012, 01:35 AM
PCHunt PCHunt is offline
 
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Location: San Diego, CA
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Default Consider this

With the oil squirts, you are removing heat from the engine by transferring it away in the hotter oil.

If you eliminate the squirts, the oil will be cooler, but the heat will stay in the engine and the engine metal itself will be hotter.

Not sure which is better, but IMHO, removing heat from the engine is a good thing.

No free lunch. All the heat generated has to go somewhere.

Are you sure you are getting really good airflow through the big oil cooler? If you have back pressure due to lack of flow out the bottom of the cowl, even if you have large air ducts to the oil cooler, it is possible to have not enough mass airflow past the oil cooler to carry away the heat.
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  #7  
Old 10-03-2012, 06:47 AM
chaskuss chaskuss is offline
 
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Location: SE Florida
Posts: 1,510
Default Try to improve the pressure differential through the oil cooler

Quote:
Originally Posted by PCHunt View Post
snipped
Are you sure you are getting really good airflow through the big oil cooler? If you have back pressure due to lack of flow out the bottom of the cowl, even if you have large air ducts to the oil cooler, it is possible to have not enough mass airflow past the oil cooler to carry away the heat.
As Pete mentioned above, the area you located your oil cooler in may have a relatively high pressure. I would suggest that you build an outlet duct for the oil cooler, aim in towards the cowl air outlet area, where the pressure will be lower. Flow through the oil cooler is affected by the pressure differential between the air inlet and the outlet.
At the least, temporarily install some pressure sensors to determine what your current inlet and outlet pressures are. You might want to check out the threads below.

http://www.vansairforce.com/communit...cts#post391630

http://www.vansairforce.com/communit...e+differential

Charlie
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  #8  
Old 10-03-2012, 06:50 AM
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rocketbob rocketbob is offline
 
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I would be looking more at the Sam James cowl and plenum because with oil squirters your CHTs should be at least 20 deg. cooler with squirters in place.
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  #9  
Old 10-03-2012, 07:12 AM
n700jl n700jl is offline
 
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Location: McCordsville IN
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Talking oil squirts

I personally do not like oil squirts. The reason is! The oil control ring can not handle the amount of oil that is being applied to the bottom of the piston. This in turn brings up oil consumption. Have you checked the Vernatherm for proper operation? Do you have a restriction in the oil system? On my RV-6 I moved the oil cooler to in front of the front left cylinder laying down flat on the intake ramp. Problem solved! This is the same location that is used on Pitts and some Piper aircraft.
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  #10  
Old 10-03-2012, 08:34 AM
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DanH DanH is offline
 
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Keep the squirters. Theory says removing them will raise your CHT. I'd much rather have low CHT and work on oil temperature.

You are feeding the oil cooler duct with warm air. I've measured roughly 15F above OAT at the oil cooler face in a similar ducted system, but my back wall inlet was a bit higher in relation to the cylinder. You may be more like 20F higher than OAT, but the only way to know is to rig a temperature sensor. Easy to do and beats the snot out of guesswork.

A air deflector at the cylinder may or may not help. I say not much; tried and measured.

The suggestion to relocate the cooler (or a cooler duct inlet) to the inlet ramp is a good one....lower inlet air temperature and higher pressure.

The transition plenum at the oil cooler face must be sealed to the cooler.

The lower cowl volume is slightly pressurized, but not a lot if you have a standard outlet size and louvers. A duct from the cooler to the cowl exit would need to extend all the way to the freestream. Most of the pressure drop between lower cowl interior and freestream is in the last few inches. Merely pointing a duct at the cowl exit (but ending it inside the cowl well short of the exit) is an attempt to increase cowl exit velocity (drag reduction), not a way to increase cooler mass flow (cooling improvement).
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