Lower takeoff rpm on a hot engine - the saga continues

[SwimmingDragon518]

I have been chasing these rpm gremlins ever since putting in my G3X. Overhauled my prop, got a new prop governor, set low pitch stops per the manual, and still having this variable takeoff rpm issue. It seems when we adjust something (low pitch stop, governor screw), we get to 2690 on the first takeoff, but takeoff rpm progressively decreases on subsequent takeoffs. I flew two days ago and was spinning 2680-2690, I thought this was all behind me. Went up today, first takeoff 2640 (after a long run up - busy KSEE), a little frustrated but went ahead w my flight. Landed, decided I could go out a bit on my low pitch stop to see if it helps, went out 1/3, took off no surging, got 2620-2630.

I’m working w BruceH and even went to a different AP on the field to pick his brain and he couldn’t think of what was causing it. He said next thing to check is the ignition system and plugs, then the fuel system, then ?? Has anyone had an issue like this before? Kind of crushing my flying experience and wallet at this point.

It’s a 7A with a O360-a1a with a hartzell constant speed metal prop (74”) and a McCauley prop gov (MT before swapping).

Mechanic said I’m safe to fly but I’ve gotta chase it so I guess I’m chasing it.

 

[lr172]

I have been chasing these rpm gremlins ever since putting in my G3X. Overhauled my prop, got a new prop governor, set low pitch stops per the manual, and still having this variable takeoff rpm issue. It seems when we adjust something (low pitch stop, governor screw), we get to 2690 on the first takeoff, but takeoff rpm progressively decreases on subsequent takeoffs. I flew two days ago and was spinning 2680-2690, I thought this was all behind me. Went up today, first takeoff 2640 (after a long run up - busy KSEE), a little frustrated but went ahead w my flight. Landed, decided I could go out a bit on my low pitch stop to see if it helps, went out 1/3, took off no surging, got 2620-2630.

I’m working w BruceH and even went to a different AP on the field to pick his brain and he couldn’t think of what was causing it. He said next thing to check is the ignition system and plugs, then the fuel system, then ?? Has anyone had an issue like this before? Kind of crushing my flying experience and wallet at this point.

It’s a 7A with a O360-a1a with a hartzell constant speed metal prop (74”) and a McCauley prop gov (MT before swapping).

Mechanic said I’m safe to fly but I’ve gotta chase it so I guess I’m chasing it.

Once you are doing 30 knots or so, you should be on the governor if you are not over speeding, so that is where I would spend my energy. Once your moving , it is rarely the fine pitch stops that hold the rpms back. Have no experience with those governors, so cant help a lot. Have you confirmed everything is tight and nothing is slipping between flights? The arm, the case bolts, limiter screw, etc. there could be wear or some issue with the speeder spring. Any chance there is an issue with the cable or knob assembly ? You would have to have some pretty serious engine issues to not be able to make 27000 at wot sea level. That is the last place i would look.

Any chance you got a governor setup for the wrong gear ratio? Lycoming has two different gear ratios across their engines. The wrong one would put you way out of the sweet spot and would be at the extreme of what the limiter spring could deal with and could lead to the variability you are seeing.

 

[SwimmingDragon518]

Once you are doing 30 knots or so, you should be on the governor if you are not over speeding, so that is where I would spend my energy. Once your moving , it is rarely the fine pitch stops that hold the rpms back. Have no experience with those governors, so cant help a lot. Have you confirmed everything is tight and nothing is slipping between flights? The arm, the case bolts, limiter screw, etc. there could be wear or some issue with the speeder spring. Any chance there is an issue with the cable or knob assembly ? You would have to have some pretty serious engine issues to not be able to make 27000 at wot sea level. That is the last place i would look.

