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Low Oil Pressure today in my RV7A

tom paul

Active Member
I've had the plane about a week. It has a Titan IOX-360-A4H1N.
All looked good on start, run-up, take off and initial cruise, but after doing some flight review maneuvers, such as slow flight, stalls, steep turns, I noticed that the oil pressure was at 55, with manifold pressure up around 22 and tach about the same. It quickly dropped to 50, at which point we decided to return to the field and land asap. The oil pressure snuck back up to 55 or 58 on the way home, but never got into a more comfortable zone.
I am now beginning the process of diagnosing and research. I pray that I am not due for a rebuild or something else very pricey. The engine has just over 1200 hours on it.
There are six quarts of AeroShell 20-50 in the engine.
The prior owner has advised that an oil and filter change might correct it. It has been about 43 hours since the last oil and filter change.
I am looking for advice on how to diagnose the issue, and potentially trace it to a sender/gauge issue. Worst case, it points to a need for a rebuild, and while I truly hope that isn't the case, I do want to be safe, as I fly out of an airport with no places to land on climb out, so I need to minimize the risk of engine failure.
 
Do you have an engine monitor where the data can be downloaded? If so, check the data and see if this is normal behavior, or something new. You can upload data to savvyanalysis for free and see all of the prior flights.

The pressure relief valve can be adjusted with adding washers to increase the oil pressure.
 
What was the oil temperature when the pressure was low? High oil temp will cause the pressure to drop. Was the pressure ok on previous flight?
Good Luck,
Mahlon
 
likely culprits are a bad saender or wiring isssues between sender and gauges. Best bet is to install a mechanical, non electric oil pressure gauge and test fly to rule in or out actual low pressure in the engine.

About a 0% chance that an oil and filter change will resolve it.

Do you have enough time to know the normal pressures? Are they low across the board? If 20 psi low at cruise, idle would likely be very low if the pump was going.
Larry
 
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Oil Pressure

The type of oil pressure sender that I have depends on a good ground. I have the ground wire hose clamped to the sender and then direct to airframe ground. Poor ground and also low voltage will cause oil pressure to read low. Best to test with mechanical gage but no need to fly to do that. Correct whatever issue you have before further flight.
 
There are a host of possible mechanical failures and faulty indication creators.

It's tough on a newish to you plane.

Let's assume, for starters, nothing is newly broken or just wore out at purchase. Look at the logs. Does the "Summer" oil show as 50 weight/100W? How old is the current oil in months for 43 hours?

The last owner may have not changed from multigrade, which some feel gives less summer cooling. Maybe that's what "change oil and filter" meant. Check the logs.

If your checkout flying overcame the oil cooling capacity and got hot enough, pressure goes down more as you then reduce power to return and land until oil temps cool off. Idle oil pressure warm, cool and hot tell a lot about engines over time, not just in one flight.

Knowing your normal temp/pressure relationship will come in time.

Could need to adjust the oil pressure regulation, could have gotten your flexible baffles misplaced/lost some sealing when last recowling the plane, could have lost proper oil cooler airflow, could be a worn vernatherm or its seat or engine bearings or a stack up of wear combination.

Start in the logs- does the engine oil change from winter multigrade to summer single weight, historically?

Multigrade might be ok at normal flight cross country profile or just flying patterns, but doing a checkout you got the oil hot enough the pressure started to fall. Too slow, too much power vs cooling air, too little exit area, marginal cooler BTU capacity- plane could just normally have marginal/improveable oil pressures/temps.

An oil change to 100W and checking the cut open filter for metals doesn't mean you won't still find what is normal vs acceptable vs worn or needing improvement. It does make a difference in summer, to some and may help going single grade oil.

Did you cut and examine a filter before purchase? Is the multigrade fresh or aged?

AeroShell multigrade is 15W50. Many swear BY and others swear AT it in summer. Those swearing AT it use single weight oil in summer heat.

Phillips is 20W50 in multigrade. Its users seem to stick with it year round, I am one of them, a convert from the Shell dance seasonally to Phillips Victory 20W50 AW year round. I'd use whatever was in the logbook during summer season, for now. Same for oil filter manufacture and part number- baseline from the logbooks for now.

Assuming you can read history in the logs, hopefully changed oil/filter in a prepurchase inspection and no making metal is newly found, your oil pump and idler gears are intact, suction screen clear, all FWF conditions are normal and proper- it might just not enough excess oil cooling for slow speed, extended flight as-is on multigrade. Big assumption, but somewhere to start. Can you find local experienced RV type builders/mechanics?

