Climbing CHT’s and settings for M20K 305

[Richard Knapp]

I have recently bought a Rocket and would like some advice on climbing to altitude. I start off at full everything, and then after 1000 feet or two drop back to a manifold pressure of 35 and 2500 RPM.  Even though I leave the mixture full rich and cowl flaps open, of course, I still find my hotest cylinder creeping above 380 and near 400 at a speed of 120 kts.  Sometimes, perhaps I’ve gone a little slower than 120 kts. I end up having to speed up to 130 kts to get the temperatures to drop a bit, and my climbing rate plummets to about 600 ft./min. I am wondering what other people do. I am not sure that reducing from full throttle and full RPM actually runs any cooler, but it’s what I was taught. Thanks!

[Niko182]

1 minute ago, Richard Knapp said:

I have recently bought a Rocket and would like some advice on climbing to altitude. I start off at full everything, and then after 1000 feet or two drop back to a manifold pressure of 35 and 2500 RPM.  Even though I leave the mixture full rich and cowl flaps open, of course, I still find my hotest cylinder creeping above 380 and near 400 at a speed of 120 kts.  Sometimes, perhaps I’ve gone a little slower than 120 kts. I end up having to speed up to 130 kts to get the temperatures to drop a bit, and my climbing rate plummets to about 600 ft./min. I am wondering what other people do. I am not sure that reducing from full throttle and full RPM actually runs any cooler, but it’s what I was taught. Thanks!

the best mooney you can spend for cooling is guy gibneys seal kits. All in its like 800 bucks, and expect a decrease of 20° at least.

@GEE-BEE

[aviatoreb]

1 hour ago, Richard Knapp said:

I have recently bought a Rocket and would like some advice on climbing to altitude. I start off at full everything, and then after 1000 feet or two drop back to a manifold pressure of 35 and 2500 RPM.  Even though I leave the mixture full rich and cowl flaps open, of course, I still find my hotest cylinder creeping above 380 and near 400 at a speed of 120 kts.  Sometimes, perhaps I’ve gone a little slower than 120 kts. I end up having to speed up to 130 kts to get the temperatures to drop a bit, and my climbing rate plummets to about 600 ft./min. I am wondering what other people do. I am not sure that reducing from full throttle and full RPM actually runs any cooler, but it’s what I was taught. Thanks!

I think something is wrong.  My rocket has always been very cool in all phases of flight. The only time I even need to think about getting hot is in summer when climbing to the upper teens.

Here is my last flight and you can see what I mean.  Its a brief flight but I pulled this one up because its a steep climb - just goofing around and getting to altitude quickly to do some testing - since you see in full power ff for about 1:45 then 85% for about another 1:00 or so to 4500 ft this being at about 90 kts if I remember - which is why I pulled up this flight.  If I am actually going somewhere I would more likely climb at 120ias esp if going to the mid to upper teens to keep from getting hot.  

https://apps.savvyaviation.com/flights/3898600/f6e155b9-3dcc-41d2-9426-d35ce1b7a04c

But keeping it warm, not keeping it cool, is often the issue - In the winter I climb with cowl flaps closed.  And see when I am running Lop all cylinders are below 300.  For 6 months of the year I have the oil cooler half to 2/3 taped off to keep it warm.

I am thinking something is wrong and your plane deserves a trouble shooting trip to the shop.  My only guess - baffling holes?

Edited May 5, 2020 by aviatoreb

[PJClark]

My Rocket is not as cool as @aviatorebs and I've owned it less than a year, but...

I climb at 130 KIAS and 35/2500 after 1000 AGL, cowl flap wide open and mixture full rich. That keeps them all below 400, although I did have to push it over to about 140 KIAS once last August enroute from KABQ to KGXY to keep under 400.

EB--do you have GeeBee baffles?  I asked him about them last Nov and he doesn't have a pattern for a Rocket--I wasn't sure if the stock K baffle seals would work on a Rocket.