Thanks for your reply. The prop governor was just replaced and the issues have carried over with it: I suppose their could be issues w the cable but every time we’ve checked it hits it’s stop and there’s a solid >1/8” cushion on it now. Engine runs very smooth and strong, no indications of engine issues and I get oil analysis every change etc

 

[lr172]

Thanks for your reply. The prop governor was just replaced and the issues have carried over with it: I suppose their could be issues w the cable but every time we’ve checked it hits it’s stop and there’s a solid >1/8” cushion on it now. Engine runs very smooth and strong, no indications of engine issues and I get oil analysis every change etc

Is this an aerobatic prop, by chance?

Any chance you got a governor setup for the wrong gear ratio? Lycoming has two different gear ratios across their engines. The wrong one would put you way out of the sweet spot and would be at the extreme of what the limiter spring could deal with and could lead to the variability you are seeing

 

[SwimmingDragon518]

Is this an aerobatic prop, by chance?

Any chance you got a governor setup for the wrong gear ratio? Lycoming has two different gear ratios across their engines. The wrong one would put you way out of the sweet spot and would be at the extreme of what the limiter spring could deal with and could lead to the variability you are seeing

Not sure about it being an aerobatic prop it’s a Hartzell constant speed standard one they ship out with the engines. Drive ratio is correct and this issue has carried forward through two different prop governors at this point :/.

 

[lr172]

Not sure about it being an aerobatic prop it’s a Hartzell constant speed standard one they ship out with the engines. Drive ratio is correct and this issue has carried forward through two different prop governors at this point :/.

So, this all started when you put in your g3x? Did it work correctly for a long time before that? If so, I would be looking for possibly inaccurate rpm indications on the g3x. Where do you pick up rpm data from?

 

[Walt]

What oil are you using? Prop shop once told me some gov's don't like the thinner Multi viscosity oils.

 

[SwimmingDragon518]

What oil are you using? Prop shop once told me some gov's don't like the thinner Multi viscosity oils.

Aeroshell W100

 

[Ralph Inkster]

Wild guess’s. Rear plug in the crank not seated properly? Or oil tube in the crank damaged?

 

[lr172]

Wild guess’s. Rear plug in the crank not seated properly? Or oil tube in the crank damaged?

Low oil pressure problems usually create over speeding problems, not underspeeding. More oil pressure is used to move the blades to a coarser pitch. An aerobatic prop would be opposite, which was why i asked.

That said, i did consider clogging of the return passages, which would prevent the gov from releasing pressure to go more fine. it seemed pretty remote. OP never answered my question, but if this all started after installing the g3x, indication errors must also be considered. just too much coincidence for the gov to fail at the exact same time as g3x installation assuming it worked reliably for some time.

 

[SwimmingDragon518]

So, this all started when you put in your g3x? Did it work correctly for a long time before that? If so, I would be looking for possibly inaccurate rpm indications on the g3x. Where do you pick up rpm data from?

I started noticing it after going to a G3x since there was a number to look at. I had the vans mechanical tach previously so it would have been difficult to see these differences. I do not know where RPM is picked up at this time but will inquire with the installer.

 

[n721dp]

I have been chasing these rpm gremlins ever since putting in my G3X. Overhauled my prop, got a new prop governor, set low pitch stops per the manual, and still having this variable takeoff rpm issue. It seems when we adjust something (low pitch stop, governor screw), we get to 2690 on the first takeoff, but takeoff rpm progressively decreases on subsequent takeoffs. I flew two days ago and was spinning 2680-2690, I thought this was all behind me. Went up today, first takeoff 2640 (after a long run up - busy KSEE), a little frustrated but went ahead w my flight. Landed, decided I could go out a bit on my low pitch stop to see if it helps, went out 1/3, took off no surging, got 2620-2630.

I’m working w BruceH and even went to a different AP on the field to pick his brain and he couldn’t think of what was causing it. He said next thing to check is the ignition system and plugs, then the fuel system, then ?? Has anyone had an issue like this before? Kind of crushing my flying experience and wallet at this point.

It’s a 7A with a O360-a1a with a hartzell constant speed metal prop (74”) and a McCauley prop gov (MT before swapping).

