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Low CHT

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glipaz

Joined: 11 Jan 2011
Posts: 110

Posted: Mon Jul 11, 2022 11:13 am Post subject: Low CHT

Hey friends.  I have a low time M-14P on my Nanchang.  I typically have low CHTs in the 140C range even with gills closed.  Fly out of SoCal so not a cold climate.  I know Richard Goode tends to point to the suction jet and being too rich, but know that I also only get around 35gph fuel flow with WOT. I have increased the suction jet as large as I can to raise temps but not get a lean surge at altitude.

Thoughts?

Gil

richard.goode(at)russiana
Guest

Posted: Mon Jul 11, 2022 10:10 pm Post subject: Low CHT

Hello Gil,



Interesting. To be honest I would first suspect the sender underneath the

spark plug. It is a very imprecise way of temperature measurement that can

be helped by rarely cleaning the cylinder head and the sending ring itself.

And then which suction jet have you got fitted? And the engine as a standard

M 14 P?



Please let me know and with regards



Richard

RICHARD GOODE AEROBATICS

Rhodds Farm, Lyonshall, Hereford, HR5 3LW, UK

Tel:  +44 (0)1544 340120   Fax:  +44 (0)1544 340129

e-mail: richard.goode(at)russianaeros.com

www.russianaeros.com

WORLD LEADERS IN SOVIET & CHINESE RADIAL AIRCRAFT ENGINES

In partnership with Aerometal Kft, Hungary.



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Vic

Joined: 12 Aug 2008
Posts: 116
Location: Southern Bavaria

Posted: Tue Jul 12, 2022 4:08 am Post subject: Re: Low CHT

Hi Richard,

off topic, but I had no luck so far trying to contact you about a set of hoses for a 18 T. Do my emails bounce back to somewhere ? I donÂ´t get error warnings when sending so still head scratching . . .



   Vic

richard.goode(at)russiana
Guest

Posted: Tue Jul 12, 2022 5:08 am Post subject: Low CHT

Hi Vic,



Richard was in email correspondence with you yesterday regarding hoses. You last emailed us today at 01:26 our time and Richard replied to you at 06:58. Did you receive that email? Are you trying to reply to that one? I'll resend it to you again now. We don't have many filters on our emails, so people don't usually struggle to reach us.



Kind regards,



Wendy

RICHARD GOODE AEROBATICS

Rhodds Farm, Lyonshall, Hereford, HR5 3LW, UK

Tel:  +44 (0)1544 340120   Fax:  +44 (0)1544 340129

e-mail: richard.goode(at)russianaeros.com

www.russianaeros.com

WORLD LEADERS IN SOVIET & CHINESE RADIAL AIRCRAFT ENGINES

In partnership with Aerometal Kft, Hungary.



--

Vic

Joined: 12 Aug 2008
Posts: 116
Location: Southern Bavaria

Posted: Tue Jul 12, 2022 5:57 am Post subject: Re: Low CHT

Hi Wendy,

thank you sooo much, your mail landed in my own spam files !! I should check this more often - well, old age I guess. Years ago there was a notice when anything arrived in spam, but no longer for some reason, now thatÂ´s computer business . Does that make sense , cannot see this. 

  I will send details to you today.



   cheers 

   Vic

glipaz

Joined: 11 Jan 2011
Posts: 110

Posted: Tue Jul 12, 2022 7:29 am Post subject: Re: Low CHT

Vic, thanks for blowing up my thread.

Vic

Joined: 12 Aug 2008
Posts: 116
Location: Southern Bavaria

Posted: Tue Jul 12, 2022 12:58 pm Post subject: Re: Low CHT

Two postings from me ? I said why, because I was unable to contact Richard . So go on with your topic . . . .



   Vic

Ttail

Joined: 24 Jun 2013
Posts: 120

Posted: Tue Jul 12, 2022 6:36 pm Post subject: Re: Low CHT

Gil. 

