CHT for Cyl 2 and 4

[Ghostrider]

Don Maxwell.. I have a question for you.. I have a 1968 M20C. Fred Blue's old plane that you used to service in TX. I recently installed a engine anylizer and can see all 4 CHT's First off.. Ignorance was bliss. My number 3 that the factory guage is on is the coolest... Go figure. Anyway, numbers 1 and 3 run cool enough.. like 380 max in climb and 330-350 in cruise... My number 2 and 4 run really hot in climb... I have to put the nose down to climb at 125MPH or more and those two still sit at 430 and 440, if I try to do a 100mph climb they will excdede 460. I have checked the baffeling and remade some of the doghouse. I am ordering a new internal cylinder baffle today. I checked my fixed cowl flaps and they are both open at least as much as the book says. My question is what prevents me from upgrading to a modern style baffel system instead of the doghouse. can this work or if not what else is different.

Anyone can answer but I figured the expert Don is one oppinion I would like to have. 
BTW no induction leaks and those two Cyl do not peak any sooner which would indicate an air leak in the induction system. Any help would be great.

[MIm20c]

Do you have a fuel flow monitor on the new guage?

[Bob_Belville]

DMax does not keep up with MooneySpace. You might contact him directly or post to the MAPA listserv if you're a member of MAPA. 

But there are lots of folks here who will be happy to advise you, and help you spend your money. Some of what you read here might even be true.

[Bob_Belville]

There are a number of C owners here who have acceptable CHTs with the old doghouse system. If I were you I think I'd have someone who knows vintage Mooneys - LASAR is about an hour north of you - take a look at your baffle system before I started throwing money at the problem that has not been diagnosed yet, there likely is something amiss. 

[Ghostrider]

I do have a FF and at full rich I am at about 18GPH...  

 

[Ghostrider]

then What CHT's do people see on the C's ? with a monitor on all 4?  if 420-440 is normal on climb and 396-400 in cruise for the left bank (2 and 4) then so be it.. but I want to know this is normal.  I get they are all high.. but HOW high....

 

Thanks

Edited August 7, 2017 by Ghostrider

[Bob_Belville]

6 minutes ago, Ghostrider said:

then What CHT's do people see on the C's ? with a monitor on all 4?  if 420-440 is normal on climb and 396-400 in cruise for the left bank (2 and 4) then so be it.. but I want to know this is normal.  I get they are all high.. but HOW high....

 

Thanks

@Hank got your ears on tonight? (Hank is in Auburn AL and I think his CHTs run 400 or less but he's on here often and will see my tag and can reply for himself.) 

Edit: come to think of it, his C is a late model so he might not have the doghouse. 

[MIm20c]

1 hour ago, Ghostrider said:

I do have a FF and at full rich I am at about 18GPH...  

 

Should be plenty of fuel to keep things cool. Normally on climb out I'm seeing 360-390 depending on climb speed and ambient temperature. Every so often one jumps to 400-405 which I can quickly bring down by increasing speed to 120 mph. I'm currently looking at some air gaps (I have a large one around my relatively new alternator) to keep the temps below 375.  I also find cyl 2 & 4 are normally the warmest during climb.  

[carusoam]

Welcome aboard GhostRider.  Your buds, Maverick and Goose will be along soon... 

There is plenty written about operations of the M20C around here...

1) the dog house is not perfect.  but getting it in its top shape always helps...

2) lower cowling closures have been supplied by different companies... do you have one?

3) When asking these types of questions it helps to share your data... do you have an engine monitor collecting data?

4) It helps to have the most modern POH you can get for your plane...  do you have a copy?

5) Climb attitude and speed have a huge effect on cooling... climbing out at 120 or faster is better for cooling, and not so bad for Vs.

6) Full mixture in at T/O maintaining 2-300°F ROP is great for maintaining CHTs and climb power.

7) Full throttle - (minus) enough to cut the second fuel jet works well for max climb power.

8) continue to do your reading.  There is plenty to read around here regarding M20C ops...

