Not reaching 2700 RPM?

[Marauder]

What I meant by correlation Bob was whether others like me are seeing the same thing with the relationship between oil temp and max rpm. We have the same data in our JPIs. Maybe you picked up on something that none of us ever noticed before.

[Bob_Belville]

BTW -- your TSOd direct factory replacement 930 should be accurate, but so was the factory tach. The 930 runs off of the mag and our planes originally had mechanical Tachs. Even my EI tach (direct replacement) and JPI 830 (secondary instrument) do not agree exactly even though they are getting the same information from the same source. At least I know they are within acceptable error of each other.

Sure, fwiw this plane had an EI electronic tach before the 930. And of course the oil temps are somewhat nominal. The 930 records on 6 sec intervals and the temps generally jump in 6degF increment and the Oil Temp probe is not in the prop hub!

[tony]

Looking at your data I was wondering if the oil pressure constant?

[Bob_Belville]

Tony, good point. I should have included the OP. Risky to guess, but I'm pretty sure my OP is inversely related to Temp but stays well in the green. I'll look at the hot flights.

 

Hottest flight: while rpm was indicating over 2720 (for 3 datum point @ 6 sec) OP was 75psi and OT was 218. The rpm then dropped to ~ 2640, I probably gave the knob a small twist, OP @67, OT @ 224.

Another flight: rpm @ 2724 for 4x 6 sec, OP 77, OT 193. When OT climbed to 212 1 minute later the OP dropped to 69.

 

Seems reasonable to me?

[N601RX]

Your governor or front bearing may be getting some wear on it.  With the thinner hot oil, the oil pump in the governor may not be making quite as much pressure, or you may be loosing a little more oil pressure around the front transfer bearing than when the oil is cooler and thicker.

[Bob_Belville]

Your governor or front bearing may be getting some wear on it.  With the thinner hot oil, the oil pump in the governor may not be making quite as much pressure, or you may be loosing a little more oil pressure around the front transfer bearing than when the oil is cooler and thicker.

What's involved in verifying?  Risk of sudden failure of something?

[N601RX]

I don't think there is a sudden risk of failure as long as you monitor it and don't let the engine grossly overspeed.  There is a Lycoming service bulletin that describes a leakdown test using air that will help determine if the leak rate past the front bearing is too high.  The governor can be removed and bench checked by a shop. A slight seasonal adjustment may be the best answer as well as monitoring it and making sure it doesn't get progressively worse..

[Bob_Belville]

This prop was new in 2009, 150 hours. Since it was a new Scimitar Top Prop I suppose the governor was new but the log book does not detail that.

[N601RX]

Looking at the table of data you posted above, it does not appear that your oil temp was getting anywhere near hot enough on the cold days.  Mine normally runs 190-200 and at that temp your prop speed is where it should be.  You may need to look at why your oil didn't get hot enough in the cold weather.  Didn't you have a previous post a few months ago about oil temps in cold weather?

[Marauder]

Looking at the table of data you posted above, it does not appear that your oil temp was getting anywhere near hot enough on the cold days.  Mine normally runs 190-200 and at that temp your prop speed is where it should be.  You may need to look at why your oil didn't get hot enough in the cold weather.  Didn't you have a previous post a few months ago about oil temps in cold weather?

 

Are there published specs on what the expected oil temps should be? It wasn't until I saw Bob's thread on oil temperatures that got me thinking that I never saw a real world expected oil temp range. I have always used the "acceptable" range provided in the POH, but we all know that is a big range and does not really show where these temps normally reside in flight.

[Bob_Belville]

Looking at the table of data you posted above, it does not appear that your oil temp was getting anywhere near hot enough on the cold days.  Mine normally runs 190-200 and at that temp your prop speed is where it should be.  You may need to look at why your oil didn't get hot enough in the cold weather.  Didn't you have a previous post a few months ago about oil temps in cold weather?

What I listed was the oil temp and rpm at startup roll. The temps quickly get to near 200 in climbeven in cold weather. Sorry for the confusion. 

[N601RX]

Yes the Lycoming Engine operating manual.  Pn 60293-12.

 

 

OPERATING CONDITIONS
Average                                                                      *Oil Inlet Temperature
Ambient Air           Desired                    Maximum
Above 80°F           180°F (82°C)            245°F (118°C)
Above 60°F           180°F (82°C)            245°F (118°C)
30° to 90°F           180°F (82°C)            245°F (118°C)
0° to 70°F             170°F (77°C)            245°F (118°C)
Below 10°F           160°F (71°C)            245°F (118°C)
* - Engine oil temperature should not be below 140°F (60°C) during continuous operation.

[Bob_Belville]

Are there published specs on what the expected oil temps should be? It wasn't until I saw Bob's thread on oil temperatures that got me thinking that I never saw a real world expected oil temp range. I have always used the "acceptable" range provided in the POH, but we all know that is a big range and does not really show where these temps normally reside in flight.

B26, redline is 245. (CHT is 475) but modern wisdom seems to be to try to keep @200 or less which I'm finding very tough at least during climb. I plan to swap out the oil cooler at annual next month. And I may try pulling back power for climb. I've been using full power but years ago SOP was to pull back to 25/2500 @ about 1000 AGL. (My oil cooler is already relocated to behind #4 cyl.)

[flyboy0681]

Same situation here. After reporting to my A&P that I'm not seeing any more than 2600 he gave me his portable Tru Tach to use in flight. The mechanical tach agreed with the optical one and I'm waiting for him to come by and adjust the governor.

 

My A&P adjusted the prop governor this week when he changed the oil. The extra 125rpm has made quite a difference and I'll leave it up to the eggheads here to figure out how much extra horsepower that adds up to.

[NotarPilot]

Problem is you need to be between 50-250mm for that first one. That's a lot closer than I care to stand next to a 2700 RPM propellor.

[flyboy0681]

Problem is you need to be between 50-250mm for that first one. That's a lot closer than I care to stand next to a 2700 RPM propellor.

 

The engine wasn't turning. As he explained it, each single turn of the adjustment screw speeds up the prop 25rpm, so he approximated and got it spot on.

[carusoam]

For the IO550....

200rpm of the prop equates to 30hp on the engine...

STC of rpm change to go from 280 to 310hp... (slight cylinder design change (-n vs. -g) cylinders)

Where the performance shows it, the ground roll is 50% less (800' vs 1200’) with the extra HP...

Of course the prop changed as well (Scimitar)...

I would hate to accidentally lose rpm, the ground roll will likely increase.

Best regards,

-a-

[FloridaMan]

I had my prop balance checked when I had the rear spinner bulkhead replaced. In my case, as I expected, the tach read 80 RPM low. 

[N601RX]

Here is a thread I started a while back about the iphone RPM App. It works great for verifying the tach.

http://mooneyspace.com/topic/9679-rpm-app-for-ipad/

[jetdriven]

From 2650 to 2700 RPM is worth  ~2 MPH in an all-out air race.