Mechanic said I’m safe to fly but I’ve gotta chase it so I guess I’m chasing it.

Had the same issue on my 6A with a Hartzell prop and McCauley governor. McCauley uses both metal and plastic housings. For rear mounted governors, the plastic housing would get hot and stick. Solved by going to a metal housing. A front mounted governor, on the other hand, stays cooler and the plastic housing doesn't have a problem.

 

[SwimmingDragon518]

Had the same issue on my 6A with a Hartzell prop and McCauley governor. McCauley uses both metal and plastic housings. For rear mounted governors, the plastic housing would get hot and stick. Solved by going to a metal housing. A front mounted governor, on the other hand, stays cooler and the plastic housing doesn't have a problem.

Called West Coast Governor, he said it's an all metal housing :/

 

[lr172]

I started noticing it after going to a G3x since there was a number to look at. I had the vans mechanical tach previously so it would have been difficult to see these differences. I do not know where RPM is picked up at this time but will inquire with the installer.

Ok. So possible it was drifting around 50-100 rpm before then. Sorry, but can’t offer much more. My best guess though is that the issue is in the governor or the linkage. Just can’t think of anything engine related that could cause this.

I know on the hartzels that if you take them apart to reclock and don’t follow the special procedures to reassemble, they will do things like this. No idea how mccaulys are built.

 

[SwimmingDragon518]

Ok. So possible it was drifting around 50-100 rpm before then. Sorry, but can’t offer much more. My best guess though is that the issue is in the governor or the linkage. Just can’t think of anything engine related that could cause this.

Hey Larry,

I read some of your responses to a similar issue some years ago from a different OP. To my understanding, if there was an issue with a loose bearing, I would lose oil pressure in the prop, which should manifest as increased rpm vs decreased. Am I thinking about this correctly? I was thrown onto the trail of doing a prop oil line leak down test, but it doesn’t seem that’s warranted since my symptoms don’t match? Is there any reason for me to do this test?

At this point I’m thinking a carb heat leak or something with my ignition system, and onto the fuel system if things keep checking out. Being that this issue has carried through two different prop governors, and several conversations with Dan at Wedt Coast, I don’t think it’s the prop governor.

Thanks for your replies!

 

[lr172]

Hey Larry,

I read some of your responses to a similar issue some years ago from a different OP. To my understanding, if there was an issue with a loose bearing, I would lose oil pressure in the prop, which should manifest as increased rpm vs decreased. Am I thinking about this correctly? I was thrown onto the trail of doing a prop oil line leak down test, but it doesn’t seem that’s warranted since my symptoms don’t match? Is there any reason for me to do this test?

At this point I’m thinking a carb heat leak or something with my ignition system, and onto the fuel system if things keep checking out. Being that this issue has carried through two different prop governors, and several conversations with Dan at Wedt Coast, I don’t think it’s the prop governor.

Thanks for your replies!

Correct, the governor takes pressurized oil from the engine and most supplement that with an additional pump. With no pressure at the prop, the springs pull it to the full fine position. To reduce rpm, the governor starts throwing oil pressure at the prop to increase the pitch. It does this by sending oil to a channel in the nose bearing, which then feeds the inner crank area. The test you are referencing is for excessive clearance in that bearing that can result in the governor being unable to supply enough pressure all the way to the prop. Basically, it bleeds out via the excessive clearance. The result is over speeding. Not your problem, so test is a waste of time.

I assume you have had this issue at less than 100% power. So, next time you are up there cruising at 75% power and have 2620 rpm, just throw in more throttle. If you pick up airspeed, your issue is NOT engine performance related!


If this is only TO & initial climb : At 90-100 knots, your engine needs to be REALLY weak to not be able to hit 2700. A full fine pitch would produce well over 3000. A am pretty confident that if this were engine performance related (i.e. not enough power to hit 2700) your plane would feel like a dog and you would be well aware of it.