9) read up on things like LOP with the M20C.  Some people have been successful with that. It covers a lot of lees deep topics as well...

10) check in with our resident M20C pilot and engineer @Hank he has no fear of writing about things he knows quite well... 

11) there is a new cowling design being built and sold around here, keep your eyes open for it...

12) CHTs below 380°F are preffered for Best cylinder health.  The M20C single CHT redline is well above this generally accepted value.

13) oil has a tendency to burn in the valve guide on cylinders that have been really hot. There is a procedure for cleaning them out called the rope trick.  Use the search function to find it.

14) crusted carbon in the valve guides can cause sticking exhaust valves.  A symptom called morning sickness.  Having an engine monitor is your best defense against this happening without a hint...

What took so long to write your first post?

Best regards,

-a-

 

[Andy95W]

I have the doghouse on my C.  I have done considerable work in patching every hole I have found on the doghouse.

OAT- upper '80s

A/S- 95-100.  CHT #3 (hottest)- about 405-410°-  at which point I lower the nose to get to about 120.

A/S 120.  CHT #3/4 (hottest)- 390-400°

A/S- 145 (cruise) all CHTs about 335-350°

A lot of people are advocates of full power climbs.  At 25/2500, 120 m.p.h., my CHTs are consistently 5-10° cooler than full power.

 

[Ghostrider]

4 minutes ago, carusoam said:

Welcome aboard GhostRider.  Your buds, Maverick and Goose will be along soon... 

There is plenty written about operations of the M20C around here...

1) the dog house is not perfect.  but getting it in its top shape always helps...

2) lower cowling closures have been supplied by different companies... do you have one?

3) When asking these types of questions it helps to share your data... do you have an engine monitor collecting data?

4) It helps to have the most modern POH you can get for your plane...  do you have a copy?

5) Climb attitude and speed have a huge effect on cooling... climbing out at 120 or faster is better for cooling, and not so bad for Vs.

6) Full mixture in at T/O maintaining 2-300°F ROP is great for maintaining CHTs and climb power.

7) Full throttle - (minus) enough to cut the second fuel jet works well for max climb power.

8) continue to do your reading.  There is plenty to read around here regarding M20C ops...

9) read up on things like LOP with the M20C.  Some people have been successful with that. It covers a lot of lees deep topics as well...

10) check in with our resident M20C pilot and engineer @Hank he has no fear of writing about things he knows quite well... 

What took so long to write your first post?

Best regards,

-a-

 

Some History.. Bought the C in 2008 as a 80 hour pilot.  Have over 1060 hours now, all in the Mooney.  I do owner assisted annuals.  Any real repairs have been done by Top Gun since I am located at KSCK.  I personally installed the Panel upgrade with the two LASAR panels.  I recently upgraded my GTX330 to ES and while running the  RS-232 wire for the Com to the 430W I knocked the Com 1 audio in wire out and had no audio.. while fixing that I knocked 2 others out from he 80 pin 430 D connector.  So I pulled the whole stack got the manuals and rewired the whole thing.. because it was a cluster after years of small upgrades at a time.  While doing this I also installed the Insight G3 engine monitor and LOVE IT!  But this is why I now am aware of the High CHT's for 2 and 4... Probably nothing new but now that I am aware I want to fix.  I am looking at the lower cowl upgrades but the date is mixed on how it really helps or not with heat and or speed. 

As for Mods I have the Flap and aileron seals, Vertical tail root and I personally installed the Horizontal tail root.  (yes all signed off and supervised by my AI if I did the work)

I do have a modern POH I believe.. and the original..

As to climb speed and additude, I used to clime at 100MPH until at 1500ft or so and again if I had terrain to clear.. and then 120MPH for better overall time to destination (unless I knew there was a kick ass tail wind waiting for me and then I would try to climb faster) but now that I know my temps for 2 and 4 I climb at 130MPH and still have temps over 420 for 2 and 4.  and now I circle to get over terrain..