Also EB--when you're running LOP what's your TIT?  I can get there, around 13.1-13.3 gph with a .3 gph GAMI spread. But my TIT at that setting is 1620 or so and I can't make myself comfortable with that.  So what's your TIT when LOP, FF, around mid teens, and how many knots do you lose LOP vs ROP?

Ok now I've looked at the flight data...your TIT really is COOLER than EGT??? How did you do that????

I'd love it if all my CHTs would run just 20 deg cooler and TIT around 1500, and I'll spend money to get there if someone can tell me what to spend it on!

[aviatoreb]

28 minutes ago, PJClark said:

My Rocket is not as cool as @aviatorebs and I've owned it less than a year, but...

I climb at 130 KIAS and 35/2500 after 1000 AGL, cowl flap wide open and mixture full rich. That keeps them all below 400, although I did have to push it over to about 140 KIAS once last August enroute from KABQ to KGXY to keep under 400.

EB--do you have GeeBee baffles?  I asked him about them last Nov and he doesn't have a pattern for a Rocket--I wasn't sure if the stock K baffle seals would work on a Rocket.

Also EB--when you're running LOP what's your TIT?  I can get there, around 13.1-13.3 gph with a .3 gph GAMI spread. But my TIT at that setting is 1620 or so and I can't make myself comfortable with that.  So what's your TIT when LOP, FF, around mid teens, and how many knots do you lose LOP vs ROP?

Ok now I've looked at the flight data...your TIT really is COOLER than EGT??? How did you do that????

I'd love it if all my CHTs would run just 20 deg cooler and TIT around 1500, and I'll spend money to get there if someone can tell me what to spend it on!

Hi PJClark - its my new trick.  I got the surefly ignition about 2 months ago - and suddenly I can run LOP wonderfully at almost any setting I want, whereas I was TIT limited before to only do it at about 55%.  Now see in that file i just sent - at about 18 min I do a sweep from ROP back to LOP.  My TIT used to be maybe 1600-1625 if I wanted to run LOP at 55%.  Which I didn't like.  Now, suddenly like night and day since I installed the surefly two months ago, I am running at 72% and TIT is 1375-1390.  I almost wouldn't believe it but look how cool every other sensor is, all 6 EGT and all 6 cylinders are cool too, all cylinders below 300.  And its smooth.  Oh and its 15.8-16 gph instead of 20.  You can see I also have a gami spread of about 0.3gph which I got several years ago just by swapping the stock injectors around rather than buying gami.

So that's my new rocket setup.  But even before 2 months ago, my rocket was not having CHT problems in climb except on a hot day in upper teens where i could easily control it below 400 but I had to pay attention and shallow the climb.

Maybe the difference there is how far north I live?

Edited May 5, 2020 by aviatoreb

[Richard Knapp]

@PJClark, Could you tell me how many FPM you climb at 130 KIAS and 35/2500, please?

[PJClark]

Winter---1000-1500 fpm. Did it last Saturday, closer to 72 deg F OAT on departure, closer to 1000.  Dropped off a bit after 10,000' but I was also running 140 KIAS to keep cool-my top end FF is set too low, being adjusted as we speak.

[Yooper Rocketman]

Try running full throttle, full RPM.  Mine always ran warmer, to a point it was a problem in really hot weather, if I pulled it back to 2500, 35".  Never had a problem at full power, full RPM.

Ironically, when I was trained to fly my mercy flight's Bonanza after the Tornado Alley turbo install, they recommended the same as I was doing with my Rocket.  Full power, full RPM.

Tom

(1,800 hours Rocket time)

[aviatoreb]

2 minutes ago, Yooper Rocketman said:

Try running full throttle, full RPM.  Mine always ran warmer, to a point it was a problem in really hot weather, if I pulled it back to 2500, 35".  Never had a problem at full power, full RPM.

Ironically, when I was trained to fly my mercy flight's Bonanza after the Tornado Alley turbo install, they recommended the same as I was doing with my Rocket.  Full power, full RPM.