My engine (M14PF) came with 1.3mm suction jet fitted. This was changed to a 1.5mm suction jet so slightly leaner. No issue controlling CHT's to say 180C. Also picked up a lesser fuel burn at crz power settings. FF reduced by 4L hr.

_________________
Sean Trestrail
ttail[at]internode.on.net

richard.goode(at)russiana
Guest

Posted: Tue Jul 12, 2022 11:42 pm Post subject: Low CHT

These engines are surprisingly "individual" when choosing a suction jet. That is that two engines of seemingly identical specification can require suction jets 0.1 mm or even 0.2 mm apart. But from my experience I would suggest that for an M 14 PF that a 1.3 mm suction jet is probably correct. But I'd also say that a 1.5 mm (larger means leaner since they are compensating jets) is too lean. Then, as I said before, the CHT measuring probe under a sparking plug is an incredibly imprecise way of measuring temperature. But it makes a huge difference if it is really clean as indeed its "seat" onto a cylinder head. Then I would suggest comparing its reading with an accurate external CHT measurement. And, finally, I wouldn't be concerned about fuel flow. I feel too many people have expensive electronic fuel flow measurements and then become obsessed by them. Engine performance and cylinder temperature are, to my mind, the only important factors!

RICHARD GOODE AEROBATICS

Rhodds Farm, Lyonshall, Hereford, HR5 3LW, UK

Tel:  +44 (0)1544 340120   Fax:  +44 (0)1544 340129

e-mail: richard.goode(at)russianaeros.com

www.russianaeros.com

WORLD LEADERS IN SOVIET & CHINESE RADIAL AIRCRAFT ENGINES

In partnership with Aerometal Kft, Hungary.



--

glipaz

Joined: 11 Jan 2011
Posts: 110

Posted: Wed Jul 13, 2022 10:18 am Post subject: Re: Low CHT

Thanks Richard!  My suction jet is 130 on my standard M-14p.  Itâ€™s not a PF.  

Accel jet is 060. I don't use the stock CHT sensor.  I have an Electronic International multi-cyl instrument.  Iâ€™d like CHTs to be at least 170C.  

Gil

Ttail

Joined: 24 Jun 2013
Posts: 120

Posted: Wed Jul 13, 2022 2:58 pm Post subject: Re: Low CHT

" I feel too many people have expensive electronic fuel flow measurements and then become obsessed by them. Engine performance and cylinder temperature are, to my mind, the only important factors! '[i]



The reduction in FF was an observation not an "obsession". Its also kind of nice to have a second independent fuel qty system.



The reason the jet was changed in the first place was consistently low CHT (on all cylinders).  After the change CHT is far more manageable.

_________________
Sean Trestrail
ttail[at]internode.on.net

richard.goode(at)russiana
Guest

Posted: Wed Jul 13, 2022 11:26 pm Post subject: Low CHT

Hello Sean,



Of course I had no idea who this might be, and "obsession" might be too strong a term. But remember that the Russians have been using these engines for 50 years without any kind of fuel flow measurement and don't seem to do too badly.



Certainly I have seen pilots adjusting suction jet purely on the basis of fuel flow; ignoring cylinder temperatures and engine performance! Why I have no idea. But the fundamental problem is that this CHT measurement system is not precise and so dependent on a good contact with the cylinder head which so many people do not provide.



And I know from long experience that suction jet sizes can make significant differences to CHT.



Richard

RICHARD GOODE AEROBATICS

Rhodds Farm, Lyonshall, Hereford, HR5 3LW, UK

Tel:  +44 (0)1544 340120   Fax:  +44 (0)1544 340129

e-mail: richard.goode(at)russianaeros.com

www.russianaeros.com

WORLD LEADERS IN SOVIET & CHINESE RADIAL AIRCRAFT ENGINES

In partnership with Aerometal Kft, Hungary.



--

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