I am still waiting for some data:
- At idle- How low does the pressure get??
- At flight power/rpm (climb & cruise)- How low/high does the pressure & temperature get?
The whole debate, is there a problem or not?? hinges on getting these figures
Data I posted above
"Runup when cold I’ll see 90PSI when below 80-90F. "
I assume you are talking oil temperature 26-32C (80-90F). By Rotax standards ( minimum 50C) this is too cold to be doing a run up . It’s no wonder that you are seeing high oil pressures.
“Climb and high cruise I’ll see 50-60 at 3200 RPM and 190F.”
88C (190F) is too cold for flight power. Engine oil should get to a sustained minimum of 100C, usually during Climb, at least once in a days flying, to drive off volatile contaminants. In Cruise, a good target temperature is 95C. Your oil pressures are high but not worryingly so - higher oil temperatures may bring the presser down somewhat.
“200F and idle it can indicate zero” “suspect that’s an instrumentation issue”
93C (200F) is not particularly hot however assuming a lower(?) temperature on descent and in low power circuit operation, I am wondering why the rise above your Climb/Cruise temperatures - could you have a cowl air flow problem.
I agree that your oil pressure gauge may be giving false readings. Can you compare current readings with a historic log? If no log - check with a Master Gauge, or just swop with another similar, to compare readings.
Your advice conflicts with the AeroVee manual. It’s not a Rotax.
Bryan,
You seem like the kind of guy who probably measured the resistance curve of the VDO sensor before installing it. If so, did you characterize it at low pressure?
I’ve wondered whether the different EFIS manufacturers all handle the calibration curve correctly/the same way. I believe the pressure→resistance curve is mostly linear, but the pressure→voltage curve is hyperbolic (compressed at the low end of the scale) because voltage is read through a voltage divider circuit. Hard to believe this isn’t done correctly, but maybe it’s worth testing the sender at low pressures.
I don’t believe I’ve ever seen my VDO senders on the MGL Enigma read zero while the engine is running. I think it’s silly how often they fail, though (always reading high), and swapped to a Kavlico sender right before Dynon reported that some had leaked oil. I’ve been planning to swap to another Kavlico sender, but this one has been working so well, so I check it for leaks during every pre-flight and it’s probably the only dry part of the engine :-).
While we’re on the topic. Does anyone know for sure that that the hole in the case is actually tapped for 1/8 NPT? I somehow became convinced it’s really M10x1 and use an M10x1-1/8NPT adapter for my Kavlico sender. The sender’s so small it’s much smaller than the VDO even with the adapter. I’ve heard of people cracking the case there and cautions not to overtighten. I didn’t have any problem with the M10x1.
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You have me figured out. It’s in a notebook at the hangar. I could tell that the pressure was under 10psi but above zero from looking at the ohmmeter.
“Your advice conflicts with the AeroVee manual. It’s not a Rotax.”
Its not advise - its observation ie there is likly some experince and/or testing that has gone into the recommendation - bring your engine to minimum operational oil temperature, before asking for high rpm’s.
I have always practised, what I was taught, a squilion years ago, about ICE management - start/warm/ minimal load, before running temperature reached. I mentioned Rotax (as another small aircraft engine) but could equally have listed cars/trucks/ tractors/motorcycles/ etc.
What makes your VW so special, that you thinks its okay to do cold oil, relativly high rpm run ups, without consequence (high oil pressure)?
It’s a handy thing to read the manual. You can find it here:
http://www.aeroconversions.com/support/instruction_sheets/AeroVee_2point1_Manual.pdf
I’ll highlight some of the points since I feel you are not going to read the manual.
Min oil temperature before takeoff: 80F
Min oil temperature in cruise: 160F
Max oil temperature: 240F (it’s really not happy here, but they don’t say that in the manual)
Max oil pressure: 100psi
Sonex has a lot of experience with this engine, and they provide a pretty comprehensive manual.
I have a little operational experience with this engine, and it can be a challenge to get to “operational temperatures” on the ground except in the heat of the summer. And if I get to “operational temperatures” on the ground and then climb at full power my oil temperature is probably going to get to 240 and my oil pressure will be really low in cruise, and will definitely indicate zero at idle even after cooling down in the descent.
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Its not for me to contradict your Sonex AeroVee operating standards however I will comment;
Modern engine oils have been engineered (formulated) to perform best within a certain temperature range - the best advise for this is the oil manufacturer (Not Sonex)
Lubrication (the ability of the oil to hold moving surfaces apart) is effected by temperature & viscosity. Morden oils may also containe a wide range of additives to enhance lubricity.
Viscosity ( how thick the oil is at a given temperature). Subjectively how it pours - watery to treacle. In the past single grade oil typically went from thick to thin, as engine temperature rose. Circulation may improve however lubricity reduced. Now we have multi grades that, in effect , do the opposite. Start thin to improve/speed circulation, minimise resistance to cranking and after start rotation. As engine/oil temperature rises ,the oils lubricity is maintained or increases. We think of it as thickening but its more like the desirable characteristics of a thicker oil, rather than an actual thickening.
Circulation/Flow - important for getting the oil to all those moving parts and dispersing heat is effected by pump rpm, gallery ID & viscosity. (Gallery ID includes leakage from bearings/bushes and pump wear).
Pressure Also effected by gallery ID, viscosity & pump speed, is just an easy way of determine that flow is happening and meets the engines requirements, or not
I note that the Sonex oil temperatures are Minimums, (can be exceeded) with only the one Maximum (should not be exceeded).
I suggest that:
Take -Off: 80F (21C) is a very low temperature to be asking any engine to go to full power, without consequence. At this temperature the oil is not operating at its optimum lubricity - bette 122-140F (50-60C). I note the Max 100psi oil pressure, again in the high side but if the internal systems of the engine will handle this, I guess I don’t have a good reason against.
Cruise: 160F (70C) Again, I suggest the oil is below its optimum.
Max Temperature 240F (116C). Personally I would not like my engine oil to go above 120C and then only for a short period. My preference is for my oil to go to 100 -110C for a period (say 10-20 minutes) in Climb, once in an operating day. In Cruise I like to see mid 90C but will accept anywhere from the low - high 90’s depending in ambient temperature and operating mode.
Talk to your oil manufacture. Get their take on what temperatures their oil performs best at.