I should mention that if you went nuts tightening the fine pitch stop, I suspect it may be possible that is governing the rpm at take off speeds. Easy to test. Measure rpm at full power while on the brakes. If it is around 2200-2300, you over did it and it is now a fixed pitch prop and explains the observed behavior. Generally we set the fine pitch to produce 2650 at full power and brakes on.

Go back and look at your engine logs. When you pour on the coals atTO, the rpm should go straight to 2650. If yours goes to 2300, then slowly climbs to 2700, then the above is the case.

 

[lr172]

Correct, the governor takes pressurized oil from the engine and most supplement that with an additional pump. With no pressure at the prop, the springs pull it to the full fine position. To reduce rpm, the governor starts throwing oil pressure at the prop to increase the pitch. It does this by sending oil to a channel in the nose bearing, which then feeds the inner crank area. The test you are referencing is for excessive clearance in that bearing that can result in the governor being unable to supply enough pressure all the way to the prop. Basically, it bleeds out via the excessive clearance. The result is over speeding. Not your problem, so test is a waste of time.

I assume you have had this issue at less than 100% power. So, next time you are up there cruising at 75% power and have 2620 rpm, just throw in more throttle. If you pick up airspeed, your issue is NOT engine performance related!


If this is only TO & initial climb : At 90-100 knots, your engine needs to be REALLY weak to not be able to hit 2700. A full fine pitch would produce well over 3000. A am pretty confident that if this were engine performance related (i.e. not enough power to hit 2700) your plane would feel like a dog and you would be well aware of it.

I should mention that if you went nuts tightening the fine pitch stop, I suspect it may be possible that is governing the rpm at take off speeds. Easy to test. Measure rpm at full power while on the brakes. If it is around 2200-2300, you over did it and it is now a fixed pitch prop and explains the observed behavior. Generally we set the fine pitch to produce 2650 at full power and brakes on.

Go back and look at your engine logs. When you pour on the coals, the rpm should go straight to 2650. If yours goes to 2300, then slowly climbs to 2700, then the above is the case.

The more I think about this, the more i think that is your issue. You pitch stop is too coarse. At take off and climb speeds, the pitch stop is limiting rpm, hence the variability. As you speed up, you need to go coarser, so the governor starts to take over. Go do a static rpm test and i bet you are well low in rpm. Keep backing off the pitch stop until you get 2650 static (full power with brakes on, not moving).

 

[SwimmingDragon518]

The more I think about this, the more i think that is your issue. You pitch stop is too coarse. At take off and climb speeds, the pitch stop is limiting rpm, hence the variability. As you speed up, you need to go coarser, so the governor starts to take over. Go do a static rpm test and i bet you are well low in rpm. Keep backing off the pitch stop until you get 2650 static (full power with brakes on, not moving).

Hey Larry,

Here is a link to a video of my most recent takeoff. You can see it reaches 2650, then goes back down to 2620 settles there.

 

[Taltruda]

Hey Larry,

Here is a link to a video of my most recent takeoff. You can see it reaches 2650, then goes back down to 2620 settles there.

What about in cruise.. or shallow dive. Does the RPM ever go to 2700? I suspect that your governor is just set too low. You claim that you don’t have a surge, but it appears that you do, it’s just not as noticeable because you apply power very gently, as you should. I would back out the governor stop screw 2 and 2/3 turns (30 rpm increase per revolution) and retest. You should make 2700 in climb, and 2650 rpm statically before any appreciable airspeed buildup.

 

[BillL]

I did not set my physical stop exactly to 2700. The logic is: the physical stop makes it into a fixed pitch prop, the RPM limit is then subject to changes in altitude and engine power (temp, mixture, ambient pressure, oil temperature etc). It was left the factory setting which seems to yield a minimum pitch of about 2720 at a static ground condition. The blue knob will effectively set the same as the governor hard stop if left fixed. Try setting when all is warm at some rpm like 2600 (in flight) then land and leave it there immediately followed by a take off with rapid throttle application. Go back and look at your data to see what RPM is doing - overshoot etc. The RPM report is rounded to nearest 10 rpm and data frequency is typically 1 second. This test will separate your stop effect from the governor effect. If it does not wander over several then extend the stop to 2720 and governor to less than that and you should be good. Use 2500 if that setting makes more sense for you.