Tom

(1,800 hours Rocket time)

What would you know about rockets? - you found your rocket so insufficient you had to dump it for a PT6 with a little airplane hanging behind it.  :-)

Edited May 5, 2020 by aviatoreb

[Yooper Rocketman]

Just now, aviatoreb said:

Who wants to listen to you - you found your rocket so insufficient you had to dump it for a PT6 with a little airplane hanging behind it.  :-)

It's just a measly 100 knots faster.  Minor upgrade from a Rocket! 

And actually, had I not bought the Rocket the new plane would have been done 12 years sooner.  The Rocket was such an amazingly capable airplane it took some of the urgency out of finishing my Lancair.

Tom

[aviatoreb]

Just now, Yooper Rocketman said:

It's just a measly 100 knots faster.  Minor upgrade from a Rocket! 

And actually, had I not bought the Rocket the new plane would have been done 12 years sooner.  The Rocket was such an amazingly capable airplane it took some of the urgency out of finishing my Lancair.

Tom

;-)

How's the cooling on the PT6?

Well for my sake - I find the rocket to be such a satisfying airplane, that it has taken the urgency out of starting a lancair project.  Haha - just kidding - I would never be able to make such a beautiful airplane like you did.

Back to our regularly scheduled program....

Right - what you said Tom - if cooling is an issue these continentals do better at 100% take off power due to the excess fuel flow, than they do at cruise climb.

[PJClark]

now why ddn't I think of that???

I'll do exactly that on my climbout from AGL tomorrow or Thursday.

[Nick Pilotte]

1 hour ago, aviatoreb said:

;-)

How's the cooling on the PT6?

Well for my sake - I find the rocket to be such a satisfying airplane, that it has taken the urgency out of starting a lancair project.  Haha - just kidding - I would never be able to make such a beautiful airplane like you did.

Back to our regularly scheduled program....

Right - what you said Tom - if cooling is an issue these continentals do better at 100% take off power due to the excess fuel flow, than they do at cruise climb.

Wasn’t the PT6 too passé for Tom?  I think he runs a 7XXhp Walters in that monster. 

[aviatoreb]

Just now, Nick Pilotte said:

Wasn’t the PT6 too passé for Tom?  I think he runs a 7XXhp Walters in that monster. 

Oh... I didn't know.  I stand corrected.

In that case Tom has a 7xxhp Walters monster with a little airplane hanging behind it.n  Just enough little airplane to carry some fuel.

Edited May 5, 2020 by aviatoreb

[Yooper Rocketman]

M601D, 724HP Walters (now GE).  No over temps to deal with.  Just manage the ITT  with the fuel lever.  It DOES like cold weather. Initial ROC 3,000’ to 4,000’ PM.  
 

It’s a beautiful plane to fly but the Rocket was an amazing plane to own and fly as well.   I have 18 years and 1800 hours worth of “speed” stories.  One of the best ones being asked to slow down going into Orlando Executive because I was running up the tail of a Boeing 7xx (can’t remember which model but my passenger still talks about that approach control instruction 15 years later).
 

Tom

[PJClark]

@Richard KnappMr. Knapp's original question has been eclipsed as usual.  Did anyone answer satisfactorily,  sir?

[Richard Knapp]

PJClark, yes, I got a lot of help. I’m checking out Gee-Bee. I hope when I’ve got a few other things done to try Surefly ignition. For now I can climb fine with full throttle/full RMP.

Thanks everyone for your help.

[aviatoreb]

43 minutes ago, Richard Knapp said:

PJClark, yes, I got a lot of help. I’m checking out Gee-Bee. I hope when I’ve got a few other things done to try Surefly ignition. For now I can climb fine with full throttle/full RMP.

Thanks everyone for your help.

I am sure we will all be interested if you get a lead on Gee-Bee baffles? I never even heard of them until this thread.

I forgot - there is one more unusual thing I have that contributes to a cooler operating engine - but it is very expensive - I have a four MT blade prop.  That is probably part of why my engine was running cooler than others even before the surefly.  But the surefly no doubt had a major effect that has made it even much cooler.

[N231BN]

PJClark, yes, I got a lot of help. I’m checking out Gee-Bee. I hope when I’ve got a few other things done to try Surefly ignition. For now I can climb fine with full throttle/full RMP.
Thanks everyone for your help.