I use full mixture until its choking now... again because of temps... and to my understanding the Mooney Carb does NOT have that full power extra rich valve (think power valve).  I could be wrong but that's what I though one of the guru's had said before. 

I will always continue reading but trust me since I started flying in 2007 I spend at least an hour or two a week up to 10 hours a week learning.. from accidents review, to Mooney specific information, ect ect... 

I have tried LOP since I got the G3 and my Gami spread has been as much as 2 GPH and when your only flowing 8 or so that's a big diff... but Today coming back from Oceano at 8500 I was playing around and with 1950RPM (I normally fly 2500 unless down low for a short hop in to RHV from SCK) I had a spread with lowest being 6.9GPH and highest at 7.1 GPH and settled out at 6.5ish with a reading of between 25 and 60 deg lean of peak... it was a ruff sounding engine but better than I have ever been able to do before.

 

Thanks

[carusoam]

Thanks for sharing your history, GR.  That will help a lot.

There are a few versions of the carburetor that have ended up in M20Cs over the years.

 A quick log search may reveal which one you got.

One MSer and NJMPer named Dev, has given some interesting detail regarding variations of the Marvell Schebler carb.  Floats, and fuel jets /nozzles and other things...

Hopefully this gives you enough to search on... Dev's screen name doesn't come to mind right now...

There are two jets in the carb.  One is only open when the throttle is wide open...  getting it to close requires pulling the throttle back a small amount.  You should be able to notice the FF step change when it closes...

Another challenge... not many M20Cs have the luxury of having full engine instrumentation including FF data combined with a pilot that is also an avid reader and technical writer...

You might review your GAMI spread info for a moment...  it is usually shared as the difference of FF from the last to peak minus the FF @ the first to peak... a difference of .1gph is tight... a half gallon is useable but can use help.  

The carb is known to be a large number. Closing the enrichment circuit helps, closing the butterfly valve a touch helps, adding some thermal energy via carb heat can help some as well.  These three items improve mixing, vaporization and distribution of the fuel mixture on its way to the cylinders...  

all stuff I learned about at MS. Written by M20C pilots...  Go Hank and Dev!

Welcome aboard, again!

Hope you can stick around.  Do you have a technical background?  Pro-pilot, Mechanic, engineer, or just like this stuff?

(some of our best hands on Mooney people don't have hands on machine type work experience)

Best regards,

-a-

[Hank]

Welcome Ghostrider! The pattern is not full tonight . . .

My 1970 C has a doghouse, and I spent two annuals making mostly sheet metal repairs to it. Since doing that and rebuilding the intake flapper in front the of the carb, I can now run LOP. But I don't cruise there, since I do not have an engine monitor. Yet.  

I do climb WOT / 2700 to my cruise altitude, leaning with Target EGT when I remember. On a recent flight here in Lower Alabama, OATs were in the mid-90s away from the runway, and I climbed 326-7500 msl, leveled off, accelerated and set power at 22" / 2400 less than fifteen minutes after turning the key. My factory CHT never reached the edge of the green stripe, and the Oil Temp (my most frequent limiting factor prior to doghouse work) was a needle's width lower.

Hope to get a monitor in soon, but am horribly conflicted about what to remove from my already full panel.

Regarding cruise:  after talking to Bob Kromer, I followed his suggestion and operated WOT for an entire flight. TAS didn't change much, but fuel burn sure did! When sufficiently high, I back off the throttle lever until I see the MP needle start to move, then generally set 2500. For low, short food runs, I often set 23 / 2300, which is also convenient for starting Instrument approaches. As above, mid-level cruise is often 22 / 2400, just to keep things simple. At WOT- / 2500, I often see TAS around 147-148 knots, pretty good for 180 hp.

P.S.--I have the guppy mouth closure, 201 windshield and a (allegedly) slow Hartzell 3-blade prop. No extra seals anywhere that aren't factory standard, or weren't in 1970.