Just remember that the prop/RPM operates on the governor nearly all the time in flight, if it fails at speed in flight then the RPM will run away at fixed stop anyway. It would only be a functional limit at static conditions and limited off throttle in-flight conditions.

IMO, it is better to refer to the recorded data rather than divided attention observations for a test flight in changing conditions. I just confuse myself after a while.

Think about how this works to help analyze what is wrong.

 

[lr172]

Hey Larry,

Here is a link to a video of my most recent takeoff. You can see it reaches 2650, then goes back down to 2620 settles there.

Still believe that next step is to set your static RPM. You mention that you have messed with it a few times now. We need to go back to a baseline to be sure that you didn't go too far and the pitch stop is limiting things. Again 2650 is typical or you could folloiw Bills advice of 2700+ Totally your call. But if you have it too low, it is going to be acting as the governor at TO speeds. FP props do what you see in the video; They peak and then settle. They also vary RPMs based upon temps, air density and airspeed. Kind of exactly what you are seeing. My confidence is now fairly high this is what is happening. Good news is it only takes a few minutes to confirm or reject that theory.

Once we set static at 2650, we know for certain that the gov is controlling the rpm and can further diagnose why it won't go to 2700.

 

[lr172]

I did not set my physical stop exactly to 2700. The logic is: the physical stop makes it into a fixed pitch prop, the RPM limit is then subject to changes in altitude and engine power (temp, mixture, ambient pressure, oil temperature etc). It was left the factory setting which seems to yield a minimum pitch of about 2720 at a static ground condition. The blue knob will effectively set the same as the governor hard stop if left fixed. Try setting when all is warm at some rpm like 2600 (in flight) then land and leave it there immediately followed by a take off with rapid throttle application. Go back and look at your data to see what RPM is doing - overshoot etc. The RPM report is rounded to nearest 10 rpm and data frequency is typically 1 second. This test will separate your stop effect from the governor effect. If it does not wander over several then extend the stop to 2720 and governor to less than that and you should be good. Use 2500 if that setting makes more sense for you.

Just remember that the prop/RPM operates on the governor nearly all the time in flight, if it fails at speed in flight then the RPM will run away at fixed stop anyway. It would only be a functional limit at static conditions and limited off throttle in-flight conditions.

IMO, it is better to refer to the recorded data rather than divided attention observations for a test flight in changing conditions. I just confuse myself after a while.

Think about how this works to help analyze what is wrong.

I would add that setting static at 2650 doesn't make it a FP prop for more than a few seconds. Increasing airspeed lowers the load on the prop. So, if we didn't have a governor and set static at 2650 as we progress from a standing stop at full power, the RPM would gradually increase from 2650 to 3000(total guess and not sure on dynamics) by lift off. Therefore setting static at 2650 will make the RPM stop briefly there, but will transition to the governor @ 2700 in 2-3 seconds. Generally, this is a good thing, as on ocassion the gov can be slow to spool up. Also, the more coarse you are on the fine stop, the less you will overspeed during a gov failure; Though I agree it is likely moot as RPMs will be too high anyway. but anything helps in that scenario.

 

[lr172]

Still believe that next step is to set your static RPM. You mention that you have messed with it a few times now. We need to go back to a baseline to be sure that you didn't go too far and the pitch stop is limiting things. Again 2650 is typical or you could folloiw Bills advice of 2700+ Totally your call. But if you have it too low, it is going to be acting as the governor at TO speeds. FP props do what you see in the video; They peak and then settle. They also vary RPMs based upon temps, air density and airspeed. Kind of exactly what you are seeing. My confidence is now fairly high this is what is happening. Good news is it only takes a few minutes to confirm or reject that theory.

