Rv-10 oil cooler size

[KatanaPilot]

Resurrecting a slightly stale thread (and having read many of the previous threads on high oil temps) -

I had been fighting higher than desired CHT's on my 9.5 to 1 PV IO-540, but have had some success in getting them where they should be with a combination of (1) additional time on a new engine (2) new baffle seals (3) careful RTV-ing of air leaks (4) a cowling exit ramp and (5) modifying the SDS fuel map at high power settings. I now need to replace the air dam in front of cylinder #1 to get those temps up a bit and help #3 & 5.

What I have been unable to accomplish is any reasonable reduction in oil temps. I have the largest oil cooler that Airflow makes (2008X) mounted horizontally on a custom mount, with Airflow designed, 5" 3D printed baffle mounted duct and oil cooler plenum.

Based on some recent testing where the oil temps did not change during a prolonged descent at reduced power, nor did they change with some closure of the oil cooler duct butterfly (but the #6 CHT did decrease as expected) - I'm beginning to suspect the Vernatherm isn't opening (closing) fully with increased oil temps. My RV-7A shows a very quick change in oil temp with modulation of the duct butterfly.

The temps were about 205 cruising LOP at 24 squared at 7500" with OAT 13 C. I know this is well within limits, but I think I should be able to attain lower temps given the size cooler I have and the 5" duct feeding it (even with piston squirters).

I'm contemplating switching to a viscosity valve and using the duct butterfly to modulate airflow through the cooler vs. a ball valve to regulate flow. I'm going to instrument the input and output of the oil cooler to check the delta T across it - maybe that will give me some idea of what is or isn't happening.

Anyone have some sure fire tips on resolving this?

[Kyle Boatright]

Two things:

1) Can you swap vernatherms to isolate that issue? I'd do that before I reengineered the system to something the next guy is gonna have to figure out.

2) I'd like to see pictures of your exit ramp.

For what it is worth, I installed an enlarged cooler on my (stock) engine in the -10. I see 200-205F on hot days. Higher on climb if I start with a heat soaked engine from something like a fuel stop on a 95F day.

[lr172]

Originally Posted by KatanaPilot

Based on some recent testing where the oil temps did not change during a prolonged descent at reduced power, nor did they change with some closure of the oil cooler duct butterfly (but the #6 CHT did decrease as expected) - I'm beginning to suspect the Vernatherm isn't opening (closing) fully with increased oil temps. My RV-7A shows a very quick change in oil temp with modulation of the duct butterfly.

If the vernatherm was stuck and not moving, a reduction in power along with increased airflow through the cowl should decrease oil temps even if a small amount though it may take a few minutes. With squirters, OT is going to more closely follow CHTs, as the oil is doing a much larger job of piston cooling than a non-squirter engine. I don't have piston squirters and get to 210 at the top of a ROP climb to above 12K and that is with a fully closed VT. If yours was stuck open, even partially, you shouild be WAY higher than that with squirters.

I would start by confirming that the OT sensor is reading accurately. The fact that it matches ambient at start up is NOT necessarilly an indication that it will be accurate at 200*. Do you have a 90* oil filter adapter? Those have a reputation of poor alignment and therefore the VT does not fully seat on the bore, meaning less than 100% of oil is going through the cooler. You can pull the VT and look for a complete circular witness mark on the cone. Less than full ciccumference mark = incomplete sealing and oil bypassing the cooler. There is an SI for dealing with this if it is wear on the crankcase that is causing it. A tool can be made to better align the filter adapter if that is the cause.

Larry

[andoman]

[quote=Kyle Boatright;1687901]

2) I'd like to see pictures of your exit ramp.

[KatanaPilot]

Thanks for the additional information. I'm going to check the temperature sensor, Vernatherm and it's seat first. I have the stock Lycoming thermostatic housing - no 90 degree adapter. I use a Challenger/K&P remote oil filter mounted on the firewall.

As to the exit ramp, I can send you a picture - but it's on a Showplanes cowling. If you have the stock Van's cowl, this won't do you much good.

[lr172]

Originally Posted by KatanaPilot

Thanks for the additional information. I'm going to check the temperature sensor, Vernatherm and it's seat first. I have the stock Lycoming thermostatic housing - no 90 degree adapter. I use a Challenger/K&P remote oil filter mounted on the firewall.

As to the exit ramp, I can send you a picture - but it's on a Showplanes cowling. If you have the stock Van's cowl, this won't do you much good.

While the VT is out, best to test it for full movement. Heat a can of oil to 190*. Measure the length from end to end. Put VT in oil for 1-2 minutes and measure again. It should grow in length. IIRC, the min. growth is .160" but don't trust my memory. It is in VAF somewhere. I was able to save one that wasn't moving enough. PUlled it apart and cleaned out a bunch of varnish type junk inside of it. Still working 1000 hours later.

[ewumnrr]

During my engine test stand first run, I had two cylinders (#1 and #5) getting hotter than the others. The root cause was an inadequate ground of the SDS ECUs. At higher rpms, the test stand thin single ground wire couldn't carry the return current of the injectors (fused at 5A each) that go through the ECUs.

Check also the SDS stainless steel fuel injector adapters that are screwed into the cylinder head. They can come loose if not properly installed: torqued to 60 (older manual listed this as an option) instead of tight plus 1 1/2 turns (current manual's only option). If so, the particular cylinder can run too lean.

[KatanaPilot]

Originally Posted by ewumnrr

During my engine test stand first run, I had two cylinders (#1 and #5) getting hotter than the others. The root cause was an inadequate ground of the SDS ECUs. At higher rpms, the test stand thin single ground wire couldn't carry the return current of the injectors (fused at 5A each) that go through the ECUs.

Check also the SDS stainless steel fuel injector adapters that are screwed into the cylinder head. They can come loose if not properly installed: torqued to 60 (older manual listed this as an option) instead of tight plus 1 1/2 turns (current manual's only option). If so, the particular cylinder can run too lean.

Interesting issue. Glad you were able to isolate the problem and solve it. I'll double check the wiring and the injectors next time the cowling is off. Thanks for the insight.

My #1 cylinder runs pretty cool right now. I had removed the air dam in front of it, but I'm testing again with an air dam. Picture is from testing yesterday with SDS running LOP. Really love the individual cylinder trim capability.

Oil temperature is still higher than desired, especially during climb and at higher power settings. With the cooler I have and 5" duct with butterfly valve, I should have better and more immediate control of the temps - but I don't.