Slow J

[Llcrt]

I own a 77 J model that will only true out at 160ish MPH or 140 knots.  It appears to be making good power, about 27" manifolf pressure on take off at 700 feet.  Typically in the Tesas summers, she only climbs at about 700 fpm, and the oil temp really starts to heat up.  I think my high oil temp is a result of my lower speeds.  The only 2 things I can think of to do now is to re-rig my flight controls because my right flap stays down ever so slightly and the ailerons are working to roll the plane back to the right.  Could be a little bit of drag.  The other thing that I was thinking was maybe a worn camshaft, but I have no oil in the filters when I cut them open and the engine appears to be running smooth.  Anybody have any ideas?

[Hank]

Check the Time to Climb thread for comparisons.

Personally, I lean towards an induction leak somewhere, you should have more than 27" MP at only 700 msl. I think I hit 27" somewhere above 2000' on climbout. I have multiple photos showing ~143 mph at 9000-9500 msl [168-170 mph True]. Your J should eat my lunch, I only have a C with a slow 3-blade prop.

[jetdriven]

you should get 29" MP on takeoff at sea level, or more precisely, around 1/2" to maybe 1" less than the current altimeter setting.

low oil temperature is a well-known characteristic of M20J's.  I've never seen it run higher than half scale, frequently its at the very bottom of the green.

Mine doesnt climb well, around 700 fm like yours, but in cruise, it does OK. 150 is reasonable. 155 is average. 160 is great.  Check the gear doors are closing tightly, the flaps and ailerons are lined up for starters.

frequently the tach is off, and 2400 RPM wont deliver the power like 2500 RPM will, its around 3 knots slower.

wash the filter in mineral spirits and pour through a coffee filter. bad cam and lifter particles are often there just not caught.

Theres an air racing thread that details some more drag reducing mods.

 

[Bob_Belville]

Quick comment, though not affecting cruise speed, you should see more like 29"on take off below 1000' AGL.

You do not say what speed you're using for climb.

[Piloto]

Check the air filter by switching air boost on and off. There should be no more than 1/2" change. Check magneto timing. A retarded mag will slow you down.

José

[Llcrt]

mags were just overhauled, again!!  lol, ram air is working good.  It doesn't really do much unless I am above 140 MPH indicated, then I gain .1 to .2 inches.  I have the new  challenger air filter, it didn't do much for me.  If i had an induction leak, I would think that it would show up on the EDM with a split in temps, but not sure. Also, my oil temp is very high, not low, I've done just about everything you can think of to bring it down.  In a shallow decent and picking up a few knots of indicated airspeed, she cools down.  Pretty sad, but unless the air temp is in the 50's or below, I have to fly with cowl flaps open to keep the oil temp under control, unfortunately, this does not help my speed issue.  Also sad, is the fact I can drop my landing gear any time I wish in level flight as I am only doing 120 kias.

 

[jetdriven]

that oil temp is not normal. on the hottest of days, in cruise, it wont exceed 1/3rd to 1/2 scale.

[WardHolbrook]

Check everything - the rigging, the tach, manifold pressure gauge, engine baffling, air filter, mag timing, gear doors, look for induction leaks, in other words, check pretty much everything. The airplane is getting close to 40 years old and this stuff needs a thorough IRAN from time to time. 10% slower than the average M20J is a lot and certainly needs to be addressed. My bet is that there is more than one thing going on so keep looking until you've gone through it all. 

[201er]

55 minutes ago, Llcrt said:

I own a 77 J model that will only true out at 160ish MPH or 140 knots.  It appears to be making good power, about 27" manifolf pressure on take off at 700 feet.  Typically in the Tesas summers, she only climbs at about 700 fpm, and the oil temp really starts to heat up.  I think my high oil temp is a result of my lower speeds.  The only 2 things I can think of to do now is to re-rig my flight controls because my right flap stays down ever so slightly and the ailerons are working to roll the plane back to the right.  Could be a little bit of drag.  The other thing that I was thinking was maybe a worn camshaft, but I have no oil in the filters when I cut them open and the engine appears to be running smooth.  Anybody have any ideas?

Are you sure you are comparing apples to apples? What RPM? What fuel flow? What EGT? What altitude and temp? What kind of mags and timing?

A good comparison test is to go to 7-8000ft, leave throttle full, leave RPM full, lean to 100ROP and calculate your TAS. This will be the best case scenario 75% cruise. I get about 160KTAS once a few hundred under gross.

[Two Oh One]

1 hour ago, jetdriven said:

frequently the tach is off, and 2400 RPM wont deliver the power like 2500 RPM will, its around 3 knots slower.

Maybe this? Mine was quite a bit off..

[Shadrach]

40 minutes ago, Llcrt said:

I own a 77 J model that will only true out at 160ish MPH or 140 knots.  It appears to be making good power, about 27" manifolf pressure on take off at 700 feet.  Typically in the Tesas summers, she only climbs at about 700 fpm, and the oil temp really starts to heat up.  I think my high oil temp is a result of my lower speeds.  The only 2 things I can think of to do now is to re-rig my flight controls because my right flap stays down ever so slightly and the ailerons are working to roll the plane back to the right.  Could be a little bit of drag.  The other thing that I was thinking was maybe a worn camshaft, but I have no oil in the filters when I cut them open and the engine appears to be running smooth.  Anybody have any ideas?

Don't have a J but can say something is definately wrong. This time of year my F would come close to if not double your climb rate with me and half tanks. 

In addition to what's been mentioned, I would verify that the tach is accurate. Do have an engine monitor? What's your take off FF.  27" is low MP on take off. You should only lose about .5" of MP.

