The International Cessna^® 170 Association

I installed my winter covers pn-0552101, and have flown for the first time last weekend.
I was very surprised, on take-off that my EGT went to 1440 f, and CHT 425 f, this was on take off
climbin through 500ft.

I have EGT on all 6 cyl and Cht on all 6 cyl. in auto the max temps were on #2 cyl. but # 5 was very
close. The out side temp was-5c. These temp values are what I would normally lean to in cruise
at 4000 or 5000 ft.

Once I leveled off at 2,000ft the temps went back pretty close to normal values at 2400 RPM.
On the next takeoff, on climb out I put carb heat on, and temps can back near normal.
When carb heat went on there was a decrease in RPM, which makes be think it is not over lean,
but near peak lean.( if it was too lean, carb heat would give it an increase in RPM ? ? )

So, is my carb perhaps setup too lean, ( when I shut down I get a very small increas in RPM ),
or is it the winter fronts, causing the higher temps ?
or should I be too concrned about this ? , and the cold temps are making the lean the carb leaner ?

John

Carb heat on...SHOULD cause a decrease in rpm due to an enriched mixture and loss of density-altitude in the intakes. When shutting down by s l o w l y pulling the mixture...ideally there will be a slight increase in RPM before the engine shuts down.

That is what I thought.
So is it too lean ?, or normal due to cold temps and winter fronts ?

John

Sounds normal. (Keep in mind that the main jets/venturi are affected by mass air flow/density. Denser air will also create greater vacuum and draw more fuel ...which is more dense anyway due to lower fuel temps. Therefore it is largely self-regulating in the full rich position of the mixture controls. Less dense air (due to altitude or high temps) are to be regulated by manual - l e a n i n g via the mixture control. In other words, no additional adjustments are necessary due to cold temps.)

Don't sweat your temperatures, You're just getting some nice, fat , cold winter air with lots of density. Gives the old O-300 a nice jab in the butt at WOT.

OK great ,

Thanks ! So all is well in the Great White North !
( out of interest many others experience this ? )
Cheers John

jatkins wrote:OK great ,
( out of interest many others experience this ? )
Cheers John

Yep, on really cold days in Alaska, on takeoff, I have seen my EGTs peg out on a Continental O-520 in a C-180. Pulling carb heat gets them back down.

Thanks richard, that makes me feel way beter !

Cheers John