P.P.S.--my WOT climbs are at Vy. Now that I'm no longer at an obstructed field, I don't routinely climb at Vx initially, since I'm not clearing obstacles.

Edited August 7, 2017 by Hank

[carusoam]

Hank, you are the best! 

-a-

[Hank]

Just now, carusoam said:

Hank, you are the best! 

-a-

Lots of time and a fair amount of money invested in figuring out all of this Mooney flying stuff . . . With  dividends in trips, scenery and memories made.  

[Hector]

I have the doghouse on my C.  I have done considerable work in patching every hole I have found on the doghouse.
OAT- upper '80s
A/S- 95-100.  CHT #3 (hottest)- about 405-410°-  at which point I lower the nose to get to about 120.
A/S 120.  CHT #3/4 (hottest)- 390-400°
A/S- 145 (cruise) all CHTs about 335-350°
A lot of people are advocates of full power climbs.  At 25/2500, 120 m.p.h., my CHTs are consistently 5-10° cooler than full power.
 

I think my C has VERY similar performance. I climb at VY to 1000 AGL then 120 for the rest. Today here in Florida with OAT at 95 I was cruising with all cylinders below 360 (22/2400). However, I wish I could say the same for takeoff. 400-425 typical at VY but then 390-400 climbing at 120. 1400 hours on the engine with good compressions so maybe ok.


Sent from my iPad using Tapatalk

[Andy95W]

My concern with Hank's numbers are that without a full 8 probe engine monitor, we really can't be sure where his CHTs really are.  The CHT limit for the O-360, according to the Type Certificate Data Sheet, is 500°F.  

Yikes!  So when his factory CHT gauge "never reached the edge of the green stripe", we really don't know what that temperature is- and it could be way over 420°.

Hank- I thought I'd noticed in one of your panel photos that you had a carburetor air temperature gauge.  That would be an ideal place to put a JPI EDM700 with an additional probe to display carb temperature. That way, you wouldn't miss anything from your current panel.

[carusoam]

Oh yeah....

As Andy pointed out...

OAT and Carb temps are great additions to the instrument panels for the M20C...

It always helps to know that ice is a possibility before it happens.

Best regards,

-a-

[jamesm]

I have same problem  my hottest  Cylinders  2 & 4 but after trying multiple things over many years . I have given up trying  figure out reasons why .

23 hours ago, Ghostrider said:

what prevents me from upgrading to a modern style baffel system instead of the doghouse. can this work or if not what else is different.

What prevents you is the  FAA. Since it is considered a Major alteration to modify baffling. The FAA and Mooney have approved this Cylinder  over temp design.  Nobody wants own their mistake and allow  someone to fix it. 

  I asked my local  FSDO  about doing temporary baffle test they when into this process about  taking an  aircraft  out of the standard category and moving it into experimental category. Just to simple Baffle around inner cylinders.  All that work for one piece of sheet metal. Just for a  15 min test.  It seems to me it should be a requirement to have technical back ground or aviation background to work for the FAA but unfortunately like most  big organizations they are  very inefficient and lacking  basic common sense and  sound reasoning  gets you no where.

Edited August 7, 2017 by jamesm

[Hank]

5 hours ago, Andy95W said:

My concern with Hank's numbers are that without a full 8 probe engine monitor, we really can't be sure where his CHTs really are.  The CHT limit for the O-360, according to the Type Certificate Data Sheet, is 500°F.  

Yikes!  So when his factory CHT gauge "never reached the edge of the green stripe", we really don't know what that temperature is- and it could be way over 420°.

Hank- I thought I'd noticed in one of your panel photos that you had a carburetor air temperature gauge.  That would be an ideal place to put a JPI EDM700 with an additional probe to display carb temperature. That way, you wouldn't miss anything from your current panel.

I think my CHT shows 450°F redline, and there's a very noticeable gap between it and the end of the green stripe.

The only problem with replacing the Carb Temp with an engine monitor is that, like my EGT, it's a little 21/2" gage . . .

