CHT too hot

[Alan Maurer]

Hello Mooney People.\

Question: in 2008 Ovation M20R , the CHT of #5 cylinder goes over 400 degrees on initial climb out. EGT's are all OK.

Thought is was probe and installed a new one and a new gasket on the air intake. Did not change anything.  TT 835 since new.

In level flight ,all seems fine. Don't have a reason for this.....any ideas?

Thanks

Alan

N913ND

[anthonydesmet]

@Alan Maurerthe experts around here I am sure will chime in shortly but they will probably need a little more info:

- did this issue just start?

- have you been in for any maintenance work?

- is this airplane new to you/if so hasn’t it always had this issue?

- what do you usually climb at a/s and throttle? Cowl flaps?

could be anything from a blocked fuel nozzle, baffling, badly tuned fuel system, etc.

just need to know a little more history and profile.

[M20S Driver]

4 hours ago, Alan Maurer said:

Hello Mooney People.\

Question: in 2008 Ovation M20R , the CHT of #5 cylinder goes over 400 degrees on initial climb out. EGT's are all OK.

Thought is was probe and installed a new one and a new gasket on the air intake. Did not change anything.  TT 835 since new.

In level flight ,all seems fine. Don't have a reason for this.....any ideas?

Thanks

Alan

N913ND

Rumor has it that it works 

[Tommooney]

my #5 is also hotest at 380ish in cruise. Not to 400 though. 20 degrees more than other cyl's. On hot oat days in SoCal. 2003 Ovation.

I keep reaching for cowl flaps....

Tom

[carusoam]

Common challenge for Most M20Rs…

You will find that somebody put an alternator really close to #5…

This somehow blocks airflow to that cylinder…

That same someone built up a faring that blocks even more air flow…

 

The union of hangar fairies, more than a decade ago… decided to cut Quarter sized holes in that faring to allow air to flow through it…

Miraculously, the airflow improved, and cht#5 was lowered…. The fairies rejoiced and spread the word…

 

Oddly, the fairies covering their tracks… blatantly called the mod a pixie hole….

 

So… nobody knows the origin of said pixie hole…

there are many pics of their work, yet no undoctored pics of hangar fairies actually exist…

 

Check in with your mechanic… for best methodology of cutting a hole in fiberglass, with out bumping into things behind it…

 

PP thoughts only, about hangar fairy rumors I heard about once…

Best regards,

-a-

[Bentonck]

12 hours ago, carusoam said:

Common challenge for Most M20Rs…

You will find that somebody put an alternator really close to #5…

This somehow blocks airflow to that cylinder…

That same someone built up a faring that blocks even more air flow…

 

The union of hangar fairies, more than a decade ago… decided to cut Quarter sized holes in that faring to allow air to flow through it…

Miraculously, the airflow improved, and cht#5 was lowered…. The fairies rejoiced and spread the word…

 

Oddly, the fairies covering their tracks… blatantly called the mod a pixie hole….

 

So… nobody knows the origin of said pixie hole…

there are many pics of their work, yet no undoctored pics of hangar fairies actually exist…

 

Check in with your mechanic… for best methodology of cutting a hole in fiberglass, with out bumping into things behind it…

 

PP thoughts only, about hangar fairy rumors I heard about once…

Best regards,

-a-

I loved that whole post.

[Alan Maurer]

Hello Everyone and thanks for the advise. We have noted that the alternator in the M20R does block the #5 cylinder. Recent annual but problem has persisted.

Usually climb at Vy for safety/ In cruise the CHT #5 still around 350 which is hotter than other cylinders. I am not sure where this so called pixie hole should be cut but sound good. new #5 CHT probe changed nothing. engine is Continental tuned. model .Spark plugs are brand new fine wire plugs. 

It could be that this is the fault of the front alternator position maybe. Still, it is worrisome and will still try somehow to correct.  Thanks everyone I have tried 

keeping mixture rich to cool engine but that does not help very much.

Alan

N913ND

[carusoam]

There are pics of the hole around here…. Somewhere.

Having the mod improves things a bit…

But, it doesn’t move the alternator out of the way… 

Best regards,

-a-

[Will.iam]

M20S driver above posted the link to the pic of the pixie hole already. 

[carusoam]

For additional pixie pics…

a sub-link in the link above….

Best regards,

-a-

[Schllc]

I had the same issue with both of my ovations. 
The pixie hole appeared on one of mine, it didn’t really help that much. 
gami injectors did help, but the biggest difference was as soon as I got to safe altitude I would level off or go down to 200-300’ a minute climb until the temp was trending down, then resume normal climb and it would stay within normal ranges. 
I  have always understood that 380 or under is perfectly acceptable, and have never had issues.  I have never had to replace a cylinder or even have cylinder work.  Bore scopes and plugs always look very good. 
I don’t ever lean in the climb (nod to mike busch), and I fly almost exclusively lop.  
I do fly very frequently and about 250-300hrs a year. 
if you were never seeing more than 405, and that was only short moments, i would say this is normal and not a big concern. 

350 is not even worth noting.