[Llcrt]

The plane has an EDM 830 for a very accurate Manifold gage and Tach.  I typically cruise between 7500 and 9500 feet full throttle, 2500 RPM, 75 ROP burning between 9.5 and 10.2 gallons per hour.  At cruise, MAP is around 22 to 23 inches.

[OR75]

Just to exhaust the list of things to look at: 

is your whole pitot static system ok / checked ? 

[Shadrach]

9 hours ago, Llcrt said:

The plane has an EDM 830 for a very accurate Manifold gage and Tach.  I typically cruise between 7500 and 9500 feet full throttle, 2500 RPM, 75 ROP burning between 9.5 and 10.2 gallons per hour.  At cruise, MAP is around 22 to 23 inches.

What is your take-off FF and the elevation of your home drome?

[N601RX]

8 hours ago, Llcrt said:

The plane has an EDM 830 for a very accurate Manifold gage and Tach.  I typically cruise between 7500 and 9500 feet full throttle, 2500 RPM, 75 ROP burning between 9.5 and 10.2 gallons per hour.  At cruise, MAP is around 22 to 23 inches.

The JPI 830 has a MP correction factor that can be set.  Do you know if it was ever set?  If so it should read 29.9 on a standard day at sea level.  Otherwise 27 is to low. Start by verifying that the throttle is opening the servo butterfly completely open.

[Bob_Belville]

4 minutes ago, N601RX said:

The JPI 830 has a MP correction factor that can be set.  Do you know if it was ever set?  If so it should read 29.9 on a standard day at sea level.  Otherwise 27 is to low. Start by verifying that the throttle is opening the servo butterfly completely open.

With engine off, the JPI should show MAP @ baro pressure minus ~ 1" per 1000' pressure altitude.   

[nels]

Has the plane ever had a gear up. If so you might check the prop diameter. The prop may be ground to the min diam or less. Or the wrong prop.

[Llcrt]

The EDM has been calibrated for pressure.  I have not visually verified the butterfly is open all the way, however, the throttle linkage goes all the way to the stop on the throttle body and the rpm does get up to 2750, haven't ajusted that stop yet.  Home field is 650 feet and take off fuel flow is right around 17.5 to 18 per hour depending on the conditions for the day,  All these thing have been checked several times.  This is why I'm thinking its a worn camshaft.  Something I can't easily verify, but can definately slow the plane.  I just need to figure out how to verify a camshaft without pulling a cylinder.  any ideas?  Also, if it is worn, its uniformly worn.  All temps in the air are only a couple of degrees from one another until I approach LOP.  If it is a cam, that will suck, this engine only has about 600 hours on it since overhaul.

[Shadrach]

No way to see the cam without pulling a cylinder. Do you have the oil analyzed? You have verified ignition timing? What is the timing spec on the data plate? 

I have seen a number of Lycoming valve trains $hit the bed; the significant damage usually starts with lifters in my experience and that usually deposits a fare amount of metal in the oil. The IO320 in my father-in-law's Decathlon failed this way. It was still performing well, but there was nearly a tablespoon of metal particulate ranging in size from sand to course ground pepper. I think the cam survived, but the lifter surfaces looked like something from the Middle Ages.

[pinerunner]

I think the high oil temperatures bother me the most in your situation. I wonder if something could be blocking air flow to and through your oil cooler. A problem with air flow inside the cowling inside the cowling might have a bigger affect on airspeed than you would think at first. At any rate oil temperatures outside of acceptable range ought to be addressed soon.

[cnoe]

This may be too obvious but are you checking speed as measured by a GPS over an appropriate 3 or 4 leg course?

Sent from my iPad using Tapatalk

[Llcrt]

There has to be a way to measure the cam, I'm thinking about pulling valve covers and measuring how much the rockers move then give Lycoming a call with my findings.  Mags are timed correctly, they have been off 3 times in the last 8 months, so unless i have 3 different mechanics doing it identically incorrectly, i will have to say they are good.  Airflow inside the cowling should have no affect on the planes speed, but it will have an effect on the oil temp which it does.  Like I stated earlier, I think the oil temp is a result of my slow speed.  The engine is doing 100% of the work, but only getting 80% of the forward speed which equals to more airflow.  I haven't done an oil analysis yet, however, I drain my oil through a coffee filter with a magnet in the bottom of it.  Both the coffee filter and magnet is clean as is the engine oil filter.  The prop "should" be the correct diameter since it was replaced during the engine overhaul, so it also has right around 600 hours on it.  Im pulling the last of my hair out trying to figure this out.  lol

[jetdriven]

the dual mag on my plane had been through annuals with two different mechanics and my guy was the third, he didnt catch it was timed at 20 degrees. A3B6 engines are supposed to be 25. I'd put the buzz box on it, only takes 20 minutes.

The oil cooler is way oversized and Ive never seen more than half scale, something is going on with that. Your speed is high enough its not that.

[N601RX]

Has it just got this way or always been like this?  The guy who was teaching a Lycoming service school a few years ago told a story about a batch of crank gears that had a "vague" timing mark on one tooth and the real timing mark on the next tooth.  A few people managed to confuse the two and had what appeared to be a good engine that didn't make normal power.  He showed how to detect this by positioning a cylinder at TDC and moving the prop back and fouth a few degrees while observing the 2 rockers. If  I remember correctly their beginning to open should be centered around TDC when the cam timing is correct

Lycoming uses hydraulic lifters so you would need to remove the valve spring pressure to get a good measurement.  It would probably be best to remove the rockers and pushrods and measure directly on top of the lifter.

[Llcrt]

True airspeed is being calculated by using information the plane gives me with current conditions, then i bounce that against my gps ground speed.  Typically only 1 to3 MPH off due to wind variations.  The timing marks are very interesting, I'm not sure if the mechanics used a buzz box or not, I've only seen a box with lights, what the difference, I don't know.