Like Larry said, it's not truly fixed with an oil and filter change alone. Hopefully you found the limits of heat in the oil cooling system as-is and not an engine issue. You might gain some margin with single weight oil, but that alone is not the full story. It could help restore a normal pulse and blood pressure on the new purchase, then systematically find the updates needed as true cures.

How was it from SoCal to NJ? Did you fly it or have ferried? What were the OP/OT trends? Could it climb max power to 10000' and keep oil temp under say 210 degrees?

Has the oil pressure been rock solid? With electric senders they are good til they are not, could be 1000 hours, can be 40 hours. I've done a bunch of edits, and like Tom says below, the gauge/sender is the easiest to rule out with a temp or added mechanical.
 
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Tom--When a usually 'normal' pressure fluxation occurs, we tell builders to install a temporary KNOWN good mechanical gauge in the system, usually with a tee off the supply side. This isolates the electrical sender, and gives a second reading to compare. If the 2 readings are the same and low, then look for a mechanical issue. If the mechanicl gauge reads more correctly and the electrical is wierd, then look for something electrical --ground, power, even the sender itself.

I defer to the electrical gurus on VAF for more info on that part.
Tom
 
Oil pressure

I always start with a mechanical gauge plumbed into the existing oil pressure line between the engine and the sending unit. Those results will dictate your next move. Agree with the others that oil and filter change is not going to make much of a difference.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
After 150h on the engine I notice fluctuations on my oil pressure (I have an electrical and a second mechanical uma gauge).
I found some dirt on the ball of the relief valve (look like plastic debris).
After cleaning the ball oil pressure came back to normal.
Georges
 
I've had the plane about a week. It has a Titan IOX-360-A4H1N.
All looked good on start, run-up, take off and initial cruise, but after doing some flight review maneuvers, such as slow flight, stalls, steep turns, I noticed that the oil pressure was at 55, with manifold pressure up around 22 and tach about the same. It quickly dropped to 50, at which point we decided to return to the field and land asap. The oil pressure snuck back up to 55 or 58 on the way home, but never got into a more comfortable zone. .

As someone else asked, what was the oil temp? The RV’s with a 360 in them don’t like slow flying and maneuvering at low airspeeds when it is warm to hot outside. The oil temp gets hot, oil pressure will drop. Since you didn’t mention oil temp in the OP, my guess that it may have been high. There is a direct relationship between oil temp and pressure when the oil is hot. In my -6, with a 360 engine, oil temp has to be monitored when doing low speed maneuvers, slow flight, stalls, low speed turns and so on, for more than a couple of minutes.
 
I don’t understand why so much talk on this, Tom (TS) alludes to the simple solutions here.
If you think there is a temperature or pressure issue then double check with a calibrated or ‘known good’ sensor - simple.:)
Then, if the problem still exists, look for other possible causes eg electrical etc.
My .02 cents.
 
Again, I defer to the electrical guru's and you pilot guys. But common sense tells me that if you do some 'steep" turns, it does add alittle extra stress on things. Quite possibly a marginal electrial power or ground for the senders that is now really marginal.
I'd ask if any of the other electrical senders are giving an anomalous reading? That would tell me ( me anyway) that there is some commonality to the issue.
I've even heard of guys insulating the pressure sender manifold from the firewall with that fireblock stuff or RTV and relying on the bolts for the ground. If the sender is screwed into the manifold without a specific ground for the manifold, it "could" be an issue. Again I defer to the electrical experts, but, not all experiment aircraft are the same, dispite premade harnesses, the same senders, etc. The builder is the one that determines al of these little things that over time may become a frustruating problem.

Tom
 
Thread size for OP sender?

This issue disappeared for most of the year, with oil pressure staying around 60 or above, then an annual condition inspection revealed some grounding issues that were corrected. On the first few flights after that, all seemed good. But now had reappeared. I will get a mechanical OP guage to check against. Can anyone tell me the thread size so I order the right one? Titan IOX360. This past weekend I flew from my home base KLDJ to N40 with a buddy for a $100 omelet at the sky manor cafe (yum) OP looked ok on the way there, but just barely, right around 55/58. On the way home it started out at 55 but continued to drop until it was around 45 or a touch less. All else seemed fine, with Oil temp was around 180, so I completed the 10 minute flight home. It was a very hot day and my oil quantity was just under five quarts. I definitely want to sort this out before flying again.
I have a couple of questions about installing a mechanical gage. Should I use a tee and keep both senders attached at the same time so I can compare, or is it better to remove the electronic sender completely first. Should I try to route it into the cockpit so I can read it from the seat while doing a run-up or is it best to just tape it to the windscreen or something like that? I assume I’ll want to spend some time bringing the temps up and running at a cruise rpm to get a valid comparison. If I don’t use a tee, I guess I’ll just run it with the current sender, then shut down and switch to the mechanical to compare.
 