[Ghostrider]

2 hours ago, Hank said:

I think my CHT shows 450°F redline, and there's a very noticeable gap between it and the end of the green stripe.

The only problem with replacing the Carb Temp with an engine monitor is that, like my EGT, it's a little 21/2" gage . . .

Mine was too... I replaced the 2.5" Carb heat with the 2.5" G3.... its easy to see and read right to the left of the yoke.. I did need to change my ign key setup... I keep the key chain with hangar keys in my pocket now and use just a single key in the ign... the keychain would hang down over the Carb heat and that was fine but with the G3 it was an issue.

 

[Ghostrider]

10 hours ago, carusoam said:

Thanks for sharing your history, GR.  That will help a lot.

There are a few versions of the carburetor that have ended up in M20Cs over the years.

 A quick log search may reveal which one you got.

One MSer and NJMPer named Dev, has given some interesting detail regarding variations of the Marvell Schebler carb.  Floats, and fuel jets /nozzles and other things...

Hopefully this gives you enough to search on... Dev's screen name doesn't come to mind right now...

There are two jets in the carb.  One is only open when the throttle is wide open...  getting it to close requires pulling the throttle back a small amount.  You should be able to notice the FF step change when it closes...

Another challenge... not many M20Cs have the luxury of having full engine instrumentation including FF data combined with a pilot that is also an avid reader and technical writer...

You might review your GAMI spread info for a moment...  it is usually shared as the difference of FF from the last to peak minus the FF @ the first to peak... a difference of .1gph is tight... a half gallon is useable but can use help.  

The carb is known to be a large number. Closing the enrichment circuit helps, closing the butterfly valve a touch helps, adding some thermal energy via carb heat can help some as well.  These three items improve mixing, vaporization and distribution of the fuel mixture on its way to the cylinders...  

all stuff I learned about at MS. Written by M20C pilots...  Go Hank and Dev!

Welcome aboard, again!

Hope you can stick around.  Do you have a technical background?  Pro-pilot, Mechanic, engineer, or just like this stuff?

(some of our best hands on Mooney people don't have hands on machine type work experience)

Best regards,

-a-

Ya I listed the spread as raw numbers for my first and last to peak...but normally when I have tried down lower but with RPM at 2300 and MP of 20 the spread is like 1.5 to 2 gallons.

Yes I have a technical background... Went to ITT Tech.. from 91 to 93 and learned Electronics.  For a job I am Technical support for FEI Company (Now Thermo Fisher Scientific) I used to be field service but now I am the guy the FSE's call when they need help.. I also answer calls from customers.  The equipment is Scanning Electron Microscopes and Dual Beam Equipment (a Focused Ion Beam column and an Electron Column on the same platform)  With this I do high level troubleshooting of Vacuum System, Electron Optics, Ion Optics, Electronics, and micro Mechanic Stages that use Piezo Electric Motors. 

Mechanically I have done projects before aviation like removing a 1990 Ford Mustang 5.0 motor and putting it into my 1984 Ford Ranger PU... Then later after the truck was inop for other reasons I put that motor into my 1974 Orion Tri-Hull boat.  I put a 1968 Lincoln Continental motor into a 1963 Ford F100 Long bed Unibody truck.  Still have that.

And most importantly .... I did stay in a Holiday Inn Express last night.....  ;-) 

[Andy95W]

3 hours ago, Hank said:

I think my CHT shows 450°F redline, and there's a very noticeable gap between it and the end of the green stripe.

The only problem with replacing the Carb Temp with an engine monitor is that, like my EGT, it's a little 21/2" gage . . .

The EDM-700 I'm talking about is the 2 1/2" model.  I like my old gauges, too, and just wanted the extra and more accurate information.

 

[Ghostrider]

My G3 in flight

[Bob_Belville]

Just an aside, if you're typically showing that 13.3V you might want to check the spec. Mine wants to be 13.8-14.0 and my Voltage Regulator can be tweaked. YMMV, but a little more cranking juice will be helpful starting after the plane has sat for a while or the OAT is low.