It sounds like you need to have the fuel injection system properly adjusted. If the previous mechanic skipped an important step you can have adequate takeoff FF but be short at partial-power settings.

[larryb]

Different engine, but hear me out. When I bought my Encore I received some transition training from a well known name on these pages. He recommended dialing back from the Encore MP of 39” to 252 MP of 36 after takeoff. I tried that for a while but it did not work out. CHT increased. If I just kept the full MP then fuel flow was higher and temps cooler.

So consider just leaving it at full MP for the climb.

[aviatoreb]

40 minutes ago, larryb said:

Different engine, but hear me out. When I bought my Encore I received some transition training from a well known name on these pages. He recommended dialing back from the Encore MP of 39” to 252 MP of 36 after takeoff. I tried that for a while but it did not work out. CHT increased. If I just kept the full MP then fuel flow was higher and temps cooler.

So consider just leaving it at full MP for the climb.

Right - it is my understanding that there is some kind of extra mechanism that surges extra fuel when its running at full power to keep it cooled.  So it will be cooler at 100% than at 95%.  100% could be cooler than 85% which might seem counter intuitive but its the extra surge of fuel acting as a cooling agent.  But the engine needs to be tuned properly so that it is for sure delivering enough fuel. Then better to climb at 100%.  Although in less than hot weather I do climb at 85% since if heat is not an issue I figure take it easy if I'm not in a hurry.

[louisut]

17 hours ago, Richard Knapp said:

PJClark, yes, I got a lot of help. I’m checking out Gee-Bee. I hope when I’ve got a few other things done to try Surefly ignition. For now I can climb fine with full throttle/full RMP.

Thanks everyone for your help.

Also, consider that the Rocket AFM specifies 34" / 2300 RPMs for normal climb, not 35" / 2500 RPMs. Full power--38" / 2650 RPMs--is specified for Vx or Vy climbs.

[aviatoreb]

1 hour ago, louisut said:

Also, consider that the Rocket AFM specifies 34" / 2300 RPMs for normal climb, not 35" / 2500 RPMs. Full power--38" / 2650 RPMs--is specified for Vx or Vy climbs.

I don't have that setting in my AFM.  That seems to be a lot of pressure in a rather lower rpm.  After 31'', starting by 32'' all recommended rpm's in my afm are for 2400 or greater.  See attached.  My recommended climb is either 35-2500 or full 38-2650 but for reasons we have been discussing the later can be cooler.  I do use 35-2500 as way up here in the north cooling is often an absolute non-issue.  Or even more so - in the winter sometimes I am struggling to get warmth and climbing with cowl flaps closed.

Definitely go 100% - 38''-2650 if cooling is an issue.

I am aware of at least two different rocket AFM's floating around, and I have copies of both on my hard drive - I believe but do not know there was an early one that was soon updated and a bit different to be the one I have that came with my airplane.

In cruise I rarely use anything beyond 75% on a regular use basis since it seems to be that is the point of diminishing returns where the gained speed really starts dropping off but the increased wear and tear my be increasing quite a bit more.  And 75% even not so often - I use 65% or 72% about 95% of the time between them for cruise.

305Rocket.pdf

Edited May 6, 2020 by aviatoreb

[Richard Knapp]

47 minutes ago, louisut said:

Also, consider that the Rocket AFM specifies 34" / 2300 RPMs for normal climb, not 35" / 2500 RPMs. Full power--38" / 2650 RPMs--is specified for Vx or Vy climbs.

@louisut that is new information to me.  I guess there's some stuff on my Rocket I've not read yet.  I'll try it out! 

[Richard Knapp]

1 hour ago, louisut said:

Also, consider that the Rocket AFM specifies 34" / 2300 RPMs for normal climb, not 35" / 2500 RPMs. Full power--38" / 2650 RPMs--is specified for Vx or Vy climbs.

@louisut what @aviatoreb has posted is what I have.  Could you possibly show us the page from your Rocket AFM, please??  I'd be grateful. :-)