Hi Tom, someone will chime in on your mechanical oil pressure sensor questions I'm sure. Different direction - have you or the previous owner inspected/cleaned the oil suction screen? This has caused low oil pressure and even total engine failures.
 
Should I use a tee and keep both senders attached at the same time so I can compare, .

This is what I would do. Should be able to compare both readings on the ground. With intermittent problems, you need a direct comparison to determine health of elec sender. Turning it off then on again doesn't gaurantee the same pressure, especially if you actually have a mechanical oil pressure issue, which can't be ruled out yet. It shouldn't be necessary to go flying to get a comparison. Also, tap the elec sender with a screwdriver as you observe. If readings start changing while tapping, that confirms a failing unit. Intermittent problems are sometimes vibration related with elec components.
 
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Oil Pressure Fitting

The 1/8" NPT fitting at the engine normally stays in place. That fitting or possibly two fittings connect to a #3 or #4 hose which connects to the oil pressure sender.
Common practice is to use a manifold at the firewall to mount the sender and the hose.
 
Tom----
since you are the 3rd owner of a 1200+ hour engine----I wonder if the sump screen has been checked? I'd ask your A&P that did the conditional if he pulled the screen.

Tom
 
Correct readings confirmed, now what?

Thanks all for the very thoughtful replies!
I connected a mechanical oil pressure gauge the other day, with a Tee installed at the firewall manifold so I could see both gauges at the same time. I ran the engine on the ground, varying the RPM and getting the oil temp up to 170. The readings on both gauges were very close, leading me to confirm that my panel-mounted gauge is displaying correct readings. That is not what I had hoped to find, as on my last short flight, the oil pressure dropped from 70 on climb out, to 45 in level cruise. Oil temp didn't go above 190, i am pretty sure, though I don't have a picture.
I don't know where to start with diagnosing and fixing this, so I am hoping an experienced engine person can offer me an idea of next steps.
In a likely unrelated matter, I also noticed a lot of engine roughness when advancing the throttle, and found that she ran very rough and had a drop of about 300 RPM on the traditional magneto, when I turned off the lightspeed ignition. The plane is about five hours out of a a fresh annual where the plugs were cleaned and checked. I do lean when taxiing and cruising. I'll do another post about that.
Both of these issues are keeping the plane in the hangar for now. I'm sad to be grounded for now, in the beautiful summer!

Thanks much for any tips.
Tom
 
Oil Pressure

If 45 is a correct reading that is way too low. You should ground the airplane until this is corrected.
 
Thanks all for the very thoughtful replies!
I connected a mechanical oil pressure gauge the other day, with a Tee installed at the firewall manifold so I could see both gauges at the same time. I ran the engine on the ground, varying the RPM and getting the oil temp up to 170. The readings on both gauges were very close, leading me to confirm that my panel-mounted gauge is displaying correct readings. That is not what I had hoped to find, as on my last short flight, the oil pressure dropped from 70 on climb out, to 45 in level cruise. Oil temp didn't go above 190, i am pretty sure, though I don't have a picture.
I don't know where to start with diagnosing and fixing this, so I am hoping an experienced engine person can offer me an idea of next steps.
In a likely unrelated matter, I also noticed a lot of engine roughness when advancing the throttle, and found that she ran very rough and had a drop of about 300 RPM on the traditional magneto, when I turned off the lightspeed ignition. The plane is about five hours out of a a fresh annual where the plugs were cleaned and checked. I do lean when taxiing and cruising. I'll do another post about that.
Both of these issues are keeping the plane in the hangar for now. I'm sad to be grounded for now, in the beautiful summer!

Thanks much for any tips.
Tom

Low OP is a tough one with few easy steps. I would start with the relief assembly, as several problems there can cause low pressure and if there is a problem there, it is easy to fix. You can search and find good info. Need to first determine if your's is the external adjustment type or or internal. First, take it apart and get everything cleaned and look for any damage to the ball or the seat that the ball goes into, as well as the spring. Then reassemble and test. If no change, try adjusting the pressure up. With the ext, just screw in the shaft. With internal, add -3 AN washers between the cap and the spring. If pressure improves, just refine things to get the pressure you want. Note that springs can wear out and this could also cause low pressure. In theory, things should improve with the adjustment process, but still need a new spring to get the OP where you want it. Also note that OP changes somewhat linearly with OT (cold OT = high OP and vice versa), so always compare pressures at the same OT.

