Franklin 220 oil pressure

[8714yy]

I own a 1968 M4 220C (N2031U from Aero101, great plane, by the way!) and since I have had it, the oil pressure, when warm, always runs right at the bottom of green at yellow/green interface from pilots position. it may run a little higher with more oil but only temporarily as the oil level evens out to about 6.5 qts when filled higher. It only burns about one qt per 10 hours. Is this normal or does it indicate a possible problem? the engine has about 225 hrs since new. I have my own thoughts but, please feel free to express opinions, like I have to say that.

[RT]

The 1st thing to do is check the oil pressure with a real gauge.

[montana maule]

You say it has 225 hrs. since new or do you mean overhaul? The new style PZL Franklin had an oil pump that is at least 50% larger than the old US built Franklins. That was to take care of the low oil pressure problem that seemed to plague the original engines.

If the engine was overhauled in the last few years you more than likely have a pump that meets service limits not new tolerances, since new certified new parts aren't available. The last overhauled engine I had wouldn't hold oil pressure in the green after the oil warmed over 125F. I tried everything and then dissasembled the pump and measured the parts. All tolerances were "servicable" by the book, but not enough to produce the needed oil pressure.

That's the problem with the Franklin engine. NO new certified parts, everyone is searching for "serviceable " parts to put engines back together and a few people out there selling bogus parts. For the last 10 years I've heard the " We are just about ready to start producing new parts" story.

I have heard of people plumbing in the new type of PZL pump, but it's not a direct replacement. That's if you can find a "servicable" newer style.

[aero101]

David-
If you want to see more oil pressure(Green Arc 55-80PSI), try Aeroshell 100W. This was a new PZL engine, not overhauled and with the 20w/50 Phillips X-C is a normal condition and you may find it a little higher with an aftermarket, more accurate indicator. Can adjust oil pressure by shimming the engine oil pressure spring which is located on the aft side of oil pressure bypass valve and it's the smaller spring size, the larger spring on fwd side is for oil cooler pressure bypass. Another question is how high is it when it's cold outside? Bottom line is that is should remain in green arc, hot or cold oil, as too high pressure can create problems too. I usually adjust oil pressures to top of green arc when cold, and don't worry about hot unless it's below published lower limit? Also how hot is temp running when you're seeing bottom of green?

[a64pilot]

The 1st thing to do is check the oil pressure with a real gauge.

I'll second that, if nothing else temporarily plumb in a direct reading automotive gauge
Usually excessively worn parts, pumps etc usually show up as way low pressure at low RPM, sometimes low operating pressure may be as simple as the oi pressure relief valve, but don't do anything until you verify the gauge.

[8714yy]

Thanks, i'll check the gauge which was my first instinct. The pressure is same at idle as in cruise for the most part so hopefully it's only the gauge. it remains in the normal operating range, just at the bottom.

[a64pilot]

Usually excessively worn clearances show up as really low oil pressure at low RPM once the engine is fully warmed up because the oil pump can't supply enough volume to keep the pressure up when it's turning slow, this is from either a worn engine or worn pump.
I'm betting if your oil pressure is almost the same at cruise and low RPM, either your gauge is wacked out, or your relief valve is set way too low.
I'm betting your gauge.
I had a customer who spent thousands of dollars installing additional oil coolers, cutting holes in his cowling etc. When I showed up and turned his battery switch on and saw an oil temp of 80c on a stone cold engine, I knew I had found the problem. Almost made him sick.
When you fix it, let us know what it was

[8714yy]

David-
If you want to see more oil pressure(Green Arc 55-80PSI), try Aeroshell 100W. This was a new PZL engine, not overhauled and with the 20w/50 Phillips X-C is a normal condition and you may find it a little higher with an aftermarket, more accurate indicator. Can adjust oil pressure by shimming the engine oil pressure spring which is located on the aft side of oil pressure bypass valve and it's the smaller spring size, the larger spring on fwd side is for oil cooler pressure bypass. Another question is how high is it when it's cold outside? Bottom line is that is should remain in green arc, hot or cold oil, as too high pressure can create problems too. I usually adjust oil pressures to top of green arc when cold, and don't worry about hot unless it's below published lower limit? Also how hot is temp running when you're seeing bottom of green?

The pressure is significantly higher when cold, say 70-75psi and operating temp is mid range say 170 or so. Sounds like it is operating/behaving normally. Next time I'm up in Fairbanks, I'll call ahead and maybe have you throw a gauge on it to check. I owe you a lunch too if I recall.

[cs409]

Your last post left me with questions. The
Numbers you posted, was this from your
Gauge in the plane or was this from a manual
Gauge hook up to get a second opp. ?

Just wondering.

[aero101]

David

Unless there's been a considerable change over the past 50-75hrs that you've put on it, I think all is normal, but hooking up a direct reading gauge would verify that if you'd like. When you headed up this way again?

[8714yy]

I agree, no changes and I would imagine as temps drop I don't want a more viscous oil.

I may be headed up next week, I'll give you a call tomorrow (friday 23 Sep) if I'm coming up.

By the way, the plane operates great and I'm getting a much better feel for it as I approach the 100 hr mark in the plane. regular flying makes for steady improvement.