Which cylinder is the best for an overall cylinder head temperature reading?

dd74 · 02-03-2008, 01:37 AM

Marks914 started a thread showing his gauge refurbishments , which look very nice.
Here is the thread showing his work: http://forums.pelicanparts.com/porsche-911-technical-forum/390669-woo-hoo-here-replace-you-clock-post3745056.html?posted=1#post3745056

A number of us are interested in replacing our ailing clocks with his volt/CHT gauge, pictured here:

The question we have is which of the Flat-6 cylinders runs the hottest in order for one to get a good overall CHT reading?
Does anyone know?

Thanks for the help.

stlrj · 02-03-2008, 05:02 AM

#2 or #5, the middle cylinders.

fireant911 · 02-03-2008, 05:20 AM

I agree with stlrj. I installed a Westach CHT gauge with two leads (one to #2 and the other to #5) and a selector switch. Of the two cylinders, #5 was the hottest. The temperature peaks that I saw were around 250°F for #5 and 230°F for #2 (normal summertime driving in Alabama). I was doing some testing therefore I was recording an abudance of CHT and oil temperature readings over multiple days. I also agree with Jack Olson in an earlier thread - a gauge reading up to 600°F is entirely too much overkill.

Porsche-O-Phile · Porsche-O-Phile's Garage

You could always get one of these (often seen on aircraft):

http://www.aircraftspruce.ca/catalog/inpages/gem1.php

Zef · Zef's Garage

Always on the cylinder that is the most far away from the source of cooling.

JohnJL · 02-03-2008, 05:54 AM

I run a Westech with 6 temp sensors, 1 on each lower plug. Number 4 always runs hottest by 15 degrees.

Zef · Zef's Garage

Quote:

Originally Posted by fireant911

I agree with stlrj. I installed a Westach CHT gauge with two leads (one to #2 and the other to #5) and a selector switch. Of the two cylinders, #5 was the hottest. The temperature peaks that I saw were around 250°F for #5 and 230°F for #2 (normal summertime driving in Alabama). I was doing some testing therefore I was recording an abudance of CHT and oil temperature readings over multiple days. I also agree with Jack Olson in an earlier thread - a gauge reading up to 600°F is entirely too much overkill.

IMHO, it's not because it's the number 5 cylinder...A cylinder at the nearest position of the cooling fan can be the hottest if something is wrong with that cylinder. The best way to assure that the engine's cylinders are kept in the normal range of operation and that no cylinder is sick is to install CHT on all of em like the aircraft engine way.