If you have the internal adjustment, also note that there are two different styles of caps and they must be matched to the case style. Mechanics often get this wrong and the mismatch can cause low OP, often intermittently. Search Mahlon's posts for details. In summary, there is a cage to hold the ball as it moves. The cage is either in the cap or on the case. WIth no cage on the case, THERE MUST be a cage on the cap. For external adjustment, there is only one style.

Also, clean out the sump strainer, as significant clogging there can also cause low OP. Something like a broken ring can cause a lot of carbon debris and quickly create a blockage. Your high oil consumption makes this possibility likely. Whenever you burn a lot of oil, hard carbon deposits likely are created. Depending upon the reason, much of this can wind up in the oil pan and then get sucked into the screen.

After that, the next two likely candidates are the oil pump or worn bearings, with the former being a much easier fix, but not necessarily easy to perform. The somewhat rapid rat of decline kind of points away from bearings.

While 45 is low and screaming for a fix, it is not so bad that you cannot do brief test flights around the airport area as you address this.

HIGHLY unlikely that the roughness is related to the OP problem

Good luck.

Larry
 
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Can't tell from the writeup if the mechanical gauge was connected during flight. Could be a wire chaffing with movement in flight. Iratic fluctuations could be a wire intermittently rubbing against the airframe ground somewhere. Won't be noticeable during ground runs since there's no/minimal movement. Air work makes sense here too since there's maneuvering movement and maneuvering loads that make the airframe flex. Lots of opportunity for wire chaffing.

The only other time I've seen oil pressure fluctuations was when there was almost no oil left. The oil pickup sucking air, then bits of oil and back to air caused wild fluctuations in pressure. Doesn't seem to be the case here as you still have oil in the sump. (Luckily that event happened on a twin, and the other engine took us to an airport).
 
Grounded

If 45 is a correct reading that is way too low. You should ground the airplane until this is corrected.

Yes she is grounded. The problem is I have no idea what steps to Take now, so I am looking for advice on what might be the cause of this. Reminding that this is a Titan IO360 with about 1250 hours, running Philips 20–50 oil, a quart of which she seems to burn every four hours or so
 
Yes she is grounded. The problem is I have no idea what steps to Take now, so I am looking for advice on what might be the cause of this. Reminding that this is a Titan IO360 with about 1250 hours, running Philips 20–50 oil, a quart of which she seems to burn every four hours or so

Gave you guidance and steps above. Have editted so re-read.
 
Yes she is grounded. The problem is I have no idea what steps to Take now, so I am looking for advice on what might be the cause of this. Reminding that this is a Titan IO360 with about 1250 hours, running Philips 20–50 oil, a quart of which she seems to burn every four hours or so

Start with Larry's advice above. Exactly what I would do first.

Did it always burn that much oil?
 
Oil suction screen

Yes she is grounded. The problem is I have no idea what steps to Take now, so I am looking for advice on what might be the cause of this. Reminding that this is a Titan IO360 with about 1250 hours, running Philips 20–50 oil, a quart of which she seems to burn every four hours or so
Hi Tom, I can't recall seeing if you confirmed that the suction screen is clean/clear. That is what I would start with if you have not already. Clogged oil suction screen has caused engine failure in flight in other aircraft. It takes about 5 mins to check - if you are not sure what it is or how to do it, just shout.
 
Thanks all for the great advice. Larry I so appreciate the detailed information! To be clear, I don’t think trying to raise the OP overall
Is what I need to do. It is really an intermittent issue. Most of the time the OP is in the 65 to 75 range. But it often drops
To 58 or 60 in cruise. And it occasionally drops to 55 or a little below. The other day it dropped to 45 which was alarming, but i hesitate to think of it as an overall low situation. But what do I know? Not that much about this stuff, so if it is still a good idea to change the relief valve setting then I will do it. The sump Screen was checked and cleaned at the annual A few weeks ago. Compressions are good. I’ll sort out the magneto issue and then fly around the pattern to check OP I guess. My airport not the best for that with 800’ Ceiling under ewr bravo though …maybe I’ll hop over to central new
Jersey to circle the airport
With some
Altitude.
Thanks again
 
As someone else asked, what was the oil temp? The RV’s with a 360 in them don’t like slow flying and maneuvering at low airspeeds when it is warm to hot outside. The oil temp gets hot, oil pressure will drop. Since you didn’t mention oil temp in the OP, my guess that it may have been high. There is a direct relationship between oil temp and pressure when the oil is hot. In my -6, with a 360 engine, oil temp has to be monitored when doing low speed maneuvers, slow flight, stalls, low speed turns and so on, for more than a couple of minutes.

what he just said...I would bet anything its getting hot oil which is reducing your pressure....got a race car....I have to run thick oil...when its hot the oil pressure drops around 30 psi....but starts at 80. check your oil temp and graph it against oil pressure...there will be a direct relationship....then work on cooling your oil.
 
