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  #11  
Old 06-06-2022, 02:42 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
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Quote:
Originally Posted by Toobuilder View Post
The reason I recommend the viscosity valve as a troubleshooting step is because it eliminates the well known issue of poor Vernatherm plunger sealing. Even with good sealing, there is still a lot of leakage with a Vernatherm, and most are far from "good". The viscosity valve plugs that leak path and lets you evaluate the rest of system performance without polluting the results with some unknown % of internal leaking. The viscosity valve plunger is $30 bucks from Spruce if you cant find one laying around an A&P's junk drawer.

Its a lot cheaper and easier than plumbing a new cooler.
Michael, could you elaborate a little on what the viscosity valve is and where it goes? A search on Aircraft Spruce turned up nothing.

I've never heard of this, and probably many others haven't either. It sounds like I might benefit from one.

Thanks.
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  #12  
Old 06-06-2022, 02:56 PM
jclemens jclemens is offline
 
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Location: FL
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He is referring to the spring and plunger shown at the top of the accessory housing in this picture.
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  #13  
Old 06-06-2022, 02:57 PM
jclemens jclemens is offline
 
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ehh that picture is pretty small. Here is the service instruction it came from.
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  #14  
Old 06-06-2022, 04:16 PM
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BillL BillL is offline
 
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Location: Central IL
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The james plenum does not have a very good diffuser function from the inlets to the heads, and is a little restrictive at front face of the heads.

Tweaking category - radius for exit flow from aft baffle to your cooler "hole" a nice radius like a penny or nickel dimension will help. Due to the low aft position of the plenum (for RV4) it is pretty close to the head and can get warmer air ingested. Any picts would help, but you should get the gist here.

Shifting the balance from engine fins to cooler fins. There is a lot of air going by the barrels on the inside and not giving a lot (if any) extra cooling. Being a parallel valve you can add some wrap up the inside about half way up with no risk and will measurably shift the airflow to the cooler. No effect on the CHT.

I see your test was extreme on purpose, but just dropping the RPM to 2500 will greatly reduce the HX to engine and oil. Climbing at 100-105 kts on hot day, and maybe dropping MAP to 25 @ 400 ft then back in at 3000 (cooler air). Are options to keep the OT in line.

I don't think the summit thing is going to do much good or fit in your FWF very well.

You mentioned cowl flap (?) , do you have the standard James IO cowl exit?

I am assuming you have done the extreme sealing of all the baffle leaks that allows air bypass fins and escape unheated?
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  #15  
Old 06-06-2022, 05:11 PM
jclemens jclemens is offline
 
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Quote:
Originally Posted by BillL View Post
Being a parallel valve you can add some wrap up the inside about half way up with no risk and will measurably shift the airflow to the cooler.
Can you elaborate on this? Pics would help if you can find some.

Of course I could pull the power back, what fun is that? Planes very flyable as it is, and the oil temp is manageable. Just trying to make it so you don't have to think about it. Standard long sam James cowl, added an electric cowl flap from antisplat aero. It helps, delta p goes from 2.8 to 3.2 with it open. Yes, I have used many tubes of sealant.
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  #16  
Old 06-06-2022, 06:31 PM
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bjdecker bjdecker is offline
 
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Default two things to try...

Two things...

1. Change the oil cooler to the HE version or the actual Stewart Warner/Southwind/Meggit-Troy version with -[solid]- end tanks (10610R or 10611R whatever fits) ; the fin spacing is different than the clones.

2. Change the diffuser on the front of the oil cooler from the flat-faceted version into a custom molded shape without any edges to trip up, or induce turbulent flow.
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  #17  
Old 06-06-2022, 08:47 PM
scsmith scsmith is offline
 
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Quote:
Originally Posted by jclemens View Post
ehh that picture is pretty small. Here is the service instruction it came from.
Thanks. So I gather that Michael (Toobuilder) is suggesting that the plunger and spring be installed. If I understand its function, it forces oil through the cooler always, unless the oil pressure is too high (as it would likely be when the engine is cold) and only then bypasses the cooler. I am inferring from Michael's suggestion that very often Vernatherms don't seal fully and always allow some oil to bypass the cooler, whereas the pressure valve would more reliably force all the oil through the cooler.

Does that about cover it?

At one time, I convinced myself that my Vernatherm was closing fully, but I don't remember how I did that. I do remember heating it in a pot of water on the stove and measuring the extension of the cone on the end, and I do remember seeing slight witness marks on the cone all the way around, suggesting that it was seating properly in the housing.
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  #18  
Old 06-06-2022, 08:54 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by scsmith View Post
Michael, could you elaborate a little on what the viscosity valve is and where it goes? A search on Aircraft Spruce turned up nothing.

I've never heard of this, and probably many others haven't either. It sounds like I might benefit from one.

Thanks.
Yep, Jake shows it. This scheme is also used with people who use a ball valve to control oil flow for winter ops. Several good threads on it here.

Though the plunger itself is cheap, the specified spring is insanely priced. I went to the local hardware store and found a suitable replacement for a fraction of the Lycoming price.


EDIT: Yes Steve, you have the concept down cold.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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Last edited by Toobuilder : 06-06-2022 at 08:56 PM.
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  #19  
Old 06-07-2022, 08:21 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by scsmith View Post
Thanks. So I gather that Michael (Toobuilder) is suggesting that the plunger and spring be installed. If I understand its function, it forces oil through the cooler always, unless the oil pressure is too high (as it would likely be when the engine is cold) and only then bypasses the cooler. I am inferring from Michael's suggestion that very often Vernatherms don't seal fully and always allow some oil to bypass the cooler, whereas the pressure valve would more reliably force all the oil through the cooler.

Does that about cover it?

At one time, I convinced myself that my Vernatherm was closing fully, but I don't remember how I did that. I do remember heating it in a pot of water on the stove and measuring the extension of the cone on the end, and I do remember seeing slight witness marks on the cone all the way around, suggesting that it was seating properly in the housing.
I did this when I suspected a vernatherm issue and it helped to rule out the vernatherm. There are two potential issues with them. First, is problems in the wax area and that can be tested by heating and observing the growth length of the plunger from room temp to 185*. The second is poor sealing. On some oil filter adapters, the holes are too big and it is hard to get it on in proper alignment with the hole that the plunger sets into (Lyc really should have put an index pin in that interface). Witness marks are a good guide and there is an SI for re-cutting the hole if it is mis-shaped or damaged.

FYI, There is a very close tolerance fit in the wax area. I had one that didn't meet the growth length spec. Upon disassembly, found some carbon build up in that area (it sees a lot of oil). After cleaning and re-assembly, it met the spec and is still working 800 hours later. It is my belief that many failed VT's can be repaired, though my experience sample size is still just one.

Larry
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Last edited by lr172 : 06-07-2022 at 08:28 AM.
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  #20  
Old 06-07-2022, 08:34 AM
KatanaPilot KatanaPilot is offline
 
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Default More info requested

Just trying to confirm what is being suggested -

Install BOTH a Vernatherm AND a viscosity valve (spring and plunger)? If I read the SB correctly, you remove the viscosity valve when you install the Vernatherm.

Does anyone know if you can do this on the standard adapter as well as the B&C angled adapter?
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