Once we set static at 2650, we know for certain that the gov is controlling the rpm and can further diagnose why it won't go to 2700.

Some of these govs are adjustable internally, like the hartzel S series. This is how they manage the different drive ratios and RPM limits (not all engines use 2700 for max). the limit adjuster on the outer spring is limited in what it can control. It is for small adjustments and only the internal adjustments can make large changes. So if set up incorrectly, you may not be able to get it set where you want it. Did you buy this new or did it come off a different engine? If new, there should have been a test card showing the RPM (both gear and prop) set during the test.

For example, I bought an S series that was set up for 2575 max RPM. there was no way I could use the limiter screw to get it to 2700. I had to take it apart and drill a new hole and stake the pin to the correct position for 2700.

 

[vinzer]

Was this done properly “set low pitch stops per the manual” ? I suspect the issue is not your governor but incorrectly set static rpms.

 

[Taltruda]

I did not set my physical stop exactly to 2700. The logic is: the physical stop makes it into a fixed pitch prop, the RPM limit is then subject to changes in altitude and engine power (temp, mixture, ambient pressure, oil temperature etc). It was left the factory setting which seems to yield a minimum pitch of about 2720 at a static ground condition. The blue knob will effectively set the same as the governor hard stop if left fixed. Try setting when all is warm at some rpm like 2600 (in flight) then land and leave it there immediately followed by a take off with rapid throttle application. Go back and look at your data to see what RPM is doing - overshoot etc. The RPM report is rounded to nearest 10 rpm and data frequency is typically 1 second. This test will separate your stop effect from the governor effect. If it does not wander over several then extend the stop to 2720 and governor to less than that and you should be good. Use 2500 if that setting makes more sense for you.

Just remember that the prop/RPM operates on the governor nearly all the time in flight, if it fails at speed in flight then the RPM will run away at fixed stop anyway. It would only be a functional limit at static conditions and limited off throttle in-flight conditions.

IMO, it is better to refer to the recorded data rather than divided attention observations for a test flight in changing conditions. I just confuse myself after a while.

Think about how this works to help analyze what is wrong.

Sorry Bill but you are totally wrong here.. you have it backwards. Setting the physical low pitch stops under the spinner to some value less than 2700 doesn’t limit you to that value forever, or make you essentially a fixed pitch prop. That’s what you want statically. As for the governor, you want 2700 in climb and cruise, but low pitch stops to 2650 static. Once you start moving, the rpm WILL increase and then the governor takes over. I see people that mistakenly set their governor to 2600 in an attempt to limit the overshoot, but this is wrong. Set the governor to 270l, then set the static (under the spinner) to 2650 and there won’t be any overshoot. The plane will be so much nicer to fly and land, it’ll glide better, and it’ll be safer in the event of power loss or oil pressure loss or governor failure.

 

[SwimmingDragon518]

What about in cruise.. or shallow dive. Does the RPM ever go to 2700? I suspect that your governor is just set too low. You claim that you don’t have a surge, but it appears that you do, it’s just not as noticeable because you apply power very gently, as you should. I would back out the governor stop screw 2 and 2/3 turns (30 rpm increase per revolution) and retest. You should make 2700 in climb, and 2650 rpm statically before any appreciable airspeed buildup.

It will go to 2690 or so if I takeoff very soon after startup. Seems to settle into 2620 on takeoffs after the oil has warmed up. Backing out the governor screw is no problem, I just don’t understand why this would only be an issue with a warmed up plane.

 

[SwimmingDragon518]

Some of these govs are adjustable internally, like the hartzel S series. This is how they manage the different drive ratios and RPM limits (not all engines use 2700 for max). the limit adjuster on the outer spring is limited in what it can control. It is for small adjustments and only the internal adjustments can make large changes. So if set up incorrectly, you may not be able to get it set where you want it. Did you buy this new or did it come off a different engine? If new, there should have been a test card showing the RPM (both gear and prop) set during the test.