Thanks all for the great advice. Larry I so appreciate the detailed information! To be clear, I don’t think trying to raise the OP overall
Is what I need to do. It is really an intermittent issue. Most of the time the OP is in the 65 to 75 range. But it often drops
To 58 or 60 in cruise. And it occasionally drops to 55 or a little below. The other day it dropped to 45 which was alarming, but i hesitate to think of it as an overall low situation. But what do I know? Not that much about this stuff, so if it is still a good idea to change the relief valve setting then I will do it. The sump Screen was checked and cleaned at the annual A few weeks ago. Compressions are good. I’ll sort out the magneto issue and then fly around the pattern to check OP I guess. My airport not the best for that with 800’ Ceiling under ewr bravo though …maybe I’ll hop over to central new
Jersey to circle the airport
With some
Altitude.
Thanks again

I still would check and clean the oil relief assembly, paying special attention to whether or not the correct parts are installed and the spring is tight. I bought a core engine for my 10. On early flights I found intermittent high and low oil pressure. Turned out the wrong parts were installed and I didn't know enough during the O/H to validate them. Didn't know there were different caps for different cases. If you send pics of the cap and the seat area on the case, I will help you confirm.

As long as the sender is confirmed to be good, even an intermittent low oil pressure situation is dangerous and MUST be addressed. At some point it may intermittently drop to 0!

There just aren't many things in the oil system that create these type of symptoms. I would consider plumbing the mechanical OP gauge temporarily into the cockpit while you fly and do some more testing. I didn't understand the intermittent nature of the problem, when I recommended ground testing. Due to the fact that you only see odd date in cruise, you need a longer term comparison with the elec. sender., as it is the most likely issue with intermittency. It is possible that your sender is only misbehaving at certain times or only when it is getting heat soaked. Knowing more now, my money is on a bad sender.

Larry
 
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what he just said...I would bet anything its getting hot oil which is reducing your pressure....got a race car....I have to run thick oil...when its hot the oil pressure drops around 30 psi....but starts at 80. check your oil temp and graph it against oil pressure...there will be a direct relationship....then work on cooling your oil.

OP said his temps never got above 190. He is seeing pressures all over the map, so it would seem unlikely he is just missing the OT - OP relationship. If he is climbing at 65-75 then gets 45 psi in cruise, OT induced low OP is quite unlikely. If I am understanding correctly he also occasionally gets 65-75 in cruise. Not sure Oil temps could be that different in the two flights for the OP not to notice and they would have to be A LOT higher to get 45 psi.

Also he is NOT running thick oil. He is using 20W50 which is quite thin when cold. Nothing like straight wt racing oils when cold.
 
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Thanks guys. Next time I can get to the hangar I will check the pressure valve and send pictures. Thank you for your generous offer to look at those Larry!
Assuming I find a quick fix to the rough running engine, I will plumb the mechanical gauge to the cockpit and go flying. I did my initial ground comparison with a test gauge with a fat 3/4” line to the hand held
Dial. I also bought an automotive mechanical gauge with about a 3/16”
Line that would be easier to route. If I can’t find passage in the firewall, should I just have it sneak out the cowling and under the (tip up) canopy, with some tape holding the line to the fuselage?
 
Thanks guys. Next time I can get to the hangar I will check the pressure valve and send pictures. Thank you for your generous offer to look at those Larry!
Assuming I find a quick fix to the rough running engine, I will plumb the mechanical gauge to the cockpit and go flying. I did my initial ground comparison with a test gauge with a fat 3/4” line to the hand held
Dial. I also bought an automotive mechanical gauge with about a 3/16”
Line that would be easier to route. If I can’t find passage in the firewall, should I just have it sneak out the cowling and under the (tip up) canopy, with some tape holding the line to the fuselage?

Nothing wrong with taping a small line to the fuse, but doubt you will have room at the seam. There should be 2 or 3 pass throughs in the firewall that should give a better path.
 
