RunRyder RC
 4  Topic Subscribe
WATCH
 1 page 637 views POST REPLY
HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Carb Smart Sensor Location
03-06-2008 05:51 PM  10 years agoPost 1
Rick_H

rrKey Veteran

Boulder City, Nevada

My Posts: All  Forum  Topic

Question for the Thermodynamics engineers.

I had read here that the best place to mount the sensor is on the side of the engine head opposite the fan. On most heli's that would put the sensor on the bottom of the heli. I would think this would give an inconsistent temperature reading. While hovering it would only have the air from the fan blowing around it. but while flying it would have the cooler air rushing past it this depending on the flying style the airflow over it would be constantly changing thus affecting the readings making the carb smart change more often than needed.

So my question is wouldn't it provide a more consistent reading by mounting it on the side of the head in the fan air flow as the air flow would be constant and the temperature would only be affected by the head temperature? not by constantly changing airflow over the bottom side of the head and sensor?

I am no Thermodynamics engineers yet, Give me a few more years here on Runryder

Thanks
Rick

PM  EMAIL  GALLERY  Attn:RR  Quote
03-06-2008 07:54 PM  10 years agoPost 2
DOKEY

rrProfessor

Northamptonshire UK

My Posts: All  Forum  Topic

But then is the airflow consistent? engine RPM increases and decreases under load etc. all the time
Its all debatable I suppose

Ryan.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
03-06-2008 10:27 PM  10 years agoPost 3
ErichF

rrElite Veteran

Sutton, NH

My Posts: All  Forum  Topic

This is exactly why this unit should be using EGT (exhaust gas temperature) for measuring engine temp. This is how full scale engines are measured for mixture, and how turbines measure for fuel delivery.

External CHT is too dependent on fan output, ambient temperature, humidity, and installation of the sensor. It's close, probably enough to work, but could be better with EGT. EGT is nearly instant in change, where CHT requires the heating up of the metal (by which time the engine is too lean). I've heard reports that during a rapid, no load descent (where the throttle is almost idle) the engine cools naturally (not making power), so the Carbsmart leans the engine way out to get the temp back up. No engine CHT at idle power should be 100°C, but the carbsmart is trying to do it.

An EGT probe could easily be installed through a typical pressure tap hole or similar.

PM  EMAIL  GALLERY  Attn:RR  Quote
03-06-2008 11:26 PM  10 years agoPost 4
Rick_H

rrKey Veteran

Boulder City, Nevada

My Posts: All  Forum  Topic

"But then is the airflow consistent? engine RPM increases and decreases under load etc. all the time"

Agreed, but not by much since we try to run our engines at a constant RPM during flight. The air flow would much more consistent from the FAN then from the wind in flight.

I like the idea of using EGT, to bad it wasn't designed into the Carb Smart.

Rick

PM  EMAIL  GALLERY  Attn:RR  Quote
03-07-2008 02:32 AM  10 years agoPost 5
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

My Posts: All  Forum  Topic

I like the idea of using EGT
A year ago when prototypes were being field-tested this was intended to be an option. I can't imagine it would be a difficult feature to incorporate -- a dip switch or a programming step to tell it which is being used. EGT would solve a lot of the 'where to put the sensor' problems as well.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

PM  EMAIL  GALLERY  Attn:RR  Quote
03-07-2008 04:49 AM  10 years agoPost 6
wings19

rrKey Veteran

Tucson, AZ

My Posts: All  Forum  Topic

I was talking about this with a buddy tonight... I do not have a carb smart(yet) but he does. We were thinking you could sort of surround the sensor with silicon to kind of make a protective covering for the sensor. You guys think this would work to cut out the airflow?

Nick
If the wings are traveling faster than the fuselage, it's probably a helicopter

PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 1 page 637 views POST REPLY
HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Carb Smart Sensor Location
 Print TOPIC  Make Suggestion 

 4  Topic Subscribe

Sunday, June 24 - 4:43 am - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online