Summer temperatures and cooling

[Bryan Cotton]

Hose on the top:

hose top connection.png (744.99 KiB) Viewed 9713 times

Hose on the bottom:

I'm close to reassembly. Looking forward to flight test.

I've also got another set of CB Performance oil control springs on the way. Thanks 429TB for the info.
111-115-421a Oil Relief Spring - OEM
111-115-425a Short Oil Relief Spring - OEM

~$12 shipped.

[bvolcko38]

Very late seeing this thread. I have top mount oil cooler with the Sonex supplied baffling. Unless its really hot outside, I duct tape some of my oil cooler to prevent over cooling

[Bryan Cotton]

Here is the reverse scoop installed on the right side. I'm not doing bodywork and paint until it is proven. The exit was initially ugly aerodynamically. I had to taper the cowl to a knife edge and then put a piece of 0.016 over it. I actually like this part.

scoop installed.png (615.92 KiB) Viewed 9666 times

[pfhoeycfi]

I've also got another set of CB Performance oil control springs on the way. Thanks 429TB for the info.
111-115-421a Oil Relief Spring - OEM
111-115-425a Short Oil Relief Spring - OEM

~$12 shipped.

What is the benefit of these springs?

[Bryan Cotton]

What is the benefit of these springs?

See thread:
viewtopic.php?f=7&t=7312

Reader's digest version:
The VW oil system has two spring/plunger systems. The one at the end of the line regulates the overall oil pressure. When the pressure gets low (which happens as the oil heats up) the one at the front of the line diverts oil to the oil cooler.

So, like me, if you have high oil pressure you may not be getting enough oil flow through the cooler.

My pressures had been about 70 psi in cruise, instead of 40-50. I shortened the spring in the back of the motor and got it down to 60ish. New member 429TB bought those springs and had good results of lower oil pressure and temperature. It's a really easy thing to try.

[pfhoeycfi]

Fyi something to consider. I measured the cooling air PD across the engine from above the engine to near the right side exit.
The values were...at IAS
2" at 65 mph
2.5" at 75 mph
3" at 85 mph
3.5" at 95 mph
4" at 100 mph
4.5" at 110 mph
5" at 120 mph

I used an old school manometer and my IAS is what it is. The values are rounded. Another airplane will likely have different results. But its a baseline. Attempts at flow improvements will yield greater (hopefully), the same or lower DPs at these speeds. I'll likely confirm the numbers before I make any changes. I'm also going to check the DP across the oil cooler.

[Bryan Cotton]

Peter, great data, thanks for posting!

I did flight test my oil cooler extraction scoop today. There was slight improvement - oil temps around 215-217 in cruise.

I really want to get my oil pressures in spec. This should be 40-50 psi per the Aerovee manual. I believe that is a key part of cooling as the oil flow through the cooler is a function of pressure dropping as the oil warms up. That is my next step. I believe my plungers & bores are good as I have had them out a few times and checked/polished them. My new springs should be here next week. My oil pressures had been running at 70psi in cruise, and 60 after I shortened the spring.

If the new springs fix the oil pressure but the temps are still high, I'll add the second reverse scoop. Right now I have the left side exit tube taped over and just have the one hose on the right side.

[Bryan Cotton]

I've installed the springs and see at least a 10 psi drop for startup and ground running. We had neither weather or daylight to fly it.

My pressures had been 70 at startup and 60 at 200-220F oil temps in cruise. Startup tonight was 60 psi and stayed there for a 5 minute ground run, including WOT at the end. Max oil temperature was under 110, so I believe that will be a lower pressure as the temperature goes up.

The new oil pressure spring is noticably softer and about the same length as the original chrome looking spring I trimmed. New oil cooler spring is about a cm longer and similar stiffness. I'm cautiously optimistic.

[Bryan Cotton]

Too many tornado warnings to fly this evening. Hope I can test my new springs tomorrow. I made this cartoon of the VW oil system:

[Area 51%]

I believe the oil that has passed through the cooler gets directed into the oil galleys and not directed to the sump.

Also, now when I read your posts, I hear Mel Blanc's voice. .