In a likely unrelated matter, I also noticed a lot of engine roughness when advancing the throttle, and found that she ran very rough and had a drop of about 300 RPM on the traditional magneto, when I turned off the lightspeed ignition. The plane is about five hours out of a a fresh annual where the plugs were cleaned and checked. I do lean when taxiing and cruising. I'll do another post about that.

Tom

Did this start immediately after the annual? If so, I would be looking for errors in re-installation of the mag or plugs. Plug wires crossed, poor connection between wires nad plugs, spring falling out of wire at plug end, as well as mag timing.
 
Did this start immediately after the annual? If so, I would be looking for errors in re-installation of the mag or plugs. Plug wires crossed, poor connection between wires nad plugs, spring falling out of wire at plug end, as well as mag timing.


No. I’ve flown about five hours since the annual. Engine ran well. I actually just noticed it when I was ground testing my oil pressure the other day. The last flight prior to that was smooth as well, with 125rpm
Drop on the mag. Now it sputters and shakes when advancing the throttle with both the mag and the light speed on, but drops 300 and runs rough when only on the mag.
 
No. I’ve flown about five hours since the annual. Engine ran well. I actually just noticed it when I was ground testing my oil pressure the other day. The last flight prior to that was smooth as well, with 125rpm
Drop on the mag. Now it sputters and shakes when advancing the throttle with both the mag and the light speed on, but drops 300 and runs rough when only on the mag.

carb or FI? Do you have EGT instruments? If so, observe EGTs when you do drop the LS ignition. That will give hints to issue with mag drop. All EGTs should rise when switching from two ignitions to one. A falling EGT on one cylinder = a problem with that plug/wire or issue in mag. If the LS is working well, most problems with the Mag will not cause sputtering and shaking as long as the LS ignition is on, just a slight roughness. Crossing plug wires is an exception. Sputtering and roughness only on acceleration is usually a fuel problem, not ignition, though a weak and failing coil can do this, though it would take two bad coils if running on two ignitions. If it is a carb, it could be the needle/seat or problems with the accelerator pump. If it only happened once, it could also be an anomaly that won't reappear.
 
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need an engine monitor system

carb or FI? Do you have EGT instruments? If so, observe EGTs when you do drop the LS ignition. That will give hints to issue with mag drop. All EGTs should rise when switching from two ignitions to one. A falling EGT on one cylinder = a problem with that plug/wire or issue in mag. If the LS is working well, most problems with the Mag will not cause sputtering and shaking as long as the LS ignition is on, just a slight roughness. Crossing plug wires is an exception. Sputtering and roughness only on acceleration is usually a fuel problem, not ignition, though a weak and failing coil can do this, though it would take two bad coils if running on two ignitions. If it is a carb, it could be the needle/seat or problems with the accelerator pump. If it only happened once, it could also be an anomaly that won't reappear.

Injected. Titan IO360 from American Aircraft Engines around 2009.
The EGT is an original Vans gauge and it is intermittent, occasionally resting on the bottom peg.
What i don't think I made clear was that when switching to the mag, it not only drops 300 rpm, but the roughness starts, which makes me think that the roughness is spark-related. It is pretty bad, perhaps as if running on three cylinders, though I don't know if it is THAT rough. I would never fly with it running like that. It has alway been smooth on runups with the mag and the LS, so this is a new condition. Here is a link to a video of a run up that shows this happening: https://photos.app.goo.gl/T9JPE9aD5cvZUv9QA

My panel is all steam except for a G5 for HSI only, a Garmin Aerea 660 GPS, and a TruTrak Gemini. I have two CHT gauges and one EGT gauge.
I am yearning for an engine monitor with all cylinders CHT and EGT. If a couple of Dynon Skyview HDX systems were available now, I would probably just pull the trigger on making a new panel, but they are not. I am considering installing a base-model JPI EDM350 in the meantime, to get my engine sensors going. I would love to subscribe to Savvy Analysis, but I don't have any data to send them.
My plan now, based on all of this conversation, is to sort out the roughness issue, plumb the mechanical gauge to the panel, and go flying to see if there is any condition where the OP gauges are inconsistent with each other.
Thanks again,
 
Making progress.

