First flight after overhaul - Issues.

[markm20b]

I have an M20B (180hp) and had my engine rebuilt earlier in the year.  Since the overhaul I have been stressed with CHTs of 440-450 on initial climb out.  They settle down in cruise and are lower if I do touch and goes.   Before my overhaul I would see 425 on climb out.  My mechanic (and everyone else I talk with) tells me to quit stressing.  My temps have come down just a little – I now have 16 hours on it.  I’m seeing FF of 16gph on climb out.  All I have is a single CHT and EGT gauge so I have less information and therefore less to worry about.

[AmigOne]

Indeed I have to stop stressing out. Orion is right I was busy flying, expecting God knows what since how often do we get to break-in an engine. I'm definitely not a test pilot. Went to the airport today and was going to go out with the mechanic/pilot who hung the engine and let him check the gauges and manage the engine but the cold front caught up with us and I postponed it. 15-20kts and 90 deg across Rwy 22 , a couple of guys came in and said it was really bumpy so who needs that. Will fly another day. A Vultee BT-13 Valiant (taildragger) went of the runway later on, by a miracle it didn't groundloop but busted one of the runway lights. We were all watching expecting something like that and it did happen. Fortunately no damage to the airplane.

[orionflt]

I have an M20B (180hp) and had my engine rebuilt earlier in the year.  Since the overhaul I have been stressed with CHTs of 440-450 on initial climb out.  They settle down in cruise and are lower if I do touch and goes.   Before my overhaul I would see 425 on climb out.  My mechanic (and everyone else I talk with) tells me to quit stressing.  My temps have come down just a little – I now have 16 hours on it.  I’m seeing FF of 16gph on climb out.  All I have is a single CHT and EGT gauge so I have less information and therefore less to worry about.

Mark,

I basically have the same set up as you, you are a little on the high side during the climb but as your mech says nothing to worry about. I do recommended that you take the time to tighten up the gaps in your baffling, I silicones all the gaps and holes I could find on mine and now my CHT's during climb are just under 400 and right around 300 in cruise with an oat in the 40's.

Brian

[David Brown]

Gentlemen, lets get something straight right from the start. At SEA LEVEL on a standard ISA day, the 200HP Lycoming should be drawing around 20GPH and no less than 19.5 USG/hr.

 

The concept of CHT exceeding 400 degrees without an alarm and letting it go beyond 410 for any period is not harmonious with good engine break in.

 

If any mechanic, hangar buddy or anyone else says otherwise I have a big cheque for them if they can provide data that proves otherwise.

 

Your new engine deserves way better than this. TCM often have flow issues but a Lycoming is most often correct.

 

I would be checking for induction leaks already, and insisting the mechanic sorts out your fuel flow. If he refuses, find a mechanic who will.

 

As for not understanding this and engine monitors telling you things, I would urge you to attend the APS class in Ada OK in March. You will learn a heap and save yourself a fortune longer term. Actually likely the short term.

 

If you want to discuss further please let me know.

 

But please put an end to the engine abuse.

[jetdriven]

I've never seen 20.0 GPH but I've seen 19.x before. Also the fuel flow on a properly functioning RSA-5 injector is not adjustable like on a Continental. I don't think it's adjustable on the carburetor either. Although some Van's RV guys drill out the main jet slightly because some of the carburetors run slightly lean on takeoff.

[orionflt]

Older mooneys are also notorious for high CHT's during climb, the limit is 500f so if your staying under 450 your doing good, by closing up the opening on the front and sealing holes and gaps in the dog. House you can improve those temps. As for fuel flow, since some one wants to get into the nitty gritty of the numbers according to the lycoming engine charts for the 180 hp engine if you are getting all 180 hp on take off your ff should be 17.4 GPH, as you climb your hp will be reduced and your ff will drop accordingly. Since we are never in optimum conditions to generate 100% hp! we usually find ourselves generating an actual brake HP of between 85-90% on take off so if you take the formula 180hp X 90%= 162 X .58 BSFC =93.96 lbs / 6 = 15.66 pph. This formula with the correct BSFC number corrected for rpm will give you your expected FF for any phase of flight if you want to calculate it.

Brian

[David Brown]

Byron, 19.X is acceptable and remember that the RSA system is a very goo MASS AIRFLOW device, so when you depart with a DA of say 1500' it has already accounted for that. If it was a DA of '0' it would flow more. You can change jets on the Carbs and you can change the flow of the fuel servo, however you need the gear to do it and this is best done by a shop with the shims the data and a flow bench set up to do it.

 

Recently I have seen some AVSTAR fuel servo's on new engines (not the Precision Airmotive) and they have not been flowing the correct flows. Go figure!

 

As Brian has calculated above a good BSFC is around 0.58-0.59 and at a DA of sea level on an ISA day, that gets you the fuel flows mentioned in this thread, the mid 19's and 17's for the 180HP.

 

Brian, I am perplexed as to why you say all you will get is 90%. I regularly get 98-102% and it is all based on DA of course. Today it is 41dC where I am so I would not expect anywhere near that 

[orionflt]

I used 90 as a round number less then 100, as you would agree that 100% is based on standard day sea level 29.92. We do not usually meet those conditions except in winter when the temps are down we are on the negative side of the curve. I would love to get out this weekend to see what kind of power I would make with sub zero temps.

[Shadrach]

Most of us in the mid-Atlantic are getting over 100% take off power this time of year. At FDK right now the DA at pattern altitude is -400ft. When I was doing "Circuits and bumps" this morning, the DA at pattern altitude was -1870ft; on the ground it was -3130ft. Well over 100% power is easy to do with numbers like these.