For example, I bought an S series that was set up for 2575 max RPM. there was no way I could use the limiter screw to get it to 2700. I had to take it apart and drill a new hole and stake the pin to the correct position for 2700.

Dan built this out for me at West Coast Governors so I guess I’d call it an overhauled unit. I’ve spoken to him several times since he says it was tested before shipping and that the governor shouldn’t be my issue. I know it doesn’t mean it’s true but that’s what I’ve got for now. I don’t have a test card.

 

[SwimmingDragon518]

Was this done properly “set low pitch stops per the manual” ? I suspect the issue is not your governor but incorrectly set static rpms.

We did do this as highlighted in the hartzell manual. We got 2660 static (after about 2 and 1/3 turns in on the prop stop) I went and flew and was getting 2620-2630. Bruce suggested I may back the prop off 1/3 of a turn, so I returned 2 days later and did so, and got 2690 that slowly degraded to 2670 on a takeoff after a much shorter run up. I thought good enough and went about my business. Returned to fly a couple days later, had a long run up, took off and got 2650/2640’ish. Did the flight, returned, thought maybe I could do another 1/3 turn out to see if it helps, and that’s the takeoff in the video I shared above at 2620. I don’t think it’s the stops.

 

[Taltruda]

I seriously think you have the governor set too low. If you are getting 2620 in cruise, your governor is set too low. Low pitch stops aren’t a factor in cruise speed. Get the governor backed off to where you can get 2700 in cruise first.. if you overshoot 2700, that’s ok, just set the Blue Knob to 2700 and come back around for landing. Then adjust the governor stop to the new lever position. After you get the “in flight” setting nailed to 2700, then you can set the low pitch stops to a static 2650.

 

[SwimmingDragon518]

I seriously think you have the governor set too low. If you are getting 2620 in cruise, your governor is set too low. Low pitch stops aren’t a factor in cruise speed. Get the governor backed off to where you can get 2700 in cruise first.. if you overshoot 2700, that’s ok, just set the Blue Knob to 2700 and come back around for landing. Then adjust the governor stop to the new lever position. After you get the “in flight” setting nailed to 2700, then you can set the low pitch stops to a static 2650.

Okay I will try this. Only thing perplexing me is the hot engine symptoms. Any way you can correlate?

 

[Taltruda]

Okay I will try this. Only thing perplexing me is the hot engine symptoms. Any way you can correlate?

I’ve seen hot engines have slightly higher rpm’s (20 rpm’s or so) but because you don’t seem to be able to make 2700 in cruise, that’s most definitely a governor setting issue

 

[lr172]

Okay I will try this. Only thing perplexing me is the hot engine symptoms. Any way you can correlate?

If the pitch stop is too coarse it acts like fp and those vary their rpm a bit due to environmental factors. It does now sound likes yours is adjusted correctly. Most governors do their thing with a speeder spring. The rpm varies tension on the spring which meters oil flow. Both the spring and the oil change with temps. Most governors are rock solid regardless of temp, however, you have a governor that very few of us use, so hard to say what to expect from it. I know the older MTs had issues with considerable rpm drifting, so it can happen when the design is sub par.

I know you keep going back to engine performance due to this temp issue, but my personal opinion is this is a gov or prop issue.

 

[skylor]

Okay I will try this. Only thing perplexing me is the hot engine symptoms. Any way you can correlate?

Have you verified that your prop speed vernier/control cable has considerably more travel than needed in the full forward/high speed position? I've heard of cases where the cable/vernier is very close to the limits of its travel when the governor arm is on the stop screw and engine compartment/cable temperature changes causes the cable length to change slightly and the governor arm will then pull off of the stop screw. Note that when the outer cable jacket gets hot it expands and if it expands more than the inner cable it has the effect or shortening the inner cable length slightly.

Skylor