Hearing my symptoms, A longtime Lycoming mechanic suggested that I clean the injector nozzles. I did that today. I first ran the engine, running very rough, then upon shutdown, I checked the exhaust temps. #4 was 30% hotter than the others. I pulled the injectors and found partial blockage in #4. That tells me
It was running lean, which would account for the higher temp in that cylinder.
I pulled and cleaned all the injectors and restrictor tubes. A couple of them had some restricting gook in the hole. Filled with hope, I put it back together and started her up. She ran strong and smooth. No more missing, and minimal
Rpm drop when cycling mags. Now, with two oil pressure units, one mechanical, it is time to go flying and see about the old oils
pressure issue.
 
You don’t have to plumb the mechanical gauge into the cockpit and fly it.. you can just have it external and do a run up on the ground. Compare mechanical gauge to the digital at idle and again at 1400 rpm or so.. that will tell you everything you need to know if your sender is bad.. I just had the same issue, and it was apparent that my sender was acting up.
 
Oil Pressure flight test

You don’t have to plumb the mechanical gauge into the cockpit and fly it.. you can just have it external and do a run up on the ground. Compare mechanical gauge to the digital at idle and again at 1400 rpm or so.. that will tell you everything you need to know if your sender is bad.. I just had the same issue, and it was apparent that my sender was acting up.

Thanks for the thought. I did a few ground runs and all looked good between the two OP gauges. Someone in the thread suggested that a comparison when flying through various phases of flight would be a better test, so I temp swapped the OAT gauge with the mechanical OP gauge. I certainly hope to find a discrepancy, as the alternative would mean that my engine is actually dropping to 45PSI in cruise, which would be a whole new journey, one that I am hoping to avoid. The sump screen has been cleaned. OP in start and runup looks good and strong.
 
update: running well

I finally got the chance to go flying with my newly cleaned injectors and my back-up OP gauge. She ran like a top. The OP gauges agree with each other, so I can no longer suspect a bad sender or something. Things all looked good until a few minutes into the 25 square, lean of peak cruise. As the oil temp crept above 200, the oil pressure dropped to 60. Having seen it drop much lower in the past, I tried to mitigate it by reducing power to see if that helped. I was happy to see that at a low power setting of 2k RPM and 22 inches of MP, the temp stabilized around 180, and the OP stabilized around 70-75. I feel like this is good news, as I perhaps join the ranks of RV7s with hot oil issues. I was worried about something more serious in the engine.
That said, if the oil gets hot, like 215, 220, but is still within the green range on the gauge, does it make sense that my OP would drop so much? I will do the same test again, with some variables.
By the way, these planes are awesome. The climb is incredible. I was getting 1600 fpm in a 40 degree climbing turn, not to mention 2,000 fpm in a straight line, and that is solo, but with topped-up tanks.
 
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That said, if the oil gets hot, like 215, 220, but is still within the green range on the gauge, does it make sense that my OP would drop so much? I will do the same test again, with some variables..

Not in my opinion. Yes there is a mostly linear relationship between oil temp and oil pressure, all else being equal. But dropping from 75 to 60, let alone 45, with temps only rising from 180 to 210 seems too much to me, though an RPM drop can cause that if your oil pump is very weak. Typically at anything above 1500 RPM, the pump is producing more volume than necessary to meet target pressure levels and therefore don't see variations in the pressure. If the pump is weak and all of its output is being used, then you will see much greater variability. That said, I have never done testing to map pressure to temperature.

Maybe someone on the board has mapped this relationship and will share. However, 45 PSI is WAY TOO LOW even if your oil was 300 degrees. Now that you have confirmed the OP instrument it is time to figure out why your pressure is dropping. My first speculation is the oil pump. Do you buy chance have an older vintage engine? They have gone through three or more iterations of pump gears due to failures.
 
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Update. Things are looking pretty good

I flew today with a new technique, recommended by my friend and mechanic.
The technique is basically to leave the throttle to the firewall, and just pull the prop back to the desired RPM. This is in an effort to keep the oil temp down by not running the engine too fast. It seemed to work well. I pulled the RPM down to 2,200, with a lean-of-peak mixture setting. My oil temp stayed steady at 173 and my OP was at 73 for the entire cruise of about 30 minutes. At this setting at 4,500' i was averaging around 158 knots. It was great to see the OP stay in a healthy range. On the return leg, I climbed aggressively at around 100-105 knots to 4,500'. By the end of the climb, the oil temp had reached 200, and the OP was down to 65. I leveled off, entered the cruise power configuration described above, and the temp and pressure returned to 173 and 73, as on the first leg.

Bottom line is I feel much better about the engine now. I will continue to explore the envelope with different tests and power configurations. Does anyone think I still have a problem or have any comments about how I am approaching this?
BTW, my friend says it may be better to close the oil cooler damper to get the steady temps up to 180 or 185. Thoughts on this?
 
I flew today with a new technique, recommended by my friend and mechanic.
The technique is basically to leave the throttle to the firewall, and just pull the prop back to the desired RPM. This is in an effort to keep the oil temp down by not running the engine too fast. It seemed to work well. I pulled the RPM down to 2,200, with a lean-of-peak mixture setting. My oil temp stayed steady at 173 and my OP was at 73 for the entire cruise of about 30 minutes. At this setting at 4,500' i was averaging around 158 knots. It was great to see the OP stay in a healthy range. On the return leg, I climbed aggressively at around 100-105 knots to 4,500'. By the end of the climb, the oil temp had reached 200, and the OP was down to 65. I leveled off, entered the cruise power configuration described above, and the temp and pressure returned to 173 and 73, as on the first leg.

Bottom line is I feel much better about the engine now. I will continue to explore the envelope with different tests and power configurations. Does anyone think I still have a problem or have any comments about how I am approaching this?
BTW, my friend says it may be better to close the oil cooler damper to get the steady temps up to 180 or 185. Thoughts on this?

2200 RPM at 4500 feet and WOT? What was your manifold pressure? I’m not afraid of going over square, but I would think that’s more over square than I would do at WOT and 4500 feet..I would have to reference some Lycoming power charts before I did that..
 
Re: "2200 RPM at 4500 feet and WOT."

Are there any RPM and MP operating limitations on your engine and C/S prop combo?

For example, some Hartzell C/S props have this limitation, depending on the engine and specific Hartzell C/S prop installed:
"Do not operate above 22” manifold pressure below 2350 RPM."​
 
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wow. Learning over here...

just saw this from Hartzell as well:

"Avoid continuous operations between 2000 and 2250 rpm."
****, I didn't know. So I guess I was a bad boy today, because I sat at 2000, then upped it to 2,200 as a "continuous" setting.

MP at WOT/4,500' was 24 or 25 for most of the flight (which was 30 minutes in total) until i reduced it to 23.

Love this forum. Live and learn. So now I have more parameters to work with for the next flight.
Thanks guys.
 
OP said his temps never got above 190. He is seeing pressures all over the map, so it would seem unlikely he is just missing the OT - OP relationship. If he is climbing at 65-75 then gets 45 psi in cruise, OT induced low OP is quite unlikely. If I am understanding correctly he also occasionally gets 65-75 in cruise. Not sure Oil temps could be that different in the two flights for the OP not to notice and they would have to be A LOT higher to get 45 psi.

Also he is NOT running thick oil. He is using 20W50 which is quite thin when cold. Nothing like straight wt racing oils when cold.

so oil temp has a direct effect....What I dont see is wether the oil temp sender and or gauge is calibrated and working correctly....has that been checked? looks like you are learning your engines characteristics and how to handle it...work on keeping your oil cool and check your oil temp sender and gauge.
 
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I have not confirmed the accuracy of the oil temp display. I initially suspected the accuracy of the OP gauge, so I installed a mechanical gauge as well, plumbed in with an oil line to the panel. That confirmed the accuracy of the original system. That mechanical gauge is still in there, though I will remove it soon. Should I do the same with the oil temp gauge? It seems to be behaving correctly, but is there a reason to suspect it?
 
I have not confirmed the accuracy of the oil temp display. I initially suspected the accuracy of the OP gauge, so I installed a mechanical gauge as well, plumbed in with an oil line to the panel. That confirmed the accuracy of the original system. That mechanical gauge is still in there, though I will remove it soon. Should I do the same with the oil temp gauge? It seems to be behaving correctly, but is there a reason to suspect it?

Not necessarily….but you are problem solving….so a back up on the temp is not a bad idea. Then at least you know what direction you are heading in….get your information first….accurate information….devise a plan….execute….or you will run around in circles. You have seen the relationship between oil temp and pressure….now imagine if your temps are actually 30 degrees higher than you think? Either way you have seen the value of cooling so look into your setup….next is oil….it might be recommended but still too thin….wear in an engine will obviously affect oil pressure with age but the fact you can change your oil pressure through oil temp leads me to believe your engine is ok but for the viscosity of your oil the oil temp is getting too hot.


Get accurate information, Go for the best cooling you can….then investigate oils and viscosity….then you are into engine work….relief valve condition, oil pick up screen, pump and finally bearings. That’s the order I’d attack it in anyway….I’m a pilot but been a mechanic in the past….
 
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